Serologic survey of wild cervids for potential disease agents in selected national parks in the United States

High Exposure to Livestock Pathogens in Southern Pudu (Pudu puda) from Chile

A significant gap in exposure data for most livestock and zoonotic pathogens is common for several Latin America deer species. This study examined the seroprevalence against 13 pathogens in 164 wild and captive southern pudu from Chile between 2011 and 2023. Livestock and zoonotic pathogen antibodies were detected in 22 of 109 wild pudus (20.18%; 95% CI: 13.34-29.18) and 17 of 55 captive pudus (30.91%; 95% CI: 19.52-44.96), including five Leptospira interrogans serovars (15.38% and 10.71%), Toxoplasma gondii (8.57% and 37.50%), Chlamydia abortus (3.03% and 12.82%), Neospora caninum (0.00% and 9.52%), and Pestivirus (8.00% and 6.67%). Risk factors were detected for Leptospira spp., showing that fawn pudu have statistically significantly higher risk of positivity than adults. In the case of T. gondii, pudu living in "free-range" have a lower risk of being positive for this parasite. In under-human-care pudu, a Pestivirus outbreak is the most strongly suspected as the cause of abortions in a zoo in the past. This study presents the first evidence of Chlamydia abortus in wildlife in South America and exposure to T. gondii, L. interrogans, and N. caninum in wild ungulate species in Chile. High seroprevalence of livestock pathogens such as Pestivirus and Leptospira Hardjo in wild animals suggests a livestock transmission in Chilean template forest.

Non-Bovine Species and the Risk to Effective Control of Bovine Viral Diarrhoea (BVD) in Cattle

Bovine viral diarrhoea virus (BVDV) is an economically important and highly prevalent virus of domestic cattle. Infections with BVDV may lead to both, reproductive and immunological effects that can result in widespread calf losses and increased susceptibility to diseases, such as mastitis and respiratory disease. While BVDV is generally considered to be host specific, it and other Pestivirus species, such as Border disease virus (BDV) in sheep, have been shown to be infecting species other than those from which they were originally isolated from. Recently BVDV was placed on the OIE’s list of notifiable disease and control and eradication programmes for BVDV have been developed throughout much of Europe, the United States, and the United Kingdom. While some countries, including Sweden and Ireland have successfully implemented eradication programmes, other countries such as New Zealand and Australia are still in the early stages of BVDV control. Despite effective control methods, incursions of BVDV into previously cleared herds still occur. While the cause of these incursions is often due to lapses in control methods, the ability of ruminant pestiviruses to infect species other than cattle poses the question as to whether non-bovine species could be impeding the success of BVDV eradication and control. As such, the aim of this review is to make mention of what is known about the cross-species transmission of BVDV, BDV and other pestiviruses between cattle and non-bovine ungulate species and draw conclusions as to the risk non-bovine species pose to the successful control and eradication of BVDV from cattle.

Molecular Detection of Selected Pathogens with Zoonotic Potential in Deer Keds (Lipoptena fortisetosa)

Deer keds are obligatory hematophagous ectoparasites of birds and mammals. Cervids serve as specific hosts for these insects. However, ked infestations have been observed in non-specific hosts, including humans, companion animals, and livestock. Lipoptena fortisetosa is a weakly studied ectoparasite, but there is evidence to indicate that it continues to spread across Europe. The existing knowledge on deer keds' impact on wildlife is superficial, and their veterinary importance is enigmatic. Lipoptena fortisetosa is a species with vectorial capacity, but potential pathogen transmission has not been assessed. The objective of this study was to evaluate the prevalence of selected pathogens in L. fortisetosa collected from cervids and host-seeking individuals in the environment. Out of 500 acquired samples, 307 (61.4%) had genetic material from at least one tested pathogen. Our research suggests that L. fortisetosa may be a potential vector of several pathogens, including A. phagocytophilum, Babesia spp., Bartonella spp., Borellia spp., Coxiella-like endosymbionts, Francisiella tularensis, Mycoplasma spp., Rickettsia spp., and Theileria spp.; however, further, more extensive investigations are required to confirm this. The results of the study indicate that keds can be used as biological markers for investigating the prevalence of vector-borne diseases in the population of free-ranging cervids.

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.

