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BackgroundDespite the morphological characterization established in the 1950s and 1960s, the identity of extant taxa that make upGlossina fuscipes(s.l.) in the Congo remains questionable. Previous claims of overlap betweenG. fuscipes(believed to beG. f. quanzensis) andG. palpalis palpalisaround Brazzaville city further complicate the taxonomic status and population dynamics of the two taxa. This study aimed to determine the phylogenetic relationships betweenG. fuscipes(s.l.) andG. p. palpalisand to assess genetic variation amongG. fuscipes(s.l.) populations in Congo Brazzaville.MethodsWe collected 263G. fuscipes(s.l.) from northern and central regions, and 65G. p. palpalisfrom southern part of the country. The mitochondrial cytochromecoxidase subunit 1 (cox1) gene was amplified using taxa-specific primer pairs. Sequence data were analyzed in DnaSP and Arlequin to assess the genetic diversity, differentiation and demographic history ofG. fuscipes(s.l.) populations.ResultsThe general BLAST analysis yielded a similarity of 99% forG. fuscipes(s.l.) andG. p. palpalis. BLASTn analysis forG. fuscipes(s.l.) showed > 98% identity with GenBank sequences forG. fuscipes(s.l.), with BEMB population showing 100% similarity withG. f. fuscipes.Glossina fuscipes(s.l.) populations showed high haplotype diversity (H = 46, Hd = 0.884), moderate nucleotide diversity ( = 0.012) and moderate (FST= 0.072) to high (FST= 0.152) genetic differentiation. Most of the genetic variation (89.73%) was maintained within populations. The mismatch analysis and neutrality tests indicated recent tsetse population expansions.ConclusionsPhylogenetic analysis revealed minor differences betweenG. fuscipes(s.l.) andG. p. palpalis.Genetic diversity ofG. fuscipes(s.l.) was high in the populations sampled except one. Genetic differentiation ranged from moderate to high among subpopulations. There was a restricted gene flow betweenG. fuscipes(s.l.) populations in the north and central part of the country. Genetic signatures based oncox1 showed recent expansion and recovery ofG. fuscipes(s.l.) populations from previous bottlenecks. To fully understand the species distribution limits, we recommend further studies involving a wider sampling scheme including the swampy Mossaka focus forG. fuscipes(s.l.) and the entire range ofG. p. palpalisin South Congo.

Tsetse flies of the palpalis group, particularly Glossina fuscipes, are the main vectors of human African trypanosomiasis or sleeping sickness in Congo-Brazzaville. They transmit the deadly human parasite, Trypanosoma brucei gambiense and other trypanosomes that cause animal trypanosomiasis. Knowledge on diversity, population structure, population size, and gene flow is a prerequisite for designing effective tsetse control strategies. There is limited published information on these parameters including migration patterns of G. fuscipes in Congo-Brazzaville. We genotyped 288 samples of G. fuscipes from Bomassa (BMSA), Bouemba (BEMB), and Talangai (TLG) locations at 10 microsatellite loci and determined levels of genetic diversity, differentiation, structuring, and gene flow among populations. We observed high genetic diversity in all three localities. Mean expected heterozygosity was 0.77 ± 0.04, and mean allelic richness was 11.2 ± 1.35. Deficiency of heterozygosity was observed in all populations with positive and significant F(IS) values (0.077–0.149). Structure analysis revealed three clusters with genetic admixtures, evidence of closely related but potentially different taxa within G. fuscipes. Genetic differentiation indices were low but significant (F(ST) = 0.049, P < 0.05), indicating ongoing gene flow countered with a stronger force of drift. We recorded significant migration from all the three populations, suggesting exchange of genetic information between and among locations. Ne estimates revealed high and infinite population sizes in BEMB and TLG. These critical factors should be considered when planning area-wide tsetse control interventions in the country to prevent resurgence of tsetse from relict populations and/or reinvasion of cleared habitats.