Physical integrity and bioefficacy of long-lasting insecticidal nets 18 months after use among Central African Republic refugees in Gado-Badzere, a high malaria burden camp in Cameroon

In Cameroon, long-lasting Insecticidal Nets (LLINs) are widely distributed as a key malaria control strategy. However, the proper use, maintenance and monitoring of their effectiveness remains a major challenge, especially in refugee settings. This study aimed to evaluate the physical condition and bioefficacy of LLINs used in households at the Gado-Badzere refugee camp in Eastern Cameroon. A cross-sectional study was conducted 18 months after LLINs distribution using a structured questionnaire to evaluate net usage and care. Physical integrity was assessed based on World Health Organisation (WHO) guidelines. WHO cone test was conducted to assess bed net efficacy against mosquitoes. Anopheles gambiae sensu lato mosquitoes were identified to species level using polymerase chain reaction (PCR). Of the 440 LLINs examined, 60.7% were in good condition, 14.5% acceptable and 24.8% deteriorated. Deteriorated nets were significantly more common among males (32.4% vs. 23.2%) and in households with more than five persons (26.1% vs. 21.9%). Significant associations were found between net deterioration and washing practices, including frequent and no washing (36.5% vs. 7.8%), washing period intervals (1–3 months: 53.4% vs. 11.4% for 4–6 months and 31.6% for >6 months) and the use of detergent, soap and bleach/brush (24.8% and 29.7% vs. 83.3%). All 30 LLINs tested were ineffective against field Anopheles gambiae s.l. populations with overall knock-down and mortality rates of 1.5% and 3.1%, respectively. An. gambiae (86.9%) and An. coluzzii (13.1%) were identified as the malaria vector species present in the study area. These findings call for urgent action by humanitarian agencies operating in high-risk settings to strengthen community awareness, with a focus on gender-sensitive approaches to educate CAR refugees on the proper use and care of LLINs. Moreover, given the apparent resistance of An. gambiae s.l. to standard LLIN insecticides, introducing next-generation LLINs and regularly monitoring their physical integrity and bioefficacy are essential to ensure sustained malaria protection in vulnerable refugee populations.