Grouping of trypanosome species in mixed infections in Glossina pallidipes

Trypanosomes in the dissection-positive proboscis of Glossina pallidipes we re identified by PCR using species-specific primers. Of the 3741 flies diss ected 643 were proboscis positive. PCR was performed on 406 dissection-posi tive probosces giving positive identifications in 352 (86.7%) and infection rates of 14.8% for congolense-type infections, 2.8% for vivax-type infecti ons and 1.4% for the unidentified group. Of the 352 PCR identified infectio ns 225 were single, 111 were double, 13 were triple infections and there we re 3 quadruple infections. Statistical analysis suggests that mixed infecti ons group into 3 largely separate divisions among the tsetse population (i) Trypanosoma congolense savannah and T. congolense Kenya coast, (ii) T. sim iae, T. congolense Tsavo and T. godfreyi and (iii) T. vivax. We conclude th at either differing feeding patterns among members of the fly population or the ability of the trypanosomes in each of the infection categories to sig nificantly influence the maturation of trypanosomes in the other categories are the most likely causes of the groupings noted. Chi-squared analysis of dissection and PCR methods of trypanosome identification revealed profound differences (chi(2) = 19.1; D.F. = 1; P > 0.05). If confirmed in other stu dies these findings have serious implications for our understanding of tryp anosome epidemiology in tsetse flies, much of which is founded on data from dissection-based trypanosome identifications.