Prevalence of trypanosoma Congolense,T. Vivax and T. Brucei infections in Cattle in Petauke district of Zambia

Abstract

One hundred Trypanosomiasis infected cattle were selected from a sample of 240 cattle located in Petauke district using the haematocrit woo method. This gave an overall trypanosomiasis prevalence of 41.7% in the area. These selected animals were further examined by the stained thin blood smear(TBS), Antigen detecting ELISA(Ag-ELISA) and the Polymerase Chain Reaction(PCR) techniques. The actual infection rates were determined by pooling the resuhs from the respective diagnostic techniques used for each individual animal. The overall Net infection rates were 96% Trypanosoma congolense, 81 % T. vivax and 76% T. b. brucei giving an infection ratio of 1.3:1.1:1 respectively.All the diagnostic techniques used have shown certain limitations in their ability to detect the three trypanosome species. Parasitological methods(Haematocrit and TBS) have shown higher sensitivity for Trypanosoma congolense than for T. vivax and T. brucei giving infection ratios of 29:3:1 by the Haematocrit and 4:2:1 by the TBS for T. congolense, T. vivax and T. brucei species respectively. Although, more mixed infections were detected by the Ag-ELISA and the PCR techniques, their sensitivity for detecting the trypanosome species, especially T. vivax and T. b. brucei was lower than was anticipated. Both Ag-ELISA and the PCR methods gave infection ratios of about 2:1:1 for T congolense, T. vivax and T. brucei respectively.Statistical analysis (ANOVA) of the resuhs showed no significant differences in the established statistical means of the Net infection rates between the three trypanosome species. These results also indicate a high rate of mixed infections of T. congolense, T. vivax and T. b. brucei in cattle suffering from trypanosomiasis in Petauke and the location of sampling(crush pen) did not show any statistical effect on the results.It is clear that the apparent predominance of Trypanosoma congolense reported in Zambia could be a result of the low sensitivity of the routine parasitological methods in use particularly, in detection of T. vivax and T. brucei. A combination of the parasitological examination with Ag- ELISA and/or PCR in the epidemiological surveys of trypanosome species is therefore highly recommended. To improve on the diagnostic performance of the Ag-ELISA and the PCR, it is also recommended that attempts to prepare monoclonal antibodies and primer sets using the local strains should be considered in order to avoid false negative results which may be. originating from some possible regional variations in the trypanosome species.