Dissertationen zum Thema „Culicoides biting midges“

The mechanisms controlling the transmission of bluetongue virus (DTV) by vector Culicoides species were studied using immunohistochemistry, virus titration assays, in vitro transmission tests, viral binding protein analyses and transmission electron microscopy. After infection with BTV by intrathoracic (IT) inoculation, 100% of C. variipennis individuals from a susceptible colony developed a fully disseminated infection and transmitted the virus through their saliva. However only 35.4% of midges were . persistently infected after ingestion of an infectious blood meal, while only 12.1 % of persistently infected midges transmitted the virus through their saliva. The titres of BTV were about 10,·oTCIDsJmidge [Standard error of means (SEM) of log-transformed data=0.15, n=1400] in IT inoculated midges and varied from 0.32 to lQs.oTCIDsJmidge in orally infected individuals. Only those midges containing ~1 03.oTCIDso of BTV could transmit the virus through their saliva. The following patterns were observed in orally (persistently) infected individuals: 1) virus was restricted to the anterior and posterior midgut, and the foregut-midgut junction; 2) virus replicated in the gut cells, disseminated into the haemocoel but could only be detected in a few sporadic fat body cells beyond the gut; 3) virus escaped from the gut cells into the haemocoel and replicated in some secondary organs/tissues but at low levels; 4) a fully disseminated infection was observed and virus replicated in the haemocoel and secondary organs/tissues, including the salivary glands, at high levels. The infection of the gut can be divided into two main types: 1) virus replication in gut cells ranging from very low to higher levels but with virus spread throughout the cytoplasm of the infected cells; 2) virus positive reaction restricted to endosome-like structures in the cytoplasm of some gut cells. BTV was detected in the anterior and posterior midgut, foregut-midgut junction, fat body, ganglia, salivary glands and ommatidia of the compound eyes of some infected midges. No virus was ever found in the hindgut cells, muscles, Malpighian tubes and oocytes/nurse cells of the ovaries. BTV infection of the salivary glands of C. l'ariipcnnis was shown to follow a typical pattern. Virus entered the acinar cells from the haemococl passing through the basement membrane, then localised and replicated in virus inclusion bodies (VIBs) in the cytoplasm of acinar cells. Mature progeny virus particles were released into acini, then transported through intermediate ducts and accumulated in crystalline arrays in the lumen of the major secretory ducts. No virus was released back into the haemocoel through the basement membrane; nor was virus released back into acinar cells from the acini. Nervous tissue of C. l'ariipennis is one of the most susceptible tissues to BTV. Ultrastructural observation showed characteristics ofBTV replication, including formation of VIBs, large amounts of progeny virus particles and tubules, in infected thoracic ganglia. A 60-kD viral protein adhered to both BHK-21 (mammalian) cells and a Culicoides cell line, KC cells. A 44-kD BTV viral protein, co-migrating with non structural protein NS2, adsorbed to BHK-21 cells but not to KC cells, while a 39.6 kD viral protein, co-migrating with major inner capsid protein VP7, adhered only to KC cells but not to BHK-21 cells.

Abstract Culicoides biting midges (Diptera: Ceratopogonidae) are responsible for the transmission of a large number of pathogens to livestock and wild animals. In this study the presence of the genus, using light traps based at four different sites within the National Zoological Gardens of South Africa, was investigated during 2002-2004. In total, 37species were recorded, including large numbers of Culicoides irnicola Kieffer, 1913, which is responsible for the transmission of economically important arboviruses in South Africa, Europe, Middle and Far East. These results are discussed with reference to the wider Culicoides fauna in the Onderstepoort area of South Africa, their vector competence as well as biosecurity at the National Zoological Gardens.

