Abstract
BackgroundOnchocerciasis in Yemen is one of the most neglected diseases, where baseline estimates of onchocerciasis and monitoring of the impact of ivermectin regularly administered to the affected individuals on its transmission are lacking. Therefore, this study aimed to determine the anti-Ov16 IgG4 seroprevalence among local communities of Hodeidah and Al-Mahwit governorates of Tihama region. The factors possibly associated with previous exposure to infection were also studied.Methodology/Principal findingsThis cross-sectional study was conducted in two ivermectin-targeted districts endemic for onchocerciasis in Hodeidah and Al-Mahwit and two untargeted districts with unknown previous endemicity in Hodeidah between February and July 2017. For 508 residents sampled by a multi-stage random approach, data were collected and blood specimens were screened for anti-Ov16 IgG4 using the SD BIOLINE Onchocerciasis IgG4 rapid tests. The study revealed an overall anti-Ov16 IgG4 rate of 18.5% (94/508) in all surveyed districts, with 10.2% (12/118) of children aged ≤10 years being seropositive. Moreover, rates of 8.0% (4/50) and 6.1% (4/66) were found in districts not officially listed as endemic for the disease. Multivariable analysis confirmed the age of more than ten years and residing within a large family as the independent predictors of exposure to infection.Conclusions/SignificanceOnchocerciasis transmission is still ongoing as supported by the higher anti-Ov16 IgG4 seroprevalence rate among children aged ≤10 years compared to that (<0.1%) previously set by the World Health Organization as a serologic criterion for transmission interruption. Further large-scale studies combining serologic and entomologic criteria are recommended for the mapping of O. volvulus in human and blackfly populations in endemic foci and their neighboring areas of uncertain endemicity. In addition, ivermectin distribution, coverage and impact on disease transmission need to be continually assessed.
Highlights
Onchocerciasis is a neglected tropical disease of the skin and eyes caused by the filarial nematode Onchocerca volvulus and transmitted by the bites of infected Simulium blackflies
Onchocerciasis is endemic in certain foci in the western governorates of Yemen
Monitoring the impact of the regular ivermectin administration to affected individuals on the transmission status and providing baseline onchocerciasis estimates in endemic areas are crucial for planning effective elimination strategies
Summary
Onchocerciasis is a neglected tropical disease of the skin and eyes caused by the filarial nematode Onchocerca volvulus and transmitted by the bites of infected Simulium blackflies. It is endemic in 31 countries in sub-Saharan Africa and in some foci in Latin America and Yemen, with approximately 187 million people being exposed to potential transmission [1, 2]. Effective efforts through mass drug administration (MDA) campaigns at repeated rounds undertaken by control programs have led to the successful elimination of the disease in four countries in Latin America as certified by the World Health Organization (WHO) between 2013 and 2016; namely, Colombia, Ecuador, Mexico and Guatemala [10]. The factors possibly associated with previous exposure to infection were studied
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