The Truth About Buffalo Gnats
June 18, 2007
An archive of Pet Columns from the University of Illinois College of Veterinary Medicine is available online at Requests for reprints of this article may be directed to Mandy Barth,

With summer fast approaching, outdoor enthusiasts and animals alike are finding themselves plagued by insects the moment they step out the door. One such culprit is the buffalo gnat, or black fly--an insect that is far from picky about its choice in prey, attacking anything from people and pets to livestock and poultry.

Buffalo gnats are blood sucking flies from the Simuliidae family. For the flies to produce eggs for reproduction it is necessary for the female of the species to consume a blood meal from its human and animal prey.

Unfortunately for us the bite of a buffalo gnat can be more serious than dealing with unseemly bug bites and incessant itchiness for the next week. Recently, according to University of Illinois at Urbana-Champaign faculty members Dr. Yvette Johnson, College of Veterinary Medicine, and Dr. Ken Koelkebeck, Department of Animal Sciences, several poultry have died and more than 40 people have sought medical attention as a result of buffalo gnat attacks.

Generally in humans, the bite of a buffalo gnat causes the same annoying symptoms of a mosquito bite: pain, itching, and swelling. However, if the individual that is bitten is allergic a single bite may warrant immediate medical attention, since such allergies can cause more serious complications.

Unfortunately, the effect of black fly bites can be more severe for animals. According to Drs. Johnson and Koelkebeck, "livestock and poultry are sometimes killed by the flies when bitten by large numbers of them. Death can be due to anaphylactic shock, toxemia, blood loss, or suffocation when the flies are inhaled." The bites of certain species of black flies are also responsible for transmitting a blood-borne parasite that affects poultry called leukocytozoon.

The month of June is peak black fly season since the adult flies emerge during late spring and early summer. The eggs of the buffalo gnat are laid in running water; however, once the adults emerge they have been known to travel over 10 miles in search of a meal. This means that few areas in the Midwest are safe from black fly attacks.

To protect yourself and your animals from black flies it is important to understand them. Dr. Johnson explains that black flies are daytime, outdoor feeders so the best form of protection is avoidance.

However, if you do venture outdoors she recommends that you wear light colored clothes and long sleeves. You may also gain some protection from the use of Permethrin treated clothing and insect repellants containing DEET, but Dr. Johnson warns that only limited success has been seen with these products.

Protection for pets is as simple as keeping them in your house as much as possible during the daytime. Animals that are housed indoors are at a much lower risk of being bitten even if the building is not fly-proof. Whether poultry and livestock are housed inside or out, the use of Permethrin-based fly control products is recommended. Dr. Johnson also recommends that poultry be kept indoors in a darkened barn during the day, using fans or some means of cooling to prevent overheating.

For more information about protecting your animals from black flies contact your local veterinarian.

An archive of Pet Columns from the University of Illinois College of Veterinary Medicine is available online at Requests for reprints of this article may be directed to Mandy Barth,

Veterinary Extension/Office of Public Engagement
University of Illinois College of Veterinary Medicine