Transmission of Ehrlichia chaffeensis from lone star ticks (Amblyomma americanum) to white-tailed deer (Odocoileus virginianus)

Amblyomma americanum is an aggressive ixodid tick that has been implicated as a vector for several bacterial agents. Among these is Ehrlichia chaffeensis, which causes human monocytic (or monocytotropic) ehrlichiosis. In this study, experimental tick transmission of E. chaffeensis from infected lone star ticks to deer was revisited, and the question of whether it would be possible to re-isolate the organism from deer was asked, because this had not been done previously. Here, we were able to transmit a wild strain of E. chaffeensis from acquisition-fed lone star ticks to white-tailed deer. Ehrlichia chaffeensis was re-isolated from one white-tailed deer on multiple days during the infection and from another deer on one day during the infection. Peak rickettsemias for E. chaffeensis-infected deer were 17 DPI with acquisition-fed ticks and 14 DPI with needle-inoculated deer. This study supports the role of the lone star tick and white-tailed deer as vector and reservoir host for E. chaffeensis, demonstrating culture re-isolation of E. chaffeensis in deer infected by experimental tick transmission for the first time.     

Experimental infection of white-tailed deer (Odocoileus virginianus) with Ehrlichia chaffeensis by different inoculation routes

The infection dynamics of the tick-transmitted organism Ehrlichia chaffeensis were investigated in white-tailed deer (Odocoileus virginianus) using different routes of inoculation. Six deer were each inoculated with 5.4 x 10(6) DH82 cells infected with E. chaffeensis (Arkansas strain) by three different routes: intravenous (n = 2), subcutaneous (n = 2), and intradermal (n = 2). Two control deer were inoculated with uninfected cells. Infections were monitored for 54 days and were continued in one deer from each E. chaffeensis inoculated group for an additional 31 days. All deer inoculated with E. chaffeensis seroconverted (> or = 1: 64) and became 16S rDNA polymerase chain reaction and/or cell culture positive by post-inoculation day 15. There was no apparent (difference in susceptibility to infection between deer inoculated by different routes for the first 50 days based on detection of E. chaffeensis infection by PCR assay of blood or culture isolation. These results demonstrate infection of (deer by intradermal and subcutaneous routes for the first time.     

Susceptibility of red and gray foxes to infection by Ehrlichia chaffeensis

Red foxes (Vulpes vulpes) and gray foxes (Urocyon cinereoargenteus) were evaluated for their susceptibility to experimental infection with Ehrlichia chaffeensis, the causative agent of human monocytotropic ehrlichiosis. Two red foxes and three gray foxes were inoculated intravenously with E. chaffeensis (15B-WTD-GA strain) and were monitored at 7, 14, 21, and 28 days post inoculation (DPI) for evidence of infection using an indirect fluorescent antibody (IFA) assay, light microscopy, polymerase chain reaction (PCR), and cell culture methods. One red fox and one gray fox served as negative controls. Red foxes were susceptible to infection based on reisolation of E. chaffeensis from blood at 7 and 14 DPI, seroconversion by 7 DPI, and positive PCR assays on spleen and lymph nodes at 28 DPI. Morulae were not found in circulating leukocytes and clinical signs or lesions of ehrlichiosis were not observed. In contrast, gray foxes were refractory to infection based on negative results on all culture, PCR, serologic, and microscopic examinations. These findings imply that red foxes, but not gray foxes, are potential vertebrate reservoirs for E. chaffeensis. These findings also illustrate the need to verify serologic evidence of E. chaffeensis infection among wild animals.     

Ehrlichia chaffeensis in archived tissues of a white-tailed deer.

White-tailed deer (Odocoileus virginianus) play an integral role in the natural history of Ehrlichia chaffeensis, the causative agent of human monocytic ehrlichiosis (HME). Paraffinized tissues from a white-tailed deer submitted as a diagnostic case to the Southeastern Cooperative Wildlife Disease Study (Athens, Georgia, USA) in October of 198.5 and originally described as infected with an unidentified rickettsial organisim were re-examined by specific nested polymerase chain reaction (PCR) for evidence of infection with Ehrlichia spp. Ehrlichia chaffeensis was identified from the bone marrow and inguinal lymph node of this deer based on amplification of a characteristic sequence-confirmed 16S rDNA fragment from these tissues. Parallel PCR tests on the same samples were negative for 16S rDNA fragments of the agent of human granulocytic ehrlichiosis (HGE) and for an Ehrlichia-like organism widely distributed in white-tailed deer populations. This report describes detection of E. chaffeensis in archived tissue from a deer collected before the index case of human monocytic ehrlichiosis was established.     

