Persistent Bovine viral diarrhea virus infection in wild cervids of Colorado

Serosurveillance and Molecular Investigation of Wild Deer in Australia Reveals Seroprevalence of Pestivirus Infection

Since deer were introduced into Australia in the mid-1800s, their wild populations have increased in size and distribution, posing a potential risk to the livestock industry, through their role in pathogen transmission cycles. In comparison to livestock, there are limited data on viral infections in all wildlife, including deer. The aim of this study was to assess blood samples from wild Australian deer for serological evidence of exposure to relevant viral livestock diseases. Blood samples collected across eastern Australia were tested by ELISA to detect antigens and antibodies against Pestivirus and antibodies against bovine herpesvirus 1. A subset of samples was also assessed by RT-PCR for Pestivirus, Simbu serogroup, epizootic hemorrhagic disease virus and bovine ephemeral fever virus. Our findings demonstrated a very low seroprevalence (3%) for ruminant Pestivirus, and none of the other viruses tested were detected. These results suggest that wild deer may currently be an incidental spill-over host (rather than a reservoir host) for Pestivirus. However, deer could be a future source of viral infections for domestic animals in Australia. Further investigations are needed to monitor pathogen activity and quantify possible future infectious disease impacts of wild deer on the Australian livestock industry.

CHALLENGES AND OPPORTUNITIES FOR WILDLIFE DISEASE SURVEILLANCE IN SRI LANKA

The Sri Lanka Wildlife Health Centre was created in 2011 as an intersectoral surveillance system intended to address gaps in emerging and zoonotic disease preparedness in the country. This study, which was conducted during August 2015 to November 2015, examined perceived obstacles and opportunities to undertake wildlife disease surveillance in Sri Lanka. Responses to a pretested postal questionnaire by 315 field officers from the Department of Wildlife Conservation (DWC) and Department of Animal Production and Health (livestock development instructors [LDIs] and field veterinary surgeons [FVSs]) were used in the analysis. Responses came from all 25 administrative districts in the country. The reported obstacles (and proportion of respondents) included lack of transport facilities (80%), skilled staff (75%), infrastructure (65%), human resources (62%), training (67%), and a mandate for getting involved in wildlife disease surveillance (28%). These obstacles have resulted in rare or sporadic collection and submission of samples and their testing for surveillance purposes. A focus on rabies surveillance found that 84 (78%) DWC officers whose mandate was to deal with wild animals and 41 (40%) LDIs whose mandate was to deal with agricultural animals had inadequate knowledge to inform rabies surveillance activities and actions. Despite being outside of their mandate, 68% of FVSs and 72% of LDI s were willing to contribute to wild animal disease surveillance. Overcoming legal impediments to handling wildlife was cited as an essential step to establishing a multisectoral surveillance system involving government branches, universities, and citizens.

Detection of persistent pestivirus infection in pudú (Pudu puda) in a captive population of artiodactyls in Chile

Background

Bovine Viral Diarrhea Virus (BVDV) is the viral agent causing the most important economic losses in livestock throughout the world. Infection of fetuses before their immunological maturity causes the birth of animals persistently infected with BVDV (PI), which are the main source of infection and maintenance of this pathogen in a herd. There is evidence of susceptibility to infection with BVDV in more than 50 species of the order Artiodactyla, and the ability to establish persistent infection in wild cervid species of South America could represent an important risk in control and eradication programs of BVDV in cattle, and a threat to conservation of these wild species. In this study, a serological and virological study was performed to detect BVDV infection in a captive population of non-bovine artiodactyl species in a Chilean zoo with antecedents of abortions whose pathology suggests an infectious etiology.

Results

Detection of neutralizing antibodies against BVDV was performed in 112 artiodactyl animals from a zoo in Chile. Three alpacas (Vicugna pacos), one guanaco (Lama guanicoe) and seven pudús (Pudu puda) resulted seropositive, and the only seronegative pudú was suspected to be persistently infected with BVDV. Then two blood samples nine months apart were analyzed by a viral neutralization test and RT-PCR. Non-cytopathogenic BVDVs were isolated in both samples. A phylogenetic analysis showed that the virus was highly related to BVDV-1b strains circulating among Chilean cattle.

Conclusions

This is the first report of a South American deer persistently infected with Bovine Viral Diarrhea Virus. Further studies are needed to determine the possible role of BVDV as a pathogen in pudús and as a threat to their conservation.

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.

