Background Glossina fuscipes fuscipes, a riverine species of tsetse, is the main vector of both human and animal trypanosomiasis in Uganda. Successful implementation of vector control will require establishing an appropriate geographical scale for these activities. Population genetics can help to resolve this issue by characterizing the extent of linkage among apparently isolated groups of tsetse.Methodology/Principal FindingsWe conducted genetic analyses on mitochondrial and microsatellite data accumulated from approximately 1000 individual tsetse captured in Uganda and neighboring regions of Kenya and Sudan. Phylogeographic analyses suggested that the largest scale genetic structure in G. f. fuscipes arose from an historical event that divided two divergent mitochondrial lineages. These lineages are currently partitioned to northern and southern Uganda and co-occur only in a narrow zone of contact extending across central Uganda. Bayesian assignment tests, which provided evidence for admixture between northern and southern flies at the zone of contact and evidence for northerly gene flow across the zone of contact, indicated that this structure may be impermanent. On the other hand, microsatellite structure within the southern lineage indicated that gene flow is currently limited between populations in western and southeastern Uganda. Within regions, the average FST between populations separated by less than 100 km was less than ∼0.1. Significant tests of isolation by distance suggested that gene flow is ongoing between neighboring populations and that island populations are not uniformly more isolated than mainland populations.Conclusions/SignificanceDespite the presence of population structure arising from historical colonization events, our results have revealed strong signals of current gene flow within regions that should be accounted for when planning tsetse control in Uganda. Populations in southeastern Uganda appeared to receive little gene flow from populations in western or northern Uganda, supporting the feasibility of area wide control in the Lake Victoria region by the Pan African Tsetse and Trypanosomiasis Eradication Campaign.

A 2-year tsetse field survey was conducted in Kajo-keji County South Sudan to determine factors influencing the seasonal abundance of Glossina fuscipes fuscipes. A total of 13,323 tsetse flies of both sexes were collected in the dry and wet seasons. Dry season catches were significantly higher than those of the wet season (DF = 10, t (2011) = 3.477, P (2011) = 0.006; DF = 10, t (2012) = 7.943, P (2012) = 0.0001). The number of male flies was significantly higher (DF = 15, t (2011) = 4.260, P (2011) = 0.0001; DF = 15, t (2012) = 5.492, P (2012 = 0.000) than the female ones during the study period. The mean apparent density of the flies/trap/day in the dry season was significantly higher (DF = 92, t (2011) = 2.147, P (2011) = 0.003; DF = 92, t (2012) = 3.764 and P (2012) = 0.0003. Average infection rate revealed 4.9% and 9.0 in the dry and wet seasons, respectively. An overall infection rate was 4.9% which varied significantly with the season (X 2 = 602, p<0.000). Positive associations were observed for atmospheric temperature, rain fall and relative humidity with monthly fly apparent density at R = 0.72, 0.71 and 0.82, respectively in 2011. However, in 2012 rainfall and relative humidity showed significantly negative association with the monthly fly apparent density at R = -0.85, P = 0.000 and R = -0.55, P = 0.031, respectively, whereas atmospheric temperature showed no statistical significant association at p<0.05 with the monthly fly density (R = 0.311, P = 0.163). Atmospheric temperature, rainfall and relative humidity seem to be influencing the seasonal abundance of G. f. fuscipes in the study area. These ecological factors could be used in developing tsetse control strategies.

Background The currently used malaria vaccine, RTS,S, is designed based on the Plasmodium falciparum circumsporozoite protein (PfCSP). The pfcsp gene, besides having different polymorphic patterns, can vary between P. falciparum isolates due to geographical origin and host immune response. Such aspects are essential when considering the deployment of the RTS,S vaccine in a certain region. Therefore, this study assessed the genetic diversity of P. falciparum in Sudan based on the pfcsp gene by investigating the diversity at the N-terminal, central repeat, and the C-terminal regions. Methods A cross-sectional molecular study was conducted; P. falciparum isolates were collected from different health centres in Khartoum State between January and December 2019. During the study period, a total of 261 febrile patients were recruited. Malaria diagnosis was made by expert microscopists using Giemsa-stained thick and thin blood films. DNA samples were examined by the semi-nested polymerase chain reaction (PCR). Single clonal infection of the confirmed P. falciparum cases, were used to amplify the pfcsp gene. The amplified amplicons of pfcsp have been sequenced using the Sanger dideoxy method. The obtained sequences of pfcsp nucleotide diversity parameters including the numbers of haplotypes (Hap), haplotypes diversity (Hapd), the average number of nucleotide differences between two sequences (p), and the numbers of segregating sites (S) were obtained. The haplotype networks were constructed using the online tcsBU software. Natural selection theory was also tested on pfcsp using Fuand Li’s D, Fuand Li’s F statistics, and Tajima’s D test using DnaSP. Results In comparison with the different pfcsp reference strains, the Sudanese isolates showed high similarity with other African isolates. The results of the N-terminal region showed the presence of 2 different haplotypes with a Hapd of 0.425 ± 0.00727. The presence of the unique insertion of NNNGDNGREGKDEDKRDGNN was reported. The KLKQP motif was conserved in all the studied isolates. At the central repeat region, 11 haplotypes were seen with a Hapd of 0.779 ± 0.00097. The analysis of the genetic diversity in the C-terminal region showed the presence of 10 haplotypes with a Hapd of 0.457 ± 0.073. Several non-synonymous amino acids changes were also seen at the Th2R and the Th3R T-cell epitope regions including T317K, E317K, Q318E, K321N, I322K, T322K, R322K, K324Q, I327L, G352N, S354P, R355K, N356D, Q357E, and E361A. Conclusions In this study, the results indicated a high conservation at the pfcsp gene. This may further contribute in understanding the genetic polymorphisms of P. falciparum prior to the deployment of the RTS,S vaccine in Sudan.

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