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Journal of Clinical Microbiology, September 1998, p. 2645-2651, Vol. 36, No. 9
Department of Companion Animal and Special
Species Medicine, College of Veterinary Medicine, North Carolina
State University, Raleigh, North Carolina 27606
Received 2 February 1998/Returned for modification 29 April
1998/Accepted 9 June 1998
Historically, disease manifestations in dogs seroreactive to
Ehrlichia canis antigens by indirect immunofluorescent
antibody testing have been attributed to infection with either
E. canis or Ehrlichia ewingii. A 1996 study by Dawson and colleagues provided PCR evidence that healthy dogs
from southeastern Virginia could be naturally infected with
Ehrlichia chaffeensis. This observation stimulated us to
determine which Ehrlichia spp. infected sick dogs that were
referred to our hospital from the same region. Based upon PCR
amplification with species-specific primers, sick dogs seroreactive to
E. canis antigens were determined to be infected with
four Ehrlichia species: E. canis,
E. chaffeensis, E. equi, and
E. ewingii. Coinfection with three
Ehrlichia species (E. canis, E. ewingii, and E. equi) was
documented for one dog. An additional canine pathogen presumed to be
tick transmitted, Bartonella vinsonii subsp.
berkhoffii, was identified in 7 of 12 dogs. Importantly, our results indicate that in naturally infected dogs, E. chaffeensis can cause severe disease manifestations that are
clinically and serologically indistinguishable from disease
manifestations of E. canis or E. ewingii. In addition, our findings support the efficacy of
doxycycline for treatment of E. canis, E. equi, and E. ewingii infections but indicate
that, based upon the persistence of E. chaffeensis DNA
for 1 year following treatment, E. chaffeensis infection in dogs may be more refractory to doxycycline treatment. Undetected coinfection with Bartonella may also complicate
the evaluation of treatment efficacy while resulting in disease
manifestations that mimic ehrlichiosis.
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Sequential Evaluation of Dogs Naturally Infected with
Ehrlichia canis, Ehrlichia chaffeensis,
Ehrlichia equi, Ehrlichia ewingii, or
Bartonella vinsonii
*
Corresponding author. Mailing address: Department of
Companion Animal and Special Species Medicine, College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough St., Raleigh, NC 27606. Phone: (919) 829-4234. Fax: (919) 829-4336. E-mail:
ed_breitschwerdt{at}ncsu.edu.
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