Prevalence of exposure to eastern equine encephalomyelitis virus in domestic and feral swine in Georgia

Eastern, Western, and Venezuelan Equine Encephalitis and West Nile Viruses: Clinical and Public Health Considerations

The continued recognition and emergence of alphavirus and flavivirus diseases is a growing veterinary and public health concern. As the global environment continues to change, mosquito-borne diseases will continue to evolve and expand. Continued development of readily available vaccines for the prevention of these diseases in humans and animals is essential to controlling epizootics of these diseases. Further research into effective antiviral treatments is also sorely needed. This article describes equine encephalitis viruses with a focus on clinical and public health considerations.

Eastern Equine Encephalitis Virus: A Scoping Review of the Global Evidence

Background: Eastern equine encephalitis virus (EEEV) is a mosquito-borne virus that is primarily found in North America and the Caribbean. Over the past decade there has been an increase in virus activity, including large outbreaks in human and horse populations. Predicted climate change is expected to affect the range of mosquitoes including vectors of EEEV, which may alter disease risk posing a public health concern. Methods: A scoping review (ScR) was conducted to identify and characterize the global evidence on EEEV. A thorough search was conducted in relevant bibliographic databases and government websites. Two reviewers screened titles and abstracts for relevance and the characteristics of relevant articles were extracted using a uniformly implemented data collection form. The study protocol was developed a priori and described the methods and tools used and this article follows the PRISMA-ScR guidelines for reporting ScRs. Results: The ScR included 718 relevant research articles. The majority of the articles originated from North America (97%) between 1933 and 2019. EEEV has been identified in 35 species of mosquitoes, over 200 species of birds, various domestic animals, wild mammals, reptiles, and amphibians. Articles identified in this ScR primarily covered three topic areas: epidemiology of hosts and vectors (344 articles) including surveillance results (138), pathogenesis of EEEV in hosts (193), and in vitro studies characterizing EEEV (111). Fewer articles evaluated the accuracy of diagnostic tests (63), the efficacy of mitigation strategies (62), transmission dynamics (56), treatment of EEEV in hosts (10), societal knowledge, attitudes, and perceptions (4), and economic burden (2). Conclusion: With the projected impact of climate change on mosquito populations, it is expected that the risk of EEEV could change resulting in higher disease burden or spread into previously unaffected areas. Future research efforts should focus on closing some of the important knowledge gaps identified in this ScR.

Serosurvey of Eastern, Western, and Venezuelan Equine Encephalitis Viruses in Wild Boars (Sus scrofa), Hunting Dogs, and Hunters of Brazil

A total of 102 free-range wild boars, 170 hunting dogs, and 49 hunters from 3 Brazilian regions were sampled and tested for antibodies to eastern equine encephalitis virus (EEEV), western equine encephalitis virus, and Venezuelan equine encephalitis virus. Three of the 102 (2.9%) wild boars were positive for antibodies against EEEV by microplate serum neutralization test. Based on our data, free-range wild boars from central-western Brazil may be exposed to EEEV, and further studies are needed to evaluate the potential of incorporating serosurveys in routine arbovirus activity surveillance specifically to identify arbovirus activity foci and to help establish thresholds for epidemic transmission.

Cross-species transmission potential between wild pigs, livestock, poultry, wildlife, and humans: implications for disease risk management in North America

Cross-species disease transmission between wildlife, domestic animals and humans is an increasing threat to public and veterinary health. Wild pigs are increasingly a potential veterinary and public health threat. Here we investigate 84 pathogens and the host species most at risk for transmission with wild pigs using a network approach. We assess the risk to agricultural and human health by evaluating the status of these pathogens and the co-occurrence of wild pigs, agriculture and humans. We identified 34 (87%) OIE listed swine pathogens that cause clinical disease in livestock, poultry, wildlife, and humans. On average 73% of bacterial, 39% of viral, and 63% of parasitic pathogens caused clinical disease in other species. Non-porcine livestock in the family Bovidae shared the most pathogens with swine (82%). Only 49% of currently listed OIE domestic swine diseases had published wild pig surveillance studies. The co-occurrence of wild pigs and farms increased annually at a rate of 1.2% with as much as 57% of all farms and 77% of all agricultural animals co-occurring with wild pigs. The increasing co-occurrence of wild pigs with livestock and humans along with the large number of pathogens shared is a growing risk for cross-species transmission.

