Low-Pathogenic Avian Influenza Viruses in Wild House Mice

Background: Avian influenza viruses are known to productively infect a number of mammal species, several of which are commonly found on or near poultry and gamebird farms. While control of rodent species is often used to limit avian influenza virus transmission within and among outbreak sites, few studies have investigated the potential role of these species in outbreak dynamics. Methodology/Principal Findings: We trapped and sampled synanthropic mammals on a gamebird farm in Idaho, USA that had recently experienced a low pathogenic avian influenza outbreak. Six of six house mice (Mus musculus) caught on the outbreak farm were presumptively positive for antibodies to type A influenza. Consequently, we experimentally infected groups of naïve wild-caught house mice with five different low pathogenic avian influenza viruses that included three viruses derived from wild birds and two viruses derived from chickens. Virus replication was efficient in house mice inoculated with viruses derived from wild birds and more moderate for chicken-derived viruses. Mean titers (EID50 equivalents/mL) across all lung samples from seven days of sampling (three mice/day) ranged from 103.89 (H3N6) to 105.06 (H4N6) for the wild bird viruses and 102.08 (H6N2) to 102.85 (H4N8) for the chicken-derived viruses. Interestingly, multiple regression models indicated differential replication between sexes, with significantly (p\u3c0.05) higher concentrations of avian influenza RNA found in females compared with males. Conclusions/Significance: Avian influenza viruses replicated efficiently in wild-caught house mice without adaptation, indicating mice may be a risk pathway for movement of avian influenza viruses on poultry and gamebird farms. Differential virus replication between males and females warrants further investigation to determine the generality of this result in avian influenza disease dynamics

An Epidemiological Study of Equine Protozoal Myeloencephalitis in Texas

Program year: 1996/1997Digitized from print original stored in HDREquine protozoal myeloencephalitis (EPM) is a debilitating neurologic disease in horses caused by the protozoan Sarcocystis neurona. While new discoveries about the life cycle of the organism and its hosts have recently been made, much still remains unanswered about treatment, prognosis, risk factors, and the spread of the disease over time. A case series with long-term follow-up and a case-control study were conducted at Texas A&M University using 82 confirmed EPM cases and five control groups. The case series was used to describe the population of EPM cases at Texas A&M and evaluate response to treatment and prognosis. The case-control study used logistic regression to assess age, breed, sex, and month of admission as risk factors for EPM. In the case series, age was found to have a significant effect on the tine of relapse and chance of survival, but not on the number of relapses. Breed and sex had no effect on the number of relapses or the chance of survival. The case-control study did not find that aqe or sex were risk factors for EPM, however there was a breed predilection in favor of Thoroughbreds. EPM cases were less likely to be admitted in the months of August, October, November, February, and March as compared to January

Vesicular stomatitis outbreak in the southwestern United States, 2012

Vesicular stomatitis is a viral disease primarily affecting horses and cattle when it occurs in the United States. Outbreaks in the southwestern United States occur sporadically, with initial cases typically occurring in Texas, New Mexico, or Arizona and subsequent cases occurring in a northward progression. The viruses causing vesicular stomatitis can be transmitted by direct contact of lesioned animals with other susceptible animals, but transmission is primarily through arthropod vectors. In 2012, an outbreak of vesicular stomatitis in the United States occurred that was caused by Vesicular stomatitis New Jersey virus serotype. Overall, 51 horses on 36 premises in 2 states were confirmed positive. Phylogenetic analysis of the virus indicated that it was most closely related to viruses detected in the state of Veracruz, Mexico, in 2000

Equine piroplasmosis associated with Amblyomma cajennense Ticks, Texas, USA

We report an outbreak of equine piroplasmosis in southern Texas, USA, in 2009. Infection prevalence reached 100% in some areas (292 infected horses). Amblyomma cajennense was the predominant tick and experimentally transmitted Theileria equi to an uninfected horse. We suggest that transmission by this tick species played a role in this outbreak

Predicting the Geographic Range of an Invasive Livestock Disease across the Contiguous USA under Current and Future Climate Conditions

