Acquired resistance in experimental giardiasis

Giardia lamblia cysts inoculated intraoesophageally could proliferate into trophozoites in the duodenum of Swiss mice and animals became infected within 4±2 days. Twenty one animals were observed up to the stage of spontaneous resolution of the infection. All the animals underwent spontaneous resolution of the infection by day 41 post-inoculation. Another batch of 15 infected animals was subjected to metronidazole therapy from the 11th day onwards, for a week, to eradicate the infection. Spontaneously cured as well as the drug-treated animals were reinfected with G. lamblia cysts. It was then observed that cysts in the stools appeared late (6±2 days), the intensity of G. lamblia infection was significantly less (P\u3c0.05) and the animals had another spontaneous cure sooner. Five of the spontaneously cured animals were found to be completely refractory to reinfection