Abstract
BackgroundIn this paper we analyse the Plasmodium sp. prevalence in three villages with different isolation status on the island of Bioko (Equatorial Guinea) where malaria is a hyper-endemic disease. We also describe the genetic diversity of P. falciparum, using several plasmodia proteins as markers which show a high degree of polymorphism (MSP-1 and MSP-2). The results obtained from three different populations are compared in order to establish the impact of human movements and interventions.MethodsPlasmodium sp. were analysed in three villages on Bioko Island (Equatorial Guinea), one of which (Southern) is isolated by geographical barriers. The semi-nested multiplex polymerase chain reaction (PCR) technique was used to determine the prevalence of the four human plasmodia species. The genotyping and frequency of P. falciparum populations were determined by PCR assay target polymorphism regions of the merozoite surface proteins 1 and 2 genes (MSP-1 and MSP-2).ResultsThe data obtained show that there are no differences in plasmodia population flow between the Northwest and Eastern regions as regards the prevalence of the different Plasmodium species. The Southern population, on the other hand, shows a minor presence of P. malariae and a higher prevalence of P. ovale, suggesting some kind of transmission isolated from the other two. The P. falciparum genotyping in the different regions points to a considerable allelic diversity in the parasite population on Bioko Island, although this is somewhat higher in the Southern region than the others. There was a correlation between parasitaemia levels and the age of the individual with the multiplicity of infection (MOI).ConclusionResults could be explained by the selection of particular MSP alleles. This would tend to limit diversity in the parasite population and leading up to the extinction of rare alleles. On the other hand, the parasite population in the isolated village has less outside influence and the diversity of P. falciparum is maintained higher. The knowledge of parasite populations and their relationships is necessary to study their implications for control intervention.
Highlights
In this paper we analyse the Plasmodium sp. prevalence in three villages with different isolation status on the island of Bioko (Equatorial Guinea) where malaria is a hyper-endemic disease
polymerase chain reaction (PCR) and microscopy identified a different malaria parasite; a P. falciparum infection by PCR was identified as P. ovale infection by microscopy
Nine of the 16 mixed infections detected only by PCR occurred in samples with low parasitaemia for the single species detected by microscopy (
Summary
In this paper we analyse the Plasmodium sp. prevalence in three villages with different isolation status on the island of Bioko (Equatorial Guinea) where malaria is a hyper-endemic disease. Equatorial Guinea is composed of three highly diverse and disparate territories and its total surface area is 28,068 km. Equatorial Guinea is composed of three highly diverse and disparate territories and its total surface area is 28,068 km2 It is divided into an insular and a continental region. Bioko Island is roughly rectangular in shape, measuring 69 km from north to south, and 32 km from east to west It has three major peaks: Pico Basile (3011 m) in the north which serves as a backdrop to the capital city of Malabo; Biao (2009 m) in the southeast, with its picturesque Caldera lake; and the Gran Caldera Volcanica de Luba (2261 m) in the southwest with its steep walls and almost inaccessible interior
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