Abstract

The present study was conducted to assess the molecular discrimination of field isolates of Trypanosoma congolense and Trypanosoma vivax of Nigeria origin in vitro (PCR) whether there will be genetic alteration of the parasites as the infections of the isolates in Yankasa sheep progresses from acute through relapses to chronic stages. A total of thirty Yankasa sheep were acquired from Kastina State in the northern part of Nigeria, screened for haemo-, ecto- and endo-parasites, treated against anaplasmosis, coccidiosis and conditioned in arthropod-free pens for two weeks. They were randomly divided into five groups of six animals each. Two groups each were infected intravenously with approximately 2.0×10⁶ of T. vivax and T. congolense. One group served as uninfected control. A group each from T. vivax-infected and T. congolense-infected groups were treated with trypanocide 6 days post parasitaemia. The other infected groups were left untreated. The animals were monitored for 8 weeks post infection (pi). Incubation period of 6 days was recorded for both parasite species. Multiplex primers polymerase chain reaction (PCR) and T. vivax species-specific PCR confirmed that the isolates used were T. congolense and T. vivax at molecular band sizes of 750 and 175 bp, respectively. Randomly amplified polymorphic DNA (RAPD)-PCR showed that the band sizes associated with the chronic form of the infection of T. congolense differed from those of the acute and relapse forms, whereas the band weights of the relapse form of the T. vivax differed from those of acute and chronic forms. Molecular characterization of T. vivax and T. congolense revealed differences through the variations in band weights of the parasites derivatives in the acute, chronic and relapse infections and this may translate into differences in antigenicity.

Key words: Trypanosoma, infection, parasitaemia, parasite, relapse, band, amplicon.