Bovine Viral Diarrhea Virus (BVDV) in White-Tailed Deer (Odocoileus virginianus)

Bovine viral diarrhea virus (BVDV) is the prototypic member of the genus Pestivirus in the family Flaviviridae. Infections with BVDV cause substantial economic losses to the cattle industries, prompting various organized control programs in several countries. In North America, these control programs are focused on the identification and removal of persistently infected (PI) cattle, enhancement of BVDV-specific immunity through vaccination, and the implementation of biosecure farming practices. To be successful, control measures must be based on complete knowledge of the epidemiology of BVDV, including the recognition of other potential sources of the virus. BVDV does not possess strict host-specificity, and infections of over 50 species in the mammalian order Artiodactyla have been reported. Over 50 years ago, serologic surveys first suggested the susceptibility of white-tailed deer (Odocoileus virginianus), the most abundant free-ranging ruminant in North America, to BVDV. However, susceptibility of white-tailed deer to BVDV infection does not alone imply a role in the epidemiology of the virus. To be a potential wildlife reservoir, white-tailed deer must: (1) be susceptible to BVDV, (2) shed BVDV, (3) maintain BVDV in the population, and (4) have sufficient contact with cattle that allow spillback infections. Based on the current literature, this review discusses the potential of white-tailed deer to be a reservoir for BVDV.

Challenges in Identifying and Determining the Impacts of Infection with Pestiviruses on the Herd Health of Free Ranging Cervid Populations

Although most commonly associated with the infection of domestic livestock, the replication of pestiviruses, in particular the two species of bovine viral diarrhea virus (BVDV), occurs in a wide range of free ranging cervids including white-tailed deer, mule deer, fallow deer, elk, red deer, roe deer, eland and mousedeer. While virus isolation and serologic analyses indicate that pestiviruses are circulating in these populations, little is known regarding their impact. The lack of regular surveillance programs, challenges in sampling wild populations, and scarcity of tests and vaccines compound the difficulties in detecting and controlling pestivirus infections in wild cervids. Improved detection rests upon the development and validation of tests specific for use with cervid samples and development and validation of tests that reliably detect emerging pestiviruses. Estimation of impact of pestivirus infections on herd health will require the integration of several disciplines including epidemiology, cervid natural history, veterinary medicine, pathology and microbiology.

Evidence of Bovine viral diarrhea virus Infection in Three Species of Sympatric Wild Ungulates in Nevada: Life History Strategies May Maintain Endemic Infections in Wild Populations

Evidence for bovine viral diarrhea virus (BVDV) infection was detected in 2009–2010 while investigating a pneumonia die-off in Rocky Mountain bighorn sheep (Ovis canadensis, canadensis), and sympatric mountain goats (Oreamnos americanum) in adjacent mountain ranges in Elko County, Nevada. Seroprevalence to BVDV-1 was 81% (N = 32) in the bighorns and 100% (N = 3) in the mountain goats. Serosurveillance from 2011 to 2015 of surviving bighorns and mountain goats as well as sympatric mule deer (Odocoileus hemionus), indicated a prevalence of 72% (N = 45), 45% (N = 51), and 51% (N = 342) respectively. All species had antibody titers to BVDV1 and BVDV2. BVDV1 was isolated in cell culture from three bighorn sheep and a mountain goat kid. BVDV2 was isolated from two mule deer. Six deer (N = 96) sampled in 2013 were positive for BVDV by antigen-capture ELISA on a single ear notch. Wild ungulates and cattle concurrently graze public and private lands in these two mountain ranges, thus providing potential for interspecies viral transmission. Like cattle, mule deer, mountain goats, and bighorn sheep can be infected with BVDV and can develop clinical disease including immunosuppression. Winter migration patterns that increase densities and species interaction during the first and second trimester of gestation may contribute to the long term maintenance of the virus in these wild ungulates. More studies are needed to determine the population level impacts of BVDV infection on these three species.

Evidence of shared bovine viral diarrhea infections between red deer and extensively raised cattle in south-central Spain

BACKGROUND

Bovine viral diarrhea virus (BVDV) is a pestivirus that affects cattle production worldwide and that can infect other ungulates such as cervids and even wild boar (Sus scrofa). It is believed that domestic livestock can become infected through contact with wild animals, though it is known that infection can spread among wild animals in the absence of contact with livestock. Little is known about the sharing of BVDV infection between wild and domestic animals in the same habitat, which is important for designing eradication campaigns and preventing outbreaks, especially on hunting estates with high animal densities.

