Abstract
BackgroundLuba is one of the four historical foci of Human African Trypanosomiasis (HAT) on Bioko Island, in Equatorial Guinea. Although no human cases have been detected since 1995, T. b. gambiense was recently observed in the vector Glossina palpalis palpalis. The existence of cryptic species within this vector taxon has been previously suggested, although no data are available regarding the evolutionary history of tsetse flies populations in Bioko.MethodsA phylogenetic analysis of 60 G. p. palpalis from Luba was performed sequencing three mitochondrial (COI, ND2 and 16S) and one nuclear (rDNA-ITS1) DNA markers. Phylogeny reconstruction was performed by Distance Based, Maximum Likelihood and Bayesian Inference methods.ResultsThe COI and ND2 mitochondrial genes were concatenated and revealed 10 closely related haplotypes with a dominant one found in 61.1% of the flies. The sequence homology of the other 9 haplotypes compared to the former ranged from 99.6 to 99.9%. Phylogenetic analysis clearly clustered all island samples with flies coming from the Western African Clade (WAC), and separated from the flies belonging to the Central Africa Clade (CAC), including samples from Mbini and Kogo, two foci of mainland Equatorial Guinea. Consistent with mitochondrial data, analysis of the microsatellite motif present in the ITS1 sequence exhibited two closely related genotypes, clearly divergent from the genotypes previously identified in Mbini and Kogo.ConclusionsWe report herein that tsetse flies populations circulating in Equatorial Guinea are composed of two allopatric subspecies, one insular and the other continental. The presence of these two G. p. palpalis cryptic taxa in Equatorial Guinea should be taken into account to accurately manage vector control strategy, in a country where trypanosomiasis transmission is controlled but not definitively eliminated yet.
Highlights
Luba is one of the four historical foci of Human African Trypanosomiasis (HAT) on Bioko Island, in Equatorial Guinea
Using data from the mitochondrial gene cytochrome oxidase 1 (COI), the average genetic distance observed between G. p. palpalis and G. p. gambiensis sequences was 6.6%, which is well above the threshold of 2% divergence for inter-species comparisons [8,9,10,11]
Mitochondrial markers We amplified the mtDNA of COI (622 bp), ND2 (501 bp) and 16S (213 bp) genes for a total of sixty tsetse flies, all coming from Equatorial Guinea
Summary
Luba is one of the four historical foci of Human African Trypanosomiasis (HAT) on Bioko Island, in Equatorial Guinea. Gambiense was recently observed in the vector Glossina palpalis palpalis. The existence of cryptic species within this vector taxon has been previously suggested, no data are available regarding the evolutionary history of tsetse flies populations in Bioko. Gambiense in West Africa [2]. Rhodesiense), Tsetse flies of the palpalis group (Nemorhina subgenus) are major vectors of T. b. This group comprises two allopatric subspecies: G. p. The phylogenetic situation is more complex since recent genetic analyses suggested the existence of at least two distinct cryptic species within G. p. According to the available data, both types are sympatric in the Fontem focus of Cameroon [11]
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