Mosquitoes, flies and gnats are among the most bothersome of summertime insect pests. In addition to being a nuisance, many mosquito and fly species spread diseases to humans. Unlike mosquitoes, however, flies spread disease by transporting bacteria to humans from filthy conditions. Gnats swarm in large numbers around filth, garbage, carcasses and decaying foods, making these insects mechanical disease vectors as well. One group of gnats from the Liohippelates genus are unique for their attraction to the mucous membranes within bodily orifices, particularly the eyes. Unsurprisingly, these gnats, commonly known as “face gnats,” can be a nuisance due to their habit of hovering around people’s faces where they can spread bacteria into eyes, resulting in conjunctivitis, or pink eye.

Flies belonging to the Liohippelates genus are similar to flies of the Hippelates genus, as species from both of these groups are attracted to the same bodily fluids. Face flies from each genus are well distributed across the United States where the insects are considered common urban pests. Clouds of swarming face flies are frequently found near garbage dumpsters. In addition to being attracted to the fluids secreted by the eyes, nose and mouth, face flies are attracted to excrement and open wounds. While face flies do not bite humans, the insects feed on human blood, mucous and other bodily fluids where they can spread numerous strains of disease-causing bacteria. The most common disease spread to humans by face flies is acute conjunctivitis, also called “pink eye.” Public health studies conducted in the United States have found that pink eye cases increase in human populations that have been exposed to face fly outbreaks. Face flies are also capable of spreading streptococcal skin infections to humans. There currently does not exist any area-wide programs to control face fly populations, and foggers, insecticides and soil treatments have not been effective at reducing face fly populations due to the massive number of larval face fly species that emerge from soil. DEET-based repellents are useful for repelling face flies for short periods of time.

Have you ever contracted a disease that had been spread by an insect?