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1
Hutchings, Michael R., Spiridoula Athanasiadou, Ilias Kyriazakis, and Iain J. Gordon. "Can animals use foraging behaviour to combat parasites?" Proceedings of the Nutrition Society 62, no. 2 (May 2003): 361–70. http://dx.doi.org/10.1079/pns2003243.
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Host-parasite interactions are often seen as an arms race, with parasites attempting to overcome host resistance to infection. Herbivory is a common route of transmission of parasites that represents the most pervasive challenge to mammalian growth and reproduction. The present paper reviews the foraging skills of mammalian herbivores in relation to their ability to exploit plant properties to combat parasites. The starting point is that foraging behaviour may ameliorate the impact of parasitism in three ways; hosts could: (1) avoid foraging in areas contaminated with parasites; (2) select diets which increase their resistance to parasites; (3) select for foods containing anti-parasitic properties (self-medication). Details are given of the pre-requisite skills needed by herbivores if they are to combat parasitism via behaviour, i.e. herbivores are able to: (a) determine their parasitic state and alter their behaviour in relation to that state (behaviours 1, 2 and 3); (b) determine the environmental distribution of parasites (behaviour 1); (c) distinguish plant species or plant parts that increase their resistance to parasites (behaviour 2) or have anti-parasitic properties (behaviour 3). Mammalian herbivores cannot detect the presence of the parasites themselves and must rely on cues such as faeces. Despite the use of these cues contacting parasites may be inevitable and so mechanisms to combat parasitism are necessary. Mammalian herbivores have the foraging skills needed to exploit the heterogeneous distributions of nutrients and parasites in complex foraging environments in order to avoid, and increase their resistance to, parasites. Current evidence for the use of plant secondary metabolites (PSM) by herbivores for self-medication purposes remains equivocal. PSM have both positive (anti-parasitic) and negative (toxic) effects on herbivores. Here details are given of an experimental approach using tri-trophic (plant-herbivore-parasite) interactions that could be used to demonstrate self-medication in animals. There is strong evidence suggesting that herbivore hosts have developed the foraging skills needed to take advantage of plant properties to combat parasites and thus use behaviour as a weapon in the host-parasite arms race.
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Pathirana, N. U. K., M. Meegaskumbura, and R. S. Rajakaruna. "Host resistance and tolerance to parasitism: development-dependent fitness consequences in Common Hourglass Tree Frog (Polypedates cruciger) tadpoles exposed to two larval trematodes." Canadian Journal of Zoology 97, no. 11 (November 2019): 1021–29. http://dx.doi.org/10.1139/cjz-2018-0126.
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Tolerance and resistance to parasites are defense strategies of host organisms. Here, we tested the development-dependent tolerance and resistance of Polypedates cruciger Blyth, 1852 tadpoles to trematode infection. We exposed the tadpoles at Gosner stages 27, 28–29, and 30–31 to two types of cercariae (furcocercous and pleurolophocercous cercariae of Acanthostomum burminis (Bhalerao, 1926)) under laboratory conditions. To determine tolerance (the ability of a host to limit health effects of a given parasite load), we exposed the tadpoles until all cercariae penetrated the host. As a measure of determining resistance, we exposed tadpoles to cercariae for a limited time and counted the number of cercariae penetrating the tadpoles. The survival of tadpoles exposed at early stages was significantly lower than that of tadpoles exposed at later stages (mixed-effect model, p < 0.05), suggesting an age-dependent tolerance to parasitism. Tadpoles exposed at early stages were also smaller, took longer to metamorphosis, showed lower resistance to parasitism (ANOVA, p < 0.001), and developed axial malformations. In the resistance experiment, fewer parasites penetrated later stage tadpoles than early stage tadpoles. Tadpoles of P. cruciger showed a development-dependent tolerance and resistance to parasitism, resulting in greater survival and fewer malformations when parasitism occurs at late stages.
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Vidal, Luísa Lauren Lima, Leopoldo Ferreira Oliveira Bernardi, and Sonia Aparecida Talamoni. "Host-parasite associations in a population of the nectarivorous bat Anoura geoffroyi (Phyllostomidae) in a cave in a Brazilian ferruginous geosystem." Subterranean Biology 39 (June 9, 2021): 63–77. http://dx.doi.org/10.3897/subtbiol.39.64552.
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Parasitic relationships between Neotropical bats and their ectoparasites are not well known, even though parasitism is one of the factors that can affect the fitness of a host population. This study characterized parasite-host relationships in relation to sex, age, body size and reproductive status in a population of Anoura geoffroyi using the indices of Prevalence, Mean Intensity and Mean Abundance. Total prevalence for 93 sampled bats was 94.6%. Two species of streblid flies that are considered primary parasites of A. geoffroyi, Exastinion clovisi (n = 203) and Anastrebla modestini (n = 152), were the most abundant ectoparasites, followed by Trichobius sp. (n = 7). Two mite species, Periglischrus vargasi (Spinturnicidae) (n = 98) and Spelaeorhynchus praecursor (Spelaeorhynchidae) (n = 11), were also found. We recorded higher mean abundance and intensity of parasitism in pregnant females compared to reproductive males and reproductively inactive females, for different specific associations of ectoparasites. Host age and body condition had no effect on the parasitological indices. Even with high rates of parasitism, parasitic load did not influence host body condition, but infestation rates by mites were higher in reproductive males and higher by flies in reproductive females, showing that ectoparasites can have variable influences between the different stages of the life history of these host bats. Thus, the reproductive activity of the hosts could be an adverse factor for resistance to parasite infestations.
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Abou Chakra, Maria, Christian Hilbe, and Arne Traulsen. "Coevolutionary interactions between farmers and mafia induce host acceptance of avian brood parasites." Royal Society Open Science 3, no. 5 (May 2016): 160036. http://dx.doi.org/10.1098/rsos.160036.
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Brood parasites exploit their host in order to increase their own fitness. Typically, this results in an arms race between parasite trickery and host defence. Thus, it is puzzling to observe hosts that accept parasitism without any resistance. The ‘mafia’ hypothesis suggests that these hosts accept parasitism to avoid retaliation. Retaliation has been shown to evolve when the hosts condition their response to mafia parasites, who use depredation as a targeted response to rejection. However, it is unclear if acceptance would also emerge when ‘farming’ parasites are present in the population. Farming parasites use depredation to synchronize the timing with the host, destroying mature clutches to force the host to re-nest. Herein, we develop an evolutionary model to analyse the interaction between depredatory parasites and their hosts. We show that coevolutionary cycles between farmers and mafia can still induce host acceptance of brood parasites. However, this equilibrium is unstable and in the long-run the dynamics of this host–parasite interaction exhibits strong oscillations: when farmers are the majority, accepters conditional to mafia (the host will reject first and only accept after retaliation by the parasite) have a higher fitness than unconditional accepters (the host always accepts parasitism). This leads to an increase in mafia parasites’ fitness and in turn induce an optimal environment for accepter hosts.
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VAGENAS, D., S. C. BISHOP, and I. KYRIAZAKIS. "A model to account for the consequences of host nutrition on the outcome of gastrointestinal parasitism in sheep: model evaluation." Parasitology 134, no. 9 (April 20, 2007): 1279–89. http://dx.doi.org/10.1017/s0031182007002624.
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SUMMARYThis paper describes sensitivity analyses and expectations obtained from a mathematical model developed to account for the effects of host nutrition on the consequences of gastrointestinal parasitism in sheep. The scenarios explored included different levels of parasitic challenge at different planes of nutrition, for hosts differing only in their characteristics for growth. The model was able to predict the consequences of host nutrition on the outcome of parasitism, in terms of worm burden, number of eggs excreted per gram faeces and animal performance. The model outputs predict that conclusions on the ability of hosts of different characteristics for growth to cope with parasitism (i.e. resistance) depend on the plane of nutrition. Furthermore, differences in the growth rate of sheep, on their own, are not sufficient to account for differences in the observed resistance of animals. The model forms the basis for evaluating the consequences of differing management strategies and environments, such as breeding for certain traits associated with resistance and nutritional strategies, on the consequences of gastrointestinal parasitism on sheep.
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Vagenas, D., SC Bishop, and I. Kyriazakis. "Development of a model to investigate the interaction between host nutrition, genotype and gastro-intestinal parasitism in lambs." Proceedings of the British Society of Animal Science 2007 (April 2007): 88. http://dx.doi.org/10.1017/s1752756200019918.
