Infection Of White-tailed Deer Research Articles

Transmission history of SARS-CoV-2 in humans and white-tailed deer

The emergence of a novel pathogen in a susceptible population can cause rapid spread of infection. High prevalence of SARS-CoV-2 infection in white-tailed deer (Odocoileus virginianus) has been reported in multiple locations, likely resulting from several human-to-deer spillover events followed by deer-to-deer transmission. Knowledge of the risk and direction of SARS-CoV-2 transmission between humans and potential reservoir hosts is essential for effective disease control and prioritisation of interventions. Using genomic data, we reconstruct the transmission history of SARS-CoV-2 in humans and deer, estimate the case finding rate and attempt to infer relative rates of transmission between species. We found no evidence of direct or indirect transmission from deer to human. However, with an estimated case finding rate of only 4.2%, spillback to humans cannot be ruled out. The extensive transmission of SARS-CoV-2 within deer populations and the large number of unsampled cases highlights the need for active surveillance at the human–animal interface.

First molecular evidence of Theileria cervi infection in white-tailed deer (Odocoileus virginianus) in Mexico.

Theileria cervi is a tick-borne protozoan that infects different deer species around the world. Clinical diseases due to Theileria cervi have been reported in white-tailed deer (Odocoileus virginianus) and mule deer (Odocoileus hemionus) in the USA, however, information about this parasite has not been documented in Mexico. Here, blood samples from three white-tailed deer (Odocoileus virginianus) from a region in northeastern Mexico were analyzed by blood smear, PCR, and DNA sequencing. The results confirmed the presence of T. cervi for the first time in white-tailed deer in Mexico.

Serological Evidence of West Nile Virus Infection in White-Tailed Deer in Central Texas.

White-tailed deer (WTD) are abundant mammals widely distributed across the United States. As a result, WTD are considered to be excellent sentinels for detecting arboviral activity in certain geographic areas. Evidence of West Nile virus (WNV) antibody in WTD has been reported previously in several states. However, WNV infection in WTD has not been reported from Texas, where the incidence of human West Nile (WN) cases is among the highest in the United States. Therefore, the aim of this study was to determine the prevalence of WNV antibody in WTD in central Texas. Sera samples (n = 644) were collected from deer during the fall and winter in western Travis County, Texas from 2014 to 2018 and tested for WNV immunoglobulin G (IgG) antibody by an indirect enzyme-linked immunosorbent assay (ELISA). ELISA antibody-positive samples were further tested for WNV and St. Louis encephalitis virus (SLEV) antibodies by an 80% plaque-reduction neutralization tests (PRNT80). Overall, 9% (n = 58) and 0.31% (n = 2) of the deer samples had serological evidence of WNV and SLEV infections, respectively. WNV seroprevalence differed significantly by age (p < 0.05), but there was no significant difference between sex. Interestingly, 3.1% (n = 20) of the samples were positive for Flavivirus IgG antibody by ELISA, but negative for SLEV and WNV antibodies, suggesting that other Flaviviruses may be circulating among WTD in Texas. Finally, these results supported WNV infection among WTD and highlight their potential role as sentinels for the detection of WNV in Texas and warrant further studies to determine the role WTD play in the maintenance and transmission of WNV.

LIMITED ANTIBODY EVIDENCE OF EXPOSURE TO MYCOBACTERIUM BOVIS IN FERAL SWINE (SUS SCROFA) IN THE USA.

Bovine tuberculosis is a chronic disease of cattle ( Bos taurus ) caused by the bacterium Mycobacterium bovis . Efforts have been made in the US to eradicate the disease in cattle, but spillover into wildlife and subsequent spillback have impeded progress in some states. In particular, infection in white-tailed deer ( Odocoileus virginianus ) has been followed by infection in cattle in some Midwestern states. Infection has also been documented in feral swine ( Sus scrofa ) on the Hawaiian island of Molokai and in various European countries, but no large-scale survey of antibody exposure to the bacteria has been conducted in feral swine in the US. We tested 488 sera from feral swine collected near previously documented outbreaks of bovine tuberculosis in cattle and captive cervids, in addition to 2,237 feral swine sera collected across the US from 1 October 2013 to 30 September 2014. While all but one of the samples were antibody negative, the results are important for establishing baseline negative data since feral swine are capable reservoirs and could be implicated in future outbreaks of the disease.

