SEROLOGIC PATTERN OF CANINE HEARTWORM (DIROFILARIA-IMMITIS) INFECTION

  • 1 January 1984
    • journal article
    • research article
    • Vol. 45  (6) , 1178-1183
Abstract
A total of 602 dogs at the Louisiana State University Veterinary Teaching Hospital [USA] were tested for antibodies to D. immitis by enzyme-linked immunosorbent assay (ELISA), using a purified adult dirofilaria-derived antigen. Most dogs also were evaluated for heartworm infection by a complete WBC [white blood cell count] count and a Knott test for circulating microfilariae. The serologic prevalence of heartworm infection was 34.7%; prevalence increased significantly (P = 0.0003) with age up to 8 years and then decreased. Dogs usually kept indoors were significantly (P = 0.005) less likely to be infected, as were dogs given diethylcarbamazine therapy (P = 0.0004). Coat length, sex, breed, and presence of intestinal parasites were not associated (P > 0.05) with a positive heartworm ELISA result. The ELISA titers showed a positive relationship with both eosinophil and basophil counts. A total of 99 dogs evaluated radiographically were grouped according to results of the Knott test and radiographic examination as follows: 1st negative Knott test and negative radiographic examination (14 dogs), 2nd negative Knott test and positive radiographic examination (57 dogs), and 3rd, positive Knott test and positive radiographic examintion (28 dogs). The serologic prevalences of D. immitis infection in each of these groups were 35.7% 56.1%, and 85.7% for the 1st, 2nd, and 3rd groups, respectively. The ELISA, when used in conjunction with the Knott test results, record of exposure, clinical signs, laboratory results, and radiographic changes, was found to be useful for studying serologic patterns and identifying risk factors for canine heartworm infection.