Infection rate of Trypanosoma brucei s.l., T. vivax, T. congolense “forest type”, and T. simiae in small wild vertebrates in south Cameroon

Abstract

In order to identify the infection rate of trypanosome species infecting wild animals in four localities (Bipindi, Campo, Fontem and Nditam) of southern Cameroon, 1,141 wild animals were sampled. These animals belonged to 36 species grouped in 8 orders including 407 primates, 347 artiodactyls, 264 rodents, 54 pangolins, 53 small carnivores, 11 saurians and crocodilians and 5 hyraxes. PCR using specific primers for Trypanosoma vivax, T. brucei s.l., T. congolense “forest type”, and T. simiae showed that 18.7% of the animals were infected by at least one of these trypanosome species. A positive PCR result may not indicate absolutely an active infection because PCR can detect also transient infections. T. vivax ( Duttonella) had the highest infection rate (9.5%) and was found in almost all the host orders studied. T. brucei s.l. mostly infected primates, rodents and some duikers ( Cephalophus dorsalis and C. monticola). Trypanosomes of the subgenus Nannomonas had a lower infection rate of 5.5% (2.4% for T. simiae and 3.1% for T. congolense “forest type”). They were harboured mainly by primates, ungulates and rodents. Trypanosome infection rates were highest in Nditam (24.5%) and Bipindi (21%). T. brucei s.l. ( Trypanozoon) had its maximum infection rate of 10.4% in Bipindi. The “Quantitative Buffy Coat” (QBC ®) and Kit for in vitro isolation techniques were used to identify 48 (6.1%) infected animals. 13 were positive using QBC ®, and 42 were positive by KIVI. However, PCR was negative on 16 of these infected animals, probably due to infections with other trypanosome species. This study showed that trypanosomes of the subgenera Duttonella, Nannomonas and Trypanozoon could infect small wild vertebrates as has been shown for large ungulates and carnivores. The presence of T. brucei s.l. in a large range of wild animals strengthens the hypothesis of the existence of a wild animal reservoir of T. b. gambiense in Cameroon.