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Gastrointestinal parasitism in lambs is usually manifested as a sub-clinical infection and causes significant losses in performance. Its control through the use of chemoprophylaxis is no longer sustainable due to the development of parasitic resistance to anthelminthics, but also due to environmental and consumer concerns. There is thus an urgent need to develop alternative, sustainable methods of controlling gastrointestinal parasitism. These include dietary supplementation of host with protein. The aim here is to develop a mathematical simulation model for the description of the joint effects of nutrition and host performance genotype on the outcome of sub-clinical challenge by gastrointestinal parasitism for growing lambs.
7
Dong, Ke, and Charles H. Opperman. "Genetic Analysis of Parasitism in the Soybean Cyst Nematode Heterodera glycines." Genetics 146, no. 4 (August 1, 1997): 1311–18. http://dx.doi.org/10.1093/genetics/146.4.1311.
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A genetic analysis of parasitic ability in the soybean cyst nematode Heterodera glycines was performed. To identify and characterize genes involved in parasitism, we developed three highly inbred H. glycines lines, OP20, OP25 and OP50, for use as parents for controlled crosses. Through these crosses, we have identified genes in the inbred parents that control reproduction of the nematode on hosts that carry resistance genes. These genes, designated as ror-* for reproduction on a resistant host, segregate in a normal Mendelian fashion as independent loci. Host range tests of F1 generation progeny indicated that at least one parasitism gene in both the OP20 and OP50 lines for host PI 88788 was dominant. Parasitism genes in OP50 for hosts “Peking” and PI 90763 are recessive. Two types of single female descent populations, a single backcrossed BC1F2-derived and a double backcrossed BC2F1-derived, were established on the susceptible soybean cultivar “Lee 68.” Host range tests for parasitism in these lines demonstrated the presence of two independent genes in OP50, one for host PI 88788 designated ror-1 and one for host PI 90763 designated ror-2. OP20 carries two independent genes for parasitism on PI 88788, designated as alleles kr3 and kr4.
8
Clarke, Christopher R., So-Yon Park, Robert Tuosto, Xiaoyan Jia, Amanda Yoder, Jennifer Van Mullekom, and James Westwood. "Multiple immunity-related genes control susceptibility of Arabidopsis thaliana to the parasitic weed Phelipanche aegyptiaca." PeerJ 8 (June 8, 2020): e9268. http://dx.doi.org/10.7717/peerj.9268.
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Parasitic weeds represent a major threat to agricultural production across the world. Little is known about which host genetic pathways determine compatibility for any host–parasitic plant interaction. We developed a quantitative assay to characterize the growth of the parasitic weed Phelipanche aegyptiaca on 46 mutant lines of the host plant Arabidopsis thaliana to identify host genes that are essential for susceptibility to the parasite. A. thaliana host plants with mutations in genes involved in jasmonic acid biosynthesis/signaling or the negative regulation of plant immunity were less susceptible to P. aegyptiaca parasitization. In contrast, A. thaliana plants with a mutant allele of the putative immunity hub gene Pfd6 were more susceptible to parasitization. Additionally, quantitative PCR revealed that P. aegyptiaca parasitization leads to transcriptional reprograming of several hormone signaling pathways. While most tested A. thaliana lines were fully susceptible to P. aegyptiaca parasitization, this work revealed several host genes essential for full susceptibility or resistance to parasitism. Altering these pathways may be a viable approach for limiting host plant susceptibility to parasitism.
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Joachim, Peyton J. "Evolution of Resistance in Potamopyrgus antipodarum." IU Journal of Undergraduate Research 1, no. 1 (June 1, 2015): 35. http://dx.doi.org/10.14434/iujur.v1i1.13714.
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Host-parasite interactions are believed to exert strong selection in natural communities. Most notably, parasites should select for increased resistance in hosts, while hosts should select for increased infectivity in parasites (Koskella & Lively, 2007; Koskella, Vergara, & Lively, 2011; Lohse, Guiterrez, & Kaltz, 2006). Under this coevolutionary process, can host populations evolve resistance to their rapidly evolving parasite populations? This experiment was designed to determine if hosts rapidly adapt to resist parasites that are themselves under selection to infect their hosts. The New Zealand freshwater snail, Potamopyrgus antipodarum, is naturally infected by the trematode Microphallus. Microphallus is a castrating parasite and is thus likely to impose strong selection on its snail host (Hechinger, 2012). Snails and parasites were collected from a natural lake in summer 2013. These hosts constitute the parental generation of the experiment: they were either exposed to parasite eggs (Exposed) or not exposed (Control). Parental snails matured and reproduced over the course of a year. Their offspring were then exposed to parasites collected from the same lake in summer 2014. These parasites would have had one to a few additional generations of evolution relative to 2013 parasites. After parasite development (~3 months), the offspring were dissected to determine infection status and thereby their resistance to infection. The offspring of Control parents had a significantly higher mean infection rate (35%: less resistant) than the offspring of Exposed parents (30%: more resistant). This result indicates that increased resistance to parasitism evolved in a single host generation. Our finding provides evidence that a host population can rapidly evolve resistance to a parasite population that is itself rapidly co-evolving to infect its host. We predict that the evolution of host resistance would be far greater after multiple generations of parasite selection, and this could be the subject of future study.
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Parrisi, Z., S. Athanasiadou, J. G. M. Houdijk, and I. Kyriazakis. "In vitro anthelmintic activity of Chicory extracts from plants of different vegetative stages on Teladorsagia circumcincta L3." Proceedings of the British Society of Animal Science 2009 (April 2009): 35. http://dx.doi.org/10.1017/s175275620002874x.
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The consumption of plants rich in plant secondary metabolites has been associated with improved resilience of parasitised hosts, i.e. their ability to perform under parasitic infection, compared to animals fed conventional feeds (Athanasiadou et al., 2007). Furthermore, such bio-active plants can improve host resistance, which refers to the host ability to regulate gastrointestinal nematode establishment, development, fecundity and survival (Athanasiadou et. al. 2008). Chichorium intybus L. (chicory) is such a bio-active forage and its potential anthelmintic activity is currently investigated as an alternative means to control parasitism in sheep production systems. In the present study we employed an in vitro assay to study a possible mechanism of anti-parasitic action arising from chicory, and to test whether this anthelmintic activity is affected by the vegetative stage of the plant.
11
Hughes, Janice M. "Taxonomic significance of host-egg mimicry by facultative brood parasites of the avian genus Coccyzus (Cuculidae)." Canadian Journal of Zoology 75, no. 9 (September 1, 1997): 1380–86. http://dx.doi.org/10.1139/z97-764.
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Black-billed (Coccyzus erythropthalmus) and Yellow-billed (C. americanus) cuckoos are facultative brood parasites that occasionally lay their eggs in the nests of 10 and 11 other bird species, respectively. This study demonstrates that both cuckoo species produce blue–green eggs that fully or nearly match the eggs of over 70% of their reported host species, a proportion significantly greater than if hosts were being selected at random from the potential host pool. These results suggest that the cuckoos may be selecting hosts on the basis of their egg colour, and support a hypothesis of egg mimicry. Since egg mimicry is unlikely to evolve in a facultative parasite, its existence in Coccyzus would imply a historically intense relationship between these birds and their hosts. This hypothesis is corroborated by recent phylogenetic analyses which suggest that the ancestral Coccyzus was an obligate parasite. Factors responsible for the loss of obligate parasitism in this genus may also have contributed to the general paucity of obligate parasitism in New World cuckoos. Competitive exclusion or resistance to invasion by parasitic cowbirds (Molothrus spp.) should be considered.
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O’Connor, Jody A., Jeremy Robertson, and Sonia Kleindorfer. "Video analysis of host–parasite interactions in nests of Darwin’s finches." Oryx 44, no. 4 (October 2010): 588–94. http://dx.doi.org/10.1017/s0030605310000086.
