Classical Swine Fever Surveillance in Feral Swine

Diseases such as classical swine fever (CSF) and foot-and-mouth disease have been eradicated in the United States, but possible reintroductions merit the development of an enhanced surveillance system. Important foreign animal or transboundary diseases like these pose a significant risk to the health of wildlife and livestock in the United States. Wildlife Services (WS) performs surveillance in targeted feral swine (Sus scrofa) populations as part of a comprehensive United States Department of Agriculture, Animal and Plant Health Inspection Service effort to demonstrate disease-free status in our nation\u27s livestock and wildlife. Surveillance is based on risk assessments which identify high risk states and the vicinity of feral swine to transitional or commercial swine production facilities. During 2007 and 2008, WS sampled and tested (n = 3661) feral swine. CSF was not detected in feral swine in the United States through this surveillance effort

Tissue tropisms opt for transmissible reassortants during avian and swine influenza A virus co-infection in swine

Genetic reassortment between influenza A viruses (IAVs) facilitate emergence of pandemic strains, and swine are proposed as a “mixing vessel” for generating reassortants of avian and mammalian IAVs that could be of risk to mammals, including humans. However, how a transmissible reassortant emerges in swine are not well understood. Genomic analyses of 571 isolates recovered from nasal wash samples and respiratory tract tissues of a group of co-housed pigs (influenza-seronegative, avian H1N1 IAV–infected, and swine H3N2 IAV– infected pigs) identified 30 distinct genotypes of reassortants. Viruses recovered from lower respiratory tract tissues had the largest genomic diversity, and those recovered from turbinates and nasal wash fluids had the least. Reassortants from lower respiratory tracts had the largest variations in growth kinetics in respiratory tract epithelial cells, and the cold temperature in swine nasal cells seemed to select the type of reassortant viruses shed by the pigs. One reassortant in nasal wash samples was consistently identified in upper, middle, and lower respiratory tract tissues, and it was confirmed to be transmitted efficiently between pigs. Study findings suggest that, during mixed infections of avian and swine IAVs, genetic reassortments are likely to occur in the lower respiratory track, and tissue tropism is an important factor selecting for a transmissible reassortant

Feral swine brucellosis in the United States and prospective genomic techniques for disease epidemiology

Brucellosis is a common infection of feral swine throughout the United States. With the recent expansion of feral swine populations across the country, this disease poses an increasing threat to agriculture and hunters. The standard approach to Brucella surveillance in feral swine has been serological testing, which gives an indication of past exposure and is a rapid method of determining populations where Brucella is present. More in-depth analyses require bacterial isolation to determine the Brucella species and biovar involved. Ultimately, for a comprehensive understanding of Brucella epizootiology in feral swine, incorporation of genotyping assays has become essential. Fortunately, the past decade has given rise to an array of genetic tools for assessing Brucella transmission and dispersal. This review aims to synthesize what is known about brucellosis in feral swine and will cover prospective genomic techniques that may be utilized to develop more complete understanding of the disease and its transmission history

Response of Captive Skunks to Microencapsulated Tetracycline

A captive striped skunk (Mephitis mephitis) study was conducted between February and June 2004 at the United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services National Wildlife Research Center, Fort Collins, Colorado, USA. The main objective was to determine the percentage of adult striped skunks that were marked after consuming placebo oral rabies vaccine (ORV) baits containing 100 mg of an experimental microencapsulated (coated microparticle) tetracycline hydrochloride biomarker. Biomarkers were identified in the canine teeth and mandibles of five of five skunks that consumed an ORV bait. A second objective was to determine if the microencapsulated tetracycline was resistant to photochemical conversion from tetracycline to epitetracycline. After 15 days of exposure, conversion from tetracycline to epitetracycline concentration in the microencapsulated product (mean 1.9% conversion, SD=1.24) was significantly less (P=0.006) than the pure-grade tetracycline powder (mean 7.5% conversion, SD=1.37). Results support the use of microencapsulated tetracycline hydrochloride as a biomarker in circumstances where the use of conventional powdered tetracycline hydrochloride is not feasible due to ORV bait design constraints

Plague Exposure in Mammalian Wildlife across the Western United States

Plague is caused by a bacterial pathogen (Yersinia pestis) that can infect a wide range of mammal species, but its presence in wildlife is often underappreciated. Using a large-scale data set (n = 44,857) that details the extent of Y. pestis exposure in wildlife, we document exposure in 18 wildlife species, including coyotes (Canis latrans), bobcats (Lynx rufus), and black bears (Ursus americanus). Evidence of plague activity is widespread, with seropositive animals detected in every western state in the contiguous United States. Pathogen monitoring systems in wildlife that are both large scale and long-term are rare, yet they open the door for analyses on potential shifts in distribution that have occurred over time because of climate or land use changes. The data generated by these long-term monitoring programs, combined with recent advances in our understanding of pathogen ecology, offer a clearer picture of zoonotic pathogens and the risks they pose

