Abstract
BackgroundMalaria is a leading cause of mortality and morbidity in tropical countries, especially in sub-Saharan Africa. In Senegal, a control plan implemented in the beginning of the 2000s has enabled a substantial reduction of mortality and morbidity due to malaria. However, eradication of malaria requires a vaccine that protects against Plasmodium falciparum the deadliest species of the parasite that causes this disease. Plasmodium falciparum is characterized by an extensive genetic diversity that makes vaccine development challenging. In this study, the diversity of P. falciparum isolates was analysed from asymptomatic children residing in the district of Toubacouta, Senegal.MethodsA nested PCR approach was used to perform genotyping of the msp-1 and msp-2 loci in samples from 87 asymptomatic children infected with P. falciparum, collected during a cross sectional survey in November and December 2010. Parasite densities in blood samples were determined by microscopic examination and statistical analyses were used to identify association of parasite genotype and parasitaemia.ResultsGenotyping was successful in 84/87 and 82/87 samples for msp-1 and msp-2, respectively. A strong genetic diversity was found with a total of 15 and 21 different alleles identified for msp-1 and msp-2, respectively. RO33 was the most frequent allelic family of msp-1 followed by MAD20, then by K1. Regarding msp-2 allelic families, 3D7 was more common than FC27. Multiple infections were predominant, since 69% and 89% of the samples genotyped for msp-1 and msp-2 showed more than one clone of P. falciparum with complexity of infection (COI) of 2.5 and 4.7, respectively. Expected heterozygosity (HE) was 0.57 and 0.55 for msp-1 and msp-2, respectively. Interestingly, polyclonal infections were significantly associated with higher parasitaemia.ConclusionsThe strong genetic diversity of P. falciparum clones and the association of polyclonal infection with high parasitaemia call for a multi-allelic approach in the design of vaccine candidates for efficient malaria eradication.
Highlights
Malaria is a leading cause of mortality and morbidity in tropical countries, especially in sub-Saharan Africa
In Senegal, 492,253 clinical cases and 526 deaths were reported in 2015. These figures represent a 12-times reduction compared to those from 2001, a substantial decrease that highlights the success of the malaria control programme that was implemented in Senegal in the beginning of the 2000s [2]. This malaria control programme was based on several approaches including widespread use of insecticide-treated mosquito nets (ITNs), rapid diagnostic testing (RDTs), treatment with artemisinin-based combination therapy (ACT), indoor residual spraying of insecticides (IRS), intermittent preventive treatment in pregnancy (IPTp) and seasonal malaria chemoprevention (SMC) in children under 10 years of age with sulfadoxine–pyrimethamine plus amodiaquine in areas of high seasonal malaria transmission [1]
The results show that polyclonality is likely to be associated with high parasitaemia
Summary
Malaria is a leading cause of mortality and morbidity in tropical countries, especially in sub-Saharan Africa. These figures represent a 12-times reduction compared to those from 2001, a substantial decrease that highlights the success of the malaria control programme that was implemented in Senegal in the beginning of the 2000s [2] This malaria control programme was based on several approaches including widespread use of insecticide-treated mosquito nets (ITNs), rapid diagnostic testing (RDTs), treatment with artemisinin-based combination therapy (ACT), indoor residual spraying of insecticides (IRS), intermittent preventive treatment in pregnancy (IPTp) and seasonal malaria chemoprevention (SMC) in children under 10 years of age with sulfadoxine–pyrimethamine plus amodiaquine in areas of high seasonal malaria transmission [1]. Despite this undisputable success, multiple factors can threaten malaria control efforts and compromise elimination including the emergence of drug-resistant parasite strains [3], insecticide-resistant mosquito vectors [4] as well as the weakness of the healthcare systems since malaria endemic countries are among the poorest in the world [5]
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