Associations among Habitat Characteristics and Meningeal Worm Prevalence in Eastern South Dakota, USA.

Few studies have evaluated how wetland and forest characteristics influence the prevalence of meningeal worm ( Parelaphostrongylus tenuis ) infection of deer throughout the grassland biome of central North America. We used previously collected, county-level prevalence data to evaluate associations between habitat characteristics and probability of meningeal worm infection in white-tailed deer ( Odocoileus virginianus ) across eastern South Dakota, US. The highest-ranked binomial regression model for detecting probability of meningeal worm infection was spring temperature + summer precipitation + percent wetland; weight of evidence (wi=0.71) favored this model over alternative models, though predictive capability was low (Receiver operating characteristic=0.62). Probability of meningeal worm infection increased by 1.3- and 1.6-fold for each 1-cm and 1-C increase in summer precipitation and spring temperature, respectively. Similarly, probability of infection increased 1.2-fold for each 1% increase in wetland habitat. Our findings highlight the importance of wetland habitat in predicting meningeal worm infection across eastern South Dakota. Future research is warranted to evaluate the relationships between climatic conditions (e.g., drought, wet cycles) and deer habitat selection in maintaining P. tenuis along the western boundary of the parasite.

CLIMATE AND HABITAT INFLUENCE PREVALENCE OF MENINGEAL WORM INFECTION IN NORTH DAKOTA, USA.

The meningeal worm (Parelaphostrongylus tenuis) is a parasite of white-tailed deer (Odocoileus virginianus) and is also a significant pathogen of moose (Alces alces) and other ungulates. Changes in climate or habitat may facilitate range expansion or increase the prevalence of meningeal worm infection in white-tailed deer, resulting in increased exposure to susceptible ungulates. We examined 3,730 white-tailed deer during 2002-05 to determine the prevalence and range of meningeal worm infection in North Dakota, US, and investigated whether these had changed since earlier surveys. We used multiple logistic regression to model potential effects of habitat and climate on prevalence in white-tailed deer. We also examined how habitat influences intermediate hosts by comparing gastropod abundance and microclimate among habitat types. Prevalence in deer was 14% statewide, and prevalence and geographic range had increased since the early 1990 s. Natural woodlands provided the best habitat for intermediate hosts, and increases in prevalence of infection in deer may be due to recent patterns in growing-season precipitation. This study has redefined the geographic distribution of meningeal worm infection and increased understanding of how climate and habitat influence the prevalence and distribution of this parasite.

Metals in obex and retropharyngeal lymph nodes of Illinois white-tailed deer and their variations associated with CWD status

ABSTRACTPrion proteins (PrPC) are cell membrane glycoproteins that can be found in many cell types, but specially in neurons. Many studies have suggested PrPC‘s participation in metal transport and cellular protection against stress in the central nervous system (CNS). On the other hand PrPSc, the misfolded isoform of PrPC and the pathogenic agent in transmissible spongiform encephalopathies (TSE), has been associated with brain metal dyshomeostasis in prion diseases. Thus, changes in metal concentration associated with protein misfolding and aggregation have been reported for human and animal prion diseases, as well as for other neurodegenerative disorders, such as Parkinson's and Alzheimer's disease. The use of metal concentrations in tissues as surrogate markers for early detection of TSEs has been suggested. Studies on the accumulation of metals in free-ranging white-tailed deer have not been conducted. This study established concentrations of copper, iron, manganese, and magnesium in 2 diagnostic tissues used for CWD testing (obex and retropharyngeal lymph nodes (RLN)). We compared these concentrations between tissues and in relation to CWD status. We established reference intervals (RIs) for these metals and explored their ability to discriminate between CWD-positive and CWD-negative animals. Our results indicate that independent of CWD status, white-tailed deer accumulate higher concentrations of Fe, Mn and Mg in RLN than in obex. White-tailed deer infected with CWD accumulated significantly lower concentrations of Mn and Fe than CWD-negative deer. These patterns differed from other species infected with prion diseases. Overlapping values between CWD positive and negative groups indicate that evaluation of these metals in obex and RLN may not be appropriate as a diagnostic tool for CWD infection in white-tailed deer. Because the CWD-negative deer were included in constructing the RIs, high specificities were expected and should be interpreted with caution. Due to the low sensitivity derived from the RIs, we do not recommend using metal concentrations for disease discrimination.

