Abstract
“Beko” disease whose causative agent is Pleistophora anguillarum is well known in eel culture. There are, however, few reports on chemotherapy of the microsporidiosis in fishes.
The present study was undertaken to induce Pleistophora infection experimentally and examine the effect of fumagillin as a chemotherapeutic agent.
Experimental infection was tried by inoculating orally Pleistophora spores into juvenile eels or immersing them in water suspension of the fresh spores. Both methods were successful in inducing the same symptom as that of naturally-occurring diseased fish. Early schizonts, cysts in the trunk muscle, and whitish lesions on the body surface were observed around 10, 20, and 25 days after inoculation, respectively. In oral infection, the whitish lesions developed mainly on the body surface around the abdomen. In the immersing infection, on the other hand, they were scattered over the whole body. These results and the histological investigations suggest that the parasite at early stages reaches the musculature via the gut wall and peritoneal fluid in oral infection, and via the skin in immersion, rather than via the blood vascular system.
From another experiment, it was found that Pleistophora infection was very weak at low temperature such as 14°C.
Fumagillin was found to have prophylactic effect on these experimental infections by oral or immersed administration immediately after inoculation.
