November 10, 2017
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Cell phone-based microscope facilitates safe treatment for river blindness

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Re-implementation of an ivermectin treatment strategy for river blindness in Cameroon, Africa, is now possible with the use of the LoaScope, which quantifies Loa loa microfilariae in peripheral blood.

Mass distribution of ivermectin was the primary strategy to eliminate lymphatic filariasis and onchocerciasis (river blindness) in Cameroon until 1999 when it was discovered that administration of this drug was associated with fatalities in those with L. loa infection.

In this study, the LoaScope, a small microscope that incorporates a cell phone, was used to quantify L. loa microfilariae in peripheral blood for those at risk for serious adverse events.

Researchers tested 16,259 people at least 5 years old throughout 92 villages in Cameroon. The median age of the population was 17 to 26 years, and 48% of participants were male.

Their test-and-not-treat process involved quantification of L. loa microfilarial density with the LoaScope, provision of treatment with ivermectin (150 µg/kg of body weight) to eligible participants and surveillance for adverse events.

A cutoff L. loa microfilarial density of 26,000 mf/mL of blood was initially selected as the threshold below which ivermectin was administered, but it was lowered to 20,000 mf/mL for the remainder of the study after a case of conjunctival hemorrhage occurred in a participant who had L. loa microfilarial density of 24,599 mf/mL.

A total of 15,522 participants received ivermectin, 340 were excluded because of a microfilarial density above the risk threshold, and 397 were excluded because of pregnancy or illness.

The prevalence of onchocerciasis in the six health areas varied from 15.3% to 29.9%, and it was 22.0% among those who received ivermectin.

The prevalence of L. loa microfilariae varied from 15.3% to 22.8%, and the percentage of participants with an L. loa microfilarial density greater than 20,000 mf/mL of blood ranged from 1.3% in the Ngoya health area to 2.4% in the Nlong and Ekekam III health areas.

Researchers reported no serious adverse events, and the adverse events recorded in 934 participants, most of whom had no detectable L. loa microfilariae, were mostly dermatologic in nature.

On average, between 50 and 100 participants were examined per village in a day. The mean time from finger prick to the LoaScope result was 2 to 3 minutes, and results were available immediately for 16,099 of the 16,259 participants. Researchers wrote that the health teams noted the ease of use and reliability of the device despite the daily use and demanding field conditions.

A test-and-not-treat strategy would target people who have not previously received ivermectin and those who are routinely nonadherent to treatments, they said. – by Abigail Sutton

Disclosures: Please see the full study for all financial disclosures.