Abstract
As morbidity and mortality due to malaria continue to decline, the identification of individuals with a high likelihood of transmitting malaria is needed to further reduce the prevalence of malaria. In areas of holoendemic malaria transmission, asymptomatically infected adults may be infected with transmissible gametocytes. The impact of HIV-1 on gametocyte carriage is unknown, but co-infection may lead to an increase in gametocytemia. In this study, a panel of qPCR assays was used to quantify gametocyte stage-specific transcripts present in dried blood spots obtained from asymptomatic adults seeking voluntary HIV testing in Kombewa, Kenya. A total of 1,116 Plasmodium-specific 18S-positive samples were tested and 20.5% of these individuals had detectable gametocyte-specific transcripts. Individuals also infected with HIV-1 were 1.82 times more likely to be gametocyte positive (P<0.0001) and had significantly higher gametocyte copy numbers when compared to HIV-negative individuals. Additionally, HIV-1 positivity was associated with higher gametocyte prevalence in men and increased gametocyte carriage with age. Overall, these data suggest that HIV-positive individuals may have an increased risk of transmitting malaria parasites in regions with endemic malaria transmission and therefore should be at a higher priority for treatment with gametocidal antimalarial drugs.
Highlights
In areas of high endemicity for malaria, adults can asymptomatically maintain Plasmodium falciparum infection through partial immunity (Druilhe and Khusmith, 1987; Smith et al, 1999)
Gametocyte prevalence within a population is known to be dependent on several factors, including age and malaria endemicity (Ouédraogo et al, 2007; Stepniewska et al, 2008; Farfour et al, 2012; Adomako-Ankomah et al, 2017), but gametocytemia has been difficult to accurately characterize because immature gametocytes sequester in the bone marrow (Rogers et al, 2000; Joice et al, 2014) and gametocytes are underreported by microscopy (Dowling and Shute, 1966; Koepfli and Yan, 2018)
The gene product pfs25, which is highly expressed by female stage V gametocytes, is commonly used as a marker for gametocyte carriage, as it most accurately reflects the presence of mature gametocytes that are infective to mosquitoes (Niederwieser et al, 2000; Schneider et al, 2004)
Summary
In areas of high endemicity for malaria, adults can asymptomatically maintain Plasmodium falciparum infection through partial immunity (Druilhe and Khusmith, 1987; Smith et al, 1999). The gene product pfs, which is highly expressed by female stage V gametocytes, is commonly used as a marker for gametocyte carriage, as it most accurately reflects the presence of mature gametocytes that are infective to mosquitoes (Niederwieser et al, 2000; Schneider et al, 2004). The majority of gametocytes appear to sequester in the bone marrow during development (Rogers et al, 2000; Joice et al, 2014), low levels of transcripts for early and intermediate stages can be detected in peripheral blood (Aguilar et al, 2014)
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