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AbstractParasites place their hosts under strong selection for adaptive traits that increase parasite resistance. The initial impact of invasive parasites has rarely been observed and can be particularly strong on naïve hosts with limited prior exposure to parasites.Philornis downsiis an introduced fly to the Galapagos Islands whose parasitic larvae cause high mortality in nestlings of Darwin's finches. We used a within-nest camera system and nest monitoring data to examine this new host–parasite interaction in the wild. ManyP. downsiflies entered finch nests with incubated eggs or nestlings but only when parent finches were not present. ParasiticP. downsilarvae were observed to emerge from the nest base at night to feed both internally and externally on nestlings. Adult and nestling Darwin’s finches exhibit grooming and avoidance behaviours in the presence ofP. downsiparasites. Specifically, in nests with high parasite intensity, nestlings increased self-preening behaviour, ate larvae and stood on top of one another. Female finches probed into their nestling’s nares (first instar larvae reside in the nares) and probed into the nest base (second and third larvae reside in the nest base during the day). These findings shed light on the emergence of anti-parasite behaviour as well as host–parasite relationships after recent parasitism in a naïve host.
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McLean, Ailsa H. C., and Benjamin J. Parker. "Variation in intrinsic resistance of pea aphids to parasitoid wasps: A transcriptomic basis." PLOS ONE 15, no. 11 (November 18, 2020): e0242159. http://dx.doi.org/10.1371/journal.pone.0242159.
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Evolutionary interactions between parasitoid wasps and insect hosts have been well studied at the organismal level, but little is known about the molecular mechanisms that insects use to resist wasp parasitism. Here we study the interaction between a braconid wasp (Aphidius ervi) and its pea aphid host (Acyrthosiphon pisum). We first identify variation in resistance to wasp parasitism that can be attributed to aphid genotype. We then use transcriptome sequencing to identify genes in the aphid genome that are differentially expressed at an early stage of parasitism, and we compare these patterns in highly resistant and susceptible aphid host lines. We find that resistant genotypes are upregulating genes involved in carbohydrate metabolism and several key innate immune system genes in response to parasitism, but that this response seems to be weaker in susceptible aphid genotypes. Together, our results provide a first look into the complex molecular mechanisms that underlie aphid resistance to wasp parasitism and contribute to a broader understanding of how resistance mechanisms evolve in natural populations.
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M'Gonigle, Leithen K., and Sarah P. Otto. "Ploidy and the evolution of parasitism." Proceedings of the Royal Society B: Biological Sciences 278, no. 1719 (February 2, 2011): 2814–22. http://dx.doi.org/10.1098/rspb.2010.2146.
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Levels of parasitism are continuously distributed in nature. Models of host–parasite coevolution, however, typically assume that species can be easily characterized as either parasitic or non-parasitic. Consequently, it is poorly understood which factors influence the evolution of parasitism itself. We investigate how ploidy level and the genetic mechanisms underlying infection influence evolution along the continuum of parasitism levels. In order for parasitism to evolve, selective benefits to the successful invasion of hosts must outweigh the losses when encountering resistant hosts. However, we find that exactly where this threshold occurs depends not only on the strength of selection, but also on the genetic model of interaction, the ploidy level in each species, and the nature of the costs to virulence and resistance. With computer simulations, we are able to incorporate more realistic dynamics at the loci underlying species interactions and to extend our analyses in a number of directions, including finite population sizes, multiple alleles and different generation times.
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Gols, Rieta, Gaylord A. Desurmont, and Jeffrey A. Harvey. "Variation in Performance and Resistance to Parasitism of Plutella xylostella Populations." Insects 10, no. 9 (September 11, 2019): 293. http://dx.doi.org/10.3390/insects10090293.
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Two major ecological factors determine the fitness of an insect herbivore: the ability to overcome plant resistance strategies (bottom-up effects) and the ability to avoid or resist attack by natural enemies such as predators and parasitoids (top-down effects). In response to differences in selection pressure, variation may exist in host-plant adaptation and immunity against parasitism among populations of an insect herbivore. We investigated the variation in larval performance of six different Plutella xylostella populations originating from four continents when feeding on a native Dutch plant species, Brassica rapa. One of the used populations has successfully switched its host plant, and is now adapted to pea. In addition, we determined the resistance to attack by the endoparasitoid Diadegma semiclausum originating from the Netherlands (where it is also native) and measured parasitoid performance as a proxy for host resistance against parasitism. Pupal mortality, immature development times, and adult biomass of P. xylostella differed significantly across populations when feeding on the same host plant species. In addition, parasitism success differed in terms of parasitoid adult emergence and their biomass, but not their development times. Variation among natural populations of insects should be considered more when studying interactions between plants and insects up the food chain.
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Soler, J. J., D. Martín-Gálvez, J. G. Martínez, M. Soler, D. Canestrari, J. M. Abad-Gómez, and A. P. Møller. "Evolution of tolerance by magpies to brood parasitism by great spotted cuckoos." Proceedings of the Royal Society B: Biological Sciences 278, no. 1714 (December 2010): 2047–52. http://dx.doi.org/10.1098/rspb.2010.2218.
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Hosts may use two different strategies to ameliorate negative effects of a given parasite burden: resistance or tolerance. Although both resistance and tolerance of parasitism should evolve as a consequence of selection pressures owing to parasitism, the study of evolutionary patterns of tolerance has traditionally been neglected by animal biologists. Here, we explore geographical covariation between tolerance of magpies ( Pica pica ) and brood parasitism by the great spotted cuckoo ( Clamator glandarius ) in nine different sympatric populations. We estimated tolerance as the slope of the regression of number of magpie fledglings (i.e. host fitness) on number of cuckoo eggs laid in non-depredated nests (which broadly equals parasite burden). We also estimated prevalence of parasitism and level of host resistance (i.e. rejection rates of mimetic model eggs) in these nine populations. In accordance with the hypothetical role of tolerance in the coevolutionary process between magpies and cuckoos we found geographical variation in tolerance estimates that positively covaried with prevalence of parasitism. Levels of resistance and tolerance were not associated, possibly suggesting the lack of a trade-off between the two kinds of defences against great spotted cuckoo parasitism for magpies. We discuss the results in the framework of a mosaic of coevolutionary interactions along the geographical distribution of magpies and great spotted cuckoos for which we found evidence that tolerance plays a major role.
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Klemme, Ines, and Anssi Karvonen. "Learned parasite avoidance is driven by host personality and resistance to infection in a fish–trematode interaction." Proceedings of the Royal Society B: Biological Sciences 283, no. 1838 (September 14, 2016): 20161148. http://dx.doi.org/10.1098/rspb.2016.1148.
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Cognitive abilities related to the assessment of risk improve survival. While earlier studies have examined the ability of animals to learn to avoid predators, learned parasite avoidance has received little interest. In a series of behavioural trials with the trematode parasite Diplostomum pseudospathaceum , we asked whether sea trout ( Salmo trutta trutta ) hosts show associative learning in the context of parasitism and if so, whether learning capacity is related to the likelihood of infection mediated through host personality and resistance. We show that animals are capable of learning to avoid visual cues associated with the presence of parasites. However, avoidance behaviour ceased after the likely activation of host resistance following consecutive exposures during learning, suggesting that resistance to infection outweighs avoidance. Further, we found a positive relationship between learning ability and boldness, suggesting a compensation of risky lifestyles through increased investment in cognitive abilities. By contrast, an increased risk of infection due to low resistance was not balanced by learning ability. Instead, these traits were positively related, which may be explained by inherent physiological qualities controlling both traits. Overall, the results demonstrate that parasitism, in addition to other biological interactions such as predation, is an important selective factor in the evolution of animal cognition.
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Tomasetto, Federico, Jason M. Tylianakis, Marco Reale, Steve Wratten, and Stephen L. Goldson. "Intensified agriculture favors evolved resistance to biological control." Proceedings of the National Academy of Sciences 114, no. 15 (March 13, 2017): 3885–90. http://dx.doi.org/10.1073/pnas.1618416114.
