Epidemiology of Relapsing and Falciparum Malaria in the Highlands of Cameroon: An Integrated Community Survey of Human Infection and Vector Abundance

  1. Samuel J. White
  2. Valery P. K. Tchuenkam
  3. Mariama Mbouh
  4. Claudia Gaither
  5. Aline Gaelle Bouopda-Tuedom
  6. Belinda Kiam
  7. Zachary R. Popkin-Hall
  8. Jacob M. Sadler
  9. Kelly Carey-Ewend
  10. Emily Hand
  11. Miriam N. Ngum
  12. Yannick N. Ngomsi
  13. Jeffrey A Bailey
  14. Darlin B. Kaunda
  15. Lethicia K. Mafo
  16. Giresse N. Lemogo
  17. Clifford L. Dinka
  18. Clifford A. Nsani
  19. Michel Noubom
  20. Varun Goel
  21. Ibrahima Ibrahima
  22. Janvier C. Onguene
  23. Feng-Chang Lin
  24. Jessica T. Lin
  25. Sandrine E. Nsango
  26. Rhoel R. Dinglasan
  27. Jonathan J. Juliano
  28. Innocent M. Ali
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Abstract

Despite global malaria control efforts, the disease caused 263 million cases and 597,000 deaths in 2023. WhilePlasmodium falciparumaccounts for most cases in Africa, non-falciparum species, such asP. ovalespp. andP. vivax, can cause relapse infections and are increasingly recognized as significant contributors to human disease. In particular, the highlands of West Cameroon have previously been reported to have highP. vivaxinfection rates. This study presents preliminary results from the Relapsing Malaria in Africa (ReMA) study, conducted in Dschang, Cameroon, to assess the prevalence and epidemiology ofP. vivaxandP. ovale. A cross-sectional survey of 3,661 participants from 871 households across seven health areas identified a low prevalence ofP. vivax(0.1%) andP. ovalespp. (0.64%) using quantitative real time PCR (qPCR), whileP. falciparumremained prevalent at 8.1%. Co-infections ofP. ovalespp. withP. falciparumwere observed in 23.1% ofP. ovalespp. cases. While gametocytemia was common among falciparum infections, leveraging a new ovale gametocyte assay, we found that gametocytemia was uncommon among the qPCR-positive ovale infections. Spatial analysis foundP. vivaxandP. ovalespp. infections concentrated in Penka-Michel and Baleveng, the former having higherAnophelesspp. abundance than other areas assessed. Risk factor analysis revealed children and those with recent domestic travel had higher odds ofP. falciparuminfection, but no significant associations were found forP. ovalespp. infections. Entomological surveys confirmed high densities ofAnopheles gambiae sensu lato(s.l.) andAn. funestus(s.l.), with significantly higher human landing capture rates forAn. gambiaes.l compared to other mosquito species. While these findings suggest that the relapsing malarias are not as widespread as previously thought in West Cameroon, understanding factors driving their persistent transmission, especially without prevalent gametocytemia, will be important for disease control.

AUTHOR SUMMARY

Malaria caused 263 million cases and 597,000 deaths in 2023, with most cases in Africa due toPlasmodium falciparum. However, the dangers of other species likeP. ovaleandP. vivax, which can cause relapsing infections, are becoming more clear in Africa. The Relapsing Malaria in Africa (ReMA) study in Dschang, Cameroon, surveyed 3,661 people from 871 households to better understand these infections. Results showed low rates ofP. vivax(0.1%) andP. ovale(0.64%) compared toP. falciparum(8.1%). Infections were more common in areas with high mosquito abundance and biting activity. While the relapsing malarias were less common than expected, understanding factors driving their persistent transmission, especially without prevalent gametocytemia, will be important for disease control.

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