Serological and histopathological studies on experimental cryptosporidiosis

120 albino rats were orally infected with Cryptosporidium oocyts isolated from diarrheal malnourished children in order to study the effect of the duration of infection on the pathology, extent of infection in the intestine and the antibody response in the sera. Small segments from different levels of the gut were processed for histological examination and cryostat sectioning. The sera of these rats were subjected to serological study using cryostat sections as antigen in the indirect immunofluorescence [IIF] test. The study declared that the duration of infection has no effect on the extent of infection. But the severity of the pathological changes and the grades of seropositivity in the sera varied with the duration of infection being maximum on the 15th day of infection. The possible role of the humoral immunity in clearance and protection from infection was discussed

Fasciola gigantica: a new method for cercarial shedding from experimentally infected lymnaea cailliaudi snails. Observations on encystment of the metacercaria and accidental excitation

Lymnaea cailliaudi were collected from the field and proved to be uninfected. The snails were maintained in the laboratory and exposed experimentally to miracidia of Fasciola gigantica. Cercarial shedding was performed by three methods reported before, and another new method was developed in this study. The new method was done by apex puncture of the shell of infected snail. It has the advantage of collection of large numbers of mature cercariae in clean and small volume of fluid within few minutes. Cercariae were found mobile and unencysted for up to one week when maintained immediately after shedding at 4C. When the cercariae were taken out of the refrigerator, encystment was observed to occur rapidly before tail detachment. Accidental excystation of metacercariae was observed during microscopic examination of samples from the stored cysts in the refrigerator. This proved that heat and light are important factors initiating excystation of the parasite