title: Trypanosoma brucei gambiense Type 1 populations from human patients are clonal and display geographical genetic differentiation.
abstract: We have rigorously tested the hypothesis that Trypanosoma brucei gambiense Type 1 is composed of genetically homogenous populations by examining the parasite population present in Human African Trypanosomiasis (HAT) patients from the Democratic Republic of Congo (DRC) and Cameroon (CAM). We amplified eight microsatellite markers by PCR directly from blood spots on FTA filters, thereby avoiding the significant parasite selection inherent in the traditional isolation techniques of rodent inoculation or in vitro culture. All microsatellite markers were polymorphic, although for four markers there was only polymorphism between the DRC and CAM populations, not within populations, suggesting very limited genetic exchange. Within the largest population from the DRC, Hardy-Weinberg equilibrium is not evident at any loci. This evidence suggests a clonal population. However, there was significant sub-structuring between the DRC and CAM samples (F(ST) = 0.32), indicating that Trypanosoma brucei gambiense Type 1 has genetically distinct clades. The data combine to indicate that genetic exchange plays a very limited role. The finding of distinct clades in different places suggests the possibility that samples from humans with clinical signs represent clonal expansions from an underlying population that requires identifying and characterising.
authors.affiliation: Wellcome Centre for Molecular Parasitology, University of Glasgow, Biomedical Research Centre, 120 University Place, Glasgow G12 8TA, United Kingdom. lm78y@udcf.gla.ac.uk
authors.forename: Liam J
authors.initials: LJ
authors.lastname: Morrison
authors.forename: Andy
authors.initials: A
authors.lastname: Tait
authors.forename: Gillian
authors.initials: G
authors.lastname: McCormack
authors.forename: Lindsay
authors.initials: L
authors.lastname: Sweeney
authors.forename: Alana
authors.initials: A
authors.lastname: Black
authors.forename: Philippe
authors.initials: P
authors.lastname: Truc
authors.forename: Anne C L
authors.initials: AC
authors.lastname: Likeufack
authors.forename: C Michael
authors.initials: CM
authors.lastname: Turner
authors.forename: Annette
authors.initials: A
authors.lastname: MacLeod
mesh_terms: D000818:Animals; D002163:Cameroon / Q000453:epidemiology; D016054:DNA, Protozoan / Q000235:genetics*; D015023:Democratic Republic of the Congo / Q000453:epidemiology; D005787:Gene Frequency; D005843:Geography; D006801:Humans; D015810:Linkage Disequilibrium; D018895:Microsatellite Repeats; D017720:Molecular Epidemiology; D010802:Phylogeny; D014347:Trypanosoma brucei gambiense / Q000235:genetics* / Q000302:isolation & purification; D014353:Trypanosomiasis, African / Q000097:blood / Q000453:epidemiology / Q000469:parasitology*
chemical_list: D016054:DNA, Protozoan