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Increased regulation of chemical pesticides and rapid evolution of pesticide resistance have increased calls for sustainable pest management. Biological control offers sustainable pest suppression, partly because evolution of resistance to predators and parasitoids is prevented by several factors (e.g., spatial or temporal refuges from attacks, reciprocal evolution by control agents, and contrasting selection pressures from other enemy species). However, evolution of resistance may become more probable as agricultural intensification reduces the availability of refuges and diversity of enemy species, or if control agents have genetic barriers to evolution. Here we use 21 y of field data from 196 sites across New Zealand to show that parasitism of a key pasture pest (Listronotus bonariensis; Argentine stem weevil) by an introduced parasitoid (Microctonus hyperodae) was initially nationally successful but then declined by 44% (leading to pasture damage of c. 160 million New Zealand dollars per annum). This decline was not attributable to parasitoid numbers released, elevation, or local climatic variables at sample locations. Rather, in all locations the decline began 7 y (14 host generations) following parasitoid introduction, despite releases being staggered across locations in different years. Finally, we demonstrate experimentally that declining parasitism rates occurred in ryegrass Lolium perenne, which is grown nationwide in high-intensity was significantly less than in adjacent plots of a less-common pasture grass (Lolium multiflorum), indicating that resistance to parasitism is host plant–dependent. We conclude that low plant and enemy biodiversity in intensive large-scale agriculture may facilitate the evolution of host resistance by pests and threaten the long-term viability of biological control.
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Råberg, Lars, Andrea L. Graham, and Andrew F. Read. "Decomposing health: tolerance and resistance to parasites in animals." Philosophical Transactions of the Royal Society B: Biological Sciences 364, no. 1513 (October 16, 2008): 37–49. http://dx.doi.org/10.1098/rstb.2008.0184.
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Plant biologists have long recognized that host defence against parasites and pathogens can be divided into two conceptually different components: the ability to limit parasite burden (resistance) and the ability to limit the harm caused by a given burden (tolerance). Together these two components determine how well a host is protected against the effects of parasitism. This distinction is useful because it recognizes that hosts that are best at controlling parasite burdens are not necessarily the healthiest. Moreover, resistance and tolerance can be expected to have different effects on the epidemiology of infectious diseases and host–parasite coevolution. However, studies of defence in animals have to date focused on resistance, whereas the possibility of tolerance and its implications have been largely overlooked. The aim of our review is to (i) describe the statistical framework for analysis of tolerance developed in plant science and how this can be applied to animals, (ii) review evidence of genetic and environmental variation for tolerance in animals, and studies indicating which mechanisms could contribute to this variation, and (iii) outline avenues for future research on this topic.
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Luikart, Gordon, Kristy Pilgrim, Judy Visty, Vanessa O. Ezenwa, and Michael K. Schwartz. "Candidate gene microsatellite variation is associated with parasitism in wild bighorn sheep." Biology Letters 4, no. 2 (February 12, 2008): 228–31. http://dx.doi.org/10.1098/rsbl.2007.0633.
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The loss of genetic variation in host populations is thought to increase host susceptibility to parasites. However, few data exist to test this hypothesis in natural populations. Bighorn sheep ( Ovis canadensis ) populations occasionally suffer disease-induced population declines, allowing us to test for the associations between reduced genetic variation and parasitism in this species. Here, we show that individual mean heterozygosity for 15 microsatellite loci is associated with lungworm abundance ( Protostrongylus spp.) in a small, recently bottlenecked population of bighorn sheep (linear regression, r 2 =0.339, p =0.007). This association remains significant for seven microsatellites located in genes ( p =0.010), but not for eight neutral microsatellites ( p =0.306). Furthermore, heterozygotes at three of four microsatellites located within disease-related genes had lower lungworm burdens. This study corroborates theoretical findings that increased parasitism and disease may be a consequence of reduced heterozygosity in wild populations, and that certain individual loci influence parasite resistance. The results illustrate the usefulness of using genomic information, strong candidate genes and non-invasive sampling for monitoring both genetic variation and fitness-related traits, such as parasite resistance, in natural populations.
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Picard, Karine, Yves Tirilly, and Nicole Benhamou. "Cytological Effects of Cellulases in the Parasitism of Phytophthora parasitica by Pythium oligandrum." Applied and Environmental Microbiology 66, no. 10 (October 1, 2000): 4305–14. http://dx.doi.org/10.1128/aem.66.10.4305-4314.2000.
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ABSTRACT The ubiquitous oomycete Pythium oligandrum is a potential biocontrol agent for use against a wide range of pathogenic fungi and an inducer of plant disease resistance. The ability ofP. oligandrum to compete with root pathogens for saprophytic colonization of substrates may be critical for pathogen increase in soil, but other mechanisms, including antibiosis and enzyme production, also may play a role in the antagonistic process. We used transmission electron microscopy and gold cytochemistry to analyze the intercellular interaction between P. oligandrum andPhytophthora parasitica. Growth of P. oligandrum towards Phytophthora cells correlated with changes in the host, including retraction of the plasma membrane and cytoplasmic disorganization. These changes were associated with the deposition onto the inner host cell surface of a cellulose-enriched material. P. oligandrum hyphae could penetrate the thickened host cell wall and the cellulose-enriched material, suggesting that large amounts of cellulolytic enzymes were produced. Labeling of cellulose with gold-complexed exoglucanase showed that the integrity of the cellulose was greatly affected both along the channel of fungal penetration and also at a distance from it. We measured cellulolytic activity of P. oligandrum in substrate-free liquid medium. The enzymes present were almost as effective as those from Trichoderma viride in degrading both carboxymethyl cellulose and Phytophthora wall-bound cellulose. P. oligandrum and its cellulolytic enzymes may be useful for biological control of oomycete pathogens, includingPhytophthora and Pythium spp., which are frequently encountered in field and greenhouse production.
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Jongepier, Evelien, Isabelle Kleeberg, Sylwester Job, and Susanne Foitzik. "Collective defence portfolios of ant hosts shift with social parasite pressure." Proceedings of the Royal Society B: Biological Sciences 281, no. 1791 (September 22, 2014): 20140225. http://dx.doi.org/10.1098/rspb.2014.0225.
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Host defences become increasingly costly as parasites breach successive lines of defence. Because selection favours hosts that successfully resist parasitism at the lowest possible cost, escalating coevolutionary arms races are likely to drive host defence portfolios towards ever more expensive strategies. We investigated the interplay between host defence portfolios and social parasite pressure by comparing 17 populations of two Temnothorax ant species. When successful, collective aggression not only prevents parasitation but also spares host colonies the cost of searching for and moving to a new nest site. However, once parasites breach the host's nest defence, host colonies should resort to flight as the more beneficial resistance strategy. We show that under low parasite pressure, host colonies more likely responded to an intruding Protomognathus americanus slavemaker with collective aggression, which prevented the slavemaker from escaping and potentially recruiting nest-mates. However, as parasite pressure increased, ant colonies of both host species became more likely to flee rather than to fight. We conclude that host defence portfolios shift consistently with social parasite pressure, which is in accordance with the degeneration of frontline defences and the evolution of subsequent anti-parasite strategies often invoked in hosts of brood parasites.
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Roy, N. C., E. N. Bermingham, I. A. Sutherland, and W. C. McNabb. "Nematodes and nutrient partitioning." Australian Journal of Experimental Agriculture 43, no. 12 (2003): 1419. http://dx.doi.org/10.1071/ea02224.
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Subclinical infection of sheep with gastrointestinal nematodes results in the diversion of nutrients from growth and development towards the repair of damaged intestinal tissues and to sustain the metabolic shifts (nutritional, hormonal and immune) occuring in tissues affected by the parasites. These metabolic effects include decreased nitrogen retention; increased amino acid utilisation and oxidation in the gastrointestinal tract; increased endogenous protein loss and altered protein synthesis in the gastrointestinal tract; increased amino acid utilisation and protein synthesis in the liver and activation of the immune system. These observations strongly suggest that there is competition between the key tissues involved in parasitism and that metabolic decisions are made resulting in the re-prioritisation of nutrient utilisation between the tissues in this inter-organ system. Nutritional status of the host can influence the pathogenesis of parasitic infection and well-nourished animals generally withstand parasitism better than those less adequately fed. Recent studies have focused on the effect of restricting intake on the acquisition of immunity in sheep selected either for resistance or susceptibility to nematodes. The major outcome of these studies was the increase of peripheral eosinophil counts in resistant animals infected with Trichostrongylus colubriformis when fed on an ad libitum diet compared with similar animals fed the same diet at a maintenance level. This was inversely correlated to the numbers of adult parasites recovered. Intake seems to be the primary determinant of the expression of immunity in sheep selected for resistance against nematodes.
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Neumann, P. "Social parasitism by honeybee workers (Apis mellifera capensis Escholtz): host finding and resistance of hybrid host colonies." Behavioral Ecology 12, no. 4 (July 1, 2001): 419–28. http://dx.doi.org/10.1093/beheco/12.4.419.
