Letteratura scientifica selezionata sul tema "Intra-species transmission"

Astroviruses are non-enveloped, single-stranded RNA viruses that infect mammalian and avian species. In humans, astrovirus infections are one of the most common causes of gastroenteritis in children. Infection has also been linked to serious neurological complications, especially in immunocompromised individuals. More extensive disease has also been characterized in non-human mammalian and avian species. To date, astroviruses have been detected in over 80 different avian and mammalian hosts. As the number of hosts continues to rise, the need to understand how astroviruses transmit within a given species as well as to new host species becomes increasingly important. Here, we review the current understanding of astrovirus transmission, the factors that influence viral spread, and the potential for cross-species transmission. Additionally, we highlight the current gaps in knowledge and areas of future research that will be key to understanding astrovirus transmission and zoonotic potential.

AbstractFactors such as the particular combination of parasite–mosquito species, their co-evolutionary history and the host's parasite load greatly affect parasite transmission. However, the importance of these factors in the epidemiology of mosquito-borne parasites, such as avian malaria parasites, is largely unknown. Here, we assessed the competence of two mosquito species [Culex pipiens and Aedes (Ochlerotatus) caspius], for the transmission of four avian Plasmodium lineages (Plasmodium relictum SGS1 and GRW11 and Plasmodium cathemerium-related lineages COLL1 and PADOM01) naturally infecting wild house sparrows. We assessed the effects of parasite identity and parasite load on Plasmodium transmission risk through its effects on the transmission rate and mosquito survival. We found that Cx. pipiens was able to transmit the four Plasmodium lineages, while Ae. caspius was unable to transmit any of them. However, Cx. pipiens mosquitoes fed on birds infected by P. relictum showed a lower survival and transmission rate than those fed on birds infected by parasites related to P. cathemerium. Non-significant associations were found with the host–parasite load. Our results confirm the existence of inter- and intra-specific differences in the ability of Plasmodium lineages to develop in mosquito species and their effects on the survival of mosquitoes that result in important differences in the transmission risk of the different avian malaria parasite lineages studied.

Abstract This study develops an integrated innovation for malaria early warning systems (MEWS), based on vulnerability monitoring, seasonal climate variability data, and epidemiologic surveillance. The main aim of the study is to examine the relationship between intra-annual climate variability and malaria transmission in Nigeria. For this study, climatic conditions considered suitable for the development of the malaria parasite and its transmission through the mosquito stage of its life cycle are temperatures within the range from 18°C to 32°C. Below 18°C the parasite development decreases significantly, while above 32°C the survival of the mosquito is compromised. Relative humidity greater than 60% is also considered a requirement for the mosquito to survive long enough for the parasite to develop sufficiently to be transmitted to its human host stage. The research findings show that seasonality of climate greatly influences the seasonality of malaria transmission. Specifically, rainfall plays an important role in the distribution and maintenance of breeding sites for the mosquito vector. Rainfall and surface water is required for the egg laying and larval stages of the mosquito life cycle and monthly rainfall above 80 mm is considered a requirement. Also, it is temperature that regulates the development rate of both the mosquito larvae and the malaria parasite (Plasmodium species) within the mosquito host. Relative humidity and temperature play an important role in the survival and longevity of the mosquito vector. This study is in conformity with the findings of the IPCC (2001) that malaria is caused by four distinct species of the Plasmodium parasite, transmitted by mosquitoes of the genus Anopheles, which are most abundant in tropical/subtropical regions, although they are also found in limited numbers in temperate climates.

Little cherry virus 1 (LChV1, Velarivirus, Closteroviridae) is a widespread pathogen of sweet or sour cherry and other Prunus species, which exhibits high genetic diversity and lacks a putative efficient transmission vector. Thus far, four distinct phylogenetic clusters of LChV1 have been described, including isolates from different Prunus species. The recent application of high throughput sequencing (HTS) technologies in fruit tree virology has facilitated the acquisition of new viral genomes and the study of virus diversity. In the present work, several new LChV1 isolates from different countries were fully sequenced using different HTS approaches. Our results reveal the presence of further genetic diversity within the LChV1 species. Interestingly, mixed infections of the same sweet cherry tree with different LChV1 variants were identified for the first time. Taken together, the high intra-host and intra-species diversities of LChV1 might affect its pathogenicity and have clear implications for its accurate diagnostics.