Landscape influence on spatial patterns of meningeal worm and liver fluke infection in white-tailed deer.

Parasites that primarily infect white-tailed deer (Odocoileus virginianus), such as liver flukes (Fascioloides magna) and meningeal worm (Parelaphostrongylus tenuis), can cause morbidity and mortality when incidentally infecting moose (Alces alces). Ecological factors are expected to influence spatial variation in infection risk by affecting the survival of free-living life stages outside the host and the abundance of intermediate gastropod hosts. Here, we investigate how ecology influenced the fine-scale distribution of these parasites in deer in Voyageurs National Park, Minnesota. Deer pellet groups (N = 295) were sampled for the presence of P. tenuis larvae and F. magna eggs. We found that deer were significantly more likely to be infected with P. tenuis in habitats with less upland deciduous forest and more upland mixed conifer forest and shrub, a pattern that mirrored microhabitat differences in gastropod abundances. Deer were also more likely to be infected with F. magna in areas with more marshland, specifically rooted-floating aquatic marshes (RFAMs). The environment played a larger role than deer density in determining spatial patterns of infection for both parasites, highlighting the importance of considering ecological factors on all stages of a parasite's life cycle in order to understand its occurrence within the definitive host.

Identification of a Mycoplasma ovis‐like organism in a herd of farmed white‐tailed deer (Odocoileus virginianus) in rural Indiana

Mycoplasma ovis is a hemoplasma parasite of sheep, goats, and reindeer; however, natural hemoplasma infection in white-tailed deer has not previously been reported. Subsequent to finding many coccoid, bacillary, and ring-shaped organisms, consistent with hemotropic mycoplasmas, on RBCs from a 72-day-old female white-tailed fawn, we sought to (1) identify the putative hemoplasma observed in blood from the fawn, (2) evaluate others in the herd for hemoplasma infection, and (3) identify clinicopathologic characteristics of hemoplasma-infected white-tailed deer. EDTA-anticoagulated whole blood was collected from the fawn and 8 apparently healthy does in the same herd. CBCs were performed on 7 nonclotted samples from the fawn and 6 does. DNA was extracted from all samples, followed by PCR amplification of bacterial (16S rDNA) and protozoal (18S rDNA) genes. The nearly complete 16S rDNA product from the fawn's sample was directly sequenced and compared with known sequences in the GenBank database. Samples from the fawn and 7 of 8 does were PCR-positive using hemoplasma-specific and M ovis-specific protocols. The fawn was PCR-negative for Anaplasma spp., Babesia spp., and Theileria spp. The 16S rDNA sequence from the fawn (GenBank accession number, FJ824847) was most closely related to M ovis (AF338268), having 98.5% sequence identity. The fawn had a mild nonregenerative anemia, a neutrophilic left-shift with toxic change, aspiration bronchopneumonia, and gastrointestinal disease. Hematologic values, including blood film evaluation, in infected does were unremarkable. The M ovis-like organism may have acted as either an opportunistic or primary pathogen in the fawn. The high occurrence of subclinical infections in the does suggests that white-tailed deer may act as wildlife reservoirs for M ovis.

