Physical condition and maintenance of mosquito bed nets in Kwale County, coastal Kenya

Abstract

BackgroundDespite the extensive ownership and use of insecticide-treated nets (ITNs) over the last decade, the effective lifespan of these nets, especially their physical integrity, under true operational conditions is not well-understood. Usefulness of nets declines primarily due to physical damage or loss of insecticidal activity.MethodsA community based cross-sectional survey was used to determine the physical condition and to identify predictors of poor physical condition for bed nets owned by individuals from communities in Kwale County, coastal Kenya. A proportionate hole index (pHI) was used as a standard measure, and the cut-offs for an ‘effective net’ (offer substantial protection against mosquito bites) and ‘ineffective nets’ (offer little or no protection against mosquito bites) were determined (pHI ≤88 (about ≤500 cm2 of holes surface area) and pHI of >88 (≥500 cm2 of holes surface area), respectively).ResultsThe vast majority (78%) of the surveyed nets had some holes. The median pHI was 92 (range: 1–2,980). Overall, half of the nets were categorized as ‘effective nets’ or ‘serviceable nets’. Physical deterioration of nets was associated with higher use and washing frequency. Young children and older children were found to use ineffective bed nets significantly more often than infants, while the physical integrity of nets owned by pregnant women was similar to those owned by infants. Estuarine environment inhabitants owned nets with the worst physical condition, while nets owned by the coastal slope inhabitants were in fairly good physical condition. The results suggest that bed nets are optimally utilized when they are new and physically intact. Thereafter, bed net utilization decreases gradually with increasing physical deterioration, with most net owners withdrawing physically damaged nets from routine use.This withdrawal commonly happens following 1.5 years of use, making bed net use the most important predictor of physical integrity. On average, the nets were washed twice within six months prior to the survey. Washing frequency was significantly influenced by the bed net colour and bed net age. Lack of knowledge on reasons for net retreatment and the retreatment procedure was evident, while net repair was minimal and did not seem to improve the physical condition of the nets. The “catch-up” bed net distribution strategies are sufficient for ensuring adequate ownership and utilization of ‘effective nets’ in the targeted groups, but bi-annual mass distribution is necessary to provide similar ownership and utilization for the other groups not targeted by “catch-up” strategies.ConclusionsMonitoring and maintenance strategies that will deliver locally appropriate education messages on net washing and repair will enhance the effectiveness of malaria control programmes, and further research to assess ineffective nets need is needed.

Long-lasting insecticidal nets in Zambia: a cross-sectional analysis of net integrity and insecticide content

“…It is likely that net owners underestimated the number of times each net was washed which is typically two or more times per year [19, 24]. The method of washing or drying, or the location of cooking (inside or outside the house) did not appear to impact deltamethrin levels.…”

Physical Durability of Two Types of Long-Lasting Insecticidal Nets (LLINs) Three Years After a Mass LLIN Distribution Campaign in Mozambique, 2008–2011

“…The location of the holes on the LLINs is consistent with respondents' reports that securing of the LLINs at night as one of the major causes of the LLIN holes. 37 In addition, the survey teams observed that in rural households in Nampula LLINs are commonly secured at the bottom of the LLIN to the reed mat or other material used as a sleeping space. Further analysis is pending to identify potential associations of LLIN damage with factors including washing and frequency of use.…”

Long-Term Insecticidal Activity and Physical Integrity of Olyset Nets in Tafea Province, Vanuatu

“…In this study, 22.8% (23 of 101) of nets had holes Ͼ200 cm 2 , which could compromise the efÞcacy of these nets. However, attempts have recently been made to standardize comparisons of the physical condition of nets by calculating the pHI (Kilian et al 2011, World Health Organization 2011, Allan et al 2012, Batisso et al 2012, Mutuku et al 2013. It has been suggested that a poor or very poor net would have a total hole surface area Ͼ700 cm 2 (Allan et al 2012).…”

“…In addition, to provide a standard method for comparing net damage, the proportional hole index (pHI) was calculated. This calculation was published in the World Health Organization guidelines for monitoring LLIN durability in 2011 (World Health Organization 2011) and has been used in recent publica- tions (Kilian et al 2011, Allan et al 2012, Batisso et al 2012, Mutuku et al 2013). An average surface area for each hole size category was estimated to beÑthumb ϭ 4 cm 2 , Þst ϭ 36 cm 2 , and larger than a Þst ϭ 225 cm 2 (Kilian et al 2011).…”