Bovine viral diarrhea virus: An updated American College of Veterinary Internal Medicine consensus statement with focus on virus biology, hosts, immunosuppression, and vaccination

Control of bovine viral diarrhea virus (BVDV) in cattle populations across most of the world has remained elusive in spite of advances in knowledge about this viral pathogen. A central feature of virus perseverance in cattle herds is the unique mechanism of persistent infection. Managing BVDV infection in herds involves controlling persistently infected carrier animals using a multidimensional approach of vaccination, biosecurity, and identification of BVDV reservoirs. A decade has passed since the original American College of Veterinary Internal Medicine consensus statement on BVDV. While much has remained the same with respect to clinical signs of disease, pathogenesis of infection including persistent infection, and diagnosis, scientific articles published since 2010 have led to a greater understanding of difficulties associated with control of BVDV. This consensus statement update on BVDV presents greater focus on topics currently relevant to the biology and control of this viral pathogen of cattle, including changes in virus subpopulations, infection in heterologous hosts, immunosuppression, and vaccination.

Preliminary serological and molecular investigation of selected viral pathogens in Croatian cervid species

A total of 131 blood samples and 175 spleen samples were collected from three cervid species: roe deer (Capreolus capreolus), red deer (Cervus elaphus) and fallow deer (Dama dama) inhabiting the continental part of Croatia. Serum samples were tested for antibodies against bovine herpesvirus 1, parainfluenza-3 virus, bluetongue virus, bovine respiratory syncytial virus, hepatitis E virus, bovine viral diarrhoea virus and enzootic bovine leukosis virus. The tested sera were negative for bovine viral diarrhoea virus, enzootic bovine leukosis virus, bluetongue virus, bovine respiratory syncytial virus and hepatitis E virus antybodies. The antibody prevalence in roe deer and red deer samples was 21.11% for bovine herpesvirus 1 and 75.55% for parainfluenza-3 virus. Sera from bovine herpesvirus 1 positive animals were subsequenty tested with comparative virus neutralization test and bovine herpesvirus 1 neutralising antibodies were found in 18 (out of 19) sera. In fallow deer, no antibodies against any of the viral pathogens were detected. All spleen samples tested for bovine viral diarrhoea virus and enzootic bovine leukosis virus came back negative, except for one red deer spleen sample found to be weakly diarrhoea virus-positive. Our findings provide the first information on the exposure of Croatia-inhabiting cervid species to viral pathogens, and could serve as valuable baseline data for future investigations regarding deer exposure to various pathogens and the distribution of diseases shared between wildlife and livestock. As of now, the epidemiology of these viruses in the Croatian cervid population has been only poorly understood, so that further research is recommended.

Failure to Detect Bovine Viral Diarrhea Virus in Necropsied Farm-Raised White-Tailed Deer (Odocoileus Virginianus) in Pennsylvania

Between January 1 and December 31, 2005 gross and histologic examinations were performed on carcasses of 61 farm-raised white-tailed deer originating from Pennsylvania. Single-tube real-time reverse transcription polymerase chain reaction (real-time RT-PCR) for the detection of bovine viral diarrhea virus type 1 (BVDV-1) and type 2 (BVDV-2) was performed on each animal. Virus isolation was performed on tissue samples from 25 of 61 animals. Immunohistochemical (IHC) staining of ear-notch skin to identify BVDV antigen was performed on each animal. All tissues samples tested negative for both BVDV-1 and BVDV-2 by real-time RT-PCR, virus isolation, and IHC. Gross or histopathologic lesions suggestive of BVDV infection were not detected. Results of this study suggest that BVD is not a common cause of mortality in farm-raised white-tailed deer in Pennsylvania.

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.

Environmental Factors Influencing White-Tailed Deer (Odocoileus virginianus) Exposure to Livestock Pathogens in Wisconsin

White-tailed deer (Odocoileus virginianus) are commonly exposed to disease agents that affect livestock but environmental factors that predispose deer to exposure are unknown for many pathogens. We trapped deer during winter months on two study areas (Northern Forest and Eastern Farmland) in Wisconsin from 2010 to 2013. Deer were tested for exposure to six serovars of Leptospira interrogans (grippotyphosa, icterohaemorrhagiae, canicola, bratislava, pomona, and hardjo), bovine viral diarrhea virus (BVDV-1 and BVDV-2), infectious bovine rhinotracheitis virus (IBR), and parainfluenza 3 virus (PI3). We used logistic regression to model potential intrinsic (e.g., age, sex) and extrinsic (e.g., land type, study site, year, exposure to multiple pathogens) variables we considered biologically meaningful to exposure of deer to livestock pathogens. Deer sampled in 2010–2011 did not demonstrate exposure to BVDV, so we did not test for BVDV in subsequent years. Deer had evidence of exposure to PI3 (24.7%), IBR (7.9%), Leptospira interrogans serovar pomona (11.7%), L. i. bratislava (1.0%), L. i. grippotyphosa (2.5%) and L. i. hardjo (0.3%). Deer did not demonstrate exposure to L. interrogans serovars canicola and icterohaemorrhagiae. For PI3, we found that capture site and year influenced exposure. Fawns (n = 119) were not exposed to L. i. pomona, but land type was an important predictor of exposure to L. i. pomona for older deer. Our results serve as baseline exposure levels of Wisconsin white-tailed deer to livestock pathogens, and helped to identify important factors that explain deer exposure to livestock pathogens.

