Impact of repeated mass ivermectin administration using a community directed approach on L. loa infection in Chrysops silacea of the rain forest and forest savanna of Cameroon

IF 2 Q3 INFECTIOUS DISEASES Parasite Epidemiology and Control Pub Date : 2024-02-17 DOI:10.1016/j.parepi.2024.e00343

Glory N. Amambo , Fanny F. Fombad , Patrick W. Chounna Ndongmo , Raphael Awah Abong , Abdel Jelil Njouendou , Amuam Andrew Beng , Theobald Mue Nji , Mathias Eyong Esum , Jerome Fru-Cho , Ritter Manuel , Deribe Kebede , Peter Ivo Enyong , Achim Hoerauf , Benjamin Koudou , Moses Bockarie , Samuel Wanji

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Abstract

Background

Loiasis is an endemic filarial infection in the rainforest zone of West and Central Africa. Repeated annual community-directed treatment with ivermectin (CDTI) delivered for several years to control onchocerciasis has been shown to reduce the prevalence and intensity of Loiasis in some Loa loa-Onchocerca volvulus co-endemic areas. However, the impact of these multiple rounds of CDTI on entomological indicators of loiasis transmission is not known, and was therefore assessed in this study in areas with contrasting histories of CDTI.

Methods

The study was conducted in the East, North-west and South-west 1 CDTI project sites of Cameroon. Two communities per CDTI project were selected for fly collection and dissection. Ivermectin treatment coverage was documented in these areas, and this was correlated to Chrysops infection and infective rates. A total of 7029 female Chrysops were collected from 6 communities of the 3 CDTI projects (East, North-west, and South-west 1) and from 2 communities in a non-CDTI district (East).

Results

Chrysops biting densities and parous rates were significantly reduced in the North-west and South-west sites post-CDTI, while in the East, biting densities were similar in non-CDTI and CDTI sites, with higher parous rates observed in the non-CDTI site. Infection and infective rates in the East non-CDTI site were 4.4% and 1.8% respectively, as compared to 3.3% and 1.3% in the CDTI site after 10 ivermectin rounds (there were no baseline data for the latter). In the North-west site, significant reductions in Chrysops infection and infective rates from 10.2% and 4.2% respectively, to 3.5% and 1.2 (after 9 rounds of ivermectin treatment), were recorded following CDTI. In the South-west, infection rate significantly increased from 1.74% to 2.8% and infective rate remained statistically unchanged after 14 rounds of CDTI (0.45% - 0.40%). Similar trends in Mean Head L3 were observed except in the East site where this indicator was similar in both CDTI and control sites. Only in the North-west site did monthly transmission potentials decrease significantly.

Conclusion

This study demonstrated that the impact of repeated annual treatment with ivermectin for the control of onchocerciasis using community directed delivery approach on the entomological indicators of loiasis varies with bioecological zones. Community directed treatment with ivermectin induced a significant reduction in the entomological indicators of loiasis in the North-West project site which lies in forest savanna area. A non-significant decrease was observed in the East project site and in contrast, a significant increase was observed in the South-West 1 project site which both lies in the rainforest zones.

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喀麦隆热带雨林和森林稀树草原中反复大量施用伊维菌素对 Chrysops silacea L. loa 感染的影响

背景卢阿丝虫病是非洲西部和中部雨林地区的一种地方性丝虫感染。在一些 Loa loa-Onchocerca volvulus 共同流行的地区，每年重复使用伊维菌素（CDTI）进行社区治疗以控制盘尾丝虫病，并持续数年之久，这已被证明能够降低 Loa loa-Onchocerca volvulus 的流行率和感染强度。然而，这些多轮 CDTI 对罗亚斯病传播的昆虫学指标的影响尚不清楚，因此，本研究对具有截然不同的 CDTI 历史的地区进行了评估。每个 CDTI 项目选择两个社区进行苍蝇收集和解剖。对这些地区的伊维菌素治疗覆盖率进行了记录，并将伊维菌素治疗覆盖率与蛹虫草感染率和感染率相关联。从 3 个 CDTI 项目（东部、西北部和西南部 1 个）的 6 个社区以及非 CDTI 地区（东部）的 2 个社区共收集了 7029 只雌性金眼蝇。结果 CDTI 后，西北部和西南部地区的金眼蝇叮咬密度和副蝇率显著降低，而在东部，非 CDTI 地区和 CDTI 地区的叮咬密度相似，但非 CDTI 地区的副蝇率更高。东部非 CDTI 地点的感染率和感染率分别为 4.4% 和 1.8%，而 CDTI 地点在使用 10 次伊维菌素后的感染率和感染率分别为 3.3% 和 1.3%（后者没有基线数据）。在西北地区，在 CDTI 后，金龟子感染率和感染率分别从 10.2% 和 4.2% 显著降至 3.5% 和 1.2（经过 9 轮伊维菌素治疗）。在西南部，感染率从 1.74% 显著上升至 2.8%，而感染率在 14 轮 CDTI 后在统计上保持不变（0.45% - 0.40%）。除东部地区外，其他地区的平均头 L3 也呈现出类似的趋势。只有西北部地区的月传播潜力显著下降。结论这项研究表明，采用社区指导方法每年多次使用伊维菌素治疗盘尾丝虫病，对不同生物生态区域盘尾丝虫病昆虫学指标的影响各不相同。在位于森林稀树草原地区的西北项目点，伊维菌素的社区指导治疗显著降低了盘尾丝虫病的昆虫学指标。东部项目点的昆虫学指标下降不明显，而西南 1 个项目点的昆虫学指标则明显增加，这两个项目点都位于热带雨林区。

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来源期刊

Parasite Epidemiology and Control Medicine-Infectious Diseases

CiteScore

5.70

自引率

3.10%

发文量

审稿时长

17 weeks

期刊介绍： Parasite Epidemiology and Control is an Open Access journal. There is an increasing amount of research in the parasitology area that analyses the patterns, causes, and effects of health and disease conditions in defined populations. This epidemiology of parasite infectious diseases is predominantly studied in human populations but also spans other major hosts of parasitic infections and as such this journal will have a broad remit. We will focus on the major areas of epidemiological study including disease etiology, disease surveillance, drug resistance and geographical spread and screening, biomonitoring, and comparisons of treatment effects in clinical trials for both human and other animals. We will also look at the epidemiology and control of vector insects. The journal will also cover the use of geographic information systems (Epi-GIS) for epidemiological surveillance which is a rapidly growing area of research in infectious diseases. Molecular epidemiological approaches are also particularly encouraged.