Original articleAnaplasma odocoilei sp. nov. (family Anaplasmataceae) from white-tailed deer (Odocoileus virginianus)
Introduction
In the United States, white-tailed deer (WTD; Odocoileus virginianus) are infected with multiple tick-transmitted rickettsiae in the genera Ehrlichia and Anaplasma (Lockhart et al., 1997a, Little et al., 1998, Yabsley et al., 2002, Yabsley et al., 2008a). Three species, E. chaffeensis, E. ewingii, and Anaplasma (A.) phagocytophilum are zoonotic pathogens and infect a wide range of mammalian species (Dumler et al., 2001). A fourth organism, detected by PCR in the blood of wild WTD, has been referred to as WTD agent or Ehrlichia sp. of WTD (Dawson et al., 1996, Little et al., 1997) and was recently isolated in tick cell culture and identified as a member of the genus Anaplasma (Munderloh et al., 2003).
This Anaplasma sp. is common among white-tailed deer populations in the southeastern United States and has been reported from Georgia, Oklahoma, Nebraska, Virginia, and Missouri (Little et al., 1997, Lockhart et al., 1997b, Arens et al., 2003; Yabsley, unpublished). A closely-related species has been detected in mule deer (O. hemionus hemionus) and black-tailed deer (O. hemionus columbianus) from California (Foley et al., 1998, Yabsley et al., 2005) and mule deer and white-tailed deer from Arizona (Yabsley et al., 2005). However, additional data are needed to determine if this Anaplasma represents a variant of the Anaplasma sp. detected in white-tailed deer in the southeastern United States. In the southeastern United States, it has significant temporal and spatial associations with lone star tick (Amblyomma americanum) infestation (Brandsma et al., 1999). Additionally, this Anaplasma sp. has been detected by polymerase chain reaction (PCR) in field-collected Amblyomma americanum ticks from Missouri (GenBank accession number ELU52514). These previous studies suggest that this Anaplasma sp. infects white-tailed deer and could be transmitted by Amblyomma americanum, similar to 2 important zoonotic rickettsiae, E. chaffeensis and E. ewingii (Ewing et al., 1995, Little et al., 1998, Yabsley et al., 2003). The significance of this organism as a pathogen of deer or as a potential zoonotic agent is currently unknown. Previous analysis of partial 16S rRNA and GroESL gene sequences of this Anaplasma sp. indicates that it is most closely related to A. platys, a canine rickettsia that infects platelets of dogs and potentially humans (Dawson et al., 1996, Arraga-Alvarado et al., 1999, Dumler et al., 2001, Sumner et al., 2003).
In the current study, we experimentally infected deer with this Anaplasma sp. in order to (i) investigate infection dynamics and cellular tropism of this organism in vivo, (ii) conduct a small-scale Amblyomma americanum transmission study, and (iii) more fully characterize the morphologic, molecular, and antigenic relationships of this so far undescribed Anaplasma sp.
Section snippets
Experimental animals and procedures
Nine orphaned white-tailed deer fawns (WTD76, 77, 81, 86, 128, and 135, and Deer 1, 2, and 3) were hand-raised and housed in a tick-free building at the College of Veterinary Medicine, UGA, Athens, GA. Fawns were acquired within 1–3 days of birth, and prior to inoculation, tested negative for E. chaffeensis, E. ewingii, A. phagocytophilum, and the Anaplasma sp. by PCR and negative for antibodies to E. chaffeensis and A. phagocytophilum by indirect fluorescent antibody (IFA) assays as described (
Infection dynamics and clinical outcome
All 6 deer experimentally inoculated with the Anaplasma sp. became infected and remained infected, as determined by RT-nPCR of blood, at every sampling date for 100–200+ days until euthanasia (Table 3). Light microscopy of Giemsa-stained thin blood smears of acutely infected deer revealed tiny, dark, spherical structures in platelets consistent with Anaplasma inclusions. Clinical signs of illness (i.e., fever, body condition, activity level) were not apparent in any of the infected deer. All 3
Discussion
Numerous studies have detected a previously undescribed Anaplasma sp. in white-tailed deer throughout the southeastern United States (Little et al., 1997, Lockhart et al., 1997b). An identical, or closely related, organism has been detected in Odocoileus spp. from the western United States (Foley et al., 1998, Yabsley et al., 2005). Recently, the Anaplasma sp. was isolated in tick cells (Munderloh et al., 2003). In the current study, we determined that white-tailed deer were experimentally
Description of Anaplasma odocoilei sp. nov.
Anaplasma odocoilei (odo coil’ei L. gen. n. odocoileus, of deer in the genus Odocoileus. The reference strain is UMUM76T (=CSUR A1). Originally isolated from a white-tailed deer fawn that was experimentally infected with A. odocoilei by inoculation with blood from naturally infected adult deer from central Georgia, USA (Munderloh et al., 2003). Has also been detected in white-tailed deer in numerous locations in the eastern United States (Little et al., 1997, Lockhart et al., 1997b).
Acknowledgments
We are grateful to David Stallknecht for insightful guidance, Jane Huffman for facilitating acquisition of fawns, Andrea Varela-Stokes and Molly Murphy for significant technical help, Mary Ard for electron microscopy expertise, and Jeff Tucker and Frank Waters for animal handling and husbandry assistance. Work was supported primarily by the National Institutes of Allergy and Infectious Diseases (5 R01 AI044235-02). Further support was provided by the Federal Aid to Wildlife Restoration Act (50
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- 1
Current address: Wyoming Department of Game and Fish, 5400 Bishop Boulevard, Cheyenne, WY 82006, USA.
- 2
Current address: Division of Microbiology and Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, 20892 USA.
- 3
Current address: Animal Clinical Investigation, LLC, 4926 Wisconsin Avenue NW, Washington, DC 20016, USA.