Development of antibodies to and PCR detection of Ehrlichia spp. in dogs following natural tick exposure

Vet Microbiol. 2014 Oct 10;173(3-4):379-84. doi: 10.1016/j.vetmic.2014.08.006. Epub 2014 Aug 15.

Abstract

Dogs exposed to ticks in the southern US may become infected with multiple species of Ehrlichia. To better define infection risk, blood samples collected from 10 dogs infested with ticks via a natural infestation model were evaluated by blood smear examination, PCR, patient-side ELISAs (SNAP® 4Dx® and SNAP® 4Dx® Plus), IFA, and peptide based ELISA for evidence of infection with Ehrlichia canis, E. chaffeensis, and/or E. ewingii. Although morulae were rarely identified in blood smears, every dog (10/10) became infected with Ehrlichia spp. as evidenced by nested PCR detection of E. chaffeensis (7/10) and E. ewingii DNA (10/10); real-time PCR detection of E. chaffeensis (0/10) and E. ewingii (9/10); seroconversion on two different patient-side ELISAs (4/10 or 10/10); seroconversion on IFA to E. canis (10/10, maximum inverse titer=128-4096, GMTMAX=548.7) and E. chaffeensis (10/10, maximum inverse titer=1024-32,768, GMTMAX=4096); and seroconversion on peptide specific ELISA to E. chaffeensis VLPT (7/10) and E. ewingii p28 (9/10). Rickettsemia with E. chaffeensis and E. ewingii, as determined by nested PCR, persisted in dogs for an average of 3.2 or 30.5 days, respectively. Ehrlichia canis was not detected in any dog by any method, and no dogs developed signs of clinical disease. Our data suggest that in areas where ticks are common, dogs are at high risk of infection with Ehrlichia spp., particularly E. ewingii and E. chaffeensis, and can serve as a sentinel for monitoring for the presence of these zoonotic pathogens.

Keywords: Dog; Ehrlichia chaffeensis; Ehrlichia ewingii; Ehrlichiosis; Ticks.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Bacterial / blood
  • Base Sequence
  • Blood Cell Count / veterinary
  • Dog Diseases / epidemiology*
  • Dog Diseases / immunology
  • Dog Diseases / microbiology*
  • Dogs / parasitology*
  • Ehrlichia / genetics
  • Ehrlichia / immunology
  • Ehrlichia / isolation & purification*
  • Ehrlichiosis / epidemiology
  • Ehrlichiosis / immunology
  • Ehrlichiosis / veterinary*
  • Enzyme-Linked Immunosorbent Assay / veterinary
  • Molecular Sequence Data
  • Oklahoma / epidemiology
  • Real-Time Polymerase Chain Reaction / veterinary
  • Sentinel Surveillance / veterinary
  • Sequence Analysis, DNA
  • Ticks / microbiology*

Substances

  • Antibodies, Bacterial