Comparison of results for serologic testing and a polymerase chain reaction assay to determine the prevalence of stray dogs in eastern Tennessee seropositive to Ehrlichia canis.
OBJECTIVE
To determine the prevalence of stray dogs in eastern Tennessee seropositive to Ehrlichia canis and examine the correlation between results for an ELISA, indirect immunofluorescent antibody (IFA) test, and polymerase chain reaction (PCR) assay.


METHODS
Blood samples obtained from 90 adult dogs admitted to an animal shelter in eastern Tennessee.


METHODS
Serum samples were analyzed for antibodies against E. canis by use of a commercially available ELISA kit, 2 IFA tests, and a PCR assay; testing was performed at the University of Tennessee (TN) and North Carolina State University (NCSU). The PCR amplification was performed by use of DNA extracted from EDTA-anticoagulated blood and primers designed to amplify DNA of Ehrlichia spp.


RESULTS
Antibodies against E. canis were detected in only 1 dog by use of the ELISA. By IFA testing at TN, 10 of 90 (11%) dogs were seroreactive against E. canis antigens, all of which had medium to high titers to E. canis. Only 5 of the 10 TN seroreactors were also reactive against E. canis antigens in IFA tests conducted at NCSU, and all 5 had low to medium titers. The DNA of Ehrlichia spp was not amplified in any blood samples by use of PCR assays conducted at the TN or NCSU.


CONCLUSIONS
The discordant ELISA, IFA, and PCR results obtained in this study were unexpected and may have been related to exposure of dogs to an Ehrlichia species other than E. canis, such as E. ewingii.
Seaman
Rebecca L
RL
Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996, USA.
Kania
Stephen A
SA
Hegarty
Barbara C
BC
Legendre
Alfred M
AM
Breitschwerdt
Edward B
EB
D000818:Animals; D004283:Dog Diseases / Q000453:epidemiology* / Q000382:microbiology*; D004285:Dogs; D041061:Ehrlichia canis; D016873:Ehrlichiosis / Q000453:epidemiology / Q000662:veterinary*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000662:veterinary; D019084:Fluorescent Antibody Technique, Indirect / Q000379:methods / Q000662:veterinary; D016133:Polymerase Chain Reaction / Q000379:methods / Q000662:veterinary; D016036:Seroepidemiologic Studies; D012698:Serologic Tests / Q000662:veterinary; D013714:Tennessee / Q000453:epidemiology