Volume 18, Number 8—August 2012
Zoonotic Pathogens among White-Tailed Deer, Northern Mexico, 2004–2009
To the Editor: Intense wildlife management for hunting affects risks associated with zoonotic pathogens (1). White-tailed deer (Odocoileus virginianus) are increasingly managed by fencing, feeding, watering, and translocation to increase incomes from hunting in northern Mexico (2). These deer also play a major role in dissemination and reintroduction of pathogens and vectors from Mexico into the United States (3,4). White-tailed deer are suitable reservoir hosts for Mycobacterium bovis (1), and an M. bovis-positive white-tailed deer was recently found in Tamaulipas in northeastern Mexico (2). Brucellosis is widespread in many animal hosts in Latin America (5) and thus of interest in white-tailed deer. Another major zoonosis, sometimes linked to raw deer meat consumption, is hepatitis E, which is caused by genotypes of hepatitis E virus (HEV) (6). HEV is increasingly prevalent in red deer (Cervus elaphus) (7), but its prevalence in white-tailed deer is unknown.
The objective of this study was to determine the prevalence of zoonotic pathogens in white-tailed deer in northern Mexico. This study was conducted under a scientific collecting permit issued by the Mexican Division of Animal and Wildlife Health and on 8 ranches in 3 states in northern Mexico (≈26–28°N, 99–100°W).
Serum samples (n = 347) were collected during 2004–2009 in a cross-sectional survey for antibodies against HEV, Brucella spp., and mycobacteria. Deer were opportunistically sampled during live-capture operations as described by Cantú et al. (8). Bleeding was performed by using jugular venipuncture and vacuum tubes without anticoagulant. Samples were allowed to clot and centrifuged to collect serum that was stored at −20°C.
Serum samples were tested for IgG against HEV by ELISA as described (7). Serum samples were also tested for antibodies against Brucella spp. by using a commercial ELISA (Ingezim Brucella Compac 2.0 Ingenasa, Madrid, Spain), according to the manufacturer’s instructions. Detection of antibodies cross-reacting with 2 widely used mycobacterial antigens, bovine purified protein derivative (PPD) and paratuberculosis protoplasmatic antigen 3 (PPA3), was conducted as described (9). The sensitivity and specificity of this assay have not been established for white-tailed deer, but it has been used in seroprevalence studies of wild boar and fallow deer (9,10).
Insufficient volumes of serum samples prevented testing for antibodies against all pathogens (Table). Limited serum volume and lack of other (organ) samples also precluded additional analyses to verify presence of pathogens.
Prevalence was 62.7% (95% CI 54%–70%) for antibodies against HEV, 0.4% (95% CI 0%–2%) for antibodies against Brucella spp., 8.9% (95% CI 6%–13%) for antibodies against bovine PPD, and 2.6% (95% CI 1%–5%) for antibodies against PPA3 (Table). Antibody responses to bovine PPD were detected in deer from at 6 of 8 sampling sites; in deer from 3 of these sites, antibodies were also detected against PPA3 antigen. Seroprevalence against bovine PPD was higher than that against PPA3 (χ2 10.9, df 1, p<0.01).
This cross-sectional survey of white-tailed deer in northern Mexico detected antibodies to several pathogens relevant to public and animal health. High prevalence of antibodies against HEV and frequent detection of antibodies against mycobacterial antigens are public health concerns. Prevalence of antibodies against HEV were 3× higher than that reported for red deer in Europe (7). This result suggests wide circulation of HEV in the study region and warrants further research, including detection and sequencing of virus RNA. Low Brucella spp. antibody prevalence confirms results of a study in this region (8).
Antibody responses to bovine PPD were detected in serum samples from deer from most sampling sites, occasionally in the absence of antibodies against PPA3. These results, and a recent report of an M. bovis–positive white-tailed deer from this region (2), suggest that these deer may be contracting M. bovis in northern Mexico. If one considers that white-tailed deer are M. bovis reservoirs in other parts of North America and that risk factors such as supplemental feeding are present in northern Mexico, there is a high risk for pathogen transmission to animals and humans (1). White-tailed deer are probably exposed to several human pathogens that are relevant to human and animal health in northern Mexico.
Although this cross-sectional survey provided only an indication of pathogen prevalence in the study populations, high antibody prevalence to HEV and mycobacterial antigens requires antigen-targeted surveillance. Risks associated with pathogen translocation by white-tailed deer are also relevant to neighboring states in Mexico and the United States.
We thank M. Villar and B. Peralta for providing ELISA antigen and A. Cantú and co-workers for providing deer serum samples.
This study was supported by the Caesar Kleberg Wildlife Research Institute, Texas A&M University–Kingsville, and European Union Framework Program grant 212414 TB-STEP.
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