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McNew, Sabrina M., Sarah A. Knutie, Graham B. Goodman, Angela Theodosopoulos, Ashley Saulsberry, Janai Yépez R., Sarah E. Bush, and Dale H. Clayton. "Annual environmental variation influences host tolerance to parasites." Proceedings of the Royal Society B: Biological Sciences 286, no. 1897 (February 27, 2019): 20190049. http://dx.doi.org/10.1098/rspb.2019.0049.
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When confronted with a parasite or pathogen, hosts can defend themselves by resisting or tolerating the attack. While resistance can be diminished when resources are limited, it is unclear how robust tolerance is to changes in environmental conditions. Here, we investigate the sensitivity of tolerance in a single host population living in a highly variable environment. We manipulated the abundance of an invasive parasitic fly, Philornis downsi , in nests of Galápagos mockingbirds ( Mimus parvulus ) over four field seasons and measured host fitness in response to parasitism. Mockingbird tolerance to P. downsi varied significantly among years and decreased when rainfall was limited. Video observations indicate that parental provisioning of nestlings appears key to tolerance: in drought years, mockingbirds likely do not have sufficient resources to compensate for the effects of P. downsi . These results indicate that host tolerance is a labile trait and suggest that environmental variation plays a major role in mediating the consequences of host–parasite interactions.
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Westwood, James H., Claude W. dePamphilis, Malay Das, Mónica Fernández-Aparicio, Loren A. Honaas, Michael P. Timko, Eric K. Wafula, Norman J. Wickett, and John I. Yoder. "The Parasitic Plant Genome Project: New Tools for Understanding the Biology ofOrobancheandStriga." Weed Science 60, no. 2 (June 2012): 295–306. http://dx.doi.org/10.1614/ws-d-11-00113.1.
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The Parasitic Plant Genome Project has sequenced transcripts from three parasitic species and a nonparasitic relative in the Orobanchaceae with the goal of understanding genetic changes associated with parasitism. The species studied span the trophic spectrum from free-living nonparasite to obligate holoparasite. Parasitic species used wereTriphysaria versicolor, a photosynthetically competent species that opportunistically parasitizes roots of neighboring plants;Striga hermonthica, a hemiparasite that has an obligate need for a host; andOrobanche aegyptiaca, a holoparasite with absolute nutritional dependence on a host.Lindenbergia philippensisrepresents the closest nonparasite sister group to the parasitic Orobanchaceae and was included for comparative purposes. Tissues for transcriptome sequencing from each plant were gathered to identify expressed genes for key life stages from seed conditioning through anthesis. Two of the species studied,S. hermonthicaandO. aegyptiaca, are economically important weeds and the data generated by this project are expected to aid in research and control of these species and their relatives. The sequences generated through this project will provide an abundant resource of molecular markers for understanding population dynamics, as well as provide insight into the biology of parasitism and advance progress toward understanding parasite virulence and host resistance mechanisms. In addition, the sequences provide important information on target sites for herbicide action or other novel control strategies such as trans-specific gene silencing.
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Amri, Moez, Zouhaier Abbes, Imen Trabelsi, Michel Edmond Ghanem, Rachid Mentag, and Mohamed Kharrat. "Chlorophyll content and fluorescence as physiological parameters for monitoring Orobanche foetida Poir. infection in faba bean." PLOS ONE 16, no. 5 (May 25, 2021): e0241527. http://dx.doi.org/10.1371/journal.pone.0241527.
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Orobanche spp. are root parasitic plants that cause yield losses in faba bean (Vicia faba L.). In Tunisia, O. crenata and O. foetida are among the major problems limiting faba bean production and productivity. Breeding for resistance and development of resistant varieties remain the most efficient control strategy to combat these parasites. In our study, field trials were conducted over two consecutive cropping seasons. A set of 42 genotypes were used in this study; 39 advanced lines and three checks; Najeh and Baraca (resistant) and Badi (susceptible). The trials were conducted in highly infested O. foetida plot at Oued-Beja Research Station in Tunisia. Results showed that advanced lines XAR-VF00.13-1-2-1-2-1 and XBJ90.04-2-3-1-1-1-2A expressed high resistance level exceeding those recorded for resistance checks Najeh and Baraca. O. foetida significantly affected the biomass, grain yield, chlorophyll content index (CCI) and the maximum quantum efficiency (Fv/Fm ratio). No significant effect was observed on host plant water content (WC). CCI decreases varied from 46.4% for the susceptible check Badi and 4.2% and 9.3%, respectively, for Baraca and XBJ90.04-2-3-1-1-1-2A. Orobanche parasitism resulted in a slight decreases of Fv/Fm ratio for the advanced lines XBJ90.04-2-3-1-1-1-2A and XAR-VF00.13-1-2-1-2-1 against important decreases observed for Badi and Baraca. Correlation between resistance to O. foetida and CCI and Fv/Fm makes this, easy-to-measure, parameter very useful as a practical screening tool for early parasitism detection, diagnosis and identification and selection of high resistant plants against this parasite.
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Nagel, Laura, Julia J. Mlynarek, and Mark R. Forbes. "Comparing Natural Parasitism and Resistance with Proxies of Host Immune Response in Lestid Damselflies." Ecological Parasitology and Immunology 3 (2014): 1–7. http://dx.doi.org/10.4303/epi/235884.
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Oliver, K. M., N. A. Moran, and M. S. Hunter. "Variation in resistance to parasitism in aphids is due to symbionts not host genotype." Proceedings of the National Academy of Sciences 102, no. 36 (August 24, 2005): 12795–800. http://dx.doi.org/10.1073/pnas.0506131102.
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ARSENOPOULOS, K., I. SYMEONIDOU, and E. PAPADOPOULOS. "Immune and other factors modulating host resistance against gastrointestinal nematode parasites in sheep." Journal of the Hellenic Veterinary Medical Society 68, no. 2 (January 29, 2018): 131. http://dx.doi.org/10.12681/jhvms.15597.
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Infection of small ruminants with gastrointestinal nematode (GIN) parasites is a significant problem with crucial impact on meat and milk production. The strategy of administrating anthelminthic drugs has been implemented for many years and has resulted in the development of resistant strains of parasites. Meanwhile, consumers demand for free of drugs products have led to the adoption of alternative control methods, which involve the selective breeding of animals, which are resistant to parasitism. The development of immunity and therefore, resistance against gastrointestinal parasites is based on the activation of specific host genes. Gene analysis has revealed areas (QTLs), which affect resistance or susceptibility of sheep to gastrointestinal infestations between animals of different breeds and between individuals of the same breed. The role of cytokines and T helper cells has been enhanced as research, strongly, supports the connection of Th2 cells with resistance and Th1 cells with susceptibility against GIN. Latest data implicates T regulatory cells and a specific cell type, Th17, in immune response mechanisms. Specific adhesion molecules (integrins, lectins, cadherins) are produced in the gut lumen in sufficient amounts and appear to boost immunity and reduce clinical signs in sheep. Additionally, the immunoglobulins IgA and IgE have been positively correlated with increased resistance against GIN. In several cases of GIN, where an increased number of eosinophils and mast cells in the intestinal epithelium have been recorded, the animals had a reduced number of parasite eggs in their feces. The genes of the Major Histocompatibility Complex have been referred to as potential resistance or susceptibility markers. Other enzymes, like chitinases, enhance the resilience of animals and protect them effectively. Animal’s nutritional status is another determinant factor of immune capability against GIN in sheep, both systemic, as well as locally. Regarding the effect of reactive oxygen and nitrogen species, some researchers support their direct effect against GIN, resulting in a natural reduction of their number, while others claim the indirect action in the intestinal epithelium by reducing local immunity. Consequently, the detection of genes associated with resistance or susceptibility to gastrointestinal infestations is promising and in line with modern requirements.
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Vieira, Paulo, and Lev G. Nemchinov. "An Expansin-Like Candidate Effector Protein from Pratylenchus penetrans Modulates Immune Responses in Nicotiana benthamiana." Phytopathology® 110, no. 3 (March 2020): 684–93. http://dx.doi.org/10.1094/phyto-09-19-0336-r.
