Plasmodium malariae contributes to high levels of malaria transmission in a forest–savannah transition area in Cameroon

Abstract

Background Malaria control efforts are highly skewed towards Plasmodium falciparum while overlooking other Plasmodium species such as P. malariae. A better understanding of the role of Plasmodium species other than P. falciparum is needed to strengthen malaria elimination initiatives. The aim of the present study was to elucidate the contribution of P. malariae to malaria transmission in Cameroon. Methods The study was conducted in the Ngatti Health District, a forest–savannah transition area in the Adamawa Region, Cameroon. A total of 497 individuals aged from 1 to 85 years were diagnosed with malaria in November 2020 using a rapid diagnostic test (RDT) and microscopy. Adult mosquitoes were collected between September 2019 and March 2020 by indoor aspiration and identified morphologically and molecularly. The infection status of Plasmodium spp. was also determined by quantitative PCR, and dried blood spots were collected from 156 participants with the aim to detect different Plasmodium species by nested PCR. Results The overall Plasmodium prevalence was 50.3%, 51.8% and 64.7%, as detected by microscopy, the RDT and PCR, respectively. Based on the PCR results, P. falciparum was the most prevalent species (43%); followed by co-infections P. falciparum/P. malariae (17%), P. falciparum/P. ovale (1.3%), P. falciparum/P. ovale/P. malariae (1.3%); and then by P. malariae mono-infection (2.5%). The same trend was observed using microscopy, with 35% of participants infected with P. falciparum, 11% co-infected with P. falciparum/P. malariae and 4% infected with P. malariae. The prevalence and parasite density of malaria infection varied significantly with age group (P < 0.05), with the highest prevalence rate observed in children aged 6–10 years (P = 0.0001) while the density of Plasmodium infection increased significantly in children aged < 5 years compared to the other age groups (P = 10−3). Among the 757 Anopheles mosquitoes collected, 737 (97.35%) were An. funestus sensu stricto, 15 (1.9%) were An. gambiae and 5 (0.6%) were An. hancocki. The Plasmodium species recorded at the head/thorax level were P. falciparum and P. malariae, with a sporozoite infection rate of 8.4%; the highest sporozoite infection rate was recorded at Mibellon village (13.6%). Conclusion The results of this study reveal the significant contribution of P. malariae, in addition to P. falciparum, to the high malaria transmission rate in this region. These findings highlight the need to deploy initiatives to also tackle this Plasmodium species to eliminate malaria in the region. Graphical Abstract

Malaria species positivity rates among symptomatic individuals across regions of differing transmission intensities in Mainland Tanzania

“…have relapsing stages like P. vivax , which likely means that their control and elimination will be more difficult, as is true of P. vivax [12]. P. malariae is thought to be more prevalent than P. ovale , particularly in West Africa[5,6,14,15]. It does not have a liver stage, but can cause long-term persistent infection[14].…”

“…Although Plasmodium falciparum is the most prevalent and deadliest human malaria species in the SSA region, four other species are present (P. vivax, P. malariae, P. ovale curtisi, and P. ovale wallikeri). Furthermore, recent research suggests that these four species are more prevalent than previously thought and their prevalence may increase in the context of intensive P. falciparum control/elimination [2][3][4][5][6][7][8]. This possibility is particularly salient in light of current malaria elimination goals stemming from the WHO Global Technical Strategy [9], which aims by 2030 to reduce the global malaria burden by 90% from 2015 levels.…”

Geographical emergence of sulfadoxine-pyrimethamine drug resistance-associated P. falciparum and P. malariae alleles in co-existing Anopheles mosquito and asymptomatic human populations across Cameroon

“…Demographic data were collected from each participant using a questionnaire with capillary blood collected from each participant aged between 2 years and 50 + years in Mibellon (September 2020) ( 36 ) and Elende (August 2021). In Gounougou (March 2021), only the 3 to 15 years age group was recruited for finger-prick blood sampling as previously published ( 37 ).…”

Plasmodium vivax in Sub-Saharan Africa: An Advancing Threat to Malaria Elimination?

“…1 The association between P. falciparum and severe morbidity and mortality and its capacity to evolve mechanisms to resist and tolerate historically important drugs (sulfadoxine-pyrimethamine, chloroquine, 2 and artemisinins 3 ), requires focus on this dangerous malaria species. Although there are cases of single and mixed species infections of P. malariae and P. ovale with and without P. falciparum , 4 – 8 cases of P. vivax have been thought to be absent in sSA due to the erythrocyte silent Duffy-negative phenotype across a substantial number of African ethnicities. 9 , 10 As has become a paradigm in the malaria literature, P. vivax appears to require the Duffy antigen to invade human erythrocytes.…”