Culicoides biting midges (Diptera: Ceratopogonidae), specifically Culicoides (Avaritia) imicola Kieffer and Culicoides (Avaritia) bolitinos Meiswinkel have been implicated as vectors of African horse sickness virus (AHSV) and equine encephalosis virus (EEV) in southern Africa. Intercontinental trade is a potential mechanism whereby midge-borne viruses, such as AHSV, may be introduced into immunologically naive horse populations. Horses in containerised air transport systems (jet stalls) may be at risk of exposure to Culicoides midges during international export from South Africa. The World Organization for Animal Health (OIE) has recently recommended that during export from, and transit through, African horse sickness (AHS) endemic countries or zones, measures of a physical and chemical nature are applied to protect horses from Culicoides midge attack. To contribute to information on effective measures of protection and to generate data on the effect of these on welfare of horses in jet stalls, the efficacy and safety of alphacypermethrin-treated high density polyethylene (HDPE) mesh applied to jet stalls as a method for protection of horses against Culicoides midges was investigated at the Faculty of Veterinary Science, Onderstepoort. Firstly, the repellent and insecticidal efficacy of alphacypermethrin-treated HDPE mesh against Culicoides midges was determined using Onderstepoort 220V downdraught black light traps and a contact bioassay. Three traps were operated overnight in four replicates of a 3 x 3 randomised Latin square design near horses. Both an untreated and alphacypermethrin-treated HDPE mesh significantly (P < 0.05) reduced the numbers of Culicoides midges, predominantly C. imicola, collected in the light traps by 4.2 and 7.2 times, respectively. A repellent effect of the alphacypermethrin-treated mesh was not confirmed because the number of midges collected in the light traps with untreated and alphacypermethrin-treated HDPE mesh were not significantly different (P = 0.656). Bioassay of the insecticidal contact efficacy indicated median C. imicola mortality of 100% from 30 and 10 min following exposure to the alphacypermethrin-treated HDPE mesh for 1 or 3 min, respectively. In the bioassay, mortality was significantly higher (P = 0.016) at 5 min post exposure in the midges exposed to the alphacypermethrin-treated mesh for 3 min (74.8%) compared to the 1 min exposure group (59.5%). Secondly, the efficacy of alphacypermethrin-treated HDPE mesh applied to jet stalls against Culicoides midges was determined by mechanical aspiration of midges from horses and using light traps in four blocks of a 3 x 2 randomised design. The alphacypermethrin-treated HDPE mesh applied to the stall significantly (P = 0.008) reduced the number of Culicoides midges, predominantly C. imicola, mechanically aspirated from horses housed in the stall. The mesh reduced the Culicoides midge attack rate in the treated stall compared to the untreated stall and a sentinel horse by 6 times and 14 times, respectively. The number of Culicoides midges and C. imicola collected in light traps from the untreated and alphacypermethrin HDPE mesh-treated stalls did not differ significantly (P = 0.82). Finally, the effect of alphacypermethrin insecticide-treated HDPE mesh on ventilation and welfare of horses housed in jet stalls was determined under temperate, climatic conditions. Jet stall microclimate, clinical variables and faecal glucocorticoid metabolites (FGM) of 12 horses were monitored during overnight housing in either a treated or untreated jet stall in two blocks of a 2 x 3 randomized crossover design. Temperature difference between the treated stall and outside differed significantly from the difference between the untreated
Thesis (PhD)--University of Pretoria, 2015.
tm2016
Companion Animal Clinical Studies
PhD

Culicoides molestus (Skuse) is the major species of biting midge that plagues human comfort in the estuarine Gold Coast region of southeast Queensland. Local authorities have initiated a search for an effective, non-chemical means of control, that would minimize human-midge interaction. The effectiveness of a program to control an organism, such as a biting midge, is dependent upon knowledge of the biology of the particular organism of interest. This project revolved examines the lifecycle of C. molestus in detail. It addresses questions regarding the location, seasonal distribution, and dispersal of its juvenile stages in the sand of infested beaches, and their response to chemical treatment, the monthly and annual cycles of the adult midge, and the possibilities of achieving laboratory oviposition, as a first step to laboratory colonisation. The distribution of eggs, larvae and pupae of C. molestus was found to be mostly concentrated around, but below, mean tide level. They also occurred well below the mean tide level. Eggs and larvae have been recovered from as deep as 10 cm in the sand. A seasonal study of the juveniles of this species indicated that they were more strongly influenced by tides than seasons. After a routine pest-control larviciding treatment, a beach recolonisation study revealed that beaches become suitable for oviposition approximately two months after treatment. Large larvae invaded the sprayed areas within days of treatment, which suggests the existence of a refuge outside of the reach of the insecticide. Larvae found in clean (egg- and larva-free), isolated sand containers, placed on the study beach, indicated that larvae could swim in or on the water as a way of moving around the beach. Extended bite-rate studies highlighted the existence of four peaks in adult midge biting activity during the course of a year, around the mid seasons. The strongest peaks of activity were found to be in autumn and spring, but the data suggest that the species undergoes four generations in a year. Through a series of trial-and-error experiments, oviposition under laboratory conditions was achieved. Although the time from blood-feeding to egg maturation is not yet well determined, it occurs within an eight day mean survival period. Blood quality appears critical for adult blood-fed midge survival. Midges fed on the blood of a volunteer who was frequently exposed to midge bites do not live long enough to mature its eggs. The partial ovarial development of one unfed adult female, reared in the laboratory, indicates that C. molestus is facultatively anautogenous.