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The root lesion nematode (RLN) Pratylenchus penetrans is a migratory species that attacks a broad range of crops. After the RLN is initially attracted to host roots by root exudates and compounds, it releases secretions that are critical for successful parasitism. Among those secretions are nematode virulence factors or effectors that facilitate the entry and migration of nematodes through the roots and modulate plant immune defenses. The recognition of the effectors by host resistance proteins leads to effector-triggered immunity and incompatible plant–nematode interactions. Although many candidate effectors of the RLN and other plant-parasitic nematodes have been identified, the detailed mechanisms of their functions and particularly, their host targets remain largely unexplored. In this study, we sequenced and annotated genes encoding expansin-like proteins, which are major candidate effectors of P. penetrans. One of the genes, Pp-EXPB1, which was the most highly expressed during nematode infection in different plant species, was further functionally characterized via transient expression in the model plant Nicotiana benthamiana and global transcriptome profiling of gene expression changes triggered by this candidate effector in plants. As a result of this investigation, the biological roles of Pp-EXPB1 in nematode parasitism were proposed, the putative cellular targets of the proteins were identified, and the molecular mechanisms of plant responses to the nematode-secreted proteins were outlined.
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Unachukwu, Nnanna N., Abebe Menkir, Adekemi Stanley, Ebenezer O. Farombi, and Melaku Gedil. "Contrasting Response Mechanisms of Maize Lines to Striga hermonthica." Agriculture 10, no. 10 (October 20, 2020): 485. http://dx.doi.org/10.3390/agriculture10100485.
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Strigahermonthica (Del.) Benth is a parasitic weed that devastates cereals in Sub-Saharan Africa. Several control measures have been proposed for the parasite, of these, host plant resistance is considered the most cost-effective for poor farmers. Some tolerant/resistant lines have been developed and these lines display tolerance/resistance mechanisms to the parasite. A series of studies was done to investigate some of the mechanisms through which a resistant (TZISTR1108) and a susceptible (5057) maize line responds to S. hermonthica infestation, as well as the effects of parasitism on these lines. In this study, TZISTR1108 stimulated the germination and attachment of fewer S. hermonthica plants than 5057, both in the laboratory and on the field. In TZISTR1108, the growth of the S. hermonthica plants, that successfully attached, was slowed. When compared to the un-infested plants, the infested resistant plants showed fewer effects of parasitism than the infested susceptible plants. The infested TZISTR1108 plants were more vigorous, taller and resembled their un-infected counterparts. There were substantial reductions in the stomatal conductance and nitrogen content of the 5057 upon infestation. The resistant inbred line showed multiple mechanisms of resistance to S. hermonthica infestation. It thrives better than the susceptible line by reducing the attachment of S. hermonthica and it delays the parasite’s development.
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Alexander, J., A. R. Satoskar, and D. G. Russell. "Leishmania species: models of intracellular parasitism." Journal of Cell Science 112, no. 18 (September 15, 1999): 2993–3002. http://dx.doi.org/10.1242/jcs.112.18.2993.
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Leishmania species are obligate intracellular parasites of cells of the macrophage-dendritic cell lineage. Indeed, the ability to survive and multiply within macrophages is a feature of a surprising number of infectious agents of major importance to public health, including Mycobacterium tuberculosis, Mycobacterium leprae, Listeria monocytogenes, Salmonella typhimurium, Toxoplasma gondii and Trypanosoma cruzi. The relationship between such organisms and their host cells is particularly intriguing because, not only are macrophages capable of potent microbicidal activity, but in their antigen-presenting capacity they can orchestrate the developing immune response. Thus, to initiate a successful infection parasites must gain entry into macrophages, and also withstand or circumvent their killing and degradative functions. However, to sustain a chronic infection, parasites must also subvert macrophage-accessory-cell activities and ablate the development of protective immunity. The leishmanias produce a wide spectrum of disease in mice, and as such they have provided excellent models for studying problems associated with intracellular parasitism. In recent years, largely using these organisms, we have made enormous progress in elucidating the mechanisms by which successful intracellular infection occurs. Furthermore, characterization of immunological pathways that are responsible for resistance or susceptibility to Leishmania has given rise to the Th1/Th2 paradigm of cellular/humoral dominance of the immune response.
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Sayers, G., and T. Sweeney. "Gastrointestinal nematode infection in sheep – a review of the alternatives to anthelmintics in parasite control." Animal Health Research Reviews 6, no. 2 (December 2005): 159–71. http://dx.doi.org/10.1079/ahr2005108.
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AbstractEfforts to curb production losses caused by nematode parasitism in sheep have led to the development of a number of control methods to complement or replace anthelmintics. The need for alternative control measures stems from the emergence of anthelmintic-resistant parasitic nematodes with reports of multi-class resistance to these drugs now emerging. A number of these control methods such as predacious microfungi, protein supplementation, plant extracts in feed and vaccines have demonstrated potential to control infection but require development and examination under natural conditions. Breeding for natural resistance to nematode infection has already shown success in controlling the disease under natural conditions. Selection for resistance is currently based on fecal egg count measurements but identification of genetic indicators of resistance will provide a more efficient method of selection. Current quantitative trait loci for nematode resistance include the MHC genes, interferon gamma gene, IgE gene and microsatellites on chromosome 1, 5 and 6. This paper reviews the current alternatives to anthelmintics to control infection, with an emphasis on breeding for host resistance and identification of genetic indicators of resistance.
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Karvonen, Anssi, and Ole Seehausen. "The Role of Parasitism in Adaptive Radiations—When Might Parasites Promote and When Might They Constrain Ecological Speciation?" International Journal of Ecology 2012 (2012): 1–20. http://dx.doi.org/10.1155/2012/280169.
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Research on speciation and adaptive radiation has flourished during the past decades, yet factors underlying initiation of reproductive isolation often remain unknown. Parasites represent important selective agents and have received renewed attention in speciation research. We review the literature on parasite-mediated divergent selection in context of ecological speciation and present empirical evidence for three nonexclusive mechanisms by which parasites might facilitate speciation: reduced viability or fecundity of immigrants and hybrids, assortative mating as a pleiotropic by-product of host adaptation, and ecologically-based sexual selection. We emphasise the lack of research on speciation continuums, which is why no study has yet made a convincing case for parasite driven divergent evolution to initiate the emergence of reproductive isolation. We also point interest towards selection imposed by single versus multiple parasite species, conceptually linking this to strength and multifariousness of selection. Moreover, we discuss how parasites, by manipulating behaviour or impairing sensory abilities of hosts, may change the form of selection that underlies speciation. We conclude that future studies should consider host populations at variable stages of the speciation process, and explore recurrent patterns of parasitism and resistance that could pinpoint the role of parasites in imposing the divergent selection that initiates ecological speciation.
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Oliveira, R. S., M. V. Sampaio, S. E. Ferreira, L. C. M. Ribeiro, and J. Tannús-Neto. "Low parasitism byDiaeretiella rapae(Hym.: Braconidae) ofLipaphis pseudobrassicae(Hemip.: Aphididae): pre- or post-ovipositional host resistance?" Biocontrol Science and Technology 23, no. 1 (January 2013): 79–91. http://dx.doi.org/10.1080/09583157.2012.736473.
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Worthen, Wade B., and Thomas M. Hart. "Resistance toArrenurusspp. Parasitism in Odonates: Patterns Across Species and Comparisons Between a Resistant and Susceptible Host." Journal of Insect Science 16, no. 1 (2016): 37. http://dx.doi.org/10.1093/jisesa/iew022.
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Normanton, Heidi, Jos G. M. Houdijk, Neil S. Jessop, Dave P. Knox, and Ilias Kyriazakis. "The effects of changes in nutritional demand on gastrointestinal parasitism in lactating rats." British Journal of Nutrition 97, no. 1 (January 2007): 104–10. http://dx.doi.org/10.1017/s0007114507205781.
