qRT-PCR versus IFA-based Quantification of Male and Female Gametocytes in Low-Density Plasmodium falciparum Infections and Their Relevance for Transmission
Year: 2019
Type: article
Study design: Observational Study
Abstract: BACKGROUND: Accurate quantification of female and male gametocytes and sex ratios in asymptomatic low-density malaria infections are important for assessing their transmission potential. Gametocytes often escape detection even by molecular methods, therefore ultralow gametocyte densities were quantified in large blood volumes. METHODS: Female and male gametocytes were quantified in 161 PCR-positive Plasmodium falciparum infections from a cross-sectional survey in Papua New Guinea. Ten-fold concentrated RNA from 800 µL blood was analyzed using female-specific pfs25 and male-specific pfmget or mssp qRT-PCR. Gametocyte sex ratios from qRT-PCR were compared with those from immunofluorescence assays (IFA). RESULTS: Gametocytes were identified in 58% (93/161) P. falciparum-positive individuals. Mean gametocyte densities were frequently below 1 female and 1 male gametocyte/µL by qRT-PCR. The mean proportion of males was 0.39 (95% confidence interval, 0.33-0.44) by pfs25/pfmget qRT-PCR; this correlated well with IFA results (Pearsons r2 = 0.91; P < .001). A Poisson model fitted to our data predicted 16% P. falciparum-positive individuals that are likely to transmit, assuming at least 1 female and 1 male gametocyte per 2.5 µL mosquito bloodmeal. CONCLUSIONS: Based on model estimates of female and male gametocytes per 2.5 µL blood, P. falciparum-positive individuals detected exclusively by ultrasensitive diagnostics are negligible for human-to-mosquito transmission.Estimating the transmission potential of ultralow-density malaria infections informs interventions. Almost all infections with ≥1 female and male gametocyte per 2.5 µL mosquito bloodmeal, and thus with highest likelihood of contributing to human-to-mosquito transmission, were detectable by standard molecular diagnostics.
Language: English
Topic: Malaria Research and Control
Field: Medicine
Domain: Health Sciences
Open Access status: hybrid
Estimated APC paid: $4,763
Funders: National Science Foundation, World Health Organization, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, National Institutes of Health, Medical Research Council, National Health and Medical Research Council, National Institute of Allergy and Infectious Diseases
Awards: Novel public health tools to control and eliminate parasitic diseases of global priority, Unravelling Plasmodium vivax transmission to Anopheles mosquitoes: Role of naturally acquired transmission blocking immunity and efficacy of novel vaccine and drug candidates, G4036121097, G4632760833, G5724525611, Epidemiology of ultra-low density malaria infections and their relevance for control and elimination, G8690818240, Understanding and Targeting the Barriers to Effective Malaria Control and Elimination in the Asia-Pacific Region
OpenAlex ID: W2969526631