Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA, 30329, USA.
Epidemic Intelligence Service, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA, 30329, USA.
Malar J. 2017 Oct 2;16(1):394. doi: 10.1186/s12936-017-2033-3.
Long-lasting insecticidal nets (LLINs) are a cornerstone of malaria prevention. Holes develop in LLINs over time and compromise their physical integrity, but how holes affect malaria transmission risk is not well known.
After a nationwide mass LLIN distribution in July 2012, a study was conducted to assess the relationship between LLIN damage and malaria. From March to September 2013, febrile children ages 6-59 months who consistently slept under LLINs (every night for 2 weeks before illness onset) were enrolled in a case-control study at Machinga District Hospital outpatient department. Cases were positive for Plasmodium falciparum asexual parasites by microscopy while controls were negative. Digital photographs of participants' LLINs were analysed using an image-processing programme to measure holes. Total hole area was classified by quartiles and according to the World Health Organization's proportionate hole index (pHI) cut-offs [< 79 cm (good), 80-789 cm (damaged), and > 790 cm (too torn)]. Number of holes by location and size, and total hole area, were compared between case and control LLINs using non-parametric analyses and logistic regression.
Of 248 LLINs analysed, 97 (39%) were from cases. Overall, 86% of LLINs had at least one hole. The median number of holes of any size was 9 [interquartile range (IQR) 3, 22], and most holes were located in the lower halves of the nets [median 7 (IQR 2, 16)]. There were no differences in number or location of holes between LLINs used by cases and controls. The median total hole area was 10 cm (IQR 2, 125) for control LLINs and 8 cm (IQR 2, 47) for case LLINs (p = 0.10). Based on pHI, 109 (72%) control LLINs and 83 (86%) case LLINs were in "good" condition. Multivariable modeling showed no association between total hole area and malaria, controlling for child age, caregiver education, and iron versus thatched roof houses.
LLIN holes were not associated with increased odds of malaria in this study. However, most of the LLINs were in relatively good condition 1 year after distribution. Future studies should examine associations between LLIN holes and malaria risk with more damaged nets.
长效杀虫蚊帐（LLINs）是预防疟疾的基石。随着时间的推移，LLINs 上会出现小孔，从而破坏其物理完整性，但小孔如何影响疟疾传播风险尚不清楚。
在 2012 年 7 月全国范围内大规模发放 LLINs 后，开展了一项研究以评估 LLIN 损坏与疟疾之间的关系。2013 年 3 月至 9 月，在马钦加区医院门诊部，连续 2 周在感染疾病前每晚都在 LLINs 下睡觉的发热 6-59 个月儿童纳入病例对照研究。通过显微镜检查，病例组疟原虫无性体寄生虫呈阳性，而对照组为阴性。使用图像处理程序分析参与者的 LLINs 的数码照片，以测量小孔。根据世界卫生组织（WHO）的比例孔指数（pHI）截断值（<79cm[良好]，80-789cm[损坏]，>790cm[太撕裂]），按四分位数和总孔面积进行分类。使用非参数分析和逻辑回归比较病例和对照 LLINs 中孔的位置和大小以及总孔面积。
在分析的 248 个 LLINs 中，有 97 个（39%）来自病例。总体而言，86%的 LLINs 至少有一个孔。任何大小的孔的中位数数量为 9[四分位间距（IQR）3，22]，并且大多数孔位于蚊帐的下半部分[中位数 7（IQR 2，16）]。病例和对照组使用的 LLINs 之间的孔数和位置没有差异。对照 LLINs 的总孔面积中位数为 10cm（IQR 2，125），病例 LLINs 的总孔面积中位数为 8cm（IQR 2，47）（p=0.10）。根据 pHI，109 个（72%）对照 LLINs 和 83 个（86%）病例 LLINs 状况良好。多变量模型显示，在控制儿童年龄、照顾者教育程度以及铁屋顶与茅草屋顶房屋后，总孔面积与疟疾之间没有关联。
在这项研究中，LLINs 上的小孔与疟疾的几率增加无关。然而，在分发后 1 年，大多数 LLINs 的状况相对良好。未来的研究应该检查 LLINs 孔与疟疾风险之间的关联，并使用更多损坏的蚊帐。
