Characterising co-infections with Plasmodium spp., Mansonella perstans or Loa loa in asymptomatic children, adults and elderly people living on Bioko Island using nucleic acids extracted from malaria rapid diagnostic tests

BackgroundRegular and comprehensive epidemiological surveys of the filarial nematodesMansonella perstansandLoa loain children, adolescents and adults living across Bioko Island, Equatorial Guinea are lacking. We aimed to demonstrate that blood retained on malaria rapid diagnostic tests, commonly deployed for malaria surveys, could be used as a source of nucleic acids for molecular based detection ofM.perstansandL.loa. We wanted to determine the positivity rate and distribution of filarial nematodes across different age groups and geographical areas as well as to understand level of co-infections with malaria in an asymptomatic population.MethodologyM.perstans,L.loaandPlasmodiumspp. parasites were monitored by qPCR in a cross-sectional study using DNA extracted from a subset malaria rapid diagnostic tests (mRDTs) collected during the annual malaria indicator survey conducted on Bioko Island in 2018.Principal findingsWe identified DNA specific for the two filarial nematodes investigated among 8.2% (263) of the 3214 RDTs screened. Positivity rates ofM.perstansandL.loawere 6.6% and 1.5%, respectively.M.perstansinfection were more prominent in male (10.5%) compared to female (3.9%) survey participants.M.perstansparasite density and positivity rate was higher among older people and the population living in rural areas. The socio-economic status of participants strongly influenced the infection rate with people belonging to the lowest socio-economic quintile more than 3 and 5 times more likely to beL.loaandM.perstansinfected, respectively. No increased risk of being co-infected withPlasmodiumspp. parasites was observed among the different age groups.Conclusions/SignificanceWe found otherwise asymptomatic individuals were infected withM.perstansandL.loa. Our study demonstrates that employing mRDTs probed with blood for malaria testing represents a promising, future tool to preserve and ship NAs at room temperature to laboratories for molecular, high-throughput diagnosis and genotyping of blood-dwelling nematode filarial infections. Using this approach, asymptomatic populations can be reached and surveyed for infectious diseases beyond malaria.