Spatial distribution of the sibling species of Anopheles gambiae sensu lato (Diptera: Culicidae) and malaria prevalence in Bayelsa State, Nigeria

Particle and Fibre Toxicology

Thomas Commander¹  Samuel N Okiwelu³  Peter I Agi³  Aline Edith Mekeu Noutcha³  Amawulu Ebenezer² 

[1] Department of Biological Sciences, Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria;Department of Biology, Isaac Jasper Boro College of Education, Bayelsa State, Nigeria;Department of Animal and Environmental Biology, University of Port-Harcourt, Port-Harcourt, Nigeria

关键词: Bayelsa- State;    Distribution;    GIS;    Malaria prevalence;    Sibling species;    An. gambiae s.l;   

Others  :  822990
DOI  :  10.1186/1756-3305-7-32

 received in 2013-07-19, accepted in 2014-01-04,  发布年份 2014

【 摘 要 】

Background

Much 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.

Methods

Mosquito 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.

Results

An. 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.

Conclusion

High 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.

【 授权许可】

   
2014 Ebenezer et al.; licensee BioMed Central Ltd.

【 图 表 】

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Figure 2.

Figure 1.

Figure 2.

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