Attempted transmission of Ehrlichia chaffeensis among white-tailed deer by Amblyomma maculatum

A deer was needle-exposed intravenously to Ehrlichia chaffeensis (Rickettsiales: Ehrlichieae) in canine macrophage (DH82) cells and 7 days later was infested with laboratory-reared Amblyomma maculatum (Koch) (Acari:Ixodidae) nymphs for acquisition feeding. After molting, the adult ticks were allowed to feed on a naive deer. The organism was reisolated from the needle-exposed deer by cell culture and E. chaffeensis DNA was detected in the deer's blood by PCR. Similar isolation/recovery techniques were used for the tick-exposed deer and no evidence of infection was found. Although these findings must be considered as preliminary owing to inadequate controls, the data suggest that A. maculatum is probably not a suitable vector for E. chaffeensis.     

Experimental and field studies of Escherichia coli O157:H7 in white-tailed deer

Studies were conducted to evaluate fecal shedding of Escherichia coli O157:H7 in a small group of inoculated deer, determine the prevalence of the bacterium in free-ranging white-tailed deer, and elucidate relationships between E. coli O157:H7 in wild deer and domestic cattle at the same site. Six young, white-tailed deer were orally administered 10(8) CFU of E. coli O157:H7. Inoculated deer were shedding E. coli O157:H7 by 1 day postinoculation (DPI) and continued to shed decreasing numbers of the bacteria throughout the 26-day trial. Horizontal transmission to an uninoculated deer was demonstrated. Although E. coli O157:H7 bacteria were recovered from the gastrointestinal tracts of deer necropsied from 4 to 26 DPI, attaching and effacing lesions were not apparent in any deer. Results are similar to those of inoculation studies in calves and sheep. In field studies, E. coli O157 was not detected in 310 fresh deer fecal samples collected from the ground. It was detected in feces, but not in meat, from 3 of 469 free-ranging deer in 1997. In 1998, E. coli O157 was not detected in 140 deer at the single positive site found in 1997; however, it was recovered from 13 of 305 dairy and beef cattle at the same location. Isolates of E. coli O157:H7 from deer and cattle at this site differed with respect to pulsed-field gel electrophoresis patterns and genes encoding Shiga toxins. The low overall prevalence of E. coli O157:H7 and the identification of only one site with positive deer suggest that wild deer are not a major reservoir of E. coli O157:H7 in the southeastern United States. However, there may be individual locations where deer sporadically harbor the bacterium, and venison should be handled with the same precautions recommended for beef, pork, and poultry.     

Selenium status and antibodies to selected pathogens in white-tailed deer (Odocoileus virginianus) in Southern Minnesota

To determine exposure to a variety of infectious diseases potentially important for native ungulates, livestock, and humans, serum samples from 114 (94 adults, 20 fawns) female white-tailed deer (Odocoileus virginianus) were collected during January 2000-03 from multiple locations in southeast (SE) and southwest (SW) Minnesota. Antibody prevalence was determined for the following pathogens: Mycobacterium avium subsp. paratuberculosis, Leptospira interrogans (six serovars), Anaplasma marginale, Borrelia burgdorferi, Brucella abortus, epizootic hemorrhagic disease virus, and bovine viral diarrhea virus (BVDV) types 1 and 2. Samples collected in 2001 were screened for antibodies against Anaplasma phagocytophilum, and whole blood was submitted for polymerase chain reaction (PCR) testing for A. phagocytophilum and B. burgdorferi. In addition, serum selenium concentrations were evaluated for samples collected during 2001-03. Antibody prevalence and selenium concentration were compared by age-class and geographic region. Antibodies to all of the infectious agents except A. marginale and B. abortus were detected; when detected, antibody prevalence was highest in adults. Deer collected from SE Minnesota had a higher antibody prevalence to B. burgdorferi than SW deer. Blood culture and PCR results for A. phagocytophilum and B. burgdorferi were negative. Antibodies against BVDV (combined types 1 and 2) were more prevalent (chi(2) = 3.617, P< or = 0.029) in deer collected in SW (41%) than in SE (25%) Minnesota. No statistically significant differences in serum selenium concentrations were detected when data were analyzed by age-class or by geographic location.     