RESULTS

We assessed the sharing of BVDV infections among hunted red deer, wild boar and cattle in south-central Spain. Sampled red deer (Cervus elaphus; n = 267) and wild boar (n = 52) were located on 19 hunting estates, and cattle (n = 180) were located on 18 nearby farms. We used ELISA kits for the serological screening, Taqman RT-PCR assay for the virus determination, and subsequent phylogenetic analysis for 17 RT-PCR positive sample amplicons. Fifty-two red deer (19.5%) and 82 cattle (45.6%) samples tested positive by ELISA. A high apparent prevalence (22.47%) was obtained for red deer, while only five cattle farms tested positive by RT-PCR. Conversely, no wild boar tested positive by both ELISA or RT-PCR. Eleven red deer (4.1%) tested positive by both ELISA and RT-PCR; these animals may have been sampled during the last phase of viremia, or they may represent previously exposed individuals infected by a different BVDV strain. The amplicons shared 92.7-100% identity and fell within the BVDV subgroup 1b, although nine of these (from four red deer and five cattle pools) formed a separate branch. This suggests that there might be a common BVDV infecting both cattle and red deer. Higher red deer abundance was significantly associated with greater risk that extensively raised cattle would test positive for BVDV by ELISA.

CONCLUSIONS

Our findings suggest that BVDV is circulating between cattle and red deer populations in proximity, but further work is required to determine whether they share the same strain(s). These results suggest the potential of BVDV to serve as a surveillance marker in these shared habitats. High seroprevalence of BVDV in red deer from our study area suggests that although BVDV infection is common, animals usually survive the infection. Further research is needed to verify and investigate the role of red deer as a BVDV reservoir.

Spatial point pattern analyses of Bovine viral diarrhea virus infection in domestic livestock herds and concomitant seroprevalence in wild white-tailed deer (Odocoileus virginianus) in New York State, USA

Bovine viral diarrhea virus (BVDV) is an economically important disease of domestic cattle that is capable of infecting cervids. A first step in the formulation of a regional BVDV management plan is a local assessment of the likelihood of pathogen transmission from wildlife to domestic livestock. To achieve this, blood samples were collected from hunter-harvested white-tailed deer (Odocoileus virginianus) throughout New York State in the fall of 2009 and 2010. The SVANOVIR BVDV p80-AB enzyme-linked immunosorbent assay (ELISA; Svanova Biotech AV, Uppsala, Sweden) was used to screen sera for anti-BVDV antibodies. Because this ELISA is not validated for use in white-tailed deer, sera that tested positive were tested again using serum neutralization to verify the presence of antibodies. Spatial data describing the geographic location of BVDV antigen-positive cattle and camelid herds and BVDV-seropositive white-tailed deer were analyzed via the dual kernel density estimation method. In white-tailed deer, 7.48% (80/1,069) were BVDV-seropositive, whereas 3.43% (144/4,195) of tested herds were positive for BVDV antigen. An exploratory cluster analysis revealed 1 significant cluster of BVDV antigen-positive herds and 2 significant clusters of BVDV-seropositive deer. There was no spatial overlap between the clusters. The spatial point pattern and exploratory cluster analyses suggest that BVDV is maintained independently in domestic livestock herds in the western part of the state and in the white-tailed deer population in the northwestern part of the state.

Diseases at the livestock-wildlife interface: status, challenges, and opportunities in the United States

In the last half century, significant attention has been given to animal diseases; however, our understanding of disease processes and how to manage them at the livestock-wildlife interface remains limited. In this study, we conduct a systematic review of the scientific literature to evaluate the status of diseases at the livestock-wildlife interface in the United States. Specifically, the goals of the literature review were three fold: first to evaluate domestic animal diseases currently found in the United States where wildlife may play a role; second to identify critical issues faced in managing these diseases at the livestock-wildlife interface; and third to identify potential technical and policy strategies for addressing these issues. We found that of the 86 avian, ruminant, swine, poultry, and lagomorph diseases that are reportable to the World Organization for Animal Health (OIE), 53 are present in the United States; 42 (79%) of these have a putative wildlife component associated with the transmission, maintenance, or life cycle of the pathogen; and 21 (40%) are known to be zoonotic. At least six of these reportable diseases-bovine tuberculosis, paratuberculosis, brucellosis, avian influenza, rabies, and cattle fever tick (vector control)-have a wildlife reservoir that is a recognized impediment to eradication in domestic populations. The complex nature of these systems highlights the need to understand the role of wildlife in the epidemiology, transmission, and maintenance of infectious diseases of livestock. Successful management or eradication of these diseases will require the development of cross-discipline and institutional collaborations. Despite social and policy challenges, there remain opportunities to develop new collaborations and new technologies to mitigate the risks posed at the livestock-wildlife interface.

