In a scenario in which the COVID-19 pandemic has reflected the importance of controlling infectious agents taking into account that they could jump from an animal to humans at any time, an in-depth study of this field is more than crucial.
Scientists have described around 40 cases of infection worldwide by different species of Onchocerca nematode worm that usually only affect animals, not counting the Onchocerca volvulus species, which causes the so-called ‘river blindness’ (human onchocerciasis ). Now, a team of Spanish researchers from the Mountain Livestock Institute (IGM), a joint center of the CSIC and the University of León and the Barcelona Institute for Global Health (ISGlobal) has set out to evaluate the probabilities that, through a vector , a human being can be infected through an animal host infected with the nematode worm Onchocerca or one of its many species; It is a genus that is spread practically all over the world, especially in fast rivers and streams since its vectors (that is, the animals that spread them), are the black flies ( Simuliidae ), native to these areas.
Taking into account that only the so-called “river blindness” was the only infection recorded in humans, the presence of these dozens of cases by other Onchocerca species that commonly affect animals, scientists believe that it is time to sound the alarm and begin to take timely measures so that, what apparently suggests that they are only isolated cases, does not turn into a catastrophic surprise as has happened with the SARS-CoV-2 coronavirus.
“The main hosts of Onchocerca are ungulates (animals whose legs end in hoofs, such as mountain goats, pigs, horses, giraffes or zebras), although some species are also found in canids such as wolves or dogs, in felines such as cats and humans, as is the case of the Onchocerca volvulus species ”, explains Maria Cambra Pellejà, researcher at the Mountain Livestock Institute and leader of the study published in the journal Pathogens.
This genus of nematodes, so widespread throughout the planet, uses black flies to form subcutaneous nodules on the skin, the larvae of which can be observed freely on the skin or even in the ocular tissues of adult animals (more than in offspring).
Once the black fly acts as a successful vector, the nematode Onchocerca volvulus causes intense itching, skin eruptions that can disfigure the skin in the most severe cases, and even visual disturbances that can lead to permanent blindness. it is popularly known as the “river blindness” disease.
Does it have a high incidence?
That’s how it is; not in vain, it is the second infectious cause of blindness worldwide with a very high morbidity.
The fact that 40 different cases of infections in humans by some species of Onchocerca have already been described could, according to the experts, set a dangerous precedent regarding the possibility that these species of animals would end up also establishing themselves in humans, especially considering our close contact with dogs or livestock that may share their habitat with us.
Reference: Cambra-Pellejà, María, Javier Gandasegui, Rafael Balaña-Fouce, José Muñoz, and María Martínez-Valladares “Zoonotic Implications of Onchocerca Species on Human Health”. Pathogens DICYT 2020 doi: 10.3390 / pathogens9090761 Pathogens. 2020 Sep; 9 (9): 761. PMCID: PMC7560048 PMID: 32957647
