The effect of controlled release copper sulfate and tributyltin fluoride on the mortality and infectivity of Schistosoma mansoni miracidia.

The experiments were conducted to assess the effect of sublethal concentration of controlled release copper sulfate (EC-8) and tribultyltin fluoride (CBL-9B) on the mortality and infectivity of Schistosoma mansoni miracidia. It was found that LC50 and LC90 of EC-8 to the miracidia were 8.5 mg/l per hr and 15.75 mg/l per hr respectively. For CBL-9B, LC50 was 19.75 microgram/l per hr and LC90 was 32.0 microgram/l per hr. Exposing of the miracidia to 0.5 mg/l of EC-8 or 4.0 microgram/l of CBL-9B respectively, for only one hour can prevent their transmission to the snail host. The results indicate that immobilization of the free living stages of the schistosome parasite was not required to interrupt their transmission to the next hosts.

Mekong schistosomiasis. 4. A parasitological survey of wild rodents, domestic pigs and cattle on Khong Island, Laos.

No evidence of infection with the Mekong Schistosoma was found in 12 Rattus exulans, 81 R. r. molliculus, and 10 Bandicota savilei caught in the vicinity of and downstream from the schistosomiasis transmission focus on Khong Island, South Laos, and examined by dissection and portal perfusion. Likewise, no eggs of the Mekong Schistosoma were detected in faeces of 15 domestic pigs or 43 domestic cattle examined on Khong Island both by merthiolate-iodine-formalin concentration and by the hatching technique. These results suggested that the wild rodents listed above, as well as pigs and cattle in the vicinity of Khong Town, may not contribute significantly to the transmission of the Mekong Schistosoma under present conditions.