Abstract
The enormity of the public health burden of onchocerciasis motivated the creation of various large-scale control programs that have depended principally on mass treatment of endemic communities with ivermectin for the elimination of the disease. Parasitological evaluation of Onchocerca species in the West Region of Cameroon indicates significant progress in the interruption of parasite transmission in some communities under ivermectin treatment. However, to verify the complete elimination of onchocerciasis, entomological assessment through O-150 PCR poolscreen of black flies is mandatory. Thus, in the present study, we assessed transmission of Onchocerca species using an O-150 PCR technique to screen pools of black flies—in seven onchocerciasis endemic communities (Makouopsap, Bankambe, Lemgo, Tsesse, Ndionzou, Kouffen, and Bayon) in Cameroon. Two thousand black flies were assessed—in each community—for the presence of Onchocerca species DNA. Our results show that the frequency of infective flies was 0.6% in Makouopsap and 0.0% in the other communities. On the other hand, the frequency of infected flies was 0.8% in Makouopsap, 0.2% in Bankambe, 0.1% in Bayon, and 0.0% in Lemgo, Tsesse, Ndionzou, and Kouffen. These results provide entomologic evidence for continuous transmission of Onchocerca species in Makouopsap, risk of active transmission in Bankambe, and Bayon, and a suppressed transmission in the four other studied communities.
Highlights
Human onchocerciasis, known as river blindness, is a filarial disease caused by the parasiteOnchocerca volvulus (O. volvulus) and is one of the most debilitating yet neglected tropical diseases [1].The infective larvae (L3) are transmitted through the repeated bites of infective black flies (Simulium), which eventually give rise to adult worms
In order to investigate if transmission of onchocerciasis is ongoing in the West Region of Cameroon, we carried out PCR analysis to assess Onchocerca parasites in black flies
The World Health Organization (WHO) 2016 guidelines for verification of onchocerciasis elimination recommend that a minimum of 6000 black flies must be collected from a transmission zone [13]
Summary
The infective larvae (L3) are transmitted through the repeated bites of infective black flies (Simulium), which eventually give rise to adult worms. The latter dwell in subcutaneous tissues in humans where. The microfilariae migrate through the skin where they can be ingested by a black fly during a blood meal. The L2 larva subsequently develops into the L3 stage, which migrates to the black fly’s proboscis rendering it infective and, as such, the fly can infect humans when taking a blood meal [3]. The O. volvulus microfilariae cause persistent itching, severe skin diseases, and frequently induce ocular lesions that may result in a progressive loss of vision and blindness [6]. In Cameroon where this study was conducted, 2.8 million people are infected by the disease and 5.2 million people are at risk of infection [8], making the disease an important public health concern
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