Comparative studies on the course of Trypanosoma (nannomons) Simiae infection in different breeds of pig

Abstract

'Ibis study sought to determine experimentally if any differences exist in the susceptibility of different breeds of pig to trypanosomiasis caused by T. simiae. Four breeds were used: pure Large White, Large White X Landrace, Landrace X Large Black and pigs belonging to an undetermined breed and bought from farms in Nderi, Muguga. Pigs of both sexes aged 2-3 months were used. Following needle or tsetse challenge, the rectal temperatures of the pigs and the haematological changes during the course of infection were measured. Parasites were detected by examination of the buffy coat using the light microscope after sping the blood in a microhaematocrit centrifuge. The parasites were quantified using the wet blood method of Walker (1968). Differences in the prepatent period occurred between

the pure Large White and the Landrace X Large Black Pig had prepatent period of 3 days. The Large White X Landrace crossbreed pigs had a mean prepatent period of 3.73±O.23 days. After tsetse challenged the Large White X crossbreed pigs and the pigs from Nderi had mean prepatent 6. 27±1. 26 ~ and 5. 88±O. 86 days ) respectively. All the pure large white pigs and some individuals from the other breeds exhibited no

ability to control or remit parasitaemia. These animals became anaemic rapidly and died during the first peak of parasitaemia. In terms of survival, the pure Large White pigs were the least resistant to trypanosomiasis. The Large White X Landrace crossbreed pigs, the Landrace X Large Black crossbreed pigs and the pigs from Nderi showed marked heterogeneity in their trypanotolerance. Some animals were resistant and survived more than two weeks of patent infection following needle or tsetse Challenge some had no resistance) while others were intermediate. One Large White X Landrace crossbreed pig lost the infection spontaneously. The resistant animals possessed a superior capacity to control parasitaemia and developed less severe anaemia. It is concluded that a degree of resistance to T. simiae infection exists in the Large White X Landrace crossbreed pigs and in the pigs from Nderi, Muguga.