Intégrité Physique et Efficacité Biologique des Moustiquaires Imprégnées d'Insecticide de Longue Durée Contre la Population Résistante d’Anopheles Gambiae s.l. à Ebolowa (Cameroun)

Introduction. 

Cameroon massively distributed long-lasting insecticidal nets (LLINs) between 2004 and 2015. In the Southern Region, 75% of households had access to at least one LLIN, compared with 54% who used them. Despite these efforts, the malaria prevalence rate among children under the age of 05 remained one of the highest (33%), just behind the East Region (35%). To understand the paradox between the high prevalence rate despite the high use of LLINs, the aim of this study was to assess the physical integrity and biological efficacy of LLINs used in households in Ebolowa. 

Methods. 

Physical integrity was assessed by calculating the proportional hole index (pHI) of each net inspected according to WHO recommendations, using the formula: pHI = (n tr1) + (n tr2 × 23) + (n tr3 × 196) + (n tr4 × 576). The biological efficacy of LLINs was assessed by comparing the mortality rate of field mosquitoes with that of sensitive laboratory mosquitoes of the “kisumu” type exposed to used field LLINs on the one hand, and to new LLINs of the same brand on the other. 

Results.

Assessment of physical integrity showed that: 72% was degraded; 20% acceptable and only 8% in good condition. In terms of biological efficacy, all the LLINs tested were effective only against the sensitive laboratory mosquito “kisumu”. PBO-based LLINs are more suitable for vector control in Ebolowa.

Conclusion. 

The majority of LLINs used in Ebolowa households are degraded. They are effective only against laboratory-susceptible mosquitoes. Resistance mechanisms would explain the loss of effectiveness of LLINs against field mosquitoes.