Physical and Chemical Integrity of Long Lasting Insecticidal Nets (Llins) Used in Control of Malaria Vector in Kirinyaga County, Kenya
Wanjiku, Nyangi Mary Sofia
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The use of treated nets specifically long-lasting insecticidal nets (LLINs) has greatly reduced morbidity and mortality due to malaria. Mosquito is the vector which is responsible for malaria transmission. One of the most effective strategies of controlling the vector is the use of treated nets by majority in a community in malaria prone areas. In order to achieve a high coverage of households with the treated nets, free mass net distribution was introduced in all malaria endemic areas in Africa by the World Health Organisation. In Kenya the first free mass net distribution was carried out in the year 2006 and there after every five years. Washing of the nets causes a decline in chemical efficacy of nets. Due to this factor, both physical integrity and insecticidal concentration of distributed nets in Kirinyaga County, Kenya was assessed. The study was carried out on an area which had received treated nets from the Ministry of Health, during the 2016 mass net distribution. Most studies that have been carried out in the area focused on the rate of net survival but little is known about the physical state and chemical content of LLINs after their distribution. The objective of the study was to evaluate use, care, physical and chemical integrity of the distributed long-lasting insecticidal nets used in control of malaria in Kirinyaga County. A total of 420 households were systematically sampled with a random start, and consent to participate in the study was sought from the household heads/spouses. A structured questionnaire assessed use, care and physical integrity while chemical content of the LLINs was analysed in the laboratory by gas chromatography mass spectroscopy (GCMS). Data was analysed using Statistical Package for Social Sciences (SPSS) version 19. Eighteen months after the November 2016 nets distribution 97.9% (95% CI: 96.4% – 99.3%) of the distributed nets were still present. Regarding the net utilization, 94.1% of household heads reported sleeping under an LLIN the previous night. On visual examination of the nets, 49.9% (95% CI: 43% - 52.8%) of the nets had at least one hole. The median number of holes of any size was 2 [inter-quartile range (IQR) 1-4], with most holes located on the lower parts of a net, [median 3 (IQR 2-5)]. Of the nets with holes, only 15% had been repaired. The mean insecticidal content for baseline nets was 40.38 ± 0.86 mg/g and 9.05 ± 2.13 mg/g for α-cypermethrin and permethrin treated nets respectively. The mean concentration of sample nets was 16.29 ± 4.08 and 1.55 ± 0.41 mg/g for α-cypermethrin and permethrin treated nets respectively. Based on proportionate hole index Chi-square test results show that net physical integrity varied significantly with the manufacturer (X (6, N = 389) = 29.124, p < 0.05). The proportion of households with good LLINs was 69% .There was no association between the extent of net damage and the location (X (2, n = 336) = 40.42, p > 0.05). There was no notable difference in mean concentration of insecticide remaining between α-cypermethrin (X2 (2) = 3.83, p > 0.05) and permethrin (X2 (2) = 4.55, p > 0.05) in nets with different number of washes. The mean concentrations of α-cypermethrin and permethrin were significantly lower than the manufacturer’s label claim, and a significant difference in physical integrity of LLINs from different manufacturers was observed (X (6, N = 389) = 29.124, p < 0.05).