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Lactating rats experience a breakdown of immunity to parasites, i.e. they carry larger worm burdens after re-infection compared to their non-lactating counterparts. Feeding high-protein foods to lactating rats results in reduced worm burdens. This could be attributed to changes in gastrointestinal environment or to overcoming effects of nutrient scarcity on host immunity. The latter hypothesis was addressed through a manipulation of nutrient demand by manipulating litter size. Twenty-three rats were immunized prior to mating and re-infected on day 2 of lactation with 1600 infective Nippostrongylus brasiliensis larvae. From parturition onwards, rats received ad libitum a low-protein food (100 g crude protein/kg). Litter sizes were standardised to nine (LS9), six (LS6) or three (LS3) pups, by day 2 of lactation. After a further 10 d, LS9 and LS6 rats carried more worms than LS3 rats. However, feeding treatments did not affect concentrations of mucosal inflammatory cells. Achieved feed intake did not differ consistently between the treatment groups. However, LS9 and LS6 rats lost weight, whilst LS3 rats gained weight during lactation. The results support the view that resistance to N. brasiliensis is sensitive to changes in nutrient demand, and the improved resistance to N. brasiliensis is likely due to effects of overcoming nutrient scarcity on host immunity.
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Hutchings, M. R., K. J. Knowler, R. McAnulty, and J. C. McEwan. "Genetically resistant sheep avoid parasites to a greater extent than do susceptible sheep." Proceedings of the Royal Society B: Biological Sciences 274, no. 1620 (May 15, 2007): 1839–44. http://dx.doi.org/10.1098/rspb.2007.0398.
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Livestock breeding programmes have created resistant (R) and susceptible (S) sheep that differ in their ability to control parasites through their immune function but potentially also their grazing behaviour (i.e. parasite avoidance). Using the Perendale genetic lines, we tested the hypothesis that R-sheep avoid parasites more effectively, reducing their parasite exposure/challenge, compared with S-sheep. However, in grazing systems, parasite-rich areas are also forage rich, suggesting that parasite avoidance behaviours are associated with nutritional penalties. We first created a naturally heterogeneous sward structure of gaps and tussocks and then used focal behavioural observations to quantify the sward selection of R- and S-sheep. Tussock swards were more nitrogen rich (41%), offered increased forage intake rates (32%) and contained 17 times more parasite larvae than gap swards. All the animals avoided grazing the tussock swards. However, the R-sheep grazed the tussock swards to a lesser degree than the S-sheep. We conclude that selection for genetic resistance has resulted in animals that, despite being well armed to fight parasitism through improved immune function, adopt parasite avoidance strategies with associated nutritional disadvantages. This experiment highlights the role of host behaviour in the control of parasitism and suggests that animals can be bred to avoid disease.
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Scasta, John D., and Travis Smith. "Commingled black and white cows (Bos taurus; Angus and Charolais) in high-elevation rangeland are differentially parasitised by Haematobia irritans." Animal Production Science 59, no. 9 (2019): 1727. http://dx.doi.org/10.1071/an18400.
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Globally horn flies (Haematobia irritans) are one of the most economically damaging parasites of beef cattle. These obligate blood-feeding external parasites take blood meals from cattle leading to blood loss, annoyance avoidance behaviours, and reductions in animal performance. Development of chemical resistance by horn flies suggests that novel management strategies are needed. More in-depth understanding of parasitism relative to hide colour and temperature, especially in a changing climate, may enhance animal production. In peak parasitism periods of 2016 and 2017, we measured horn fly loads on commingled black Angus and white Charolais cows in a cold high-elevation rangeland in Wyoming, USA. We tested how breed, year, and interactions explained horn fly parasitism and economic thresholds. In 2016 we also measured ambient and external cow temperatures to further elucidate thermal ecology mechanisms explaining horn fly hide colour preferences. Mean annual horn fly infestations were always four times greater or more on black cows than white cattle both years, but not all cattle reached economic thresholds all years and the breed by year interaction was not significant. Difference in horn fly preference for black cattle over white cattle in our cold high-elevation environment may be explained by greater absolute and relative external surface temperatures of black hided cows. Host colour and thermal preferences of horn flies could be incorporated into integrated pest management strategies that only treat darker hided cattle and producers in cold high-elevation environments conduct real-time monitoring to determine if treatments are even needed on a year-by-year basis.
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Donaldson, J., M. F. J. van Houtert, and A. R. Sykes. "The effect of nutrition on the periparturient parasite status of mature ewes." Animal Science 67, no. 3 (December 1998): 523–33. http://dx.doi.org/10.1017/s1357729800032951.
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AbstractThe rôle of nutrition in the periparturient breakdown of resistance to gastrointestinal parasitism in mature ewes was investigated. Host resistance around this period, as measured by faecal egg concentration and worm burden, was sensitive to protein supply and to a lesser extent energy supply and body condition. Resistance was significantly less in ewes bearing and suckling twin lambs than those with singles. Differences in larval intakes spanning the range likely to be experienced in practice did not appear to be important. In dual infection with Teladorsagia circumcincta and Trichostrongylus colubriformis, the breakdown of resistance occurred almost exclusively with T. circumcincta confirming previous evidence of parasite species specificity in the periparturient breakdown of resistance.
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Kaunisto, Kari M., Pipsa Kaunisto, Jaakko J. Ilvonen, and Jukka Suhonen. "Parasitism, immune response, and egg production of the spearhead bluet (Coenagrion hastulatum) damselfly." Canadian Journal of Zoology 95, no. 5 (May 2017): 367–72. http://dx.doi.org/10.1139/cjz-2016-0146.
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Theoretical models predict that parasites reduce reproductive success of their hosts, but very few empirical studies have given support to this. Using the spearhead bluet (Coenagrion hastulatum (Charpentier, 1825)) damselfly, we tested how immune response, wing length, and the number of both endo- and ecto-parasites affect egg production of host damselflies. The study was conducted with four different populations in southwest Finland. We found a negative association between endoparasitic gregarines and number of host eggs. Furthermore, immune response increased with the number of water mites, but decreased with the number of eggs. Contrary to previous studies with other damselfly species, the number of ectoparasitic water mites did not affect the number of eggs. Moreover, wing length, used as an indicator of individual size, was not associated with egg numbers. The negative effect of gregarine parasites on egg numbers is likely to affect the composition of host populations, i.e., damselflies that show higher resistance to these endoparasites will have more of their offspring represented in subsequent generations. In future, more experimental research on the varying effects of different parasite species on the number of eggs is needed.
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Masanga, Joel, Beatrice Njoki Mwangi, Willy Kibet, Philip Sagero, Mark Wamalwa, Richard Oduor, Mathew Ngugi, et al. "Physiological and ecological warnings that dodders pose an exigent threat to farmlands in Eastern Africa." Plant Physiology 185, no. 4 (January 29, 2021): 1457–67. http://dx.doi.org/10.1093/plphys/kiab034.
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Abstract Invasive holoparasitic plants of the genus Cuscuta (dodder) threaten African ecosystems due to their rapid spread and attack on various host plant species. Most Cuscuta species cannot photosynthesize and hence rely on host plants for nourishment. After attachment through a peg-like organ called a haustorium, the parasites deprive hosts of water and nutrients, which negatively affects host growth and development. Despite their rapid spread in Africa, dodders have attracted limited research attention, although data on their taxonomy, host range, and epidemiology are critical for their management. Here, we combine taxonomy and phylogenetics to reveal the presence of field dodder (Cuscuta campestris) and C. kilimanjari (both either naturalized or endemic to East Africa), in addition to the introduction of the giant dodder (C. reflexa), a south Asian species, in continental Africa. These parasites have a wide host range, parasitizing species across 13 angiosperm orders. We evaluated the possibility of C. reflexa to expand this host range to tea (Camelia sinensis), coffee (Coffea arabica), and mango (Mangifera indica), crops of economic importance to Africa, for which haustorial formation and vascular-bundle connections in all three crops revealed successful parasitism. However, only mango mounted a successful postattachment resistance response. Furthermore, species distribution models predicted high habitat suitability for Cuscuta spp. across major tea- and coffee-growing regions of Eastern Africa, suggesting an imminent risk to these crops. Our findings provide relevant insights into a poorly understood threat to biodiversity and economic wellbeing in Eastern Africa, and provide critical information to guide development of management strategies to avert Cuscuta spp. spread.
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Ronquim, Júlio Cesar, Josué Marques Pacheco, and Carlos Cesar Ronquim. "Occurrence and parasitism of aphids (Hemiptera: Aphididae) on cultivars of irrigated oat (Avena spp.) in São Carlos, Brazil." Brazilian Archives of Biology and Technology 47, no. 2 (June 2004): 163–69. http://dx.doi.org/10.1590/s1516-89132004000200001.
