Amazonia ICEMR2- Brazil Rio Azul

Background: Malaria remains common among native Amazonians, challenging Brazil′s elimination efforts.

Objectives: We examined the epidemiology of malaria in riverine populations of the country′s main hotspot, the upper Juruá Valley in Acre state close to the Brazil-Peru border, where Plasmodium vivax accounts for >80% of cases.

Methodology:

Geographic Location/Study Sites: Municipality of Mâncio Lima, in the upper Juruá Valley region of Acre state, westernmost Brazil, close to the border with Peru.

Dates of Data Collection: The first survey was carried out between 9-12 July, 2018; the second survey was carried out between 9-12 July, 2019.

Study Design: Prosepective panel study

Eligibility: The participants must have met the following criteria- Permanent residents in riverine communities situated along Azul River, Acre, Brazil.

Data Collection: For the first survey in 2018, 246 individuals aged between 1 and 72 years were invited to provide a finger-prick blood sample. For the second survey 2019, 244 participants aged < 1-75 years, coming from nine villages, were interviewed using the same structured questionnaire applied in 2018.

Overall, we enrolled 386 individuals and tested 262 (67.9%) of them for malaria parasites during at least one survey; 36 (9.3%) participants were tested during both surveys. Those who reported recent signs or symptoms at or up to 7 days were classified as “symptomatic”.

The first survey, 2018: house-to-house visits (in 10 riverine villages or “communities” on the banks of the Azul River, a tributary of the Moa River, all of them originated from former rubber-tapper settlements: Três Unidos, Valparaíso, Barro Vermelho, Belo Horizonte, Buritis, Nova Lição, Bom Sossego, Bela Vista, Bom Jesus and Queimadas) by using structured questionnaire to obtain sociodemographic and morbidity information. In addition, finger-prick blood sample from the participants was collected as well.

For the second survey 2019, residents in the area were invited to attend medical and dental care, routine vaccination and cervical cancer screening in health posts or schools situated in one of three largest villages (Três Unidos, Nova Lição and Bom Sossego), using the same structured questionnaire applied in 2018 and finger-prick blood sample.

Laboratory Methods:
Thick blood smears were stained with Giemsa and had at least 100 fields examined for malaria parasites, under 1,000x magnification, by an experienced microscopist. P. vivax infections diagnosed by onsite microscopy were treated with chloroquine (25 mg/kg of body weight over 3 days) and primaquine (3.5 mg/kg over 7 days); Plasmodium falciparum infections were treated with a 3-day course of artemether (2 to 4 mg/kg/day) plus lumefantrine (12 to 24 mg/kg/day) and a single dose of 0.25 mg/kg primaquine for gametocyte clearance.

Molecular screening for malaria was carried out with a genus-specific, SYBR Green-based quantitative PCR. Positive samples were further tested with newly designed TaqMan assays that target species-specific cytb gene fragments.

ClinEpiDB Data Integration: Coming soon

Acknowledgements: The authors thank Ajucilene (Joice) G. Mota, Francisco Melo and their team at the Secretaria de Saúde de Mâncio Lima for overall logistic support, Igor C. Johansen for expert data management and figure preparation and Maria José Menezes for excellent administrative and laboratory support.

Financial Support: NIH (U19 AI089681 subcontract to MUF); FAPESP (research grant 2016/18740-9 to MUF and scholarships to PTR, PSF, PMS); CNPq (scholarship to LBB and senior research fellowships to MAC and MUF); FCT (institutional GHTM project, UID/04413/2020).

Ethics Statement: Study protocols have been approved by the Institutional Review Board of the University Hospital of Universidade de São Paulo and by the National Committee of Ethics in Research, Brazilian Ministry of Health (CAAE number 64767416.6.0000.5467). Written informed consent was obtained from all study participants or their parents/guardians.

Last Updated: November 13, 2023Epidemiology of malaria transmission in riverine communities- Rio Azul, Acre, Brazil