Countries invest significant amounts of their domestic resources in malaria vector control and have varying levels of success. The Pan American Health Organization (PAHO) is working to support countries in the region to improve their coverage and appropriate use of ITNs and IRS to increase the effectiveness of these interventions. Fundamental questions remain regarding the efficacy of these tools in Latin America and the Caribbean (LAC), even as countries work with PAHO to develop their strategic approaches to improve malaria vector control. A variety of studies have documented early biting and outdoor biting in areas of persistent malaria transmission, and a recent observational study in Haiti showed no evidence that mass ITN campaigns reduced clinical malaria (Steinhardt et al. 2017).
USAID’s priority in LAC related to malaria vector control is the strengthening of entomological surveillance systems to generate data that directly inform decisions on where and how to invest resources in vector control for malaria. This includes determining where to focus vector control activities, what type of vector control will be most effective in each setting, and how to evaluate the impact of these efforts to ensure the most effective and efficient use of resources.
In direct partnership and close collaboration with the Colombian Ministry of Health and Social Protection (MSPS), the Colombian National Institute of Health (INS), the PMI VectorLink LAC Project (also referred to as the Project), funded by USAID with technical assistance from the Centers for Disease Control and Prevention (CDC), propose to develop and co-implement a comprehensive two-armed controlled randomized evaluation/study on the efficacy of ITNs and IRS (refer to section 1.2 for details regarding key objectives of this study).
The evaluation is designed to determine the expected impact of ITNs and IRS on Anopheles albimanus, one of the principal malaria vectors in LAC. This study will support the development and application of evidence-based approaches on how and where to best apply vector control tools in LAC. USAID and PMI selected Colombia based on high levels of malaria transmission for the region and its broadly representative entomological and ecological profiles. The results from Colombia will be analyzed and extrapolated to inform other regional approaches and interventions in vector control.
An. albimanus is one of the main vectors of malaria in the Americas (Sinka et al. 2010), and while it usually bites at night and indoors, scientific literature and observations by the local government’s entomologists suggest that they can also bite at dawn and outdoors (Ahumada et al. 2016, Solarte et al. 2017, Ryan et al. 2017, Montoya-Lerma et al. 2011). The most recent insecticide resistance testing in the study area (Guapi, Cauca department), conducted by the PMI VectorLink LAC Project and the Cauca Department Health Secretariat (Vector-borne disease Unit) in February 2020, reported a mortality of 100% to diagnostic concentrations of deltamethrin (12.5 µg/ml), alpha-cypermethrin (12.5 µg/ml) and fenitrothion (50 µg/ml ) for An. albimanus.
The primary entomological indicators for this study are indoor and outdoor human biting rates measured through the use of human landing catches (HLCs) and the entomological inoculation rates estimated through sporozoite rates and mosquito densities in the municipalities of Guapi and Timbiquí in the Cauca Department. The MSPS and INS will be responsible for ITN distribution and IRS implementation in the study areas, while the PMI VectorLink LAC Project will focus on post-intervention entomological monitoring through HLCs, Prokopack aspirators, and cone bioassays, a qualitative study which includes Focus Group Discussions (FGDs) and a Knowledge, Attitudes and Practices (KAP) survey related to the interventions. The project will also focus on capacity building as outlined in section 5.
The objective of this evaluation is to determine the entomological impact of ITNs and IRS when delivered under ideal circumstances in a key malaria transmission site in Colombia, where An. albimanus is the primary vector. LAC countries can use the results to make informed decisions on if, how, when, and where to invest in each of these vector control interventions in order to achieve maximum impact with available resources.
In Year Two, the PMI VectorLink LAC Project will carry out the following activities in the intervention sites that were identified in close collaboration with all key partners including the Cauca Department Health Secretariat in the municipalities of Guapi and Timbiquí in the Cauca Department:
- Monitor the density, species composition, resting behavior, and infectivity of malaria vectors in the forty clusters distributed along the municipalities of Guapi and Timbiquí.
- Determine the Plasmodium natural infection rate of the Anopheles species present in the study area and estimate the entomological inoculation rate (EIR).
- Determine the susceptibility of the primary malaria vector albimanus to insecticides in four sentinel sites distributed across the two municipalities.
- Establish the effect of ITNs and IRS on the density, resting behavior and parity of albimanus in the indoor and outdoor areas.
- Assess residual efficacy of insecticides and quality of spray operations through the World Health Organization (WHO) cone bioassays.
- Assess net durability (integrity) and attrition according to WHO and PMI protocols.
- Characterize the knowledge, attitudes, and practices (KAP) with respect to malaria, its vectors, and vector control activities among the population of Guapi and Timbiquí.
- Describe characteristics of the behavior of the human population in the intra-domicile and peri-domicile that can be related to the biting activity of albimanus in Guapi and Timbiquí.
National Capacity Building
- Train entomology technicians from the Cauca Department Health Secretariat and INS on standard operating procedures (SOPs) for entomological methods including quality data collection, data analysis, and use of data for vector control decision-making.