Proliferation of Cryptosporidium sp. in Immunosuppressed Balb/c and C57bl/6 Mice for Modeling of Cryptosporidiosis in Immunodeficiency

Cryptosporidiosis is a parasitic disease caused by protozoan parasite Cryptosporidium and leads to an acute and/or chronic gastroenteritis. The disease appears as a self-limiting infection in immunocompotent person, but it causes a chronic disease and extra-intestinal infection, which finally leading to death in immunocompromised patients. With respect to the prevalence of infected immunodeficient patients worldwide and in Iran, there is a need for modeling cryptosporidiosis in laboratory animals.

Samples were collected from human and animal stools, centrifuged by Paraseb kit, and smear was prepared and assessed with acid fast staining method. After identification of oocysts, it was separated, and concentrated by sucrose floatation. Balb/c and C57bl/6 mice were immunosuppressed by intraperitoneal dexamethasone injection, the immonusuppression was confirmed by lymphocyte proliferation assay, and finally cryptosporidium oocysts were orally inoculated into inbred mice. Having proved the infection, the animals were humanely killed and the target organs including lungs, liver, intestine and spleen were collected, stained with hematoxyline & eosine method and examine for histopathological effects of the organism in samples.

The results of lymphocyte proliferation assay showed that the C57bl/6 mice were more immunesuppressed than the Balb/c one; which facilitate them to be more susceptible to the infection than Balb/c mice. Therefore, the majority (80%) of C57bl/6 mice infected with cryptosporidium oocysts and 40% of them died, whereas only 20% of Balb/c mice were infected and none of them died due to infection. No histopathological alterations were observed in H&E stained sections of liver, spleen, lung and intestine in control and test groups. Moreover, no infection was detected in impression smears.

This study is the first report of experimental cryptosporidiosis and modeling of infection in immunodeficiency in laboratory animals in Iran. The findings indicated that immunosuppressed C57bl/6 mice were more susceptible to Cryptosporidium infection than Balb/c ones. No extra-intestinal infection was detected in study groups, which may be due to short period of infection in experimental animals.