Genetic susceptibility to chronic wasting disease in free-ranging white-tailed deer: Complement component C1q and Prnp polymorphisms

The genetic basis of susceptibility to chronic wasting disease (CWD) in free-ranging cervids is of great interest. Association studies of disease susceptibility in free-ranging populations, however, face considerable challenges including: the need for large sample sizes when disease is rare, animals of unknown pedigree create a risk of spurious results due to population admixture, and the inability to control disease exposure or dose. We used an innovative matched case–control design and conditional logistic regression to evaluate associations between polymorphisms of complement C1q and prion protein (Prnp) genes and CWD infection in white-tailed deer from the CWD endemic area in south-central Wisconsin. To reduce problems due to admixture or disease-risk confounding, we used neutral genetic (microsatellite) data to identify closely related CWD-positive ( n = 68) and CWD-negative ( n = 91) female deer to serve as matched cases and controls. Cases and controls were also matched on factors (sex, location, age) previously demonstrated to affect CWD infection risk. For Prnp, deer with at least one Serine (S) at amino acid 96 were significantly less likely to be CWD-positive relative to deer homozygous for Glycine (G). This is the first characterization of genes associated with the complement system in white-tailed deer. No tests for association between any C1q polymorphism and CWD infection were significant at p < 0.05. After controlling for Prnp, we found weak support for an elevated risk of CWD infection in deer with at least one Glycine (G) at amino acid 56 of the C1qC gene. While we documented numerous amino acid polymorphisms in C1q genes none appear to be strongly associated with CWD susceptibility.

T-Cell mRNA Expression in Response toMycobacterium bovisBCG Vaccination andMycobacterium bovisInfection of White-Tailed Deer

Understanding immune responses of white-tailed deer (WTD) to infection with Mycobacterium bovis provides insight into mechanisms of pathogen control and may provide clues to development of effective vaccine strategies. WTD were vaccinated with either M. bovis BCG strain Pasteur or BCG strain Danish. Both vaccinees and unvaccinated controls were subsequently inoculated with virulent M. bovis via the intratonsillar route. Real-time PCR was used to assess T-cell mRNA expression in peripheral blood leukocytes (PBL) from animals following vaccination and infection. Recall T-cell responses were measured by assessing the relative expression of gamma interferon (IFN-gamma), T-cell-specific T-box transcription factor (Tbet), interleukin 12p40 (IL-12p40), IL-12p35, IL-23p19, FoxP3, IL-17, and GATA3 in PBL stimulated in vitro with purified protein derivative (PPD) of M. bovis or a recombinant fusion protein, ESAT6-CFP10. Animals vaccinated with BCG Danish expressed more IFN-gamma and Tbet than either BCG Pasteur-vaccinated animals or unvaccinated controls. BCG Pasteur-vaccinated animals expressed more GATA3 than either group. After infection, unvaccinated controls expressed more Tbet and IL-12p40 than vaccinated animals. BCG Pasteur-vaccinated animals expressed more GATA3 than either the unvaccinated controls or the BCG Danish-vaccinated animals after infection. Animals were divided into pathology groups to correlate gene expression with severity of pathology. Animals in the visible lesion group expressed more Tbet and IFN-gamma than animals that were culture negative, while Tbet and IFN-gamma expression in the culture-positive, no-visible-lesion group was intermediate. GATA3 expression inversely correlated with pathology. Overall, expression of immune response genes correlated more closely with pathology than vaccination treatment.

Spatial analysis of Mycobacterium bovis infection in white-tailed deer ( Odocoileus virginianus) in Michigan, USA