Culicoides molestus (Skuse) is the major species of biting midge that plagues human comfort in the estuarine Gold Coast region of southeast Queensland. Local authorities have initiated a search for an effective, non-chemical means of control, that would minimize human-midge interaction. The effectiveness of a program to control an organism, such as a biting midge, is dependent upon knowledge of the biology of the particular organism of interest. This project revolved examines the lifecycle of C. molestus in detail. It addresses questions regarding the location, seasonal distribution, and dispersal of its juvenile stages in the sand of infested beaches, and their response to chemical treatment, the monthly and annual cycles of the adult midge, and the possibilities of achieving laboratory oviposition, as a first step to laboratory colonisation. The distribution of eggs, larvae and pupae of C. molestus was found to be mostly concentrated around, but below, mean tide level. They also occurred well below the mean tide level. Eggs and larvae have been recovered from as deep as 10 cm in the sand. A seasonal study of the juveniles of this species indicated that they were more strongly influenced by tides than seasons. After a routine pest-control larviciding treatment, a beach recolonisation study revealed that beaches become suitable for oviposition approximately two months after treatment. Large larvae invaded the sprayed areas within days of treatment, which suggests the existence of a refuge outside of the reach of the insecticide. Larvae found in clean (egg- and larva-free), isolated sand containers, placed on the study beach, indicated that larvae could swim in or on the water as a way of moving around the beach. Extended bite-rate studies highlighted the existence of four peaks in adult midge biting activity during the course of a year, around the mid seasons. The strongest peaks of activity were found to be in autumn and spring, but the data suggest that the species undergoes four generations in a year. Through a series of trial-and-error experiments, oviposition under laboratory conditions was achieved. Although the time from blood-feeding to egg maturation is not yet well determined, it occurs within an eight day mean survival period. Blood quality appears critical for adult blood-fed midge survival. Midges fed on the blood of a volunteer who was frequently exposed to midge bites do not live long enough to mature its eggs. The partial ovarial development of one unfed adult female, reared in the laboratory, indicates that C. molestus is facultatively anautogenous.
Thesis (Masters)
Master of Philosophy (MPhil)
School of Environmental and Applied Science
Full Text

