Susceptibility of Anopheles gambiae to Pyrethroids on Long Lasting Insecticide Treated Nets (LLINs) in Wukari, Taraba State, Nigeria

The use of Long Lasting Insecticide Nets is one of the strategies in malaria prevention and control. This study which was conducted within July to September 2014, comparatively determines the susceptibility of Anopheles gambiae to pyrethroids on Long Lasting Insecticide Treated Nets (LLINs) in Kinkiso, Mission and Wapan-ngaku areas of Wukari Local Government Area of Taraba State, Nigeria. LLINs were collected from households and primary health care clinics. A total of 450 laboratory bred female Anopheles gambiae mosquitoes were used in the test. A total of 12 used LLINs comprising 1, 2, 3 and 4 year old were sampled from each of the three communities and Bio-assayed. The larvae were collected from these communities and reared in the laboratory. The result of the susceptibility test showed that the mosquitoes were more susceptible to the pyrethroids in 0 - 2 years old nets than in 3 – 4 years. This could be as a result of the usage and the number of times the nets were washed leading to degradation of active ingredients. The highest knockdown rate was observed in Kinkiso (72.5 %) while Wapan-ngaku had the least (68.3 %). Within 24 hours, 100 % mortality was recorded Wapan-ngaku area. There was no significant difference in knock-down and mortality rate across the three communities. (χ2cal=0.173, χ2tab=9.49, df=4, P>0.05). Mean number of mosquitoes knocked-down after 3 minutes exposure among the communities and net ages showed that Kinkiso had the highest knock-down of 9.0 in one year old nets. The least was in Wapan-ngaku community with 4.3 knocked-down in 4 years old net (χ2Cal= 0.903, χ2tab=12.59, df=6, P˃0.05). These indicate a gradual decrease in the efficacy of the chemical (pyrethroid) on the nets with age.