Genetic diversity and allele frequencies of Plasmodium falciparum msp1 and msp2 in parasite isolates from Bioko Island, Equatorial Guinea

Abstract

BackgroundMalaria is still a serious public health problem on Bioko Island (Equatorial Guinea), although the number of annual cases has been greatly reduced since 2004 through the Bioko Island Malaria Control Project (BIMCP). A better understanding of malaria parasite population diversity and transmission dynamics is critical for assessing the effectiveness of malaria control measures. The objective of this study is to investigate the genetic diversity of Plasmodium falciparum populations and multiplicity of infection (MOI) on Bioko Island 7 years after BIMCP.MethodsA total of 181 patients with uncomplicated P. falciparum malaria diagnosed with microscopy were collected from Bioko Island from January 2011 to December 2014. Parasite DNA was extracted using chelex-100 and species were identified using a real-time PCR followed by high-resolution melting. Plasmodium falciparum msp1 and msp2 allelic families were determined using nested PCR.ResultsThree msp1 alleles (K1, MAD20, and RO33) and two msp2 alleles (FC27 and 3D7) were analysed in all samples. In msp1, the MAD20 allelic family was predominant with 96.69% (175/178) followed respectively by the K1 allelic family with 96.07% (171/178) and R033 allelic family with 70.78% (126/178). In msp2, the FC27 allelic family was the most frequently detected with 97.69% (169/173) compared to 3D7 with 72.25% (125/173). Twenty-six different alleles were observed in msp1 with 9 alleles for K1, 9 alleles for MAD20 and 8 alleles for R033. In msp2, 25 individual alleles were detected with 5 alleles for FC27 and 20 alleles for 3D7. The overall MOI was 5.51 with respectively 3.5 and 2.01 for msp1 and msp2. A significant increase in overall MOI was correlated with the age group of the patients (P = 0.026) or parasite densities (P = 0.04).ConclusionsThe present data showed high genetic diversity and MOI values among the P. falciparum population in the study, reflecting both the high endemic level and malaria transmission on Bioko Island. These data provide valuable information for surveillance of P. falciparum infection and for assessing the appropriateness of the current malarial control strategies in the endemic area.

Kelch13 and MDR1 Polymorphisms, and Drug Effectiveness at Day 3 after Dihydroartemisinin-Piperaquine Treatment for Plasmodium falciparum Malaria on Bioko Island, Equatorial Guinea: 2014-2017

“…Among the 320 patients evaluated on D3, 5.9% (19/320) showed D3 positivity by microscopy, which was also confirmed and identified the Plasmodium species by PCR-HRM (14,15). These 19 patients had D0 and D3 parasite densities of 900 to 8000 and 40 to 2120 parasites/μl, respectively.…”

“…Although DHA-PIP remains efficacious in the study region and those ART-resistance mutations are not found, ACT may pose positive selection on the parasites. In additionally, the rate of transmission and the diversity of vector species on Bioko Island may also increase selection pressure on parasite strains (14). More isolates from cases with delayed parasite clearance after DHA-PIP treatment indicated that in vitro and in viv o monitoring for ART derivatives and ACT partner drugs should be regularly performed on Bioko Island, Equatorial Guinea.…”

“…Bioko is an island 32 km off the west coast of Africa, and the northernmost part of Equatorial Guinea. It’s population, of approximately 334, 463 (2015 census, of which approximately 90% live in Malabo, the capital city) are at risk of malaria year-round (14). Before the launch of the BIMCP in 2004, entomological inoculation rates (EIR) on the island were in excess of 750 infectious bites per person per year (14).…”

“…Consent was obtained from all participating subjects or their parents. Laboratory screening for malaria was done using an Immunochromatographic Diagnostic Test (ICT Malaria Combo Cassette Test) and confirmed using microscopic examination of blood smears (13,14). Extra blood drops were collected for a malaria smear and onto Whatman 903® filter paper (GE Healthcare, Pittsburgh, USA).…”

“…Extra blood drops were collected for a malaria smear and onto Whatman 903® filter paper (GE Healthcare, Pittsburgh, USA). The Plasmodium species were identified by a real-time PCR followed by high-resolution melting (PCR-HRM) as our previous reports (14,15). Patients positive for P. falciparum were treated with DHA-PIP according to the national treatment guidelines.…”