Fleas are small, wingless insects that feed on the blood of animals and people. Americans spend about $9 billion a year controlling fleas - one of the biggest expenses for pet owners.
Most flea problems are caused by the cat flea, Ctenocephalides felis. This flea feeds on cats, dogs and wildlife. Other kinds of fleas, like the dog flea, human flea and rat flea, are less common on pets and in homes. Fortunately, fleas need not be a serious problem because there are many effective treatments.
Adult cat fleas are about 1/8 inch long (1 to 3 mm). They are brownish-black, flattened-looking and without wings. Backward-pointing bristles help fleas move through the hairs or feathers of host animals and make them more difficult to remove by grooming. The six legs, especially the hind pair, are long and adapted for jumping.
Flea larvae are less than 1/4 inch long (6 mm), legless and dirty-white in color. The most likely place to find larvae is in infested pet bedding.
During their life cycle fleas pass through four stages: egg, larva, pupa and adult. Although they can jump, adult fleas do not usually travel long distances without a host. Fleas prefer to wait and jump onto a passing animal. Once aboard, they remain until they are dislodged or groomed from the animal. Without a host, adult fleas live only a few days to two weeks. On short-haired cats and dogs, fleas survive an average of 8 days; they live longer on long-haired animals.
The female flea begins laying eggs within two days of her first blood meal. Four to nine days later she produces an average of 27 eggs per day, consuming about 15 times her body weight in blood daily. Much of this blood is excreted as partially digested feces. Flea feces are a fine, reddish-black dust seen in pet fur and bedding.
Flea larvae feed on adult flea excrement. Without it, they cannot survive, although they also may feed on organic matter like food particles, dead skin or feathers. Larvae develop in five to 11 days.
Fleas do not survive well outdoors in hot, sunny lawns. Relative humidity less than 50 percent or soil temperature higher than 95 degrees F kills flea larvae. Moist, shaded spots near pet resting areas are the places to find fleas. Indoors, flea larvae are usually found under furniture and in pet bedding.
The pupa is the transition stage between the larva and adult. The pupa forms inside a cocoon spun by the larva. After a week or two the pupa becomes an adult. The adult flea may remain in the cocoon for up to five months. But when stimulated by a passing animal, the adult can emerge within seconds. Long-vacant homes or apartments can "come alive" with such fleas when new inhabitants move in.
Fleas can be a source of both irritation and disease. Dogs and cats scratch constantly when heavily infested, resulting in soiled and roughened coats and, sometimes, in nervous conditions. The most serious effects occur when a pet develops an allergy to flea bites. As few as one or two bites can cause severe itching and scratching in allergic pets.
Cat fleas do not normally live on humans, but do bite people who handle infested animals. Flea bites cause small, red, itchy bumps, usually on the ankles and lower legs. People with allergies to flea bites suffer from hives, rashes or generalized itching. Allergic reactions usually appear 12 to 24 hours after a bite and may last a week or more.
Fleas that have fed on rodents may transmit diseases, including plague and murine typhus. For this reason, avoid close contact with wild rodents like squirrels and rats. Their fleas can bite you and may transmit disease. Cat fleas, however, do not carry plague.
An integrated flea control program includes good sanitation and treatment of the pet and environment. You can eliminate fleas from your home with proper treatment, but it may take time, especially if the infestation is heavy.
Change pet bedding regularly and vacuum thoroughly. Vacuuming removes up to 30 percent of the larvae and up to 60 percent of flea eggs from a carpet, as well as the larvae’s food supply of dried blood.
Vacuum under furniture, cushions, chairs, beds and along walls. Discard vacuum cleaner bags at least once a week. Fleas can continue to develop inside vacuum cleaner bags and re-infest the house.
Your pet’s first line of defense against fleas is a flea comb and a good bath. Soap acts as a gentle insecticide and helps control light infestations on your pet. Though time-consuming, combing helps reduce the need for insecticides. Flea combs have fine teeth that remove adult fleas from fur. Most dogs and cats seem to enjoy this treatment; pay special attention to the face, neck and the area in front of the tail. Dip the comb frequently in soapy water or an alcohol solution to kill fleas removed from the pet.
Insect growth regulators, or IGRs, are a safe preventative treatment for fleas. These products work by disrupting the normal development of flea eggs and larvae. When exposed to IGRs, adult fleas are unable to reproduce, eggs fail to hatch and larvae die before they complete their development. Because most IGRs kill only eggs and larvae, they do not eliminate adult fleas quickly. For this reason, they are usually mixed with a mild insecticide.
Spot-on treatments (pesticides applied to one or more spots on the animal’s back) control adult fleas effectively. Natural oils on the fur help transfer the pesticide to all parts of the pet’s body. With all products, read and follow label directions carefully. Products designed for use on adult dogs should not be used on puppies or cats, unless specified on the label.
It’s important to wear the proper protective clothes when applying pesticides. Long pants, a long-sleeved shirt, socks and shoes are the minimum. Check the pesticide label for additional safety requirements. When mixing liquid pesticides, wear unlined, chemical-resistant gloves. Allow pesticide sprays to dry thoroughly before letting people or pets into a treated area.
Botanical (plant-based) insecticides kill adult and larval fleas and are relatively low in toxicity. Botanical insecticides include pyrethrum (or pyrethrins) and citrus oil extracts (limonene and linalool). Use botanical insecticides with care. Though usually safe when applied according to label directions, some pets (especially certain cat breeds) are sensitive to botanicals - especially citrus oil products.
It is sometimes claimed that garlic, Brewer’s yeast, cedar bedding and various herbal sachets control fleas, but there is little scientific evidence to support such claims. Volatile oils in fresh cedar chips are toxic to fleas, but the effect lasts a very short time. Tests have shown Brewer’s yeast does not protect pets from fleas.
Don’t wait until fleas get out of hand. Begin your flea control program early for best results. Start a frequent and thorough sanitation program, regularly inspect your pet for fleas, carefully follow the label directions of the insecticide product you choose and dispose of all pesticides safely. These steps will help you reduce the need for extra pesticide treatments.
Mike Merchant and James Robinson are with Texas A&M.