Prospective assessment of malaria infection in a semi-isolated Amazonian indigenous Yanomami community: Transmission heterogeneity and predominance of submicroscopic infection

Abstract

In the Amazon basin, indigenous forest-dwelling communities typically suffer from a high burden of infectious diseases, including malaria. Difficulties in accessing these isolated ethnic groups, such as the semi-nomadic Yanomami, make official malaria data largely underestimated. In the current study, we longitudinally surveyed microscopic and submicroscopic malaria infection in four Yanomami villages of the Marari community in the northern-most region of the Brazilian Amazon. Malaria parasite species-specific PCR-based detection of ribosomal and non-ribosomal targets showed that approximately 75% to 80% of all malaria infections were submicroscopic, with the ratio of submicroscopic to microscopic infection remaining stable over the 4-month follow-up period. Although the prevalence of malaria infection fluctuated over time, microscopically-detectable parasitemia was only found in children and adolescents, presumably reflecting their higher susceptibility to malaria infection. As well as temporal variation, the prevalence of malaria infection differed significantly between villages (from 1% to 19%), demonstrating a marked heterogeneity at micro-scales. Over the study period, Plasmodium vivax was the most commonly detected malaria parasite species, followed by P. malariae, and much less frequently P. falciparum. Consecutive blood samples from 859 out of the 981 studied Yanomami showed that malaria parasites were detected in only 8% of the previously malaria-positive individuals, with most of them young children (median age 3 yrs). Overall, our results show that molecular tools are more sensitive for the identification of malaria infection among the Yanomami, which is characterized by heterogeneous transmission, a predominance of low-density infections, circulation of multiple malaria parasite species, and a higher susceptibility in young children. Our findings are important for the design and implementation

Human mobility and urban malaria risk in the main transmission hotspot of Amazonian Brazil

“…Malaria in the Amazon has traditionally been perceived as a disease affecting poor rural communities, with most reported infections acquired in remote riverine villages [3,4], frontier farming settlements [5,6], gold mining [7,8], and Amerindian reserves [9][10][11]. Indeed, malaria rates tend to be lower in cities and towns, compared to surrounding rural settings, due to multiple factors such as improved housing and access to healthcare and limited availability of mosquito vector habitats [12].…”

Vector-Focused Approaches to Curb Malaria Transmission in the Brazilian Amazon: An Overview of Current and Future Challenges and Strategies

“…For instance, malaria control in areas of special interest such as native people settlements, areas of mining and national borders, present their own challenges. Malaria incidence in Brazilian native people is associated with environmental changes, their difficulty in accessing health services, and their mobility, at times resulting in migration to areas of more intense malaria transmission [ 35 , 36 ]. Furthermore, culturally determined activities such as hunting, fishing, working in the fields, and bathing along rivers and streams expose indigenous people to the risk of malaria infection.…”

Vector-focused Approaches to Curb Malaria Transmission in the Brazilian Amazon: An Overview of Current and Future Challenges and Strategies

“…For instance, malaria control in areas of special interest such as native people settlements, areas of mining and national borders, present their own challenges. Malaria incidence in Brazilian native people is associated with environmental changes, their difficulty in accessing health services, and their mobility, at times resulting in migration to areas of more intense malaria transmission [34,35]. Furthermore, culturally determined activities such as hunting, fishing, working in the fields, bathing along rivers and streams expose indigenous people to the risk of malaria infection.…”