Prevalence and spatial distribution of antibodies to bovine viral diarrhea virus and Coxiella burnetii in white-tailed deer (Odocoileus virginianus) in New York and Pennsylvania

Significant pathogens of domestic livestock and public-health related pathogens, such as bovine viral diarrhea virus (BVDV) and Coxiella burnetii, are commonly diagnosed in some wildlife species. BVDV is an economically important pathogen of domestic bovids and Coxiella burnetii is a highly infectious zoonotic bacterium. As a result of recent shifting patterns of disease, it is critical that baseline information regarding the status of both significant pathogens of domestic livestock and public-health related pathogens are established for commonly encountered wildlife such as white-tailed deer (Odocoileus virginianus). White-tailed deer are susceptible to both BVDV and C. burnetii infection, and the purpose of this study was to investigate for the presence of antibodies to these two pathogens in New York and Pennsylvania white-tailed deer. Exposure to BVDV and C. burnetii was determined using sera collected from 333 (219 males and 114 females) wild white-tailed deer in New York and 291 (130 males and 161 females) wild white-tailed deer from Pennsylvania. Samples were collected from hunter-harvested deer in central New York State in 2009 and live-captured deer in Pennsylvania in 2010. Sera were screened for anti-BVDV antibodies via a commercial blocking BVDV enzyme-linked immunosorbent assay. Coxiella burnetii phase II whole-cell antigen-coated slides were used to screen sera via an indirect microimmunofluorescence assay. Antibody prevalence was compared by sex class and location of collection. Deer in New York had higher antibody prevalence to BVDV (6.01%) than did deer in Pennsylvania (0.34%). Conversely, C. burnetii phase II antibodies were more common in Pennsylvania (20.96%) than in New York (14.41%). No statistically significant difference between locations was observed in either BVDV or C. burnetii antibody prevalence when data were analyzed by sex-class. Overall, C. burnetii seroprevalence was not significantly higher in Pennsylvania than in New York.

Serosurveillance for livestock pathogens in free-ranging mule deer (Odocoileus hemionus)

Routine disease surveillance has been conducted for decades in mule deer (Odocoileus hemionus) in California for pathogens shared between wildlife and domestic ruminants that may have implications for the animal production industry and wildlife health. Deer sampled from 1990 to 2007 (n = 2,619) were tested for exposure to six pathogens: bluetongue virus (BTV), epizootic hemorrhagic disease virus (EHDV), bovine viral diarrhea virus (BVDV), Leptospira spp., Anaplasma spp. and Brucella spp. We evaluated the relationship between exposure to these pathogens and demographic risk factors to identify broad patterns in seroprevalence across a large temporal and spatial scale. The overall seroprevalence for the entire study period was 13.4% for BTV, 16.8% for EHDV, 17.1% for BVDV, 6.5% for Leptospira spp., 0.2% for Brucella spp., and 17% for Anaplasma spp. Antibodies against BTV and EHDV were most prevalent in the deer populations of southern California. Antibodies against Leptospira spp. and Anaplasma spp. were most prevalent in coastal and central northern California whereas antibodies against BVDV were most prevalent in central-eastern and northeastern California. The overall seroprevalence for Anaplasma spp. was slightly lower than detected in previous studies. North and central eastern California contains large tracts of federal land grazed by livestock; therefore, possible contact between deer and livestock could explain the high BVDV seroprevalence found in these areas. Findings from this study will help to establish baseline values for future comparisons of pathogen exposure in deer, inform on long-term trends in deer population health and provide relevant information on the distribution of diseases that are shared between wildlife and livestock.

The occurrence of Bovine viral diarrhea virus in hunter-harvested white-tailed deer (Odocoileus virginianus) in the state of Georgia, southeastern United States

The prevalence of Bovine viral diarrhea virus (BVDV) in free-ranging white-tailed deer (WTD, Odocoileus virginianus) in the state of Georgia was evaluated using ear notches collected from hunter-harvested deer during the hunting season of 2010-2011. From September to December 2010, 367 ear samples from WTD were collected from 37 counties in Georgia. The samples were from 178 (48.5%) female deer, 187 (51%) male deer, and 2 (0.5%) of unknown sex. The age of the animals varied from 6 months to 6.5 years. The age was not recorded in 34 animals (9.3%). Of the animals with known ages, 42% were under 2 years. Screening of 367 samples for BVDV using an antigen-capture enzyme-linked immunosorbent assay (AgELISA) resulted in 364 negative samples and 3 suspect samples. The 3 suspect samples were negative for BVDV reverse transcription polymerase chain reaction (RT-PCR), virus isolation, and immunohistochemistry. A subpopulation of samples (n = 89) selected from various geographical regions also tested negative for BVDV RT-PCR. In conclusion, although a few of the samples were suspect for the presence of BVDV by AgELISA, the presence of the virus within the deer population studied could not be confirmed further.

