Identification of Brugia malayi in dogs in Kerala, India

Identification of filarial species in dogs is clinically important because of zoonotic concerns and therapeutic implications. The present study was carried out to identify the filarial parasites causing microfilaraemia in dogs in Thrissur District, Kerala- an endemic area for human Brugian filariasis. Out of the 1600 dogs screened by wet blood film examination, 130 were positive for microfilariasis. Giemsa staining of blood smears revealed that 90 out of 130 dogs had unsheathed microfilariae, 24 had sheathed microfilariae and 16 had combined infection of sheathed and unsheathed microfilariae. Results of micrometry and histochemical staining of the sheathed microfilariae were in conformity with that of Brugia malayi. The DNA isolated from the sheathed microfilariae amplified the primers specific for the Hha 1 repeats of the B. malayi. Cloning and sequencing revealed that the amplified fragment corresponded to the 140-292 base pairs of the 320 base pair Hha1 repeat of Brugia malayi. The amplified DNA fragment also contained restriction sites for Alu 1 and Rsa 1which confirmed that the present isolate is Brugia malayi. The present study confirmed the presence of B. malayi in dogs in Kerala, India.