Abstract :Bluetongue (BT) is a vector-borne infectious disease primarily transmitted to even- toed ungulates by the bite of several Culicoides species. The global distribution of BT can be attributed to the ubiquity of its vectors and its rapid spread, likely to the enhancement of human activities (intensification of animal production, trans- port, changing habitat). During the last decades, BT established in Southern Europe and more recently emerged in Northern Europe, causing the death of millions of domestic ruminants. On the same time, a Belgian research project has been set up to develop remote-sensing tools to study the EPidemiology and Space-TIme dynamicS of infectious diseases (EPISTIS). In that general framework, this thesis aimed to study the space-time distribution of the main Culicoides vectors occurring in Italy and Belgium, at two different scales. Firstly, we aimed to clarify the role of several eco-climatic factors on the regional-scale distribution of C. imicola in time, based on weekly samplings achieved throughout Italy from 2001 to 2006 and to develop an easy-to-use and reproducible tool, which could be widely validated on the basis of former vector sampling and freely accessible remote-sensing data. Secondly, we aimed to investigate how Culicoides species were distributed in the fine-scale habitat encountered throughout the agro-ecological landscapes of Belgium, while recent studies have suggested that the landscapes configuration could explain the spatial distribution of BT. In the first part, we showed that an autoregressive model where the observed monthly growth rate is predicted by monthly temperature, allowed predicting >70% of the seasonal variability in C. imicola trap catches. The model predicted the seasonality, the altitudinal gradient, and the low populations’ activity taking place during the winter. Incorporating eco-climatic indices such as the Normalized Difference Vegetation Index into the model did not enhance its predictive power. In the second part, we quantified how Culicoides populations are spatially structured in the neighbourhood of farms, and demonstrated the unexpectedly high level of population found in forest. We also showed how four classes of land use could influence the relative abundances of Culicoides species in the agro-ecological landscapes of Belgium. Although in summer, BT vectors were abundant in each of the four classes investigated, their relative abundances varied strongly as a function of sex, species and environmental conditions, and we quantified these variations. Finally, we also presented a new method to quantify the interference between Onderstepoort light traps, and used it to measure their range of attraction for several of the most common BT vectors species in Northern Europe. The model developed on C. imicola in Italy provided enthusiastic perspectives regarding the regional-scale analyses of its distribution in time, although further improvements are nevertheless required in order to assess the broad scale ecology of BT vectors throughout Europe. Mapping the abundances of C. imicola in Sardinia high- lighted an important lack of reliability attributable to the many land use classes that are currently not sampled in the vector surveillance achieved across Europe. Together with the novelties presented in the second part and the recent findings establishing that BT could circulate among wild hosts in both epidemiological systems (i.e. in Southern and Northern Europe), we call for increasing epidemiological and entomo- logical studies at the interface between farms and the surrounding natural habitats. Last, depicting in time the landscape-scale findings for Northern Europe highlighted how dramatic could be the role played by intensive farming practices to maintain BT within the agro-ecological landscapes studied and to facilitate its circulation between them. Quantifying the amplitude of the risk of disease transmission linked to these practices would require a further complex modeling approach accounting simultaneously for the diel activity of hosts, mainly resulting from the farming activities, the diel activities of different vector species and the landscapes configuration found in contrasted agro-ecological systems.

