Mechanical transmission of trypanosoma evansi and trypanosoma congolense by African stomoxys species.

Abstract

Simulated mechanical transmission rates of T. congolense and T. evansi were studied using wild and blood-fed S. n. niger, S. taeniatus, and laboratory reared teneral S. n. niger. The flies were caught in the Nairobi National Park forest and in the thickets and woodlands at Nguruman, Kenya. Direct microscopy and mouse inoculation techniques were able to detect live Trypanosoma congolense only up to 210 minutes, and T. evansi up to 480 minutes after an infective blood meal. Individual flies were interrupted after 1-2 minutes of feeding on infective bloodmeal and immediately transferred to non-infected mice to complete their meal. Wild and teneral S. n. niger transmitted T. congolense at transmission rates of 7.5% and 10.0% respectively and T. evansi at transmission rates of 20.0% and 35.0% respectively. Blood-fed and wild S. taeniatus were not able to transmit T. congolense but they transmitted T. evansi at transmission rates of 17.5% and 13.3% respectively. There was no significant difference in the transmission of either T. evansi or T. congolense by teneral, wild and blood-fed S. n. niger. Laboratory rearing of wild stable flies was attempted using the following media: rhinoceros dung; mice pellets, saw dust and water; wheat bran, saw dust and water. The latter was the best medium for rearing S. n. niger. S. inornatus, S. taeniatus, S. n. bilineatus did not develop well in all the three media. The life cycle for S. n. niger was approximately 23.5 days.