The wild white-tailed deer ( Odocoileus virginianus) population in Michigan, USA, has endemic Mycobacterium bovis. We determined whether there were spatial clusters of retrospective TB cases in white-tailed deer in northeastern Michigan and identified specific factors associated with the spatial clusters. Data from hunter-harvested deer (age, gender, TB status, and geographic section) were collected by the Michigan Department of Natural Resources (MDNR) during TB surveillance from 1995 to 2002. Land cover (vegetation, land-use) and land type (soil types and drainage characteristics, landforms) described potential deer habitats. Specific locations of large-scale supplemental feeding sites were collected from the MDNR aerial surveillance program from 1997 to 2002. Analyses were conducted using principal components derived from environmental data (and other risk factors) on spatial clusters of disease (identified by the spatial scan statistic). Spatial effects were incorporated into the multivariable analyses by using a neighborhood approach. A total of 420 deer with M. bovis infection were identified from 1995 to 2002, out of 39,451 harvested deer from 3216 TRS units, and spatial clusters of cases were identified. A total of seven principal components of environmental data were generated. Clusters were associated with the presence of large expanses of deciduous forests on moraine ridges separated by low areas of forested wetlands, and the presence of many small lakes. Factors that promoted congregation of deer for extended periods of time (natural cover, access to water, and less human contact) appeared to be associated with increased odds of TB positivity. This suggests that there are specific areas where interventions can be implemented to reduce congregation of animals and disrupt the cycle of infection transmission.

Serologic Evidence of West Nile Virus and St. Louis Encephalitis Virus Infections in White-Tailed Deer (Odocoileus virginianus) from New Jersey, 2001

Serum samples from 689 hunter-killed white-tailed deer (Odocoileus virginianus) collected during the 2001 fall hunting season in New Jersey were tested for neutralizing antibodies to West Nile virus (WNV) and St. Louis encephalitis virus (SLEV) by plaque-reduction neutralization tests. WNV-neutralizing antibodies were detected in six (0.9%) of the samples, and SLEV-neutralizing antibodies were found in 11 (1.6%) of the samples. We provide the first report of WNV infection in white-tailed deer.

Nitric oxide production as an indication of Mycobacterium bovis infection in white-tailed deer (Odocoileus virginianus).

White-tailed deer (Odocoileus virginianus) are reservoirs for Mycobacterium bovis in northeast Michigan, USA. Production of nitric oxide (NO) by activated macrophages is a potent mechanism of mycobacterial killing. The capacity of macrophages to produce NO, however, varies among mammalian species. The objective of this study was to determine if mononuclear cells from white-tailed deer produce nitrite as an indication of NO production and, if so, is NO produced in response to stimulation with M. bovis antigens. Supernatants were harvested from adherent peripheral blood mononuclear cell (PBMC) cultures that had been stimulated with either Mannheimia haemolytica lipopolysaccharide (LPS) or media alone (i.e., no stimulation). Nitrite levels within M. haemolytica LPS-stimulated culture supernatants exceeded (P < 0.05) those detected within supernatants from non-stimulated cultures as well as those detected within supernatants from cultures receiving an inhibitor of NO synthase in addition to M. haemolytica LPS. In response to stimulation with M. bovis antigens, nitrite production by PBMC from M. bovis-infected deer exceeded (P < 0.05) the production by PBMC from non-infected deer. The response of PBMC from infected deer to M. bovis antigens exceeded (P < 0.05) the response of parallel cultures from the same deer receiving no stimulation. The response of PBMC from M. bovis-infected deer to M. avium antigens did not differ from that of PBMC from M. bovis-infected deer to no stimulation or from that of PBMC from non-infected deer to M. avium antigens. These findings indicate that adherent PBMC from white-tailed deer are capable of NO production and that mononuclear cells isolated from M. bovis-infected white-tailed deer produce NO in an antigen-specific recall response.

Tuberculin skin testing in white-tailed deer (Odocoileus virginianus).

The comparative cervical skin test for antemortem diagnosis of tuberculosis was done 169 times on 116 different white-tailed deer of known Mycobacterium bovis infection status. The sensitivity and specificity were 97 and 81%, respectively. The magnitude of change in skin thickness at test sites was not significantly influenced by dosage of inoculum, dissemination of the disease process, or repeated skin testing. However, the magnitude of change in skin thickness was significantly greater in deer infected for less than 109 days than in deer infected for more than 109 days. As used in the present study, the comparative cervical skin test is a sensitive method of antemortem diagnosis of M. bovis infection in white-tailed deer.