What attracts elk onto cattle pasture? Implications for inter-species disease transmission

In Southwest Alberta, beef cattle and wild elk (Cervus elaphus) have similar habitat preferences. Understanding their inter-species contact structure is important for assessing the risk of pathogen transmission between them. These spatio-temporal patterns of interactions are shaped, in part, by range management and environmental factors affecting elk distribution. In this study, resource selection modeling was used to identify factors influencing elk presence on cattle pasture and elk selection of foraging patches; furthermore, consequences for inter-species disease transmission were discussed. Data on pasture management practices and observations of elk were collected from 15 ranchers during interviews. Pasture use by elk was defined based on telemetry data (from GPS collars deployed on 168 elk in 7 herds) and rancher observations. At the patch scale, foraging patches used by elk were identified by spatio-temporal cluster analysis of telemetry data, whereas available patches were randomly generated outside the area delimited by used patches. For pastures and patches, landscape and human-managed features were characterized using remote sensing data and interviews, respectively. Attributes of available and used pastures (or patches) were compared using resource selection functions, on annual and seasonal (or annual and monthly) time scales. Additionally, intensity of pasture use was modeled using negative binomial regression. Cultivated hay land and mineral supplements were associated with elk presence on cattle pastures, whereas pastures with manure fertilization and higher traffic-weighted road densities were less likely to be used by elk. The effects of landscape (elevation, aspect, water access) and vegetation (forest cover, Normalized Difference Vegetation Index) characteristics on patch selection were consistent with typical elk habitat requirements. The presence of cattle and the traffic-weighted road density were negatively associated with patch selection. The apparent avoidance of cattle by elk reduced the risk of direct transmission of pathogens, except during winter months. However, human-managed features attracting elk to cattle pastures (e.g. hay land and mineral supplements) may increase inter-species pathogen transmission through indirect contacts.

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.

Emergence of diseases from wildlife reservoirs

Interest in the epidemiology of emerging diseases of humans and livestock as they relate to wildlife has increased greatly over the past several decades. Many factors, most anthropogenic, have facilitated the emergence of diseases from wildlife. Some livestock diseases have "spilled over" to wildlife and then "spilled back" to livestock. When a population is exposed to an infectious agent, depending on an interaction of factors involving the host, agent, and environment, the population may be resistant to infection or may become a dead-end host, a spillover host, or a maintenance host. Each exposure is unique; the same species of host and agent may respond differently in different situations. Management actions that affect the environment and behavior of a potential host animal may allow the emergence of a new or as yet undetected disease. There are many barriers in preventing, detecting, monitoring and managing wildlife diseases. These may include political and legal hurdles, lack of knowledge about many diseases of wildlife, the absence of basic data on wildlife populations, difficulties with surveillance, and logistical constraints. Increasing interaction between wildlife and humans or domestic animals may lead to disease emergence and require innovative methods and strategies for disease surveillance and management in wildlife.

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.

Persistent Bovine viral diarrhea virus infection in wild cervids of Colorado

Bovine viral diarrhea virus (BVDV) is a significant viral pathogen of domestic cattle. Worldwide, there is evidence of BVDV exposure and infection in wild ungulates; however, the frequency and significance of such events are unknown. To determine the prevalence and distribution of Colorado deer, elk, and moose persistently infected (PI) with BVDV, a cross-sectional study was conducted using full-thickness ear tissue samples collected from animals presented to the Colorado Division of Wildlife for chronic wasting disease surveillance in the 2005-2006 hunting season. Tissue from 5,597 harvested animals (2,934 mule deer, 2,516 elk, 141 white-tailed deer, and 6 moose) was paraffin-embedded and stained for BVDV using immunohistochemistry. A single adult male mule deer had BVDV antigen in the skin; staining distribution was consistent with that seen in PI cattle. Skin and lymph node were also positive for viral RNA by polymerase chain reaction, and the virus was determined to be a type 1. The prevalence of BVDV PI cervids in Colorado is very low. However, the identification of a naturally infected adult PI animal in the wild suggests that the virus infects free-ranging populations. The source of the BVDV is unknown and is assumed to be spillover from cattle or maintenance within wildlife populations. Consideration of a potential wild animal reservoir is important in the design and implementation of BVDV management practices in cattle.

