Research Article: An Observational Study of Material Durability of Three World Health Organization–Recommended Long-Lasting Insecticidal Nets in Eastern Chad

Date Published: September 05, 2012

Publisher: The American Society of Tropical Medicine and Hygiene

Author(s): Richard Allan, Laura O’Reilly, Valery Gilbos, Albert Kilian.


A total of 876 nets (229 Interceptor®, 363 Olyset®, and 284 PermaNet®) were collected 14 months post-distribution of long-lasting insecticidal nets (LLINs) from 811 households of internally displaced and host communities in Dar Sila District in eastern Chad to examine their physical condition. Holes were recorded by using three hole categories (average diameter = 2, 3.5, and 15 cm) and a Proportionate Hole Index (pHI). A total of 69.5% were in poor or very poor condition. There was no significant difference in the performance between the polyester 75 denier LLINs, but they had 4.22 times the odds of having a pHI ≥ 175 (poor or very poor condition) than polyethylene 150 denier LLINs; and 39.2% were unserviceable (pHI ≥ 300) compared with only 7.7% of the polyethylene LLINs. These results provide the first comparative data on LLIN material durability to guide procurement and replacement practice, and to inform urgently needed changes in LLIN international minimum specifications and product standards.

Partial Text

The international public health community is currently focused on achieving the Millennium Development Goals; reducing infant and child mortality by two-thirds by 2015 is a central goal. Malaria is the single greatest contributor of mortality in children less than five years of age across sub-Saharan Africa. Reducing malaria transmission and sustaining that reduction relies primarily on achieving universal coverage and use long-lasting insecticidal nets (LLINs).1 In 2009, the estimated investment in this intervention was $2.0 billion, and there is an estimated additional demand of $1.7 billion annually until 2015.2

The study results show that of the total LLINs observed, less than one-third (30.5%) were in serviceable condition after an average of 14 months use in the semi-arid conditions of eastern Chad. The results also show that 39.2% of PET-75D and 7.7% of PE-150D were badly torn and considered unserviceable (Figure 1). If one considers that the study did not include houses that no longer had LLINs, the level of damage may in fact be greater than that presented here. Households without nets were likely to have discarded them because of severe damage. This has been confirmed by follow-up studies that asked respondents why LLINs were missing. Within this short time frame, PET-75D LLIN had 4.22 times greater odds of having a pHI ≥ 175 compared with PE-150D LLINs. The PET-75D and PE-150D displayed reverse performance pHI profiles when used under these field conditions. After LLIN material type and denier, sleeping without a mattress was the next significant factor likely to further reduce the serviceable life of an LLIN. Although it would be of interest to estimate the average useful life of these products under the conditions of eastern Chad, this is not possible with sufficient reliability based on our data. As outlined by the WHO guideline on monitoring of LLIN durability,10 the attrition rate, i.e., nets lost because of damage or other reasons, is needed in addition to the physical condition of the nets and this is not possible based on the applied sampling approach.




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