Gnat's Proteins May Help HumansBy
Proteins that a pesky gnat secretes when biting sheep or cattle might
someday be used in new vaccines and other drugs to help animals or humans.
In nature, the proteins help a tiny gnat enhance blood flow to the bite
area. At the same time, the gnat may be transmitting particles of viruses that
cause bluetongue, a livestock disease, according to scientists with USDA's
Agricultural Research Service in
The gnat, grayish-black and about one-sixteenth-inch long, is known as Culicoides
variipennis (KOO-lee-COY-deez vary-uh-PENN-uss). The virus gets its
name from one of its symptoms-- a bluish, swollen tongue. The virus does not
cause disease in humans.
Gnat salivary-gland proteins forestall blood clotting, dilate the victim's
blood vessels and inhibit immune system cells that would fight off the virus.
The proteins may be of use to medical researchers seeking, for example, new
compounds to fight clotting that can lead to heart disease and strokes. The
proteins may also be useful in blocking immune system responses in patients with
arthritis or other disorders caused by an overactive immune system.
Researchers elsewhere have shown that the saliva of several other biting
insects and ticks has similar specialized proteins. The ARS team was the first
to find that C. variipennis gnats also secrete them.
The gnat proteins may make a suitable target for future vaccines to protect
animals from viruses. This approach would differ from today's conventional
vaccines that target a disease- causing virus itself. The U.S. has no generally
approved bluetongue vaccine.
Bluetongue can kill sheep and, rarely, cattle. It costs the U.S. livestock
industry an estimated $120 million in lost trade annually. Countries without the
disease won't accept some U.S. livestock exports.
An article in the current issue of the agency's Agricultural Research
magazine tells more. View it on the World Wide Web at:
Scientific contact: Walter J. Tabachnick, USDA-ARS
Arthropod-borne Animal Diseases
Research Laboratory, P.O. Box 3965, University Station, Laramie, WY
82071-3945. Phone: (307) 766-3600, Fax (307) 766-3500, e-mail