Diagnosis of microfilaria in dogs and its species identification by histochemical staining technique

Stray dogs in and around Mangalore, Karnataka, which were trapped for sterilization under Animal Birth Control programme, were screened for microfilaria. A total of 590 blood samples were examined by wet mount, Giemsa staining, modified Knotts method, citrate saponin and quantitative buffy coat methods. Among the 590 blood samples screened, 327 (55.42%) dogs were found positive for microfilaria. Out of 327 microfilaraemic dogs, 218 (66.66%), 196 (59.93%) and 307 (93.88%) were positive in wet mount, Giemsa's staining and by modified Knott's methods respectively. All 327 samples were found positive in citrate saponin and quantitative buffy coat method. The microfilaria species identification was done by histochemical staining technique, which revealed enzyme activity, indicated as red azo dye, restricted only to the anal pore region. The findings of morphology, micrometry and histochemical staining technique confirmed that the microfilariae were those of Dirofilaria repens. The adult worms that were recovered from the subcutaneous tissues while conducting sterilization were processed in the laboratory and identified as D. repens.