Histopathologic and immunohistochemical findings in two white-tailed deer fawns persistently infected with Bovine viral diarrhea virus

Bovine viral diarrhea virus (BVDV) is an important pathogen of domestic cattle. Serologic, experimental, and individual case studies explored the presence and pathogenesis of the virus in wild ungulates; however, there remain large gaps in knowledge regarding BVDV infection in nonbovine species. Live twins were born from a white-tailed deer (Odocoileus virginianus) doe infected with noncytopathic BVDV during its first trimester of pregnancy. The twins died at 1 day of age from trauma unrelated to the infection, and tissues were collected for histologic and immunohistochemical examination. The most significant histologic abnormality was diffuse depletion of B-lymphocytes in both fawns. The BVDV antigen was distributed widely throughout many tissues and cell types, most notably epithelium and vascular endothelium, consistent with that reported in cattle. In contrast to cattle, lymphocytes exhibited only very rare positive staining.

Evaluation of Hunter-Harvested White-Tailed Deer for Evidence of Bovine Viral Diarrhea Virus Infection in Alabama

Bovine viral diarrhea virus (BVDV) is one of the most relevant pathogens affecting today's cattle industries. Although great strides have been made in understanding this virus in cattle, little is known about the role of wildlife in the epidemiology of BVDV. While persistently infected cattle are the most important reservoir, free-ranging ungulates may become infected with BVDV as demonstrated by serosurveys and experimental infections. Therefore, free-ranging wildlife may maintain BVDV as the result of an independent cycle and may serve as a reservoir for the virus. Systematic studies on prevalence of BVDV-specific antibodies or frequency of persistent BVDV infection in North American wildlife are sparse, and no information is available from the southeastern United States. The objective of this study was to evaluate blood and skin samples from hunter-harvested white-tailed deer (Odocoileus virginianus) for evidence of BVDV infection. Virus-neutralizing antibodies were detected in 2 of 165 serum samples. Skin biopsy immunohistochemistry (IHC) was performed on samples from 406 deer using a BVDV-specific monoclonal antibody (MAb) (15c5), and BVDV antigen was detected in one sample. A similar IHC staining pattern was obtained using a second BVDV MAb (3.12F1). Viral antigen distribution in the skin sample of this deer resembled that found in persistently infected cattle and in a previously described persistently infected white-tailed deer; thus, the deer was presumed to be persistently infected. Evidence of BVDV infection in free-ranging white-tailed deer should encourage further systematic investigation of the prevalence of BVDV in wildlife.

Acute and latent infection by bovine herpesvirus type 5 in experimentally infected goats

The ability of alphaherpesviruses to infect different ruminant species may have important implications for control/eradication efforts. Serological data indicate that goats may be naturally infected with bovine herpesviruses. To investigate the susceptibility of goats to bovine herpesvirus-5 (BoHV-5), 3-4-month-old kids were inoculated intranasally with each of three Brazilian BoHV-5 isolates (G1, n=8; G2, n=5; G3, n=5). The acute infection was characterized by virus shedding in nasal secretions for up to 14 days (titers up to 10(5.97)TCID(50)/mL), mild respiratory signs and conjunctivitis. All animals seroconverted to BoHV-5, developing virus neutralizing (VN) titers from 4 to 32 to the homologous viruses. At day 60 post inoculation (pi), two animals from each group were euthanized for tissue collection and the remaining goats were submitted to dexamethasone administration (0.4 mg kg(-1) for 5 days). Dexamethasone treatment resulted in virus reactivation in 9 out of 12 animals, as ascertained by virus shedding and/or by increase in VN titers. Virus shedding was detected in 8/12 animals and lasted from 1 to 9 days. Latent viral DNA was detected by PCR in the olfactory bulb and/or trigeminal ganglia of 6/6 goats euthanized at day 60 pi and in 12/12 animals euthanized 40 days post-dexamethasone. These results show that young goats are susceptible to BoHV-5 and may shed virus upon reactivation of latent infection. Thus, it is reasonable to expect that goats raised in close contact with cattle in areas where BoHV-5 is endemic may be infected and therefore should be considered potential reservoirs of the virus.