Résumé :La fièvre catarrhale ovine (FCO), encore appelée maladie de la langue bleue, est une maladie infectieuse des ruminants transmise par la piqûre d’un vecteur de type moucheron appartenant au genre Culicoides (Diptera :Ceratopogonidae). L’ubiquité de ses vecteurs peut expliquer son succès d’installation à l’échelle globale. Par ailleurs, sa rapide expansion a été grandement facilitée par l’importante activité anthropique (élevage, transport, modification de l’habitat) et peut-être même par les changements climatiques globaux. La FCO a été récemment qualifiée de maladie infectieuse émergente en Europe du fait de (i) son récent établissement dans la région, bien au delà de son aire de répartition traditionnelle, (ii) de sa forte capacité de dispersion affectant chaque jour un nombre plus important d’hôtes et enfin (iii) de sa forte virulence. Après avoir détaillé les caractéristiques majeures des deux principaux foyers de FCO rencontrés en Europe depuis 1998, la présente thèse s’est plus particulièrement intéressée à l’étude de la distribution spatio-temporelle de ses principaux vecteurs dans le sud (partie 1) puis dans le nord (partie 2) de l’Europe, à différentes échelles. Dans la première partie, un modèle discret, spatialement et temporellement explicite, a été développé afin de mesurer l’influence de différents facteurs éco-climatiques sur la distribution de Culicoides imicola, principal vecteur de la FCO dans le Bassin Méditerranéen. Les profils mensuels de distribution rencontrés en Sardaigne durant 6 années consécutives ont ainsi pu être reconstitués, principalement sur base de la température. Une cartographie de l’abondance de C. imicola sur le territoire a permis de mettre à jour le manque d’information sur sa distribution en dehors des exploitations agricoles. Dans la deuxième partie du travail, nous nous sommes penchés sur la distribution spatiale des Culicoides tels qu’on peut les rencontrer au sein de différents paysages agro-écologiques de Belgique. Nous avons ainsi pu décrire la structure adoptée par les populations de Culicoides au voisinage des fermes ainsi que quantifier l’importante population présente dans les forêts avoisinantes. Nous avons par ailleurs montré l’influence de différentes catégories d’utilisation du sol sur l’abondance et la composition en espèces. Enfin, nous avons présenté une méthode permettant de quantifier l’interférence entre des pièges lumineux utilisés dans un même paysage pour échantillonner les populations, et l’avons utilisé afin de mesurer leur rayon d’attractivité sur les espèces vectrices les plus communément rencontrées dans le nord de l’Europe. En guise de conclusion générale et conjointement aux récentes découvertes de cas de FCO au sein de la faune sauvage européenne, nous appelons à réaliser un plus grand nombre d’études éco-épidémiologiques à l’interface entre exploitations agricoles et zones (semi-) naturelles avoisinantes. En outres, les résultats présentés dans la seconde partie ont été mis en relation avec le mode de fonctionnement journalier de nos exploitations agricoles. Nous avons ainsi pu déduire le rôle dramatique joué par les pratiques agricoles intensives dans le maintien du virus de la FCO au sein de nos paysages agro-écologiques, ainsi que dans sa circulation d’un paysage à l’autre. Un cadre de modélisation complexe permettant une analyse simultanée de l’activité nycthémérale des hôtes de la FCO et de ses vecteurs Culicoides en fonction de la configuration des paysages agro-écologiques est néanmoins requis afin de quantifier l’amplitude du risque de transmission de la FCO lié aux pratiques agricoles intensives.
Doctorat en Sciences agronomiques et ingénierie biologique
info:eu-repo/semantics/nonPublished

This study investigates aspects of the biology of C. impunctatus with a view to producing an optimised laboratory culture of this species. Artificial membrane feeding of C. impunctatus is shown to be enhanced by the addition of blood vestiges to the outer surface of the feeding apparatus. The effects of holding temperature, environment and conspecific density upon oogenesis in blood fed female midges are assessed through mortality, digestion of the blood meal and development of the eggbatch over time. Oviposition in C. impunctatus is investigated through choice and nochoice bioassays which show Sphagnum spp. Mosses to be highly effective in this regard. Juncus articulatuslacutiflorus infusions also significantly increase the number of eggs laid by females in comparison to oviposition substrates used in colonisation of other midge species. Preliminary studies are also carried out to provide a suitable larval medium for colonisation purposes. The possibility of future colonisation is discussed with reference both to those experiments carried out, and to those areas not yet addressed in the C. impunctatus lifecycle. Dispersal of C. impunctatus is also examined, both on a local scale and in terms of gene flow between UK populations. Capture, mark, recapture studies showed the marked population of C. impunctatus remained relatively close to the release site in the habitat used for the study. The effect of prevailing winds, however, was found to be highly important in terms of passive directional movements of individuals. Daily survival rates of parous females were calculated as very low in relation to other species of midge making this species an unlikely candidate for pathogen transfer in Scotland. Polymorphism in the molecular markers used to examine gene flow in C. impunctatus across the UK was minimal and precluded phylogenetic analysis. This result is interpreted in terms of both possible long-distance dispersal and the effects of rapid post-glacial popUlation expansion into the UK.

