Treatment and control of onchocerciasis
Vector control involves killing the larvae of the blackfly vectors using environmentally safe insecticides. The Onchocerciasis Control Progamme in West Africa (OCP) achieved vector control by weekly aerial spraying of insecticides over fast-flowing rivers and streams – the breeding sites of the blackflies. Spraying continued for more than 14 years to break the life-cycle of the parasite, and was combined with treatment of eligible populations with ivermectin.
In four areas of Uganda, the United Republic of Tanzania, and Equatorial Guinea, APOC’s strategy of community-directed treatment with ivermectin has been supplemented by activities to eliminate the blackfly vector. Elsewhere in APOC countries, vector control is not considered feasible or cost-effective.
The vector control method of choice in APOC has been ground larviciding. In all four areas, larviciding activities continued for two to three years and finished by 2005. APOC is now monitoring the areas and providing support for entomological surveillance to confirm the elimination of the vector in Itwara and Mpamba-Kusi in Uganda, and Bioko Island in Equatorial Guinea.
The treatment for onchocerciasis is ivermectin (Mectizan®). Ivermectin paralyses and kills microfilariae, relieving intense skin itching and halting the progression towards blindness. It also prevents adult worms from producing more microfilariae for a few months following treatment, so reduces transmission.
A single dose of ivermectin needs to be taken annually to be effective. The manufacturer of ivermectin – Merck & Co., Inc. – has provided the drug free of charge since 1987. This donation is administered through the Mectizan Donation Program, which works with ministries of health and other partners to distribute the drug.
From 1988 onwards, mobile teams distributed ivermectin as part of the OCP. This supplemented OCP’s vector control activities, and contributed to the success of the Programme, which came to an end in 2002.
Ivermectin is at the core of APOC’s strategy, which uses community-directed treatment to reach the people who need it. A third programme – the Onchocerciasis Elimination Programme for the Americas (OEPA) – also relies on ivermectin to control the disease.
A third programme – the Onchocerciasis Elimination Programme for the Americas (OEPA) – also relies on ivermectin to control the disease.