Accuracy of a dog test for heartworm and tick diseases antibodies

Abstract

OBJECTIVE: To evaluate the sensitivity and specificity of a commercially available in-clinic ELISA for detection of heartworm infection and tick-borne diseases in dogs. SAMPLE POPULATION: 846 serum, plasma, or blood samples obtained from dogs. PROCEDURES: Samples were evaluated via the in-clinic ELISA to detect antibodies against Anaplasma phagocytophilum, Ehrlichia canis, and Borrelia burgdorferi and Dirofilaria immitis (heartworm) antigen. True infection or immunologic status of samples was assessed by use of results of necropsy, an antigen assay for D immitis, and immunofluorescence assay or western blot analysis for antibodies against B burgdorferi, E canis, and A phagocytophilum. RESULTS: Sensitivity and specificity of the in-clinic ELISA for detection of heartworm antigen (99.2% and 100%, respectively), antibodies against B burgdorferi (98.8% and 100%, respectively), and antibodies against E canis (96.2% and 100%, respectively) were similar to results for a similar commercial ELISA. In samples obtained from dogs in the northeast and upper Midwest of the United States, sensitivity and specificity of the in-clinic ELISA for antibodies against Anaplasma spp were 99.1% and 100%, respectively, compared with results for an immunofluorescence assay. Samples from 2 dogs experimentally infected with the NY18 strain of A phagocytophilum were tested by use of the in-clinic ELISA, and antibodies against A phagocytophilum were detected by 8 days after inoculation. Antibodies against Anaplasma platys in experimentally infected dogs cross-reacted with the A phagocytophilum analyte. Coinfections were identified in several of the canine serum samples. CONCLUSIONS AND CLINICAL RELEVANCE: The commercially available in-clinic ELISA could be used by veterinarians to screen dogs for heartworm infection and for exposure to tick-borne pathogens.