Transmission of Neospora caninum between wild and domestic animals

To determine whether deer can transmit Neospora caninum, brains of naturally infected white-tailed deer (Odocoileus virginianus) were fed to 4 dogs; 2 of these dogs shed oocysts. Oocysts from 1 of the dogs were tested by polymerase chain reaction and found to be positive for N. caninum and negative for Hammondia heydorni. The internal transcribed spacer 1 sequence of the new strain (designated NC-deer1) was identical to N. caninum from domestic animals, indicating that N. caninum is transmitted between wild and domestic animals, often enough to prevent divergent evolution of isolated populations of the parasite. NC-deerl oocysts were administered to a calf that developed a high antibody titer, providing evidence that N. caninum from wildlife can infect cattle. In addition, N. caninum antibody seroprevalence was detected in 64/164 (39%) free-ranging gray wolves (Canis lupus), 12/113 (11%) coyotes (Canis latrans), 50/193 (26%) white-tailed deer, and 8/61 (13%) moose (Alces alces). These data are consistent with a sylvatic transmission cycle of N. caninum between cervids and canids. We speculate that hunting by humans favors the transmission of N. caninum from deer to canids, because deer carcasses are usually eviscerated in the field. Infection of canids in turn increases the risk of transmitting the parasite to domestic livestock.     

Natural and experimental infection of white-tailed deer (Odocoileus virginianus) from the United States with an Ehrlichia sp. closely related to Ehrlichia ruminantium

An Ehrlichia sp. (Panola Mountain [PM] Ehrlichia sp.) closely related to Ehrlichia ruminantium was recently detected in a domestic goat experimentally infested with lone star ticks (LSTs, Amblyomma americanum) collected from Georgia, USA. The infected goat exhibited pyrexia and mild clinical pathologic abnormalities consistent with ehrlichiosis. At least two other Ehrlichia species (Ehrlichia chaffeensis and Ehrlichia ewingii) are maintained in nature by a cycle involving LSTs as the primary vector and white-tailed deer (Odocoileus virginanus) as a known or suspected reservoir. To investigate the possibility that white-tailed deer are potential hosts of the PM Ehrlichia sp., whole blood samples collected from 87 wild deer from 2000 to 2002 were screened with a species-specific nested PCR assay targeting the citrate synthase gene. In addition, two laboratory-raised white-tailed deer fawns were each infested with 120 wild-caught LST adults from Missouri, USA, and blood samples were periodically collected and tested for the PM Ehrlichia sp. Of 87 deer tested from 20 locations in the southeastern United States, three (3%) deer from Arkansas, North Carolina, and Virginia were positive for the PM Ehrlichia sp. Wild-caught ticks transmitted the PM Ehrlichia sp. to one of two deer fawns, and colony-reared nymphal LSTs acquired the organism from the deer, maintained it transstadially as they molted to adults, and transmitted the PM Ehrlichia sp. to two na?ve fawns. These findings indicate that white-tailed deer are naturally and experimentally susceptible to infection with an Ehrlichia sp. closely related to E. ruminantium and are able to serve as a source of infection to LSTs.     

Experimental and Field Studies of Escherichia coli O157:H7 in White-Tailed Deer

Studies were conducted to evaluate fecal shedding of Escherichia coli O157:H7 in a small group of inoculated deer, determine the prevalence of the bacterium in free-ranging white-tailed deer, and elucidate relationships between E. coli O157:H7 in wild deer and domestic cattle at the same site. Six young, white-tailed deer were orally administered 10⁸ CFU of E. coli O157:H7. Inoculated deer were shedding E. coli O157:H7 by 1 day postinoculation (DPI) and continued to shed decreasing numbers of the bacteria throughout the 26-day trial. Horizontal transmission to an uninoculated deer was demonstrated. Although E. coli O157:H7 bacteria were recovered from the gastrointestinal tracts of deer necropsied from 4 to 26 DPI, attaching and effacing lesions were not apparent in any deer. Results are similar to those of inoculation studies in calves and sheep. In field studies, E. coli O157 was not detected in 310 fresh deer fecal samples collected from the ground. It was detected in feces, but not in meat, from 3 of 469 free-ranging deer in 1997. In 1998, E. coli O157 was not detected in 140 deer at the single positive site found in 1997; however, it was recovered from 13 of 305 dairy and beef cattle at the same location. Isolates of E. coli O157:H7 from deer and cattle at this site differed with respect to pulsed-field gel electrophoresis patterns and genes encoding Shiga toxins. The low overall prevalence of E. coli O157:H7 and the identification of only one site with positive deer suggest that wild deer are not a major reservoir of E. coli O157:H7 in the southeastern United States. However, there may be individual locations where deer sporadically harbor the bacterium, and venison should be handled with the same precautions recommended for beef, pork, and poultry.     

