Studies on Onchocerciasis in Korean Cattle: 1. Morphology of Microfilaria

The genus Onchocerca has received much attention due to the medical and veterinary importance of certain species within the genus. Recently, additional interest on onchocerciasis of domestic animals has been stimulated by the report of human infections with Onchocerca of animal origin.

In Korea, so-called worm nodules have been encountered in cattles slaughtered at abattoirs. From this reason, it is considered to be very important to carry-out epizootiologic studies on onchocerciasis in Korean cattle and other domestic animals.

The present work was designed to investigate the incidence and morphology of microfilariae of Onchocerca sp. in Korean cattle.

For study, skin tissues on the umbilical region of cattles were taken and sliced into small pieces, and kept in saline for 2 hours. Microfilariae were collected and fixed in pure alcohol and in 2% formalin solution, and stained with Giemsa stain solution respectively.

The results are summarized as follows;

1) Microfilariae were found in 49 (24.5%) among total 200 cattles examined.

2) Average length and width of microfilariae were 249.7µ × 3.6µ in pure alcohol fixed specimen and 248.8µ × 3.9µ in 2% formalin fixed specimen, respectively.

3) Distances of each significant structure from the anterior end of head of microfilariae reveales; BNC 6.5µ(4.5~8.2µ), AMNR 59.2µ(53.8~67.3µ), PMNR 62.3µ(58.2~69.9µ), EP 86.8µ(82.4~94.1µ), EC 96.6µ(86.9~103.5µ), G₁ 178.3µ(162.2~192.8µ), AP 221.0µ(189.5~237.5µ) and ENC 240.4µ(226.2~258.9µ).

4) Four G cells and 3 or 4 small rod shaped caudal nuclei proceeded to a bar shaped terminal nucleus were observed.

From the characteristics of body length, clear portion of the head and caudal nuclei and general apperance expressed with a percentage of the distance from the anterior end to body length the microfilariae examined in the present study can be identified as O. gibsoni.