Abstract
Despite a long history of community-directed treatment with ivermectin (CDTI), a high ongoing Onchocerca volvulus transmission is observed in certain onchocerciasis-endemic regions in Africa with a high prevalence of epilepsy. We investigated factors associated with higher microfilarial (mf) density after ivermectin treatment. Skin snips were obtained from O. volvulus-infected persons with epilepsy before, and 3 to 5 months after ivermectin treatment. Participants were enrolled from 4 study sites: Maridi (South Sudan); Logo and Aketi (Democratic Republic of Congo); and Mahenge (Tanzania). Of the 329 participants, 105 (31.9%) had a post-treatment mf density >20% of the pre-treatment value. The percentage reduction in the geometric mean mf density ranged from 69.0% (5 months after treatment) to 89.4% (3 months after treatment). A higher pre-treatment mf density was associated with increased probability of a positive skin snip after ivermectin treatment (p = 0.016). For participants with persistent microfiladermia during follow-up, a higher number of previous CDTI rounds increased the odds of having a post-treatment mf density >20% of the pre-treatment value (p = 0.006). In conclusion, the high onchocerciasis transmission in the study sites may be due to initially high infection intensity in some individuals. Whether the decreasing effect of ivermectin with increasing years of CDTI results from sub-optimal response mechanisms warrants further research.
Highlights
With an estimated 20.9 million people infected worldwide, of whom over 99% live in sub-SaharanAfrica [1], Onchocerca volvulus (O. volvulus) infections are an important global health problem
We performed the study among persons with epilepsy (PWE) with the intention to investigate the effect of ivermection on microfilarial density and to evaluate whether ivermectin could decrease the frequency of seizures in PWE infected with O. volvulus
The logistic regression model is used to assess the effect of predictors on the probability of having a positive skin snip after ivermectin treatment, whereas the truncated Poisson regression approach studies the effects of covariates on post-ivermectin O. volvulus mf densities conditional on having a positive skin snip after ivermectin treatment
Summary
Alfred Dusabimana 1 , Dan Bhwana 2 , Stephen Raimon 3 , Bruno P. Mmbando 2 , An Hotterbeekx 1 , Floribert Tepage 4 , Michel Mandro 5 , Joseph N. Siewe Fodjo 1 , Steven Abrams 1,6 and Robert Colebunders 1,7, *. Interuniversity Institute for Biostatistics and statistical Bioinformatics, Data Science Institute, Hasselt University, 3590 Diepenbeek, Belgium.
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