SEROLOGIC EVIDENCE OF WEST NILE VIRUS EXPOSURE IN NORTH AMERICAN MESOPREDATORS

Sera from 936 mammalian mesopredators (Virginia opossums, gray foxes, striped skunks, hooded skunks, raccoons, a bobcat, and a red fox) were collected during 2003 and 2004 in California, Arizona, Texas, Louisiana, Ohio, and Wyoming and screened for flavivirus-specific antibodies by an epitope-blocking enzyme-linked immunosobent assay (blocking ELISA). Serum samples positive for antibodies against flaviviruses were screened for West Nile virus (WNV)– specific antibodies by blocking ELISA and selectively confirmed with plaque-reduction neutralization tests. High prevalence rates were observed in raccoons (45.6%) and striped skunks (62.9%). The high WNV antibody prevalence noted in mesopredators, their peridomestic tendencies, and their overall pervasiveness make these species potentially useful sentinels for monitoring flaviviruses in defined areas

Identification of Putative Origins of Introduced Pigs in Indiana Using Nuclear Microsatellite Markers and Oral History

Feral swine (Sus scrofa) have been introduced throughout North America from various global locations (Mayer and Brisbin 1991). In some cases, sources for feral swine are provided through historical records, but for many newly established populations, the origins of feral swine are not known. Understanding the origins and dispersal patterns of feral swine is an important management consideration, because of the introduction of diseases to new locations, for prosecution of individuals who have trans-ported feral swine across state lines, and for allocating swine removal efforts appropriately to address swine translocations within a state or a management area

Apparent prevalence of swine brucellosis in feral swine in the United States

Samples were collected in 35 states as part of a national monitoring system to detect multiple diseases in feral swine (Sus scrofa). During March 2009 through December 2010, we collected serum samples from 4,479 feral swine from 13 states, and 159 animals tested were seropositive for brucellosis. No difference in likelihood of infection was found between males and females, but adults were more likely than sub-adults or juveniles to be exposed to brucellosis. Feral swine sampled during winter months also were more likely to be seropositive than animals sampled during other seasons. Apparent prevalence varied among states, and seropositive animals often were clustered in specific counties within a state. We recommend improved diagnostics and stricter regulations on movement of feral swine both intra- and inter-state to minimize further spread of the disease and to decrease the risk of reintroduction of brucellosis into livestock

Raccoon (\u3ci\u3eProcyon lotor\u3c/i\u3e) biomarker and rabies antibody response to varying oral rabies vaccine bait densities in northwestern Pennsylvania

Distribution of oral rabies vaccine baits has been used as a strategy for managing rabies in the United States since the 1990s. Since that time, efforts have been made to improve baiting strategies with a focus on bait density to maximize both efficiency and cost effectiveness. An optimal rabies management strategy includes a vaccine bait preferred by the target species that is distributed at the minimal density needed to achieve population immunity to prevent rabies spread. The purpose of our pilot study was to examine the effect of 75, 150, and 300 baits/km2 vaccine bait densities on rabies virus neutralizing antibody (RVNA) seroprevalence in raccoons (Procyon lotor). Raboral V-RG_ fishmeal polymer baits (Merial Inc. (now a part of Boehringer Ingelheim), Athens, Georgia) contain a tetracycline biomarker that was used to estimate bait consumption as another measure of intervention impact. Our results suggest that raccoon RVNA response increases as bait density increases, but the effect may not be sufficient to justify the cost except in the case of contingency actions or an epizootic. Non-target species, especially opossums (Didelphis virginianus) in certain areas, should be considered when determining an appropriate bait density to ensure sufficient baits are available for consumption by the target species

Large-Scale Avian Influenza Surveillance in Wild Birds throughout the United States

Avian influenza is a viral disease that primarily infects wild and domestic birds, but it also can be transmitted to a variety of mammals. In 2006, the United States of America Departments of Agriculture and Interior designed a large-scale, interagency surveillance effort that sought to determine if highly pathogenic avian influenza viruses were present in wild bird populations within the United States of America. This program, combined with the Canadian and Mexican surveillance programs, represented the largest, coordinated wildlife disease surveillance program ever implemented. Here we analyze data from 197,885 samples that were collected from over 200 wild bird species. While the initial motivation for surveillance focused on highly pathogenic avian influenza, the scale of the data provided unprecedented information on the ecology of avian influenza viruses in the United States, avian influenza virus host associations, and avian influenza prevalence in wild birds over time. Ultimately, significant advances in our knowledge of avian influenza will depend on both large-scale surveillance efforts and on focused research studies