Insights into Plasmodium vivax Asymptomatic Malaria Infections and Direct Skin-Feeding Assays to Assess Onward Malaria Transmission in the Amazon

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  • 1 Division of Infectious Diseases, Department of Medicine, University of California San Diego, La Jolla, California;
  • | 2 Instituto de Medicina Tropical “Alexander von Humboldt,” Universidad Peruana Cayetano Heredia, Lima, Peru;
  • | 3 Laboratorio ICEMR-Amazonia, Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru;
  • | 4 Laboratorio de Malaria, Parásitos y Vectores, Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru;
  • | 5 Facultad de Salud Pública, Universidad Peruana Cayetano Heredia, Lima, Peru;
  • | 6 Department of Biomedical Sciences, School of Public Health, University at Albany–State University of New York, Albany, New York;
  • | 7 Wadsworth Center, New York State Department of Health, Albany, New York;
  • | 8 Departamento de Ciencias Celulares y Moleculares, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru;
  • | 9 Section of Infectious Diseases, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
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Understanding the reservoir and infectivity of Plasmodium gametocytes to vector mosquitoes is crucial to align strategies aimed at malaria transmission elimination. Yet, experimental information is scarce regarding the infectivity of Plasmodium vivax for mosquitoes in diverse epidemiological settings where the proportion of asymptomatically infected individuals varies at a microgeographic scale. We measured the transmissibility of clinical and subclinical P. vivax malaria parasite carriers to the major mosquito vector in the Amazon Basin, Nyssorhynchus darlingi (formerly Anopheles). A total of 105 participants with natural P. vivax malaria infection were recruited from a cohort study in Loreto Department, Peruvian Amazon. Four of 18 asymptomatic individuals with P. vivax positivity by blood smear infected colony-grown Ny. darlingi (22%), with 2.6% (19 of 728) mosquitoes infected, in contrast to 77% (44/57) symptomatic participants being infectious to mosquitoes and 51% (890 of 1,753) mosquitoes infected. Infection intensity was greater in symptomatic infections (mean, 17.8 oocysts/mosquito) compared with asymptomatic infections (mean, 0.28 oocysts/mosquito), attributed to parasitemia/gametocytemia level. Paired experiments (N = 27) using direct skin-feeding assays and direct membrane mosquito-feeding assays showed that infectivity to mosquitoes was similar for both methods. Longitudinal studies with longer follow-up of symptomatic and asymptomatic parasite infections are needed to determine the natural variations of disease transmissibility.

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Author Notes

Address correspondence to Katherine Torres, Malaria Laboratory, Laboratorios de Investigación y Desarrollo, Faculty of Science and Institute of Tropical Medicine Alexander von Humboldt, Universidad Peruana Cayetano Heredia. E-mail: katherine.torres.f@upch.pe

These authors contributed equally to this work.

Financial support: This research was funded by NIH National Institute of Allergy and Infectious Diseases (NIAID) (U19AI089681) to J. M. V. and was funded in part by NIH-NIAID (R01AI110112) to J. E. C.

Authors’ addresses: Marta Moreno, Department of Infection Biology, London School of Hygiene & Tropical Medicine, London, UK, E-mail: marta.moreno@lshtm.ac.uk. Katherine Torres, Instituto de Medicina Tropical “Alexander von Humboldt,” Universidad Peruana Cayetano Heredia, Lima, Peru, E-mail: katherine.torres.f@upch.pe. Carlos Tong, Gerson Guedez, Lutecio Torres, Manuela Herrera-Varela, Layné Guerra, Mitchel Guzman, Daniel Wong, and Roberson Ramirez, Laboratorio ICEMR-Amazonia, Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru, E-mails: ctong32@gmail.com, gersonerick@hotmail.es, eddie.torres.t@upch.pe, manuelahv82@gmail.com, laygueva.12@gmail.com, guzman.mitch@gmail.com, danielantonio@outlook.com.pe, and roberson.ramirez.s@upch.pe. Stefano S. García Castillo, Laboratorio de Malaria, Parásitos y Vectores, Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru, E-mail: stefano.garcia.c@upch.pe. Gabriel Carrasco-Escobar and Alejandro Llanos-Cuentas, Department of Epidemiology, University of California San Diego, La Jolla, CA, E-mails: gabriel.carrasco@upch.pe and alejandro.llanos.c@upch.pe. Jan E. Conn, Department of Biomedical Sciences, School of Public Health, University at Albany–State University of New York, Albany, NY, and Wadsworth Center, New York State Department of Health, Albany, NY, E-mail: jan.conn@health.ny.gov. Dionicia Gamboa, Instituto de Medicina Tropical “Alexander von Humboldt,” Universidad Peruana Cayetano Heredia, Lima, Peru, Laboratorio de Malaria, Parásitos y Vectores, Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru, and Departamento de Ciencias Celulares y Moleculares, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru, E-mail: dionigamboa@yahoo.com. Joseph M. Vinetz, Division of Infectious Diseases, Department of Medicine, University of California San Diego, La Jolla, CA, Instituto de Medicina Tropical “Alexander von Humboldt,” Universidad Peruana Cayetano Heredia, Lima, Peru, and Section of Infectious Diseases, Department of Internal Medicine, Yale School of Medicine, New Haven, CT, E-mail: joseph.vinetz@yale.edu.

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