Comparison of Postmortem Techniques for the Detection ofMycobacterium Bovisin White-Tailed Deer (Odocoileus Virginianus)

A retrospective study of various diagnostic postmortem techniques used in a 4-year surveillance program for detection of Mycobacterium bovis infection in wild white-tailed deer (Odocoileus virginianus) was conducted. The tests evaluated were routine histopathology, acid-fast staining, detection of acid-fast bacilli in culture, and an M. tuberculosis group-specific genetic probe applied to pure cultures. Each of these techniques were compared with a reference or "gold standard" of mycobacterial culture and identification. Histopathology, the most rapid form of testing for M. bovis infection in white-tailed deer samples, had a sensitivity of 98% and a specificity of 87%, resulting in a positive predictive value of 94%. The detection of acid-fast bacilli by staining was less sensitive than histopathology (90%), but its higher specificity (97%) resulted in a positive predictive value of 99%. The detection of acid-fast bacilli on culture was both highly specific (93%) and sensitive (100%). The group-specific genetic probe had the highest sensitivity and specificity and produced results in complete agreement with those of mycobacterial culture, suggesting that this technique could be used as the new "gold standard" for this particular wildlife tuberculosis surveillance program.

Evaluation of excretory-secretory products and somatic worm antigens for the serodiagnosis of experimental Parelaphostrongylus tenuis infection in white-tailed deer.

Three different antigen preparations of Parelaphostrongylus tenuis were assessed for their effectiveness in an indirect enzyme-linked immunosorbent assay (ELISA) to diagnose experimental infection of white-tailed deer (WTD). The antigen preparations were the excretory-secretory products of third-stage larvae (ES-L3), somatic antigens of third-stage larvae (sL3), and somatic antigens of the adult stage (sA) of P. tenuis. The relative sensitivities of the antigen preparations in indirect ELISA were ES-L3 > sL3 > sA. Immunoglobulin G (IgG) antibodies to ES-L3 and sL3 could be detected 14 days postinfection and were consistently present in all infected animals from the first month to the end of the experiment at 5 months. In contrast, IgG antibodies to sA could not be detected at any time in 2 infected WTD. ES-L3 and sL3 proved reliable in the early detection of anti-P. tenuis antibodies and in the serological monitoring of experimentally infected animals. Significant cross-reactivity between all P. tenuis antigen preparations and sera from animals infected with parasites other than P. tenuis may preclude their use for field diagnosis. Nevertheless, isolation of unique P. tenuis antigen(s) should lead to the development of a specific serological test for infected white-tailed deer.

Development of a model of natural infection with Mycobacterium bovis in white-tailed deer.

The objective of this study was to develop a suitable experimental model of natural Mycobacterium bovis infection in white-tailed deer (Odocoileus virginianus), describe the distribution and character of tuberculous lesions, and to examine possible routes of disease transmission. In October 1997, 10 mature female white-tailed deer were inoculated by intratonsilar instillation of 2 x 10(3) (low dose) or 2 x 10(5) (high dose) colony forming units (CFU) of M. bovis. In January 1998, deer were euthanatized, examined, and tissues were collected 84 to 87 days post inoculation. Possible routes of disease transmission were evaluated by culture of nasal, oral, tonsilar, and rectal swabs at various times during the study. Gross and microscopic lesions consistent with tuberculosis were most commonly seen in medial retropharyngeal lymph nodes and lung in both dosage groups. Other tissues containing tuberculous lesions included tonsil, trachea, liver, and kidney as well as lateral retropharyngeal, mandibular, parotid, tracheobronchial, mediastinal, hepatic, mesenteric, superficial cervical, and iliac lymph nodes. Mycobacterium bovis was isolated from tonsilar swabs from 8 of 9 deer from both dosage groups at least once 14 to 87 days after inoculation. Mycobacterium bovis was isolated from oral swabs 63 and 80 days after inoculation from one of three deer in the low dose group and none of four deer in the high dose group. Similarly, M. bovis was isolated from nasal swabs 80 and 85 days after inoculation in one of three deer from the low dose group and 63 and 80 days after inoculation from two of four deer in the high dose group. Intratonsilar inoculation with M. bovis results in lesions similar to those seen in naturally infected white-tailed deer; therefore, it represents a suitable model of natural infection. These results also indicate that M. bovis persists in tonsilar crypts for prolonged periods and can be shed in saliva and nasal secretions. These infected fluids represent a likely route of disease transmission to other animals or humans.

