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Pull up your socks, early fall is "flea season"

Flea bites can cause irritation and serious allergic reactions in animals and humans. The most common flea found in school environments, the cat flea (Ctenocephalides felis), can carry or transmit tapeworms as well as the organisms that cause bubonic plague and murine typhus. Even if no pets are kept in the building, staff, students and visitors can bring in adult fleas on their clothing without realizing it. Urban wildlife, such as feral cats, squirrels and birds, can be a source of infestation as well.

Identification and biology

Adult cat fleas are small (1/16 inch long), oval, wingless, reddish-brown to black insects with powerful hind legs. After mating and feeding, adult females lay oval, white eggs that fall into cracks, crevices, carpet, bedding or lawn covering. A mature female can lay up to 25 eggs a day for three weeks. Within 48 hours, wormlike larvae hatch. Larvae feed primarily on "flea dirt" (adult flea feces, which is relatively undigested dried blood) that falls from the host's fur. They develop in areas protected from rain and sun, where the relative humidity is at least 70 percent and the temperature is 70ºF to 90ºF. In eight to 24 days the larvae spin cocoons in which they will develop into adults. Under optimal conditions, new adults are ready to emerge from their cocoons within two weeks, but they can remain in their cocoons up to a year. Vibrations stimulate them to emerge. As soon as adults emerge, they look for a blood meal. Adults can live a month or two without a meal and up to six months with one. These variations in flea development time account for the sudden appearance of large numbers of adult fleas in "flea season," usually in the late summer and early fall. The flea population has been building up all year long in the form of eggs, larvae and pupae (cocoons), but rapid development into biting adults cannot be completed until the temperature and humidity are optimal and host cues signal adults to emerge.

Detection and monitoring

If pets are kept in the building, check their bodies and the areas around their cages often. One sure sign of infestation is the presence of flea dirt. It is important to also check in places where animals might find harborage, such as basements, crawlspaces, attics, eaves, roof structures and shrubs near buildings. Long, white athletic socks worn over the shoes and trouser legs allow you to easily see and count adult fleas as you walk through an infested area. Socks also provide some protection from bites. In situations where the flea population is likely to be small, light traps are especially useful. A small electric light attracts fleas to a sheet of sticky paper. Research has shown that the most effective traps are those with a green light that can flicker on and off. Check the traps once a week. If only a few fleas are caught, the infestation is very small and probably can be controlled by the monitoring traps themselves. If 20 or more fleas are caught in a single trap in a week, this probably indicates a more serious infestation.

Physical management options

Vacuuming on a regular basis will keep developing flea populations low. Flea larvae are likely to escape capture in carpet because they coil themselves around the fibers. Vibrations caused by vacuuming will stimulate new adult fleas to emerge from their cocoons. These new adults will then be captured in the next vacuuming. Dust in the vacuum bag will kill most fleas by blocking their breathing apparatus, but to be sure, vacuum up a tablespoon of cornstarch. Dispose of the used vacuum bag immediately. Badly infested areas should be vacuumed every day. Wash any removable floor coverings, such as rugs. Severe infestations may require the services of a steam-cleaning firm. This process kills adult and larval fleas and probably some eggs as well. Remaining eggs will hatch a day or two after the cleaning. Continue vacuuming to remove these last few fleas. Comb classroom pets in infested rooms with a flea comb, dropping fleas and eggs into soapy water. Wash classroom pets' bedding regularly. Ultrasonic flea collars are completely ineffective. Trained animal-control technicians can remove wild animals with traps. Ask your county Cooperative Extension Service agent for a recommendation. Repairs can then be made to the building to exclude animals.

For more information, including chemical and biological control options, please visit the University of Florida's School IPM Web site (http://schoolipm.ifas.ufl.edu).

Edited by: Angela Brammer, University of Florida