Cryptosporidium spp. Infection: Cryptosporidiosis
An outbreak of diarrhea and high mortality among infant rats of the Rapp hypertensive strain has been described. Surviving pups were runted and their fur was stained with feces. Lesions in convalescing 21-day-old rats were restricted to the mucosa of the small intestine, primarily jejunum.
The mucosa was hyperplastic and villi were shortened and fused, with cryptosporidia attached to the brush borders of enter- ocytes toward the villus tips (Fig. 2.48). Cryptosporidiosis can be induced experimentally in rats, but is transient and mild unless rats are immunosuppressed or athymic.Trypanosoma lewisi: Trypanosomiasis
Naturally occurring infections with Trypanosoma lewisi are now a rarity in laboratory rats. However, there have been isolated reports of infections with T. lewisi in laboratory and wild rats in developing countries. This flagellate is a species-specific nonpathogenic blood parasite. Infected rats are normally subclinical, and procedures such as irradiation are used to induce parasitemia in subclinically infected animals. Rats are infected principally by the ingestion of infected fleas or flea feces from T. lewisi-infected rats. The diagnosis of trypanosomiasis is usually made by identification of the organism in Giemsa-stained blood films. A PCR technique has also been developed to identify infected animals.