Identification of trypanosomes in Glossina pallidipes and G. longipennis in Kenya

Abstract

The polymerase chain reaction (PCR) was used to identify trypanosomes in Glossina pallidipes and G. longipennis caught in Kenya. Of 3826 flies dissected, 188 (4.9%) were parasitologically positive overall. The infection rate in G. pallidipes was 5.7% (187 of 3301 flies), but only one of 525 G. longipennis was infected (infection rate 0.2%). There was a higher infection rate in female G. pallidipes flies than male flies (chi(2) = 18.5, P < 0.001) and odds ratio = 2.5 (95% 1.6, 3.7). The infected flies were analysed by PCR using 10 sets of primers specific for species and subgroups within the subgenera Nannomonas, Trypanozoon and Duttonella. Of 188 parasitologically positive samples, PCR identified 137 (72.9%), leaving 51 (27.1%) non-identified. We recorded infection rates of 47.2% for Trypanosoma congolense savannah, forest and kilifi subgroups, 20.9% for T. simiae/T. simiae tsavo/T. godfreyi, 14.9% for T. brucei ssp. and 13.8% for T. vivax. Thirty-nine (26.7%) flies had mixed infections, with a minor association between T. congolense savannah/T. simiae tsavo/T. godfreyi (chi(2) = 6.93, d.f. = 1, P < 0.05). The relative proportion of each trypanosome species or subgroup varied between fly belts with T. congolense (all subgroups) being the most abundant and T. godfreyi the least. Statistical analysis showed that dissection method and PCR test classified infections independently (chi(2) = 10.5, d.f. = 1, P < 0.05 and kappa = 0.38). This study shows that pathogenic trypanosomes are widespread in all sampled testes fly belts with G. pallidipes as the main vector. Further, PCR test is more reliable in detecting and identifying trypanosomes than dissection method.

The taxonomic and phylogenetic relationships of Trypanosoma vivax from South America and Africa

“…Lack of detection of Kenyan T. vivax using PCR primers derived from a West African isolate indicates the widespread occurrence of genetic variants of this species (Njiru et al 2004), a fact corroborated in this study by the failure of the PCR based on SL gene sequences of South American/West African T. vivax (Ventura et al 2001) to detect the East African isolate examined in this study. Other distinct genetic variants of T. vivax may well exist, for example that represented by a partial SSU rRNA sequence amplified directly from tsetse collected in Tanzania, East Africa (Malele et al 2003).…”

The use of ITS1 rDNA PCR in detecting pathogenic African trypanosomes

“…In our analysis, we picked out four isolates that had been previously categorised as single infections to be mixed infections. Direct sequencing of these products showed that KETRI 2729 contained a T. vivax [not the West African type because it was negative with TVW1 and TVW2, Masiga et al (1992) but positive with universal T. vivax primers (Masake et al 1997;Morlais et al 2001] (Mugittu et al 2000), while triple and quadruple infections may be a rare occurrence in animals, although common in tsetse flies (Njiru et al 2004). The use of universal tests for pathogenic trypanosomes would reduce the cost of PCR three to five times as the number of reactions required per sample would be reduced to one (Desquesnes and Davila 2002).…”

“…Further, characterised trypanosome DNA from tsetse samples that had been analysed previously were included in this study (Njiru et al 2004).…”

“…In Kenya, ten pathogenic trypanosomes occur and overlap in most of the tsetse belt (Njiru et al 2004), such that multiple infection of both host and vector is to be expected. This implies that several PCR tests have to be made to ascertain whether a collected sample is positive, negative or even of mixed infection.…”

A tsetse and tabanid fly survey of African great apes habitats reveals the presence of a novel trypanosome lineage but the absence of Trypanosoma brucei

“…and snake has been documented previously (Waiswa et al, 2006;463 Bouyer et al, 2007;Farikou et al, 2010) and is further corroborated 464 by our data. Recently, several new trypanosome species or genotypes have 489 been discovered in tsetse flies (Adams et al, 2006(Adams et al, , 2010b498 Our nested 18S rRNA-based PCR assay proved to be highly sen- (Njiru et al, 2004;Hamilton et al, 2008;Adams et al, 2010a,b;511 Simo et al, 2012). Our findings further increase this diversity: Trypanosomes were detected by PCR only in the thorax and abdomen.…”