Infections of granulocytic ehrlichiae and Borrelia burgdorferi in white-tailed deer in Connecticut

Serum or whole blood samples, obtained from 141 white-tailed deer (Odocoileus virginianus) in Connecticut (USA) during 1980, 1991, and 1996, were analyzed to detect past or current infections of Ehrlichia phagocytophila genogroup organisms and Borrelia burgdorferi. When the BDS or NCH-1 strains of granulocytic ehrlichiae were used separately in indirect fluorescent antibody (IFA) staining methods, antibody positivity rates varied from 25 to 64% in 1991 and 1996, respectively. All 50 sera tested from 1980 collections were negative. Although percentages of sera with B. burgdorferi antibodies, as detected by an enzyme-linked immunosorbent assay, also differed (23 to 53%), there were coexisting antibodies to both bacteria in 20 (49%) of 41 sera. In tests on specificity, 19 deer sera with ehrlichial antibodies also were tested by IFA staining procedures for Anaplasma marginale antibodies; one serum with a titer of 1:5,120 to ehrlichial antigen reacted to A. marginale antigen at a serum dilution of 1:320. In parallel analyses of 69 sera, results of Western blot analyses for ehrlichial infections in deer were concordant (72% agreement) with those of IFA staining methods containing ehrlichial antigen. All positive immunoblots showed bands to peptides of the NCH-1 strain of the human granulocytic ehrlichiosis (HGE) agent having molecular masses of about 44, 105, or 110 kDa. In polymerase chain reaction (PCR) studies of blood samples from 63 deer, 11 (18%) specimens were positive for 16S ribosomal DNA of an Ehrlichia phagocytophila genogroup organism, whereas 23 (37%) samples were positive for the DNA of the 44 kDa gene of the HGE agent. White-tailed deer are exposed to different tick-borne bacteria in areas where Ixodes scapularis ticks are abundant and may, in some instances, have had concurrent infections.     

Review of the 2012 Epizootic Hemorrhagic Disease Outbreak in Domestic Ruminants in the United States

An unusually large number of cases of Epizootic hemorrhagic disease (EHD) were observed in United States cattle and white-tailed deer in the summer and fall of 2012. USDA APHIS Veterinary Services area offices were asked to report on foreign animal disease investigations and state diagnostic laboratory submissions which resulted in a diagnosis of EHD based on positive PCR results. EHD was reported in the following species: cattle (129 herds), captive white-tailed deer (65 herds), bison (8 herds), yak (6 herds), elk (1 herd), and sheep (1 flock). A majority of the cases in cattle and bison were found in Nebraska, South Dakota, and Iowa. The majority of cases in captive white-tailed deer were found in Ohio, Iowa, Michigan, and Missouri. The most common clinical sign observed in the cattle and bison herds was oral lesions. The major observation in captive white-tailed deer herds was death. Average within-herd morbidity was 7% in cattle and bison herds, and 46% in captive white-tailed deer herds. The average within-herd mortality in captive white-tailed deer herds was 42%.     

Prevalence and isolation of Toxoplasma gondii from white-tailed deer in Alabama

Nineteen white-tailed deer (Odocoileus virginianus) from 5 counties in Alabama were examined for infection with Toxoplasma gondii. Twenty-gram samples of heart tissue were bioassayed in mice, serum was examined for T. gondii antibodies using the direct agglutination test, and sections of heart muscle were examined histologically for tissue cysts. Toxoplasma gondii was isolated from 4 of 19 (21%) white-tailed deer hearts. Antibody titers of greater than or equal to 1:50 were found in sera from 7 of 16 (44%) white-tailed deer. Histological examinations of tissue sections from white-tailed deer hearts were negative for T. gondii.     