Influenza A viruses (IAVs) cause acute, highly transmissible infections in a wide range of animal species. Understanding how these viruses are transmitted within and between susceptible host populations is critical to the development of effective control strategies. While viral gene sequences have been used to make inferences about IAV transmission dynamics at the epidemiological scale, their utility in accurately determining patterns of inter-host transmission in the short-term—i.e. who infected whom—has not been strongly established. Herein, we use intra-host sequence data from the viral HA1 (hemagglutinin) gene domain from two transmission studies employing different IAV subtypes in their natural hosts—H3N8 in horses and H1N1 in pigs—to determine how well these data recapitulate the known pattern of inter-host transmission. Although no mutations were fixed over the course of either experimental transmission chain, we show that some minor, transient alleles can provide evidence of host-to-host transmission and, importantly, can be distinguished from those that cannot.

English: Common warthogs (Phacochoerus africanus) and bushpigs (Potamochoerus larvatus), were experimentally infected with classical swine fever virus (CSFv) following the diagnosis of classical swine fever (CSF) subtype 2.1 in 2005 in domestic pigs in South Africa. At that time, no data regarding their susceptibility or the potential lesions in these wild suids were available. Seven sub-adult warthogs and six bushpigs were captured, taken to the high containment facilities of the Transboundary Animal Diseases Programme of the Agriculture Research Council (ARC) - Onderstepoort Veterinary Research Institute, and infected intranasally with the South African isolate. In each experiment, two in-contact control animals of the same species verified intraspecies transmission, while two domestic pigs were used to demonstrate virus virulence and viability. Surviving animals were euthanized 44 days post infection. Formalin-fixed tissue samples collected from all experimental animals were evaluated for histological lesions. The warthogs, which remained clinically normal throughout the study, developed histological lesions that were inconsistently present and sometimes subtle. Three warthogs, including one in-contact control, developed distinct perivascular lymphoplasmacytic cuffing in their brains. Subtle lesions included scant lymphoplasmacytic infiltration of various organs, occasionally accompanied by perivascular cuffing. In contrast, the bushpigs developed overt clinical signs similar to CSF in domestic pigs. Four animals out of six, including two in-contact controls, died or were euthanized during the trial. On post mortem examination, intestinal necrosis and ulceration, purulent rhinitis and pneumonia were present. Acutely affected animals developed lymphoid necrosis and depletion whilst surviving individuals showed perivascular lymphoplasmacytic cuffing in multiple organs. Immunohistochemical demonstration of CSFv antigen using a commercially available mouse monoclonal antibody, WH303, revealed intense, widespread labelling in most tissues of all the warthogs and bushpigs as well as the four domestic pigs used as controls during the trial. A wide range of cell types and tissues reacted with the antibody. These included: mononuclear cells (monocyte-macrophages, lymphocytes and plasma cells), follicular reticular cells, epithelial cells, vascular endothelial cells, mesothelial cells, smooth muscle cells and fibroblasts. Tissues that were labelled included tonsil, lymph nodes, spleen, third eyelid, adrenal gland, urinary bladder, skin, liver, kidney, lung, certain cells within central nervous tissue like the choroid plexus, various parts of the gastro-intestinal tract as well as glandular tissue like the pancreas and salivary gland. The tonsils were the most consistently labelled tissue, while no labelling was noted in myocytes of skeletal or cardiac muscle. From the present work, it was concluded that these wild Suidae are susceptible to CSFv and intra-species transmission under experimental conditions can occur.
Afrikaans: Wilde Afrika varke, nl. vlakvarke (Phacocoerus africanus) en bosvarke (Potamochoerus larvatus) was eksperimenteel infekteer met europese varkpes virus nadat die siekte in kommersiële mak varke diagnoseer is in 2005 (dit was tipeer as subtipe 2.1). Geen inligiting oor die vatbaarheid of potensiële letsels weens europese varkpes infeksie in hierdie wilde varke was beskikbaar nie. Sewe wilde onvolwasse vlakvarke en ses bosvarke is gevang, na die isolasie eenheid van die Onderstepoort Veterinêre Instituut se oor-grens siekte afdeling geneem en intranasal geïnfekteer met die Suid-Afrikaanse isolaat van 2005. Twee in-kontak kontrole diere van dieselfde spesie is gebruik in elke eksperiment om intra-spesie oordraging vas te stel en twee mak varke om virus lewensvatbaarheid en virulensie te demonstreer. Oorlewende diere is uitgesit na 44 dae. Formalien gefikseerde weefsel monsters is versamel van hulle, sowel as van diere wat uitgesit is tydens die eksperiment. Die vlakvarke was klinies normal regdeur die eksperiment, maar het wel histologiese letsels ontwikkel wat subtiel was en ook nie altyd teenwoordig in alle gevalle nie. Drie vlakvarke, waarvan een ‘n in-kontak dier was, het prominente limfo-plasmasitiese perivaskulêre flensing in hul breine ontwikkel. Subtiele letsels het klein hoeveelhede limfoplasmasitiese infiltrasies in verskeie organe en somtyds perivaskulêre flensing ingesluit. In teenstelling, het die bosvarke uitgesproke kliniese tekens soortgelyk aan Europese varkpes in mak varke, ontwikkel. Vier uit die ses diere, insluitend twee in-kontak diere is dood of uitgesit tydens die eksperiment. Met nadoodse ondersoek is daar intestinale nekrose en ulserasie, purulente rinitis en pneumonie gevind. Diere wat dood is, het limfoïede nekrose en limfoïede uitputting getoon, terwyl die oorlewende bosvarke perivaskulêre flensing met limfo-plasma selle in verskeie organe ontwikkel het. Immunohistochemiese demonstrasie van Europese varkpes virus antigen deur gebruik van ‘n kommersieël beskikbare muis monoklonale teenligaam, WH303, het duidelike wydverspreide kleuring in meeste weefsel van die die vlakvarke, bosvarke en mak varke getoon. ‘n Wye reeks van weefsel en sel tipes het met die teenliggam reageer naamlik: mononukliêre selle (monosietmakrofage en limfo-plasma selle), follikulêre retikulêre selle, epiteel, vaskulêre endoteel, mesoteel, gladde spier selle en fibroblaste. Weefsel wat gemerk is met die teenliggaam het ingesluit: mangels, limfknope, milt, derde ooglid, adrenaal klier, urienblaas, vel, lewer, nier, long, sekere selle in die sentrale senuwee stelsel, soos die koroïed pleksus, verskeie dele van die gastro-intestinale stelsel sowel as klier weefsel soos die pankreas en speekselklier. Die mangels was die mees konsekwent gemerkte weefsel, terwyl geen kleuring gevind is in miosiete van skelet of hartspier nie. Uit hierdie werk kon daar afgelei word dat vlakvarke en bosvarke vatbaar is vir Europese varkpes en dat intra-spesie oordraging plaasvind onder eksperimentele omstandighede.
Dissertation (MMedVet)--University of Pretoria, 2011.
Paraclinical Sciences
Unrestricted

