article · The Journal of Infectious Diseases
Asymptomatic carriers of malaria often carry low parasite densities that standard rapid tests miss, but they continue to spread the parasite to mosquitoes. Using direct skin feeding assays in Bagamoyo, Tanzania, researchers tested how efficiently individuals older than five years transmitted malaria to Anopheles gambiae mosquitoes. Out of 491 participants with low median parasite levels, 22 percent infected mosquitoes. Transmission was heavily skewed: just three percent of tested participants were responsible for 57 percent of all infected mosquitoes. In addition, school-age children who tested positive by rapid diagnostic tests accounted for 58 percent of all mosquito infections. Mosquitoes were successfully infected even by people with parasite levels at or below the limit of PCR detection at the time of feeding. The assays also revealed widespread, unexpected co-transmission of Plasmodium ovale alongside Plasmodium falciparum.
Malaria elimination efforts are challenged by individuals who show no symptoms but still transmit parasites to mosquitoes. Demonstrating that a tiny fraction of carriers, especially school-age children, drives the majority of transmission shows that control programmes can achieve larger impacts by targeting these specific groups. It also highlights that hidden species like Plasmodium ovale are being actively transmitted.
The findings are early-stage field research that could guide public health bodies and vector control programmes targeting high-transmitting groups, such as school-age children. Developers of malaria diagnostic tools might also use these insights to evaluate sensitivity requirements, as current rapid tests and standard PCR miss transmissible infections. However, the abstract does not describe a direct commercial product or technology pathway ready for deployment.
AI-generated from the published abstract. Always read the original work before citing.
BACKGROUND: Asymptomatic malaria carriers often harbor low parasite densities missed by rapid diagnostic tests (RDTs), yet they contribute to transmission. Direct skin feeding (DSF) assays can sensitively measure their infectiousness to mosquitoes. METHODS: To characterize human-to-mosquito transmission from the asymptomatic reservoir in Bagamoyo, Tanzania, DSFs were performed in persons >5 years of age positive for Plasmodium falciparum by RDT or real-time PCR. Fifty colony-reared Anopheles gambiae were fed on the posterior calves. Successful mosquito infection was defined as ≥1 oocyst-positive mosquito midgut among 25 dissected eight days postskin feeding. RESULTS: Among 491 participants with median parasite density of 5.1 parasites/μL who underwent DSF, 22% were infectious to mosquitoes. RDT-positive participants infected roughly twice as many mosquitoes compared to RDT-negative/PCR-positive persons. However, up to 21% of infectious carriers were PCR-negative at the time of skin feeding, after screening PCR-positive a few days earlier. Overall, 9.1% (342/3741) of mosquitoes fed on infectious carriers were parasite-positive at dissection. Half of infectious individuals infected a single mosquito, while the top 16 transmitters (3% of those undergoing DSF) cumulatively infected 57% of infected mosquitoes. RDT-positive school-age children (6-15 years), 27% of the DSF cohort, contributed to 58% of infected mosquitoes. Unexpectedly, mosquito midguts from 39 DSFs (44% of oocyst-positive feeds analyzed) tested positive for Plasmodium ovale. CONCLUSIONS: Parasites circulating at the limit of PCR detection commonly infect mosquitoes. However, a small proportion of highly infectious carriers contribute disproportionately to transmission, offering potential for targeted interventions. P. ovale was frequently co-transmitted with P. falciparum to mosquitoes.
This page summarises published work. The authoritative version sits with the publisher.
DOI: 10.1093/infdis/jiaf634
Is something wrong with this record? Report it or request removal.
Discussion
Have you built on this work, tried to replicate it, or seen it applied in practice? Share what you know. Verified researchers and MARATTO™ domain experts can open a discussion, and any member can reply. Contributions are reviewed before they appear.
No discussion yet. Open the first thread.
New to MARATTO™? Create a free account.
