Amazonia ICEMR Peru Cohort

Related Studies:

Amazonia ICEMR Brazil Cohort

Background: The study is an open cohort study population.

Objectives:

Estimate the prevalence and incidence of asymptomatic carriers of malaria parasites, by combining molecular and microscopic diagnosis, and characterize the risk factors for clinical disease among carriers of parasites in the Amazon Estimate the prevalence, incidence, and risk factors of being a carrier of gametocytes in asymptomatic and symptomatic infections
Estimate the average duration of gametocytemia in asymptomatic infections. Determine the immune response (humoral and cellular) in symptomatic and asymptomatic carriers of malaria parasites
Estimate prospectively the risk of subsequent episodes of clinical malaria among asymptomatic carriers of parasites
Determine if consecutive episodes of malaria diagnosed during follow-up of the cohort of asymptomatic carriers are due to strains of parasites that persist in human populations due to parasites or are novel, genetically unrelated, introduced by migration of asymptomatic carriers and symptomatic individuals
Compare the genetic complexity of the parasites obtained from asymptomatic and symptomatic subjects with and without gametocytemia; test if competition within the host of multiple parasite clones, genetically different, contributes to increased virulence, increased risk disease, and increased production of gametocytes

Methodology:

Geographic Location/Study Sites: The study areas correspond to San Jose de Lupuna, Maynas province of San Juan District in Loreto - Peru, which includes communities located on the banks of the Nanay River just before it flows into the Amazon River. This area involves several small rural communities including three on the right bank of the Nanay River, the town of Santo Tomas, La Union, and Doce de diciembre, and 4 communities in the left margin of the Nanay River, such as San José de Lupuna, San Pedro, Santa Rita and Fray Martin. The total population is approximately 3896 inhabitants distributed in 702 households. It also includes the town of Cahuide in the district of San Juan, which has about 500 inhabitants distributed in 100 houses.

Dates of Data Collection:

Main cohort

2012: August, September, October, November, December
2013: March, June, September, December
2014: March, June, September, December
2015: March, June, September, December

Sub-cohort

2013: January - April, June - December
2014: January - April, June - December
2015: March - June

Study Design: Longitudinal open cohort study located in two study areas, Cahuide and Lupuna, in the province of Maynas, Loreto, Peru. The study consisted of a main cohort and a sub-cohort, where the sub-cohort consisted of subjects from the main cohort to compare humoral and cellular immune responses of asymptomatic infection with another status.

Eligibility Criteria: An initial population census enumerated all houses in each of the study areas. The houses surveyed in the study communities make up the population sample that is the primary basis for the cohort study. In addition, subjects were selected for a sub-cohort from the main cohort to compare the humoral and cellular immune responses of asymptomatic infection with another status.

Inclusion criteria:

Reside in the selected community
3 years of age or older
Signing of the informed consent by adults or parents/guardians/assent for minors
Have family plans to remain in the study area for at least two years. For taking larger quantities of blood from the sub-cohort, enrollment is limited to subjects greater or equal to 18 years of age

Exclusion criteria: Acute or chronic conditions which in the opinion of the medical attendant may affect the study results or availability to give informed consent or preclude safety of involvement in the study.

Inclusion of children: Children under 3 years of age were excluded from the study because there is known to be a negative perception of parents regarding the taking of a blood sample in this age group. The inclusion of children 3 years of age and older is essential to the goals of the study, since different age groups may have different acquired immunity and therefore differences in the risk of developing symptoms when they are carriers of malaria parasites.

Data Collection: A standardized questionnaire was applied to all study participants to collect demographic, health, and socioeconomic data. Information on selected household assets, land ownership, and house characteristics were collected to derive a wealth index, from which socioeconomic status was estimated.

The study field team monitored the clinical cases of malaria using active and passive case detection for five years. Active detection: a member of the study visited the study sites once per week (cohort study) in the search of any subject with a symptom that could be malaria. Passive detection: a member of the team visited health centers daily to search if the study population has been evaluated for malaria symptoms.

Six groups of people greater than 18 years old were ask to join a sub-cohort when the following criteria matched:

Group A: Symptomatic carriers of P. vivax (positive Blood smear and positive/negative PCR)
Group B: Symptomatic carriers of P. vivax (positive PCR, negative blood smear)
Group C: Control - Symptomatic (negative PCR, negative blood smear)
Group D: Control - Asymptomatic (positive/negative P. vivax PCR, positive blood smear)
Group E: Control - Asymptomatic (positive P. vivax PCR, negative blood smear)
Group F: Control - Asymptomatic (negative P. vivax PCR, negative blood smear)

Study Documentation:

Data dictionary - Each tab contains the data dictionary for a distinct datafile

ClinEpiDB Data Integration: Data files were provided to ClinEpiDB as flat files. These datasets were merged by unique ID and redundant or administrative columns were dropped from presentation on ClinEpiDB.org. All dates were obfuscated per participant through the application of a random number algorithm that shifted dates no more than seven days to comply with the ethical conduct of human subjects research.

Acknowledgements: We thank all residents and local authorities from the Loreto villages of Cahuide and Lupuna for their enthusiastic participation in the study, as well as all field workers for their dedication during the fieldwork.

Financial Support: This study was funded by cooperative agreement U19AI089681 from the United States Public Health Service, NIH/NIAID, funded as the Amazonian International Center of Excellence in Malaria Research.

Ethics Statement: Ethics approval was received from the Institutional Ethics Committee (CIE) of the Universidad Peruana Cayetano Heredia (UPCH)

SIDISI 57395: July 04, 2012 - July 03, 2013. Renewed for July 03, 2013 - July 09, 2014; July 09, 2014 - July 08, 2015; July 09, 2015 - July 08, 2016; and November 22, 2016 - November 21, 2017
SIDISI 60429: December 04, 2012
SIDISI 64024: February 24, 2015 - February 23, 2016. Renewed for June 14, 2016 - June 13, 2017

Last updated: December 23, 2021
A longitudinal cohort study of malaria was conducted at two sites in the Peruvian Amazon. Residents 3 years or older who planned to remain within the study area over the next two years were recruited. Participants were visited roughly every 3 months.