The eco-epidemiology of bovine tuberculosis (Tb) in wild deer (mainly red deer Cervus elaphus) in New Zealand was investigated. Bovine Tb is caused by Mycobacterium bovis. Specific aims were to clarify the likely routes of infection in deer, and to determine the status of deer as hosts of Tb, the likely rates and routes of inter- and intra-species transmission between deer and other wildlife hosts, the role of deer in spreading Tb, and the likely utility of deer as sentinels of Tb presence in wildlife. As the possum (Trichosurus vulpecula) is the main wildlife host of Tb, the research also included some investigation of transmission routes in possums. Patterns of infection were measured in 994 deer killed between 1993 and 2003. Tb prevalence varied between areas (range 8–36%). Few deer had generalised infection, with 21–68% of infected deer having no visible lesions, depending on the area. The retropharyngeal lymph nodes and oropharyngeal tonsils were commonly infected. No dependent fawns less than 0.75 years old were infected, indicating intra-species transmission is rare in wild deer. Where possums were not controlled, the net (cumulative) force of infection in young (1–4 y) deer was 0.10–0.24 per year in males and 0.09–0.12 per year in females, but much lower in older deer (less than 0.05 per year). Possum control reduced the net force of infection quickly, and eventually to zero. However, Tb persisted in possum-controlled areas through immigration of infected deer and, for almost a decade, through the survival of resident deer infected before possum control. Tb was lost from infected deer at an exponential rate of 0.13 per year, mostly as a result of deer recovering from infection rather than dying from it. Wild deer do die of Tb, but there was no discernible effect on age structure. The occurrence of infection in deer was not linked to the local deer or possum density at their kill sites (i.e. in their home range), but the area-wide prevalence of Tb in deer was closely correlated with Tb levels in possums, which were in turn correlated with area-wide measures of possum density. For wild deer in New Zealand, Tb is a persistent but usually inconsequential disease of the lymphatic system. It is acquired mainly by young independent deer, usually orally via the tonsils, and probably as a result of licking infected possums. Many species fed on deer carrion, including possums. Most possums encountering carrion did not feed on it, but a few fed for long periods. Other scavengers such ferrets (Mustela furo), hawks (Circus approximans), and weka (a hen-sized flightless native bird; Gallirallus australis) fed in a way that probably increased the infectivity of carrion to possums. Commercial deer hunting may have facilitated the historical establishment of Tb in possums. Scavenging (including cannibalism) and interactions with dead and dying possums are identified for the first time as potentially important routes for transmission of Tb to possums, and I develop new hypotheses involving peri- and post-mortem transmission in possums that explain many of the epidemiological patterns that are characteristic of the disease in possum. In continuous native forest, deer home range size averaged 250 hectares for six young females, and over twice that for two males. Over 90% of infected deer are likely to die within 2 km (females) or 6 km (males) of where they acquired Tb, but deer could occasionally carry Tb up to 30 km. Deer will be useful as sentinels, but only where other sentinels are rare, because the force of infection for a deer with a single infected possum in its home range is only 0.004 per year, compared to greater than 0.2 per year for deliberately released pigs. Deer are occasionally capable of initiating new cycles of infection in wildlife, but deer control is not essential to eradicate Tb from wildlife.