Vesicular stomatitis (VS) is the most common vesicular livestock disease in North America. Transmitted by direct contact and by several biting insect species, this disease results in quarantines and animal movement restrictions in horses, cattle and swine. As changes in climate drive shifts in geographic distributions of vectors and the viruses they transmit, there is considerable need to improve understanding of relationships among environmental drivers and patterns of disease occurrence. Multidisciplinary approaches integrating pathology, ecology, climatology, and biogeophysics are increasingly relied upon to disentangle complex relationships governing disease. We used a big data model integration approach combined with machine learning to estimate the potential geographic range of VS across the continental United States (CONUS) under long-term mean climate conditions over the past 30 years. The current extent of VS is confined to the western portion of the US and is related to summer and winter precipitation, winter maximum temperature, elevation, fall vegetation biomass, horse density, and proximity to water. Comparison with a climate-only model illustrates the importance of current processes-based parameters and identifies regions where uncertainty is likely to be greatest if mechanistic processes change. We then forecast shifts in the range of VS using climate change projections selected from CMIP5 climate models that most realistically simulate seasonal temperature and precipitation. Climate change scenarios that altered climatic conditions resulted in greater changes to potential range of VS, generally had non-uniform impacts in core areas of the current potential range of VS and expanded the range north and east. We expect that the heterogeneous impacts of climate change across the CONUS will be exacerbated with additional changes in land use and land cover affecting biodiversity and hydrological cycles that are connected to the ecology of insect vectors involved in VS transmission

Landscape dynamics of a vector‐borne disease in the western US: How vector–habitat relationships inform disease hotspots

Abstract Vesicular stomatitis (VS) is a vector‐borne viral disease that causes lesions in livestock, premises, county and state quarantines, and important economic losses. We investigated vector–habitat characteristics for vectors associated with VS in regions of recurrent disease within the western United States (US) that consistently lead to the environment where vector, host, and pathogen populations intersect to enable pathogen transmission. We analyzed the habitats of previously identified insect vectors, including black flies (BFs) (Simulium vittatum complex), biting midges (BMs) (Culicoides variipennis complex, which includes Culicoides sonorensis), and sand flies (SFs) (Lutzomyia shannoni) in six regions of interest (ROIs) containing hotspots of VS ranging from Texas (TX) to Wyoming. This analysis broadened the understanding of (1) how regions of reoccurring VS differ from the broader western US, (2) how geographically separated regions and hotspots are similar across time, and (3) how vector–environment habitat a priori knowledge relates to observed hotspots. Analysis of watershed factors (livestock densities, land‐cover proportions, stream and lake densities, and irrigation methods) indicated a complex system separating areas with high, recurring VS from the broader western US. Although no single characteristic separated the six ROIs from other areas, we found two distinct emerging groups (northern ROI and TX). Hotspots, estimated from monthly VS concentrations, evolved northward throughout the year and most hotspots were closer to flowing water and agricultural land than the broader ROI. All ROIs contained environmental conditions suitable for multiple vectors at some point in the year, but BFs had the highest suitability scores, whereas BM scores were lower and varied annually with higher suitability in summer. SFs had the lowest suitability score in all ROIs, consistent with their low likelihood of being vectors. BM habitat patches were often orders of magnitude smaller than BF patches, and hotspot patches reinforce the likelihood that BF may be the most critical vector in northern ROI, whereas both BM and BF have similar likelihood in southern ROI. Given limited existing vector data, this analysis provides an alternate pathway for using habitat information to associate likely vectors responsible for transmission. Results could support early warning and mitigation efforts to reduce the incidence of VS

Model selection results for multiple regression models testing the relationship between viral RNA concentrations in lung tissues as a function of virus subtype, sex, and day post inoculation and interactions between the three variables.

<p>Only models with a ΔAICc<6 are shown. K is the number of parameters. Adj. R² is the R² value adjusted for the number of parameters in the model; it indicates the amount of variation explained in the model. AICc is Akaike's information criterion adjusted for small sample size. ΔAICc values indicate the difference between a given model and the best model. The AIC weight shows the relative support for each model.</p

Avian influenza viruses used in this study.

<p>Avian influenza viruses used in this study.</p