I find it somewhat ironic that Onchocerciasis a.k.a River Blindness is a neglected tropical disease simply because there is sad poetry in being blind to the second most common infectious cause of blindness.
The disease of river blindness itself occurs when larvae of the parasite Onchocerca volvulus. Beyond this basic pathogenesis, in terms of the biology, two key points must be considered before shifting into my main argument. First is the fact that Onchocerca volvulus, the filarial worm responsible for the condition, requires the black fly as a vector. The second related point is that while O. volvulus and its primary Simulium vector are native to Sub-Saharan Africa, Simulium species exist globally. As evidence of their range, ancient Serbs were extremely familiar with black flies ascribing their origin to demons associated with hailstorms, madness, and disease, and the association of the flies with river blindness was made not on the African continent but instead in Guatemala. Finally, it must be made clear that the filarial parasites in Africa and South America are not two distinct closely related species but have been known to be one and the same since the 1920’s.
While the biology is fascinating, my main frustration, and consequently focus here, is how this condition reveals blind spots in social views of medicine that persist into the modern era. The first lesson to be derived from Onchocerciasis is that we cannot idly leave the past behind. In emphasizing that the same parasite is responsible on both continents where Onchocerciasis occurs I hope the question of how naturally springs up in the reader’s mind. The answer is that at the same time Europeans encountering malaria and other tropical disease assumed a resistance in enslaved Africans as a result of their origins, they failed to consider that this self-same similarity of climate may allow the disease of the old world to find a new home. In the case of O. Volvulus this was precisely what happens as blackflies native to South and Central America readily assumed the role of the vector.
They continue this role today, nearly a decade after the anticipated elimination of the disease in the Americas by 2012. Elimination only occurring in Colombia in 2013, Ecuador in 2014, and Mexico in 2015 and hundreds of thousands of people still threatened with blindness yearly. In its overt presentation marking the faces of its victims’, river blindness may perhaps ironically turn our eyes to considerations of other conditions which are easily yet rarely linked back to hundreds of years of accepted suffering for the sake of profit. The other key lesson, perhaps more relevant than ever, is that no nation is ever truly isolated. Whether through a mutually beneficial partnership or horrific exploitation our world has always been united. What is less predictable is how the products of that exchange will impact their new settings. No one could have predicted the sequences of events whereby an African parasite would find at the end of a journey of thousands of miles a home as perfect as the one it left. As interaction is so inevitable in helping others we are often unwittingly helping ourselves and the karma of atrocity can often be visited if not on the perpetrator but on their descendants for centuries. In considering river blindness, we can see how far-sighted the ancient Serbs perhaps were in their early encounters with the blackfly. The horror and madness of slavery born of the demons of avarice that assail humanity allowed disease on the wings and in the mouths of blackflies to spread across two continents, leaving the world literally and figuratively darker for too many for too long.