The scaling down of commercial products has fueled the rapid development of micro- and nano-electromechanical systems (MEMS/NEMS). The enabling technologies of surface micromachining for silicon has made it compatible with industry strategies towards integrated circuits used in actuation and controls of systems. During the silicon processing, microdefects do occur. If properly controlled, they act as gettering sites for metallic species and hence remove unwanted impurities in the active device regions of semiconductor devices. On the other hand, microdefects can be responsible for plastic deformation of silicon wafer. The occurrence of dislocations in the active device regions causes current leakage and even failure of devices. Determination of the optimum point at which bulk microdefects can be considered to have beneficial gettering effect in silicon wafer and the exact mechanisms by which mobile dislocations are generated in the bulk of an initially dislocation free silicon wafer are not well understood. The purpose of this study is to analyze types of dislocation misfits and the corresponding defect size that is responsible for effective gettering due to cavitation impacts. The authors have already studied electrical characteristics of backside damage gettering by cavitation impact [1–3]. Polysilicon has been grown on thin silicon suboxide layer by a gas-source molecular beam epitaxy (MBE). MBE was done by placing the silicon substrate in an ultra-high vacuum chamber and heating it to 800 °C for 10 min and then at 700 °C for 3 hours at a flow rate of 2.5 sccm. The atomic force microscopy (AFM), micro Raman spectroscopy and transmission electron microscopy (TEM) were used to characterize the Czochralski silicon (CZ–Si) in the plane (100) and poly-Si/SiO2 in the atomic scale before and after gettering the specimen. AFM results showed that the surface roughness and threshold deformation were 2.3 nm and 4.4 nm, respectively. Plan-view TEM analysis of silicon showed the coexistence of single dislocation and narrow dipoles. It can be concluded that cavitation impacts causes dislocation dipoles on CZ-Si(100) which are associated with dislocation loops. The initiation point takes the form of a micro Frank-Read dislocation source, less than 50 nm, that cause dislocation dipoles which are associated with dislocation loops. Plan view TEM observations reveal that the size of the dislocation misfits was approximately 100 nm. The polysilicon surface had a higher residual stresses when it was subjected to cavitation impacts. The cross-sectional TEM observation on poly-Si revealed random crystals on the noncavitated specimens while a mixer of columnar-textured grains on the specimen treated by cavitation. The textured grains have rough edges and the intra-grain size is about 40 nm. Deformation twins and set of streaks from an array of dislocations were observed in the cavitated poly-Si/SiO2 specimens. The spacing between the large grains was 8 nm.