Serological Diagnosis of Parelaphostrongylus tenuis Infection in White-Tailed Deer and Identification of a Potentially Unique Parasite Antigen

Serological diagnosis of Parelaphostrongylus tenuis infection should offer many advantages over the currently used method of fecal analysis that relies on a patent infection. Toward this end, we investigated the presence of P. tenuis-specific antibodies in experimentally infected white-tailed deer (WTD) and of unique P. tenuis antigens that may be exploited for serodiagnosis. WTD infected with 6, 20 or 100-150 P. tenuis third-stage larvae (L3) had anti-parasite antibodies from as early as 21 days postinoculation (dpi) until the end of the experiment (147 dpi). Peak anti-P. tenuis enzyme-linked immunosorbent assay (ELISA) titers in individual animals ranged from 1:70 to 1:5,700. Serum from infected WTD reacted with 5 distinct P. tenuis L3 antigens (105, 45, 37, 32, and 19 kDa) as detected by the immunoblotting technique. Serum from caribou infected with Parelaphostrongylus andersoni or Elaphostrongylus rangiferi reacted with all antigens except the 37-kDa antigen of L3, indicating that it may be unique to P. tenuis and can serve as a serodiagnostic antigen. The 37-kDa antigen appears to be present in the adult P. tenuis but not adult E. rangiferi or E. cervi. The development of an ELISA utilizing the unique antigen of P. tenuis should lead to a reliable diagnostic assay for P. tenuis infection in WTD.

Host defense responses associated with experimental hemorrhagic disease in white-tailed deer.

Our objectives were to examine the immunity conferred by epizootic hemorrhagic disease virus serotype 2 (EHDV-2) infection in white-tailed deer (Odocoileus virginianus) and determine if this immunity was protective during challenge with homologous (EHDV-2) or heterologous (bluetongue virus serotype 10; BTV-10) virus. Trials were conducted in the fall of 1992 and 1993. In the first experiment, naive white-tailed deer were infected intradermally and subcutaneously with EHDV-2 and monitored via physical examinations, complete blood counts, alpha and beta interferon (IFN) assays, viral isolation, and serology. Infected deer had a wide range of clinical signs in response to infection. Eleven of the 16 deer had body temperature elevations > or = 0.5 C between post-infection day (PID) 4 and 8. Infected deer had decreased lymphocyte counts between PID 6 and 10 that returned to normal levels by PID 17. Severely lymphopenic animals had the most severe clinical signs; five of 10 deer with lymphocyte counts less than 1000 cells/microliters succumbed to the infection. Viremia was detected in all 16 EHDV-2 infected animals by PID 4, and peak viremias occurred between PID 4 and PID 10. Three deer remained viremic until PID 56, the study endpoint. Interferon was first detected between PID 2 and 6. Peak alpha and beta IFN levels coincided with peak viremia in 11 deer. Precipitating and neutralizing antibodies were detected in infected deer by PID 10. In the second experiment, convalescent deer were challenged subcutaneously and intradermally with either EHDV-2 or BTV-10 and similarly monitored. Virus was detected in the blood of all four deer challenged with BTV-10, but viremia was not detected in three EHDV-2-challenged deer. Temperature fluctuations, blood cell parameter changes, and IFN and antibody responses seen in BTV-10-challenged deer were similar to those seen in the initial experiment. Deer challenged with EHDV-2 had mildly increased temperatures, but minimal IFN response and lymphocyte alterations.