Browsing by Author "Sistrom, Mark"

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    Genetic Diversity and Population Structure of Trypanosoma brucei in Uganda: Implications for the Epidemiology of Sleeping Sickness and Nagana
    (PLoS neglected tropical diseases, 2015) Echodu, Richard; Sistrom, Mark; Bateta, Rosemary; Murilla, Grace; Okedi, Loyce; Aksoy, Serap; Enyioha, Chineme; Enyaru, John; Opiyo, Elizabeth; Gibson, Wendy; Caccone, Adalgisa
    While Human African Trypanosomiasis (HAT) is in decline on the continent of Africa, the disease still remains a major health problem in Uganda. There are recurrent sporadic outbreaks in the traditionally endemic areas in south-east Uganda, and continued spread to new unaffected areas in central Uganda. We evaluated the evolutionary dynamics underpinning the origin of new foci and the impact of host species on parasite genetic diversity in Uganda. We genotyped 269 Trypanosoma brucei isolates collected from different regions in Uganda and southwestern Kenya at 17 microsatellite loci, and checked for the presence of the SRA gene that confers human infectivity to T. b. rhodesiense. Results Both Bayesian clustering methods and Discriminant Analysis of Principal Components partition Trypanosoma brucei isolates obtained from Uganda and southwestern Kenya into three distinct genetic clusters. Clusters 1 and 3 include isolates from central and southern Uganda, while cluster 2 contains mostly isolates from southwestern Kenya. These three clusters are not sorted by subspecies designation (T. b. brucei vs T. b. rhodesiense), host or date of collection. The analyses also show evidence of genetic admixture among the three genetic clusters and long-range dispersal, suggesting recent and possibly on-going gene flow between them. Conclusions Our results show that the expansion of the disease to the new foci in central Uganda occurred from the northward spread of T. b. rhodesiense (Tbr). They also confirm the emergence of the human infective strains (Tbr) from non-infective T. b. brucei (Tbb) strains of different genetic backgrounds, and the importance of cattle as Tbr reservoir, as confounders that shape the epidemiology of sleeping sickness in the region.
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    Genetically Distinct Glossina fuscipes fuscipes Populations in the Lake Kyoga Region of Uganda and Its Relevance for Human African Trypanosomiasis
    (BioMed research international, 2013) Echodu, Richard; Sistrom, Mark; Hyseni, Chaz; Enyaru, John; Okedi, Loyce; Aksoy, Serap; Caccone, Adalgisa
    Tsetse flies (Glossina spp.) are the sole vectors of Trypanosoma brucei—the agent of human (HAT) and animal (AAT) trypanosomiasis. Glossina fuscipes fuscipes (Gff ) is the main vector species in Uganda—the only country where the two forms of HAT disease (rhodesiense and gambiense) occur, with gambiense limited to the northwest. Gff populations cluster in three genetically distinct groups in northern, southern, and western Uganda, respectively, with a contact zone present in central Uganda. Understanding the dynamics of this contact zone is epidemiologically important as the merger of the two diseases is amajor health concern.We used mitochondrial and microsatellite DNA data fromGff samples in the contact zone to understand its spatial extent and temporal stability.We show that this zone is relatively narrow, extending through central Uganda alongmajor rivers with south to north introgression but displaying no sex-biased dispersal. Lack of obvious vicariant barriers suggests that either environmental conditions or reciprocal competitive exclusion could explain the patterns of genetic differentiation observed. Lack of admixture between northern and southern populations may prevent the sympatry of the two forms of HAT disease, although continued control efforts are needed to prevent the recolonization of tsetse-free regions by neighboring populations.
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    Taking advantage of genomic data to develop reliable microsatellite loci in Trypanosoma brucei
    (Molecular Ecology Resources, 2013) Sistrom, Mark; Echodu, Richard; Hyseni, Chaz; Enyaru, John; Aksoy, Serap; Caccone, Adalgisa
    Taking advantage of the annotated genome of Trypanosoma brucei, a unicellular eukaryotic parasite which causes sleeping sickness across sub3Saharan Africa, this study develops 11 variable microsatellite loci, which reliably amplify in poor and unknown quality DNA samples. We provide insights into effective screening methods to develop microsatellite loci from genomic resources and a set of markers to study regional population variation in this important parasite.