This post was co-authored by Didier Bakajika, formerly Programme Epidemiologist for NTDs at Sightsavers, and Ruth Dixon, Sightsavers’ Technical Advisor for NTD Research.
‘Test and treat’ is an alternative treatment strategy that Sightsavers is trialling in Cameroon in its work to eliminate onchocerciasis (also known as river blindness) – a disease transmitted by the bite of the black fly that allows parasitic worms to live and breed in the human body. The baby worms (microfilariae) that they produce can live up to two years and migrate around the body. When they die, they cause an inflammatory response that leads to skin rashes, lesions, intense itching and skin depigmentation. Microfilariae also migrate to the eye, where they can lead to blindness.
The usual strategy to combat onchocerciasis is to annually treat all of the eligible population (excluding young children, pregnant and breastfeeding women and people who are severely ill) with a medication called ivermectin which kills any microfilariae living in endemic regions. With test and treat, instead of giving out ivermectin to everyone, we first test them to see if they have the disease. If the test comes back positive then a course of a different medication, doxycycline, is given daily for four weeks. Doxycycline gets rid of the adult worms that are breeding and producing the microfilariae.
Test and treat is being trialled in Massangam health district in Western Cameroon. This area was chosen because it’s had many years of treatment with ivermectin but so far, transmission of onchocerciasis hasn’t been broken.
There can be many reasons for this. If people have very intense infections and there are a lot of black flies, microfilariae soon build up and transmission starts again quickly. Sometimes not enough people can be treated to really impact transmission – for example if they don’t attend due to ill health, disability or work considerations or stay away as they fear the treatment will have negative side effects. For these reasons and others, a change of strategy is required if the disease is to be eliminated.
The test and treat project will run over two years. There’ll be an assessment after this time where we look to see if the area is closer to reaching elimination targets, and if transmission of the disease has been broken.
As well as the test and treat initiative, we’re increasing the number of rounds of ivermectin treatment given (from one to two per year), and we’re also carrying out focused ground larviciding – which uses insecticide at sites where black flies are known to breed, killing them in their larval stage. As onchocerciasis is transmitted by the black fly bites, reducing their numbers should reduce the amount of transmission.
We’re hopeful that these new strategies will prove effective and that test and treat, complemented by larviciding, will help bring Cameroon closer to eliminating onchocerciasis by 2025.