TY - JOUR
T1 - Changing Clinical Epidemiology of Plasmodium vivax Malaria as Transmission Decreases
T2 - Population-Based Prospective Panel Survey in the Brazilian Amazon
AU - Fontoura, Pablo S
AU - Macedo, Evelyn G
AU - Calil, Priscila R
AU - Corder, Rodrigo M
AU - Rodrigues, Priscila T
AU - Tonini, Juliana
AU - Esquivel, Fabiana D
AU - Ladeia, Winni A
AU - Fernandes, Anderson R J
AU - Johansen, Igor C
AU - Silva, Marcos F
AU - Fernandes, Amanda O S
AU - Ladeia-Andrade, Simone
AU - Castro, Marcia C
AU - Ferreira, Marcelo U
N1 - This work was supported by the Fundacao de Amparo a Pesquisa do Estado de Sao Paulo, Brazil (2016/18740-9 to M. U. F.); the David Rockefeller Center for Latin American Studies, Harvard University (to M. C. C.); the National Institutes of Health (grant U19 AI089681 subcontracts to M. U. F. and M. C. C.); the Fundacao para a Ciencia e Tecnologia, Portugal (institutional Global Health and Tropical Medicine project, UID/04413/2020); the Fundacao de Amparo a Pesquisa do Estado de Sao Paulo provided fellowships to P. S. F., F. D. E., P. T. R., and I. C. J.; and the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, Brazil, provided research fellowships to E. G. M. and M. U. F.
© The Author(s) 2024. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For permissions, please e-mail: [email protected].
PY - 2024/4/15
Y1 - 2024/4/15
N2 - BACKGROUND: Malarial infections are often missed by microscopy, and most parasite carriers are asymptomatic in low-endemicity settings. Whether parasite detectability and its ability to elicit symptoms change as transmission declines remains unclear.METHODS: We performed a prospective panel survey with repeated measurements on the same participants over 12 months to investigate whether Plasmodium vivax detectability by microscopy and risk of symptoms upon infection varied during a community-wide larviciding intervention in the Amazon basin of Brazil that markedly reduced vector density. We screened 1096 to 1400 residents in the intervention site for malaria by microscopy and quantitative TaqMan assays at baseline and twice during intervention.RESULTS: We found that more P vivax infections than expected from their parasite densities measured by TaqMan assays were missed by microscopy as transmission decreased. At lower transmission, study participants appeared to tolerate higher P vivax loads without developing symptoms. We hypothesize that changes in the ratio between circulating parasites and those that accumulate in the bone marrow and spleen, by avoiding peripheral blood microscopy detection, account for decreased parasite detectability and lower risk of symptoms under low transmission.CONCLUSIONS: P vivax infections are more likely to be subpatent and remain asymptomatic as malaria transmission decreases.
AB - BACKGROUND: Malarial infections are often missed by microscopy, and most parasite carriers are asymptomatic in low-endemicity settings. Whether parasite detectability and its ability to elicit symptoms change as transmission declines remains unclear.METHODS: We performed a prospective panel survey with repeated measurements on the same participants over 12 months to investigate whether Plasmodium vivax detectability by microscopy and risk of symptoms upon infection varied during a community-wide larviciding intervention in the Amazon basin of Brazil that markedly reduced vector density. We screened 1096 to 1400 residents in the intervention site for malaria by microscopy and quantitative TaqMan assays at baseline and twice during intervention.RESULTS: We found that more P vivax infections than expected from their parasite densities measured by TaqMan assays were missed by microscopy as transmission decreased. At lower transmission, study participants appeared to tolerate higher P vivax loads without developing symptoms. We hypothesize that changes in the ratio between circulating parasites and those that accumulate in the bone marrow and spleen, by avoiding peripheral blood microscopy detection, account for decreased parasite detectability and lower risk of symptoms under low transmission.CONCLUSIONS: P vivax infections are more likely to be subpatent and remain asymptomatic as malaria transmission decreases.
U2 - 10.1093/infdis/jiad456
DO - 10.1093/infdis/jiad456
M3 - Article
C2 - 38324758
SN - 0022-1899
VL - 229
SP - 947
EP - 958
JO - Journal of Infectious Diseases
JF - Journal of Infectious Diseases
IS - 4
M1 - jiad456
ER -
