qRT-PCR versus IFA-based quantification of male and female gametocytes in low-density Plasmodium falciparum infections and their relevance for transmission

Gruenberg, Maria, Hofmann, Natalie E., Nate, Elma, Karl, Stephan, Robinson, Leanne J., Lanke, Kjerstin, Smith, Thomas A., Bousema, Teun, and Felger, Ingrid (2020) qRT-PCR versus IFA-based quantification of male and female gametocytes in low-density Plasmodium falciparum infections and their relevance for transmission. Journal of Infectious Diseases, 221 (4). pp. 598-607.

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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.

Item ID: 63607
Item Type: Article (Research - C1)
ISSN: 1537-6613
Keywords: male gametocytes, sex ratio, transmission reservoir, low density, Plasmodium falciparum, ultrasensitive diagnostics
Copyright Information: © The Author(s) 2019. Published by Oxford University Press for the Infectious Diseases Society of America. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs licence (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reproduction and distribution of the work, in any medium, provided the original work is not altered or transformed in any way, and that the work is properly cited. For commercial re-use, please contact journals.permissions@oup.com
Funders: Swiss National Science Foundation (SNSF), World Health Organisation (WHO), Netherlands Organization for Scientific Research (NOSR), National Health and Medical Research Council (NHMRC)
Projects and Grants: SNSF 310030_159580, WHO Special Programme for Research and Training in Tropical Diseases WCCPRD4426109 2016/63907, NOSR 016.158.306, NHMRC GNT1161627, NHMRC GNT1141441
Date Deposited: 07 Jul 2020 00:31
FoR Codes: 32 BIOMEDICAL AND CLINICAL SCIENCES > 3202 Clinical sciences > 320211 Infectious diseases @ 100%
SEO Codes: 92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920109 Infectious Diseases @ 100%
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