LLIN attrition
After 30 months of use, an average loss of 55.9% (n=503, 95% CI: 52.6-59.2) out of 900 LLINs initially enrolled was observed. The LLIN attrition was similar between the LLIN between the LLIN products with a loss of 56.7% (95% CI: 47.8-59.4) of Dawa 2.0, 52% (95% CI: 46.2-57.8) of PN 2.0 and 62% (95% CI: 56.2-67.5) of Dura. The most frequently cited cause for loss of LLINs was physical deterioration: 29.7% (95% CI: 26.7-32.8) (Table 2).
LLINs fabric integrity
Assessment of holes
At the 6th month assessment visit, the LLINs with holes represented 29% (95% CI: 23.6-35.1) for Dawa 2.0, 36% (95% CI: 29.3-42.2) for PN2.0 and 36% (95% CI: 29.3-42.2) for Dura (Figure 2). After 18 months of use, more than 50% of each type of LLINs have already holes (Dawa 2.0: 56%, Dura: 64%, and PN 2.0: 73%) (Figure 2). After the 24th and 30th month follow-up, the observed physical deterioration increased with hole proportions ranging from 70 to 89% of the LLINs found (all types). Overall, Dura was the most damaged LLIN (Figure 2). The Figure 3 showed, from T6 to T30, an increase in the proportions of size 1 holes for the three types of LLIN. This increase was much more remarkable between T18 and T30.
For Dawa 2.0 and PN 2.0 LLINs, no significant increase in the proportions of Size 2, Size 3 and Size 4 holes was observed from T6 to T30. For Dura, the proportions of the Size 2, Size 3 and Size 4 holes observed at T24 were significantly different from those observed during the other monitoring visits.
In both rural and urban settings, there was no significant difference between the different hole sizes for the three types of LLINs after 6, 18 and 24 months of use. However, a significant difference was observed for the size 3 holes for the PN 2.0 LLINs at 24 months and the size 4 holes for the Dura LLINs at 30 months. However, the hole proportions per size category varied from one location to another, among LLIN products, and over time (Table 3).
Variation of proportionate hole index(pHI) of the LLINs over time
Table 4 showed that the pHI gradually increased from one period to another for the three types of LLINs and were: from 39.8 (at 6 months) to 366 (at 30 months) for Dawa 2.0, 63.6 (at 6 months) to 321 (at 30 months) for PN 2.0, and 176 (at 6 months) to 1431 (at 30 months) for Dura (Figure 4). No significant difference in the pHI was observed from the 6 to 18 months for the three LLINs. A significant difference was noted from at the 24 and 30 months (p <0.001) when the highest pHI was noted.
Comparison of the proportionate hole index between LLIN products
The data showed that the means pHI of Dawa 2.0, Dura and PN 2.0 during the 12 and 18 months were similar (p> 0.05) (Table 5). However, at T6, T24 and T30 respectively, the mean pHI of Dura was significantly higher (176, 893 and 1431) than those of Dawa 2.0 (39.8, 345 and 366) and PN 2.0 (63.6, 167 and 321) (p <0.001). However, no significance difference was noted between Dawa 2.0 and PN 2.0 LLINs.
Variation of the physical conditions of the LLINs
After 6 months of use, the proportions of the 3 types of LLINs in "good ", "seviceable" or "torn" categories were respectively 85.5% (95% CI: 82.5-88.1), 11.6% (95% CI: 9.3 -14.3) and 2.9% (95% CI: 1.8-4.5) (Table 6). After 18 months of use, 66.8% (95% CI: 61.7-71.5) of the LLINs were in "good", 26% (95% CI: 21.6-30.8) were "serviceable", and 7.2% (95% CI: 4.8-10.4) in "torn" condition (Table 6). After 30 months, only 29.5% (95% CI: 23-36.7) of the LLINs still present in the households were in "good" condition, 28.4% (95% CI: 22-35.5) were "serviceable" and 16.9% (95% CI: 11.8-23.2) were "torn" (Table 6).
At LLIN brand level, 39.1% (95% CI: 27.6-51.6) of PN 2.0 were "in good" condition, 26.1% (95% CI: 16.3-38.1) were "serviceable" and 8.7% (95% CI: 3.3-17.9) were in "torn" after 30 months of follow-up. In the same period 28.6% (95% CI: 18.4-40.6), 27.1% (95% CI: 17.2-39.1) and 14.3% (95% CI: 7.1-24.7) of the Dawa 2.0 were respectively in "good" condition, "serviceable" and "torn" conditions. For the Dura LLINs, the proportions of the LLINs in "good" condition, "serviceable" and "torn" conditions were respectively 15.9% (95% CI: 6.6-30.1), 34.1% (95% CI: 20.5-49.9) and 34.1% (95% CI: 20.5-49.9) (Table 6).
Factors associated with the loss of LLINs physical integrity
Table 7 shows that most of the recorded factors were significantly associate to the physical damages of the LLINs (p <0.05). LLINs often used are more holed than those used every night for DawaPlus 2.0 without statistical difference (p> 0.05) unlike Dura and PN 2.0 (p <0.05). Households where the sleeping beds are cut bamboo or palm branch, with poor maintenance of the LLINs (dirty), having the kitchen indoor close to the LLINs and which have a washing frequency more than 6 times have their LLIN with more holes than households where the mats were used as sleeping material, where the LLINs are well maintained (clean) and where the kitchen were outside with a washing frequency less than 6 times. There was a correlation between these factors and loss of the physical integrity of the LLINs (p <0.001).