Isolation of a human serum-resistant Trypanosoma brucei from a naturally infected pig in the Nsukka area of Enugu State

Abstract

A strain of trypanosome was isolated from one of the trade pigs held at the Orie Orba market lairage in Udenu Local Government Area of Enugu State. It was identified by its motility in wet blood film and morphological characteristics in Giemsa-stained thin blood film as Trypanosoma brucei. To further characterize the parasite and identify to which of the brucei-type sub-species it belonged, it was subjected to the blood incubation infectivity test. Trypanosomes were incubated in phosphate-buffered saline glucose (PSG), normal pig serum or normal human serum for 4 hours at 37˚ C before aliquots of 200 μl containing 106 trypanosomes were used to infect each mouse in three groups of 10 mice per group. The animals were monitored daily for parasitaemia for a period of 30 days using routine parasitological techniques. All mice infected with parasites incubated in PSG and pig serum became parasitaemic with a mean pre-patent period of 3 and 8 days respectively. In contrast, only one of the 10 mice infected with trypanosomes incubated in human serum did not become parasitaemic, indicating that the strain is resistant to human serum and potentially infective to humans. It was concluded that this isolate is possibly Trypanosoma brucei gambiense and that this study supports the epidemiological claim that domestic pigs may serve as reservoir hosts for humansleeping sickness due to T. b. gambiense.


Key Words: Trypanosoma brucei, Human serum resistance, Pigs, Reservoir host, T. b. gambiense


(Nigerian Veterinary Journal: 2003 24(1): 37-43)