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Ehrlichia spp. in cervids from California
J E Foley1, J E Barlough, R B Kimsey
1Center for Companion Animal Health, School of Veterinary Medicine, University of California, Davis 95616, USA.
Insights
Cervids like deer and elk may play a role in maintaining Ehrlichia equi, a cause of human granulocytic ehrlichiosis (HGE), in California. Studies found E. equi in elk and related Ehrlichia species in deer, suggesting their importance in pathogen cycles.
Area of Science:
- Veterinary Pathology
- Infectious Diseases
- Molecular Epidemiology
Background:
- Human granulocytic ehrlichiosis (HGE) and human monocytic ehrlichiosis (HME) are emerging tick-borne diseases.
- Cervids, including deer and elk, are potential reservoirs for tick-borne pathogens.
Purpose of the Study:
- To investigate the role of cervids in the maintenance of Ehrlichia species, including those causing HGE, in California.
- To determine the seroprevalence and PCR prevalence of Ehrlichia species in mule deer, black-tailed deer, and tule elk.
Main Methods:
- Blood samples were collected from cervids between 1992-1997.
- Assays included polymerase chain reaction (PCR), DNA sequencing, and serology.
- Ehrlichia equi isolates were propagated in cell cultures.
Main Results:
- 17% of elk were seropositive for Ehrlichia equi, while deer were seronegative.
- PCR detected Ehrlichia-like species in 38% of deer and E. equi in 5% of deer.
- PCR detected E. equi in 31% of elk.
- DNA sequencing confirmed E. equi in elk and related Ehrlichia species in deer, closely related to strains found in other states.
Conclusions:
- Cervids, particularly elk, may be significant reservoirs for Ehrlichia equi in California.
- These findings suggest cervids contribute to the natural enzootic cycle of E. equi in the region.
- Further research is needed to fully elucidate the role of cervids in Ehrlichia transmission dynamics.
Abstract:
Blood samples from six mule deer (Odocoileus hemionus hemionus), 15 black-tailed deer (O. hemionus columbianus), and 29 elk (Cervus elaphus nannodes) were assayed for human monocytic and human granulocytic ehrlichiosis (HGE) by polymerase chain reaction (PCR), DNA sequencing, and serology to determine whether or not cervids are involved in the maintenance of these potential human pathogens in California (USA). The deer were sampled in August to October 1992-95. The 29 tule elk from Point Reyes National Seashore were sampled in August 1997. All deer were seronegative for antibodies to HGE/Ehrlichia equi, while the E. equi seroprevalence among elk was 17%. The 16S rDNA PCR prevalence in deer was 38% (in mule deer and black-tailed deer) for Ehrlichia-like sp. of white-tailed deer, 5% (one black-tailed deer only) for E. equi, and 0% for E. chaffeensis. The PCR prevalence in elk was 0% for Ehrlichia-like sp. of white-tailed deer, 31% for E. equi, and 0% for E. chaffeensis. The E. equi from two positive elk samples was successfully propagated in HL-60 cell cultures. DNA sequencing confirmed that the Ehrlichia-like sp. sequences from deer in California were closely related to sequences reported from white-tailed deer from Oklahoma and Georgia. The E. equi strain from deer and elk resembled other E. equi strains from California. These results suggest that cervids may be important in the natural maintenance of E. equi in California.