Canine Heartworm (Dirofilaria immitis) Infection and Immunoglobulin G Antibodies Against Wolbachia (Rickettsiales: Rickettsiaceae) in Stray Dogs in Bangkok, Thailand

Abstract

Canine heartworm (Dirofilaria immitis) infection in stray dogs was studied by using parasitological (fresh blood smear, thin blood smear, thick blood smear, and modified Knott’s test) and serological methods. Blood samples were collected from stray dogs in Bangkok metropolitan area during 2006 and 2008. There were 10% (50/500) of stray
dogs infected with D. immitis, which was indicated by using parasitological methods. Microfilaria levels were evaluated from 36 infected dogs and the range of microfilarial levels were between 17 and 78,417 microfilariae per milliliter of blood. Fifty serum samples from D. immitis infected dogs and 310 serum samples from non-infected dogs were subjected to the study of total immunoglobulin G (IgG) against Wolbachia bacteria, the endosymbiont of the parasite, by using Indirect Enzyme-Linked ImmunoSorbent Assay (ELISA). The sensitivity and specificity of ELISAwere analyzed by comparing with the parasitological methods. The ELISA has 52% sensitivity and 85% specificity when the cut-off level was 1.73 (mean+SD). The ELISA from this study which detected the total IgG response to
Wolbachia bacteria infection may not be a useful method for using as a diagnostic tool to distinguish between D. immitis infected and non-infected dogs because of its low sensitivity. Further study of the IgG subclass responses against Wolbachia would be useful to evaluate the diagnostic potential.