Mapping eastern equine encephalitis virus risk for white-tailed deer in Michigan

Eastern equine encephalitis (EEE) is a mosquito-borne viral disease that is often fatal to humans and horses. Some species including white-tailed deer and passerine birds can survive infection with the EEE virus (EEEV) and develop antibodies that can be detected using laboratory techniques. In this way, collected serum samples from free ranging white-tailed deer can be used to monitor the presence of the virus in ecosystems. This study developed and tested a risk index model designed to predict EEEV activity in white-tailed deer in a three-county area of Michigan. The model evaluates EEEV risk on a continuous scale from 0.0 (no measurable risk) to 1.0 (highest possible risk). High risk habitats are identified as those preferred by white-tailed deer that are also located in close proximity to an abundance of wetlands and lowland forests, which support disease vectors and hosts. The model was developed based on relevant literature and was tested with known locations of infected deer that showed neurological symptoms. The risk index model accurately predicted the known locations, with the mean value for those sites equal to the 94th percentile of values in the study area. The risk map produced by the model could be used refine future EEEV monitoring efforts that use serum samples from free-ranging white-tailed deer to monitor viral activity. Alternatively, it could be used focus educational efforts targeted toward deer hunters that may have elevated risks of infection.

Evaluation of the human host range of bovine and porcine viruses that may contaminate bovine serum and porcine trypsin used in the manufacture of biological products

Current U.S. requirements for testing cell substrates used in production of human biological products for contamination with bovine and porcine viruses are U.S. Department of Agriculture (USDA) 9CFR tests for bovine serum or porcine trypsin. 9CFR requires testing of bovine serum for seven specific viruses in six families (immunofluorescence) and at least 2 additional families non-specifically (cytopathicity and hemadsorption). 9CFR testing of porcine trypsin is for porcine parvovirus. Recent contaminations suggest these tests may not be sufficient. Assay sensitivity was not the issue for these contaminations that were caused by viruses/virus families not represented in the 9CFR screen. A detailed literature search was undertaken to determine which viruses that infect cattle or swine or bovine or porcine cells in culture also have human host range [ability to infect humans or human cells in culture] and to predict their detection by the currently used 9CFR procedures. There are more viruses of potential risk to biological products manufactured using bovine or porcine raw materials than are likely to be detected by 9CFR testing procedures; even within families, not all members would necessarily be detected. Testing gaps and alternative methodologies should be evaluated to continue to ensure safe, high quality human biologicals.

Protection of pigs by vaccination of pregnant sows against eastern equine encephalomyelitis virus

Serum-virus neutralizing antibodies were detected in serum and colostrum of sows vaccinated during pregnancy with commercially available vaccines against eastern equine encephalomyelitis virus (EEEV), and antibodies were detected in serum from nearly all pigs from vaccinated sows following colostrum uptake. Serum-virus neutralizing antibody (SVN) test titers were measured in colostrum and pigs at the next farrowing, and additional vaccination of sows prior to the third farrowing led to elevated SVN titers in serum, colostrum and all pigs. Six pigs from vaccinated sows challenged at 8 to 9 days of age with 1 x 10(6) TCID50 EEEV did not develop the high temperatures or signs of central nervous system disease that 6 pigs from non-vaccinated sows developed. Virus was isolate from blood and oropharyngeal swabs from all pigs from non-vaccinated sows with blood virus titers as high as 9.3 x 10(4) TCID50, while only low levels of virus were detected in blood and oropharyngeal swabs from pigs from vaccinated sows. Virus was also isolated from tonsils collected at necropsy from 3 pigs from non-vaccinated and 1 pig from vaccinated sows. Vaccination of pregnant sows leads to development of maternal antibodies that are transmitted via colostrum to pigs and are protective against clinical EEEV related disease after experimental challenge with EEEV. In addition, vaccination prevents amplification of virus in infected pigs and could result in protection of animals and farm labor in the environment of infected pigs.