Doctor of Philosophy
Division of Biology
Kristin Michel
The biting midge, Culicoides sonorensis, vectors orbiviruses of economic importance, such as epizootic hemorrhagic disease virus (EHDV). Due to the limitations in available molecular tools, critical Culicoides-orbivirus interactions underlying vector competence remain unclear. To provide a foundation for the study of midge-EHDV interactions, RNA interference (RNAi) was developed as a reverse genetic tool, and EHDV-2 infection dynamics were determined within C. sonorensis. To develop RNAi, exogenous double-stranded RNA (dsRNA) was injected into C. sonorensis adults specific to the C. sonorensis inhibitor of apoptosis protein 1 (CsIAP1) ortholog (dsCsIAP1). A significant decrease in CsIAP1 transcripts was observed in whole midges, with highest reduction in the midgut. In addition, dsCsIAP1-injected midges had increased mortality, a loss of midgut tissue integrity, and increased caspase activity. The longevity and midgut phenotypes were partially reversed by the co-injection of dsRNA specific to the C. sonorensis initiator caspase Dronc ortholog and CsIAP1. These results demonstrated that RNAi can be achieved in the midge midgut through injection of target dsRNAs into the hemolymph. Furthermore, the time course of EHDV-2 infection within C. sonorensis was characterized. EHDV-2 infection was observed in the midgut and secondary tissues, including the salivary glands, by 5 days post-feeding (dpf). These data are consistent with dissemination of EHDV-2 to secondary susceptible tissues throughout the midge via the hemolymph and indicate that virus transmission by C. sonorensis may occur as early as 5 dpf. This work provides a foundation for the future study of Culicoides-orbivirus interactions, including the antiviral role of RNAi at the midgut barrier.

Behavioural studies using a Y-tube olfactometer confirmed the differential attractiveness of human volunteers to the yellow fever mosquito, Aedes aegypti.  Volatile chemicals were collected from all volunteers by air entrainment.  The extracts were analysed behaviourally with Ae. aegypti and the Scottish biting midge, Culicoides impunctatus in a Y-tube olfactometer.  The behavioural responses were similar to those previously observed to the hands of the volunteers.  Electrophysiological responses of Ae. aegypti and C. impunctatus, to volatiles from the air entrainment extracts, were recorded using coupled gas chromatography-electroantennography (GC-EAG).  EAG-active compounds were tentatively identified using GC-mass spectrometry (GC-MS) and were confirmed by peak enhancement.  A quantitative and qualitative analysis of compounds within the extracts revealed significant differences in chemical profiles.  The mean absolute amounts of benzaldehyde, 6-methyl­-5-hepten-2-one, octanal, nonanal, naphthalene, decanal and geranylacetone were significantly greater in the unattractive group than the attractive group.  Similarly, the mean relative amounts of 6-­methyl-5-hepten-2-one, octanal and decanal in the unattractive group were significantly greater than the attractive group.  Five compounds caused significant reductions in behavioural responses of Ae. aegypti when presented alongside a human hand in the Y-tube olfactometer, thus accounting for the lack of attraction towards the volunteers’ hands in the unattractive group.  The identification of such behaviourally active compounds could lead to improved control technologies, whereby such compounds could potentially be incorporated into new, safe and natural repellents against biting insects.

碩士
國立中興大學
昆蟲學系所
98
Culiciodes spp. are the major vectors of bovine ephemeral fever. These investigations showed that the population density of Culicoides spp. was low in Winter, and increased in Spring, then the highest population density were found in Summer and Autumn. The results of Culicoides circadian rhythm showed that both Culicoides oxytoma and Culicoides nipponensis occurred in dairy. These investigations showed Culicoides spp. active in all day, and the low population of Culicoides spp. was active at noon, and then the highest population was active at dusk and dawn. By using the correlation analysis, the relative humidity were most correlative with activity of Culicoides population, whereae the temperature was not correlative with it. The numbers of outdoor and indoor were significantly different. However Culicoides were occurred mostly indoor. The numbers of females and males were significantly different. Female was more easily caught by light trap than male. The numbers of bloodfed and non-bloodfed midges were significantly different. The non-bloodfed midges were more than the bloodfed ones. In view of Culicoides control, the light trap could catch non-bloodfed female and do not turn off the trap could get most effective in control. The survey of Culicoides spp. in different animal farms showed that Culicoides oxytoma were the major species in many animal farms, while Culicoides arakawae was the major one in poultry farms. We found that find Culicides spp. was mainly active inside dairy, and the in numbers declined greatly at a distance 30m away from farm houses. Six different insecticides of pyrethroids exhibited that cyphenothrin was the most effective pyrethoid against female adults of Culicoides among three pyrethroids tested, and that cyphenothrin in combination with tetramethrin was more effective than without combination. Pyrethroide are lower toxic in mammal, so it can use in emergency control.