"We hypothesize that blackflies infected with Onchocerca volvulus microfilariae may also transmit another pathogen," notes lead investigator Robert Colebunders, MD, PhD, who is head of the HIV/STD Unit, Department of Clinical Sciences at the Institute of Tropical Medicine, and Professor of Infectious Diseases at the University of Antwerp.
"This may be a novel neurotropic virus or an endosymbiont of the microfilariae, which causes not only NS, but also epilepsy without nodding."
The hypothesis draws on other research that shows that parasites and viruses can have a symbiotic relationship, allowing insects to pass on diseases they would not normally be able to transmit.
"Many laboratory studies have shown that arboviral transmission is enhanced in mosquitoes and other blood feeding flies that concurrently ingest microfilariae, and the same could be true for blackflies," explains Dr. Colebunders
suggests several courses of action based on the new theory, including collecting more precise incidence data on NS, epilepsy, and onchocerciasis in relation to blackfly distribution; continuing and increasing the systematic use of larvicides to control the blackfly population; and improving ivermectin coverage and increasing the frequency of its administration, as it appears it may limit the blackfly's ability to transmit the novel NS pathogen.
"The burden of disease may be considerable, as the 'NS pathogen' may also cause epilepsy without nodding," concludes Dr. Colebunders