The host-parasite relationship between the Saudi Arabian Schistosoma mansoni and its intermediate and definitive hosts. 2. Effects of temperature, salinity and pH on the infection of mice by S. mansoni cercariae.

The infectivity of cercariae of the Saudi Arabian isolate of S. mansoni was found to be influenced by factors such as water temperature, salinity and pH. The optimum exposure temperature which resulted into the highest worm burdens and worm recovery rates in mice was 28 degrees C. However, the percentage infection rate was highest at a temperature range of 10 degrees to 34 degrees C. Mice were successfully infected with cercariae of S. mansoni at salinities of 0.5 to 6,400 mg/l. The highest worm burden and worm recovery rate occurred in mice infected by cercariae at a salinity of 100 mg/l, while the percentage infection rate was highest at a salinity range of 0.5 to 1,600 mg/l. Mice exposed to cercariae at the pH of 4.4 and 9.4 did not develop any infection. The percentage infection rate was highest in mice exposed to cercariae at a pH range of 6.4 to 8.4. However, both the worm burden and worm recovery rates were highest in mice at pH 5.4.