High susceptibility of Neotricula aperta gamma-strain from Krakor and Sdau in Cambodia to Schistosoma mekongi from Khong Island in Laos

Abstract Neotricula aperta γ-strain snails collected from Krakor and Sdau in Cambodia were found to have the same or higher susceptibility to Schistosoma mekongi as N . aperta originally isolated from Khong in Laos. Infection rates of N . aperta γ-strain snails exposed to 3 miracidia at week 8 were: Khong γ-strain, 22.6%; Krakor γ-strain, 33.3%; and Sdau γ-strain, 67.4%. At week 10, the Sdau γ-strain showed the highest infection rate of 83.3%. We thus found significantly high susceptibility of the Sdau γ-strain to S . mekongi originally isolated from Khong. However, in another experiment, susceptibility of the Sdau γ-strain was rather comparable to that of Khong and Krakor γ-strain. We also found no significant differences in infection and survival rates between the Khong and Krakor γ-strain when the snails were exposed to 3 or 6 miracidia. This is the first report to confirm the high susceptibility in the laboratory of N . aperta γ-strain snails from endemic areas in Cambodia to S . mekongi originally isolated from Laos. The high susceptibility of N . aperta γ-strain snails to S . mekongi in distant areas may be an important factor in the endemic transmission of human schistosomiasis.