Immunologic and molecular identification of Babesia bovis and Babesia bigemina in free-ranging white-tailed deer in northern Mexico

The suitability of white-tailed deer (Odocoileus virginianus) as hosts for the cattle ticks Rhipicephalus (Boophilus) microplus and Rhipicephalus (Boophilus) annulatus, has been well documented. These ticks have a wide host range, and both transmit Babesia bovis and Babesia bigemina, the agents responsible for bovine babesiosis. Although this disease and its vectors have been eradicated from the United States and some states in northern Mexico, it still is a problem in other Mexican states. It is not known if wild cervids like white-tailed deer can act as reservoirs for bovine babesiosis. The purpose of this study was to determine if B. bovis and B. bigemina or antibodies against them occur in white-tailed deer in the states of Nuevo Leon and Tamaulipas, Mexico. Twenty blood samples from white-tailed deer from two ranches were collected and tested with a nested polymerase chain reaction (nested PCR) and indirect immunofluorescence antibody test (IFAT) for B. bovis and B. bigemina. Eleven samples were positive for B. bigemina and four for B. bovis by nested PCR; amplicon sequences were identical to those reported in GenBank for B. bovis (Rap 1) and B. bigemina. Results of the IFA test showed the presence of specific antibodies in serum samples. This is the first report of the presence of B. bovis and B. bigemina in white-tailed deer using these techniques and underscores the importance of cervids as possible reservoirs for bovine babesiosis.     

Serological evidence of bovine herpesvirus 1-related virus infection in the white-tailed deer population on Anticosti Island, Quebec

High white-tailed deer (Odocoileus virginianus) population densities and the occurrence of harsh environmental conditions are present on Anticosti Island, located in the Gulf of Saint-Lawrence (Quebec, Canada). This island is the northernmost region of white-tailed deer distribution in northeastern North America. The aim of this work was to determine whether a herpesvirus serologically related to bovine herpesvirus 1 (BHV1) may occur in a stressed white-tailed deer population. One hundred one deer sera were collected from apparently healthy animals during the hunting season from September to late November 1985. Fifty-three percent of tested deer were positive to the seroneutralization test using Colorado strain of BHV1 virus. Higher percentages of seropositivity were observed in animals of both sexes greater than 4-yr-old. Analysis of antibody titers in seropositive animals according to age suggests that BHV1-related viral infection is endemic in the Anticosti Island deer population. It is postulated that environmental stress may induce immunosuppression of certain infected and/or carrier animals in their population that shed virus for long periods of time.     

Parasites, diseases and health status of sympatric populations of sambar deer and white-tailed deer in Florida

From December 1983 to December 1984 a study on parasites, diseases and health status was conducted on sympatric populations of sambar deer (Cervus unicolor) and white-tailed deer (Odocoileus virginianus) from St. Vincent Island, Franklin County, Florida. Ten sambar and six white-tailed deer were examined. White-tailed deer had antibodies to epizootic hemorrhagic disease virus and bluetongue virus. Serologic tests for antibodies to the etiologic agents of bovine virus diarrhea, infectious bovine rhinotracheitis, vesicular stomatitis, parainfluenza 3, brucellosis, and leptospirosis were negative in both species of deer. White-tailed deer harbored 19 species of parasites; all were typical of the parasite fauna of this species in coastal regions of the southeastern United States. Sambar deer harbored 13 species of parasites, which apparently were derived largely from white-tailed deer. The only exception was Dermacentor variabilis which occurs frequently on wild swine on the island. The general health status of sambar deer appeared to be better than that of white-tailed deer. This was hypothesized to result from the sambar deer's utilization of food resources unavailable or unacceptable to white-tailed deer and to the absence and/or lower frequency of certain pathogens in sambar deer.     

Parasites and condition of coexisting populations of white-tailed and exotic deer in south-central Texas.

