Oral route of transmission: Trypanosoma evansi in a mice model experiment

Twelve Swiss albino mice of either sex and equal body weight were randomly divided in 2 groups (I and II), consisting of 9 and 3 mice respectively and were used to conduct the study. A dose of 2.5 × 10⁴ number of Trypanosoma evansi was instantly fed to each mouse of group I. Each mouse of group II was inoculated intraperitoneally with same dose of parasites through infected mice blood and kept separate. The tail blood of each mouse was examined daily up to 30 days post infection by examination of wet blood film and Giemsa-stained blood smears for presence of any trypanosomes. Out of 9 mice of group I those were infected orally, 3 (33.33%) mice became positive for presence of T. evansi both by examination of wet blood film and Giemsa-stained blood smears after 4, 6 and 7 days post infection. After 2 days post infection all intraperitoneally infected mice were found positive for T. evansi. Thus incubation period in orally infected mice was longer than the intraperitoneally infected mice. All the positive mice of both the groups died with high parasitaemia after 3-4 days of first appearance of parasitaemia. From the present study, it can be concluded that besides mechanical or parenteral means of transmission, T. evansi could also be transmitted through oral route. Thus zoo carnivores might be infected with T. evansi and develop disease by eating infected blood or flesh of the infected animals, as a prey and predator relationship.