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The interactions between aphids and their Hymenopteran parasitoids on irrigated oats as well as the response of different cultivars of cereals regarding the resistance to these aphids and the influence on the host/parasitoid relationships were studied during two years in São Carlos, Brazil. Rhopalosiphum padi (L.) was the predominant aphid observed throughout the study, while the other species were rarely found. Five species of parasitic Hymenoptera were found: three primary parasitoids, Lysiphlebus testaceipes (Cresson), Aphidius colemani (Viereck) and Diaeretiella rapae (M'Intosh) and two hyperparasitoids, Syrphophagus aphidivorus (Myer) and Alloxysta brassicae (Ashmead). The UPF 86081 cultivar presented significant results regarding lower Rhopalosiphum padi contamination and higher aphid parasitism rates than those observed on some other cultivars. No significant effect on the percentage variation of parasitoid emergence on the mummified aphids was observed throughout this study.
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Roberts, M. G., and J. A. P. Heesterbeek. "The dynamics of nematode infections of farmed ruminants." Parasitology 110, no. 4 (May 1995): 493–502. http://dx.doi.org/10.1017/s0031182000064830.
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SUMMARYIn this paper the dynamics and control of nematode parasites of farmed ruminants are discussed via a qualitative analysis of a differential equation model. To achieve this a quantity, ‘the basic reproduction quotient’ (Q0), whose definition coincides with previous definitions of R0 for macroparasites, but extends to models with periodic time-varying transition rates between parasite stages or management interventions, is introduced. This quantity has the usual threshold property: if Q0 is less than one the parasite population cannot maintain itself in the host population, and in the long term becomes extinct; but if Q0 is greater than one the parasite can invade the host population. An alternative quantity, R(E), that is often easier to calculate is also introduced, and shown to have the same threshold property. The use of these two quantities in analysing models for the dynamics of nematodes in complex situations is then demonstrated, with reference to the dynamics of mixed parasite species in one host; the effects of breeding host animals for resistance to parasitism; and the development of parasite strains that are resistant to chemotherapy. Five examples are discussed using parameters for the dynamics of nematode infections in sheep, and some statements on control policies are derived.
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Koprivnikar, Janet, Chris H. Gibson, and Julia C. Redfern. "Infectious personalities: behavioural syndromes and disease risk in larval amphibians." Proceedings of the Royal Society B: Biological Sciences 279, no. 1733 (November 16, 2011): 1544–50. http://dx.doi.org/10.1098/rspb.2011.2156.
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Behavioural consistency or predictability through time and/or different contexts (‘syndromes’ or ‘personality types’) is likely to have substantial influence on animal life histories and fitness. Consequently, there is much interest in the forces driving and maintaining various syndromes. Individual host behaviours have been associated with susceptibility to parasitism, yet the role of pre-existing personality types in acquiring infections has not been investigated experimentally. Using a larval amphibian–trematode parasite model system, we report that tadpoles generally showed consistency in their activity level in response to both novel food and parasite exposure. Not only were individual activity level and exploration in the novel food context correlated with each other and with anti-parasite behaviour, all three were significant predictors of host parasite load. This is the first empirical demonstration that host behaviours in other contexts are related to behaviours mitigating infection risk and, ultimately, host parasite load. We suggest that this system illustrates how reliably high levels of activity and exploratory behaviour in different contexts might maximize both energy acquisition and resistance to trematode parasites. Such benefits could drive selection for the behavioural syndrome seen here owing to the life histories and ecological circumstances typical of wood frog ( Lithobates sylvaticus ) larvae.
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Kamath, Pauline L., Wendy C. Turner, Martina Küsters, and Wayne M. Getz. "Parasite-mediated selection drives an immunogenetic trade-off in plains zebras ( Equus quagga )." Proceedings of the Royal Society B: Biological Sciences 281, no. 1783 (May 22, 2014): 20140077. http://dx.doi.org/10.1098/rspb.2014.0077.
Full textAbstract:
Pathogen evasion of the host immune system is a key force driving extreme polymorphism in genes of the major histocompatibility complex (MHC). Although this gene family is well characterized in structure and function, there is still much debate surrounding the mechanisms by which MHC diversity is selectively maintained. Many studies have investigated relationships between MHC variation and specific pathogens, and have found mixed support for and against the hypotheses of heterozygote advantage, frequency-dependent or fluctuating selection. Few, however, have focused on the selective effects of multiple parasite types on host immunogenetic patterns. Here, we examined relationships between variation in the equine MHC gene, ELA -DRA , and both gastrointestinal (GI) and ectoparasitism in plains zebras ( Equus quagga ). Specific alleles present at opposing population frequencies had antagonistic effects, with rare alleles associated with increased GI parasitism and common alleles with increased tick burdens. These results support a frequency-dependent mechanism, but are also consistent with fluctuating selection. Maladaptive GI parasite ‘susceptibility alleles’ were reduced in frequency, suggesting that these parasites may play a greater selective role at this locus. Heterozygote advantage, in terms of allele mutational divergence, also predicted decreased GI parasite burden in genotypes with a common allele. We conclude that an immunogenetic trade-off affects resistance/susceptibility to parasites in this system. Because GI and ectoparasites do not directly interact within hosts, our results uniquely show that antagonistic parasite interactions can be indirectly modulated through the host immune system. This study highlights the importance of investigating the role of multiple parasites in shaping patterns of host immunogenetic variation.
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Dietemann, Vincent, Jochen Pflugfelder, Stephan Härtel, Peter Neumann, and Robin M. Crewe. "Social parasitism by honeybee workers (Apis mellifera capensis Esch.): evidence for pheromonal resistance to host queen’s signals." Behavioral Ecology and Sociobiology 60, no. 6 (June 21, 2006): 785–93. http://dx.doi.org/10.1007/s00265-006-0222-0.
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Heath, Michèle C. "Signal exchange between higher plants and rust fungi." Canadian Journal of Botany 73, S1 (December 31, 1995): 616–23. http://dx.doi.org/10.1139/b95-303.
Full textAbstract:
The rust fungi appear to have evolved a sophisticated complex of molecular interactions with their host plants that govern both plant resistance and susceptibility. It is suggested that many of these interactions relate to the maintenance and effective exploitation of biotrophy, and that host specificity and the obligacy of parasitism are a consequence of the resulting interactive molecular control of plant and fungal activities. For the dikaryon, plant signals are required for locating stomata and the formation of infection structures, haustorial mother cells, and haustoria. Host susceptibility to both the monokaryon and the dikaryon appears to involve the suppression of defensive secretory processes, the induction of cellular alterations in invaded cells, and, for the dikaryon at least, changes in nutrient translocation. Parasite-specific resistance involves cultivar-specific fungal signals (elicitors) of defense responses such as cell death and callose deposition. The nature of, and evidence for, the signals involved in these interactions are reviewed. Key words: biotrophy, elicitors, rust fungi, signal exchange.
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SACCAREAU, M., C. R. MORENO, I. KYRIAZAKIS, R. FAIVRE, and S. C. BISHOP. "Modelling gastrointestinal parasitism infection in a sheep flock over two reproductive seasons:in silicoexploration and sensitivity analysis." Parasitology 143, no. 12 (June 30, 2016): 1509–31. http://dx.doi.org/10.1017/s0031182016000871.
Full textAbstract:
SUMMARYIn reproducing ewes, a periparturient breakdown of immunity is often observed to result in increased fecal egg excretion, making them the main source of infection for their immunologically naive lambs. In this study, we expanded a simulation model previously developed for growing lambs to explore the impact of the genotype (performance and resistance traits) and host nutrition on the performance and parasitism of both growing lambs and reproducing ewes naturally infected withTeladorsagia circumcincta. Our model accounted for nutrient-demanding phases, such as gestation and lactation, and included a supplementary module to manage the age structure of the ewe flock. The model was validated by comparison with published data. Because model parameters were unknown or poorly estimated, detailed sensitivity analysis of the model was performed for the sheep mortality and the level of infection, following a preliminary screening step. The parameters with the greatest effect on parasite-related outputs were those driving animal growth and milk yield. Our model enables different parasite-control strategies (host nutrition, breeding for resistance and anthelmintic treatments) to be assessed on the long term in a sheep flock. To optimizein silicoexploration, the parameters highlighted by the sensitivity analysis should be refined with real data.