We examined the parasites and physical condition of coexisting white-tailed deer (Odocoileus virginianus), axis deer (Axis axis), fallow deer (Dama dama), and sika deer (Cervus nippon) on the YO Ranch (Kerr County, Texas, USA) during December 1982 to January 1984. White-tailed deer harbored 12 species of parasites. Exotic deer were infected with nine species of parasites. All parasites recovered from exotic deer and white-tailed deer have been reported from white-tailed deer. Exotic deer had higher condition ratings than white-tailed deer.     

Antibodies to vesicular stomatitis New Jersey type virus in white-tailed deer on Ossabaw Island, Georgia, 1985 to 1989.

From 1985 to 1989, 491 serum samples were collected from white-tailed deer (Odocoileus virginianus) on Ossabaw Island, Georgia (USA) and were tested for neutralizing antibodies to New Jersey and Indiana type vesicular stomatitis viruses. Prevalence of antibodies to vesicular stomatitis New Jersey (VSNJ) virus in deer for the 5-yr period was 43%. Prevalence of antibodies differed by year (P less than 0.0001), and was dependent on age class (P less than 0.0001) and location on the island (P less than 0.0001). Of 173 deer sampled from other locations in the southeastern United States, only two had VSNJ antibody titers normally considered positive (greater than or equal to 1: 32). The positive deer were from Union County, Arkansas (USA) and Wakulla County, Florida (USA). No evidence of exposure to vesicular stomatitis Indiana Virus was observed.     

Serologic survey of white-tailed deer on Anticosti Island, Quebec for bovine herpesvirus 1, bovine viral diarrhea, and parainfluenza 3.

In 1985 unusual mortality was observed among the 3- to 4-yr-old white-tailed deer (Odocoileus virginianus) on Anticosti Island, Québec (Canada). A viral pathogen was suspected to be the cause of the deaths. Thus, a serologic survey for bovine herpesvirus 1 (BHV-1), bovine viral diarrhea (BVD) virus and parainfluenza-3 (PI-3) virus was conducted. We examined 396 deer sera from 1985. Results indicated that the high mortality mainly afflicted 3- to 4-yr-old deer. In 1985, 57% of deer sampled were seropositive for viral neutralizing antibodies against BHV-1. Prevalences decreased over the next 2 yr of the survey. Prevalence of antibodies against PI-3 virus, determined by hemagglutination inhibition test, remained high (82% to 84%) for the 3 yr period. No deer were seropositive for neutralizing antibodies against BVD virus during the survey period. Analysis of antibodies against BHV-1 and PI-3 viruses according to sex, age and antibody titers revealed that an epizootic BHV-1 infection occurred in 1985; PI-3 infection appears to be enzootic in Anticosti deer.     

Seroconversion rates to Jamestown Canyon virus among six populations of white-tailed deer (Odocoileus virginianus) in Indiana

The annual seroconversion of fawns, yearlings, and adult white-tailed deer (Odocoileus virginianus) to Jamestown Canyon virus (California group) was followed at six Indiana sites from 1981 through 1984. In all, sera from 1,642 deer (515 fawns, 618 yearlings, and 509 adults) were tested for neutralizing antibody to three California serogroup viruses: Jamestown Canyon, La Crosse, and trivittatus. Virtually all deer with specific neutralizing antibody showed evidence of a prior infection with Jamestown Canyon virus; only three deer showed evidence of a prior infection with only La Crosse virus and none showed evidence of an infection with only trivittatus virus. While there were no significant differences in antibody prevalence to Jamestown Canyon virus between yearling and adult deer at any site, fawns had significantly lower antibody prevalences than either of the two older age groups. Significant differences in antibody prevalence were found between northern versus southern populations of white-tailed deer in Indiana, however, no significant differences were found among the four northern populations or between the two southern populations. The mean antibody prevalences in the two southern fawn, yearling, and adult populations were 15%, 38%, and 41% respectively, while the prevalences in the four northern fawn, yearling, and adult populations were 5%, 67%, and 67% respectively. These different prevalences (northern vs. southern) correlate with the higher Jamestown Canyon virus antibody prevalence in human residents of northern Indiana (2-15%) compared to residents of southern Indiana (less than 2%) found in other studies. The significantly lower prevalence of antibody to Jamestown Canyon virus in fawns is attributed to maternal antibody protecting them from a primary infection their first summer. Yearling deer showed high rates of seroconversion following their second summer of life. These results suggest that infection of white-tailed deer in Indiana with Jamestown Canyon virus is a common phenomenon.