BackgroundMuch of the confusing ecophenotypic plasticity of Anopheles gambiae sensu lato is attributable to the differential biological traits of the sibling species, with their heterogeneous geographical distribution, behavioral dissimilarities and divergent population dynamics. These differences are critical to their roles in malaria transmission. Studies were, therefore, undertaken on the spatial distribution of these species and malaria prevalence rates in Bayelsa State, September, 2008-August 2010.MethodsMosquito sampling was in 7 towns/villages in 7 Local Government Areas (LGAs) in 3 eco-vegetational zones: Fresh Water Swamp Forest (FWSF): Sagbama, Yenagoa, Kolokuma-Opokuma LGAs; Brackish Water Swamp Forest (BWSF): Ogbia, Ekeremor, Southern Ijaw LGAs; Mangrove Water Forest (MWF): Nembe LGA. Adults were collected twice quarterly by the Pyrethrum Spray Catch (PSC) technique. Anopheles was separated morphologically and the sibling species PCR- identified. Simultaneously, malaria prevalence rates were calculated from data obtained by the examination of blood smears from consenting individuals at hospitals/clinics.ResultsAn. gambiae s.s. was dominant across the 3-eco-vegetational zones. Spatial distribution analyses by cell count and nearest neighbor techniques indicated a tendency to clustering of species. An. gambiae s.s. and An. arabiensis clustered in Ekeremor LGA while these 2 species and An. melas aggregated in Nembe. The gonotrophic (physiological) status examination revealed that 34.3, 23.5, 23.1 and 18.4% of the population were fed, unfed, gravid and half gravid respectively. The highest malaria prevalence rates were obtained at Kolokuma-Opokuma and Nembe LGAs. Variation in prevalence rates among LGAs was significant (t = 5.976, df = 6, p-value = 0.002, p < 0.05). The highest prevalence rate was in the age group, 30-39 yrs, while the lowest prevalence was in the 0-9 yrs group.ConclusionHigh malaria prevalence rates were associated with An. gambiae s.s. either in allopatry or sympatry across eco-vegetational zones. In areas where the sibling species clustered, they probably formed nidi for transmission. Socio-economic conditions might have contributed to reduced prevalence in Yenagoa, State Capital.

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Seven hundred and eighty blood samples were obtained and examined using standard parasitological techniques. Of this number, 227 (25.5%) samples were infected with filarial spp as follows: Mansonella perstans 121 (43.8%), Wuchereria bancrofit 80 (28.8%), Loa loa 75 (27.1%) and Onchoceria volvulus 1 (0.3%). Peak infection (44.3%) occurred in the 30-39 years age bracket. The lowest infection rate was observed in the candidates above 70 years old. Microfilarial density (mfd) was highest in this age bracket. The lowest mfd occurred in 1-9 years old. Infection was higher (38.9%) in the males than in the females (33.9%). Higher infection in the males was attributed to fishing, which was predominantly a male occupation. Three of the five mosquito spp collected from the community hardboured microfilariae: Anopheles gambiae (9.5%), A-funestus (6.6%), Culex quinquefestus (4.1%), Anopheles nili (-%), Aedes aegypti (0%). The presence of the microfilariae confirms that filarial infections in the study area are endemic. Entomological survey was done in the night and insects that were active in day-time were not trapped. @ JASEM

Blood samples collected from 272 volunteers in two communities of Bayelsa State in the Niger Delta area were investigated for falciparum malaria parasite using the rapid test based on the detection of soluble antigen and laboratory microscopy test. The data showed that out of the 272 samples collected, 40(14.7%) falciparum malaria cases were identified by microscopic examination. 53(19.5%) were detected by rapid test. The Global (p.f) malaria test kit yielded 22 false negative and 35 false positive results when compared with microscopic findings. Only 18 cases shows true positive results. The specificity and sensitivity of the kit was 80% and 45% respectively when the parasite density is below 100 parasite/ µl. These results shows that rapid test would not give justifiable results as most of the low parasite density cases could escape detection, therefore, it cannot replace laboratory microscopic diagnosis in an active malaria surveillance programme in the study area. Therefore, regulatory agencies should insist on regular laboratory microscopic diagnosis in the surveillance of malaria. @ JASEM

Malaria is a life threatening vector borne disease caused by parasites that are transmitted to people through the bites of infected female Anopheles mosquitoes. In this paper, we study and analyze mathematical model of ordinary differential equations for human and mosquito with saturated incidence function. The stability of the system was analyzed for the Malaria-Free Equilibrium (MFE) through the reproduction number R 0 which was obtained using the next generation matrix method. The MFE is locally asymptotical stable if R 0 < 1 and unstable otherwise. Moreover, our sensitivity analysis shows that the most effective parameter is, a, mosquito biting rate and the less effective one is α h , human progression rate. Our numerical simulations show that, reducing the biting rate of mosquitoes will reduce the number of exposed humans as well as infected individuals and increase the number of treated individuals. This can be achieved by increasing the proportion of antibodies.