Abstract
Presence of mature gametocyte forms of malaria parasites in peripheral blood is a key requirement for malaria transmission. Yet, studies conducted in most malaria transmission zones report the absence of gametocyte in the majority of patients. We therefore sought to determine the risk factors of both all-stage and mature gametocyte carriage in an area with high stable transmission of Plasmodium falciparum in Cameroon. Gametocyte positivity was determined using three complementary methods: thick blood smear microscopy, RT-PCR and RT-LAMP, whereas exposure to the infection was assessed by enzyme-linked immunosorbent assay. Of 361 malaria endemic residents randomly included in the study (mean age: 28±23 years, age range: 2–100 years, male/female sex ratio: 1.1), 87.8% were diagnosed with P. falciparum infection, of whom 45.7% presented with fever (axillary body temperature ≥37.5°C). Mature gametocyte positivity was 1.9% by thick blood smear microscopy and 8.9% by RT-PCR targeting the mature gametocyte transcript, Pfs25. The gametocyte positivity rate was 24.1% and 36.3% by RT-PCR or RT-LAMP, respectively, when targeting the sexual stage marker, Pfs16. Multivariate analyses revealed anemia as a common independent risk factor for both mature and all-stage gametocyte carriage, whereas fever and low anti-gametocyte antibody levels were independently associated with all-stage gametocyte carriage only. Taken together, the data suggest important differences in risk factors of gametocyte carriage depending on stage analyzed, with anemia, fever and low antiplasmodial plasma antibody levels representing the major contributing risk factors.
Highlights
Despite considerable global efforts against malaria, the disease remains a major public health problem globally
Carriers of the sexual parasite stages known as mature gametocytes are infectious to mosquitoes, and gametocyte carriage is dependent on host and parasite factors that may vary between individuals or geoepidemiological transmission zones[4,5,6]
To determine possible risk factors of gametocyte carriage in an area of high stable transmission of P. falciparum, a total of 361 participants with a mean age of 28 ± 23 years were randomly enrolled in this study
Summary
Despite considerable global efforts against malaria, the disease remains a major public health problem globally. Carriers of the sexual parasite stages known as mature gametocytes are infectious to mosquitoes, and gametocyte carriage is dependent on host and parasite factors that may vary between individuals or geoepidemiological transmission zones[4,5,6]. Under certain stress conditions including antimalarial medication [21,22,23,24], anemia [15], and host immune activity [9], a strong gametocyte surge can be observed [25,26] It is not known if all or some of the above factors constitute risk factors for sexual commitment and circulation of early gametocyte forms in infected persons. Methods based on the early gametocytogenesis marker Pfs and the mature gametocyte stage marker Pfs are the most widely used [27,28,29,30,31]
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