Researchers expect an increase in black flies in Germany. Black flies are as small as harmless fruit flies, but their bites itch like those of ticks.
They are also vector-competent, meaning they are able to transmit pathogens that cause infectious diseases. The best-known pathogen transmitted by black flies is a nematode native to Africa that can cause river blindness, according to the World Health Organization (WHO) More than 1.15 million people worldwide have suffered vision loss as a result of the disease.