Benin Study Assesses Long-Lasting Insecticidal Nets

Examining Effectiveness and Durability in Pregnant Women

A comprehensive study conducted in Benin between 2019 and 2021 investigated the physical integrity and bio-efficacy of long-lasting insecticidal nets (LLINs) among pregnant women. The research aimed to understand LLIN performance in real-world conditions across diverse climatic and geographic settings within the country.

Study Design and Regions

The research spanned three distinct regions of Benin: Southern, Central, and Northern. The Southern area experiences a sub-equatorial climate with two dry and two rainy seasons. The Central and Northern regions have a tropical climate, characterized by a single rainy season from May to October and a dry season from November to April, with the Northern region exhibiting more pronounced seasonal shifts.

Study sites were selected in partnership with Benin’s National Malaria Control Program. A total of 14 maternity clinics were chosen, with five in the Southern region, five in the Central, and four in the Northern part of the country. These sites included both public and private health centers in rural and urban environments, ensuring a representative sample. Health districts were randomly selected, and clinics were stratified based on location, type, and setting, requiring a minimum of 20 antenatal care (ANC) visits monthly.

Data Collection Methodology

Data were systematically gathered using the KoBo Toolbox platform, with questionnaires designed in XLSForm for optimized data quality. Field teams received thorough training on the data collection tool, utilizing the KoBo Collect mobile app for electronic data entry. This approach allowed for real-time data capture, even in offline conditions, and facilitated secure data transfer.

The study targeted approximately 240 pregnant women in each of the three regions, aiming for a total of 720 participants. Ultimately, 718 women were enrolled. Participants were recruited during their first antenatal care visit (ANC1). They underwent two home visits: one within 48 hours of recruitment and another a month later. Initial data collection focused on LLIN ownership, usage patterns, and the age of LLINs prior to the ANC1 visit. Information on LLIN distribution during ANC1, including installation, and attendance at sensitization sessions regarding LLIN use was also recorded.

Assessing Net Condition and Performance

During the second home visit, LLINs were collected for laboratory analysis to evaluate their physical integrity and bio-efficacy. Physical integrity was assessed by counting and categorizing holes based on size: Size 1 (0.5–2 cm), Size 2 (2–10 cm), Size 3 (10–25 cm), and Size 4 (>25 cm). The hole index (HI) was calculated using a weighted formula derived from WHO guidelines, categorizing nets as “good” (0–64 HI), “acceptable” (65–642 HI), or “bad” (>643 HI).

The bio-efficacy of the LLINs was determined using the standard WHO cone test. Mosquitoes were exposed to net samples to measure knock-down (Kd) and mortality rates at 1 and 24 hours, respectively. According to WHO criteria, an LLIN is considered bio-effective if its Kd rate reaches at least 95% or its mortality rate is 80% or higher.

Statistical Analysis and Findings

Statistical analysis was performed using STATA version 15 to determine proportions and confidence intervals for various indicators, including LLIN ownership, distribution, and usage, alongside physical integrity and bio-efficacy metrics. Chi-square tests were employed to compare these indicators across different regions, urban/rural settings, and public/private health center statuses. All analyses accounted for the clustered nature of the data by using STATA’s survey data analysis module, ensuring robust standard errors and adjusted confidence intervals.

The study’s findings are crucial for understanding the ongoing effectiveness of malaria prevention strategies in Benin. Globally, the World Health Organization reports that in 2022, 24 countries in Africa reported more than 10,000 malaria cases each, highlighting the persistent need for reliable LLINs (Source: WHO Malaria Dashboard, 2023).