Monitoring of asymptomatic individuals with subpatent parasitemia by Plasmodium vivax and their potential for transmission to Anopheles (Nyssorynchus) darlingi

Infection with Plasmodium vivax, the predominant cause of malaria in Asia and Latin America, affects approximately 14 million individuals annually, with considerable adverse effects on health and socioeconomic development. In addition, asymptomatic infections by P. vivax, resulting from the development of clinical immunity, are commonly reported even in places of low endemicity, as in most regions of the Amazon basin. Many of these individuals have asymptomatic subpatent infection (that is, undetectable by conventional microscopy or rapid diagnostic tests), but they can infect vector mosquitoes, constituting a silent infectious reservoir that defies efforts to eliminate malaria. Due to the difficult detection of patients with asymptomatic malaria, without clinical signs of disease and negative thick gout microscopy, this subset of patients infected with P. vivax is little known, despite its potential relevance in maintaining the parasite cycle in hypoendemic areas. In this proposal, the intent is to pursue two main objectives. Recently, we developed a rapid immunochromatographic test to detect IgM and IgG against P. vivax malaria and determined their sensitivity and specificity in comparison to thick-drop microscopy and quantitative PCR to detect symptomatic patients and asymptomatic individuals, respectively. Until now, the efficiency of the transmission of P. vivax from asymptomatic patients to A. darlingi, as well as its relevance in maintaining the parasite’s life cycle in the field, is unknown. The group recently established one of the first colonies of A. darlingi in the world and certainly the first in Brazil, which is currently in its twentieth generation.  The individuals detected by the rapid test will have total parasitemia and gametocytemia defined by quantitative PCR and the blood will be used to feed the mosquito in the blood feeding tests. Having the ability to identify asymptomatic individuals in the field and understanding the importance of these individuals in transmitting P. vivax to the mosquito is fundamental to the worldwide effort to eliminate malaria in Brazil and in other countries affected by this devastating disease.

Asymptomatic Reservoir
Diagnostics
P. vivax

Jan 2020 — Dec 2022

Brazil