Distribution of bovine viral diarrhoea virus antigen in persistently infected white-tailed deer (Odocoileus virginianus)

Infection with bovine viral diarrhoea virus (BVDV), analogous to that occurring in cattle, is reported rarely in white-tailed deer (Odocoileus virginianus). This study evaluated the distribution of BVDV antigen in persistently infected (PI) white-tailed deer and compared the findings with those from PI cattle. Six PI fawns (four live-born and two stillborn) from does exposed experimentally to either BVDV-1 or BVDV-2 were evaluated. Distribution and intensity of antigen expression in tissues was evaluated by immunohistochemistry. Data were analyzed in binary fashion with a proportional odds model. Viral antigen was distributed widely and was present in all 11 organ systems. Hepatobiliary, integumentary and reproductive systems were respectively 11.8, 15.4 and 21.6 times more likely to have higher antigen scores than the musculoskeletal system. Pronounced labelling occurred in epithelial tissues, which were 1.9-3.0 times likelier than other tissues to contain BVDV antigen. Antigen was present in >90% of samples of liver and skin, suggesting that skin biopsy samples are appropriate for BVDV diagnosis. Moderate to severe lymphoid depletion was detected and may hamper reliable detection of BVDV in lymphoid organs. Muscle tissue contained little antigen, except for in the cardiovascular system. Antigen was present infrequently in connective tissues. In nervous tissues, antigen expression frequency was 0.3-0.67. In the central nervous system (CNS), antigen was present in neurons and non-neuronal cells, including microglia, emphasizing that the CNS is a primary target for fetal BVDV infection. BVDV antigen distribution in PI white-tailed deer is similar to that in PI cattle.

Bovine viral diarrhea virus infections in heterologous species

Infections with Bovine viral diarrhea virus (BVDV) are not limited to cattle, but may be detected in various species in the mammalian order Artiodactyla. Despite epidemiological evidence of BVDV infections in species other than cattle, current knowledge regarding the impact of BVDV on heterologous species is incomplete. In heterologous hosts, BVDV infections with clinical signs analogous to those in cattle have been described and include disease of multiple organ systems, most notably the reproductive tract and immune system. Clinical infections may negatively impact the health and well-being of heterologous species, including camelids and captive and free-ranging wildlife. Of additional importance are BVDV infections in small ruminants and swine where difficulties arise in laboratory testing for Border disease virus (BDV) and Classical swine fever virus (CSFV), respectively. Pestiviruses are antigenically closely related and their cross-reactivity requires additional efforts in virological testing. In cattle populations, persistently infected animals are considered the main source of BVDV transmission. This phenomenon has also been detected in heterologous species, which could facilitate reservoirs for BVDV that may be of great importance where control programs are in progress. This review summarizes the current epidemiological and clinical knowledge on heterologous BVDV infections and discusses their implications.

Epidemiology and control of BVD in the U.S

The apparent prevalence of bovine viral diarrhea virus (BVDV) persistently infected cattle has been found to be low in U.S. dairies, beef herds and feedlots. Current management practices within U.S. cattle industries that impact the epidemiology of BVDV infections include purchasing untested cattle, lack of biosecurity procedures, large herd sizes, mixing cattle from multiple sources, high cattle densities in dairy and feedlot operations, synchronous breeding of beef herds, communal grazing and widespread vaccination. Evidence for BVDV infection has been found in farmed and free-ranging wildlife in North America; however the risk of BVDV transmission from wildlife to cattle is not known. The perception of a low prevalence of BVDV herd infections, the unrestricted sale of PI cattle, lack of economic data, intensive marketing of vaccines, reluctance to accept federal regulations, and a "gambler's" attitude among producers are impediments to implementation of a national systematic BVD control program. Since 2004, voluntary BVDV control programs have been organized in nine states reflecting the recognition of BVD as an important and preventable problem in the U.S.