Fleas are tiny blood-feeding insects from the Siphonaptera order of insects, a group that includes thousands of flightless parasitic insects. Adults fleas are about 1/8 inch in length, with dark brown bodies that are flattened sideways, allowing them to easily penetrate long fur to reach the skin. They have sharp mouthparts for piercing skin, strong claws to cling, and strong back legs that allow them to jump long distances. Fleas are extremely well adapted for their function: seeking out furry, warm-blooded hosts, taking blood meals, and reproducing with vigor.
Fleas are often considered to be pests that mostly affect pets such as dogs and cats, but even a home without pets can occasionally be subject to a flea infestation. And when fleas infest furniture, beds, and carpets, it is a serious problem that poses human health risks.
Getting rid of fleas is made especially difficult by the speed with which the insects reproduce and their ability to resist pesticides during the pupal stage. There are four approaches you can use to getting rid of fleas, but you should be prepared to use them all and to follow up at regular intervals. Because furry pets are the primary target for fleas, dealing with your pets and their bedding and sleeping areas is the main focus of eradication strategies.
4 Steps to Get Rid of Fleas
Homeowners can control flea infestations themselves, but it is important to read all label directions for all products and ensure that the correct product is used for the animal being treated. In addition, it is recommended that pet owners talk with their veterinarian prior to beginning a control program and that you take steps to prepare your home for the flea treatment—whether DIY or professional.
The best method of flea control is a four-step approach that attacks all stages of the flea's lifecycle.
Treat Pets for Adult Fleas
Freeing pets of mature fleas is achieved by treating the pet with a product from the veterinarian or pet store. Although over-the-counter soaps, shampoos, and combs are available, it is recommended that pet owners consult with their veterinarian even when using these products. This shampooing with a medicated product should be done at the same time that the home is being treated—or make sure the pet kept out of the home until after both are treated to ensure it doesn't get reinfested.
Adult fleas spend most of their time on furry warm-blooded animals, so it is essential that your pets be the primary focus of your eradication efforts.
Eliminate Larvae in the Home
Wash any bedding with which the pet has come in contact, particularly its own bed and the sheets and blankets of any family members with whom the animal sleeps. Vacuum carpets anywhere in the home that the pet has been. With severe infestations, it is possible you will need to launder virtually all bedding in the house, and perhaps even steam-clean furniture. Use hot water and a warm temperature on the clothes dryer to ensure all stages of the insect are killed.
Treat the Home
Treat carpets, upholstery, and baseboards with a pesticide product specifically labeled as an indoor insect growth regulator (IGR) for fleas. If pet bedding cannot be washed, it also can be treated. These chemicals work by disrupting the reproductive cycle of fleas so that they die off before reaching the adult stage. There are three principal chemicals used in IGRs: fenoxycarb, pyriproxyfen, and methoprene. Of these, methoprene is considered relatively safe, a biologic rather than a toxic pesticide.
Whatever spray you use, make sure to use a product labeled for indoor use when spraying indoors, and an outdoor-approved spray for outdoor use. It is beneficial to use an outdoor product in the yard if the animal spends time outdoors. Focus outdoor efforts on shady areas where your pets rest.
Allow pesticide to dry thoroughly (generally about three to five hours) before returning or bringing pets back into the home. This time is important to ensure the home is completely aired out. Treated areas should not be cleaned for at least two weeks after treatment.
To get rid of all fleas in all life-cycle stages, follow up with at least two additional IGR treatments within five to 10 days after the first application.
The complex lifecycle of the flea means that you will need to practice good sanitation for some time in order to ensure that dormant pupae don't emerge and gain a foothold again. Vacuum carpets and rugs daily for several weeks, and launder pet bedding weekly to ensure all eggs and pupae have been eliminated
What Causes Fleas?
Fleas thrive in warm, moist environments where there are warm-blooded animals to provide food—these insects must have blood meals in order to survive. They are more likely to be an ongoing problem in warm, humid climates where there is no cold weather to kill off outdoor populations. In colder climates, fleas can proliferate during the summer months, largely disappearing in winter. Domestic pets that spend time outdoors are the most common victims of fleas—and the most common cause of indoor flea infestations.
How to Prevent Fleas
While the IGRs will provide prevention by keeping eggs from hatching and not enabling larvae to grow, it is wise to also use flea-control products to keep pets from bringing pests into the home and starting a new infestation. These products may be in the form of a pill that is given to your pet once a month; a collar that is replaced every six months; or topical medication that is dispensed on the pet's skin between the shoulder blades. Use only products that are labeled for the type and age of your pet.
Many of these products also include active ingredients to kill ticks as well as fleas. In warmer areas, the products should be used year-round. In northern climates where insects become relatively inactive in the winter, the use of the products can sometimes be limited to the potential flea seasons. Discuss the options with your veterinarian.
To reduce fleas in your yard:
- Mow frequently, which exposes the soil to flea-killing sunlight.
- Don't overwater, because fleas thrive in humid environments.
- Treat kennels and dog runs frequently with insecticides.
- Rake the lawn and garden frequently to remove debris and eliminate breeding places.
- Control rodent populations because rats, mice, opossums, and other rodents are prime carries of fleas. Seal up gaps in your home through which rodents can enter.
The CDC recommends several strategies to avoid flea bites:
- Use an insect repellant that is listed o the EPA's registered list, containing DEET, picaridin, IR3535, Oil of Lemon Eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone.
- Cover skin with long clothing and pants to minimize exposure to bites. The lower legs and feet are especially vulnerable to flea bites.
- Treat outdoor clothing and camping gear with products containing 0.5 percent permethrin—a safe pesticide made from a flower extract. This application will last through several washings. Or, you can buy clothing already treated with permethrin.
- Never feed or touch wild animals or unfamiliar domestic animals.
Fleas vs. Bed Bugs
Because the symptoms of bites are so similar, it can be hard to know if you are facing a problem with fleas or bed bugs. Both insects are very tiny, so visually identifying the culprit can be challenging.
With bed bug bites, you rarely feel the bite when it is happening—it may take several days for the itchy welts to become evident. The skin marks will closely resemble mosquito bites, and will usually be found in a linear pattern across your skin. Bed bug bites sometimes have a purplish color. And if you have no pets in your house, it is quite likely that your bites are caused by bed bugs.
Fleas bites look quite similar to bed bugs and mosquito bites, but they are more often found in the creases of the skin (elbows, back of knees, waist, groin, etc.) rather than on open expanses of skin. As with bed bug bites, you may not immediately feel the bites. Flea bites often present as three small bites spaced close together. And if your own itchiness coincides with your dog or cat scratching frequently, it's almost sure you've been bitten by fleas.
What Is the Life Cycle of the Flea?
Fleas go through four life cycle stages: egg, larvae, pupae, and adult. An adult flea, after finding a blood meal, will seek out a mate then lay eggs, often in a shady, moist area. The eggs hatch in one to ten days (faster in warm, humid conditions). After five to 20 days the larvae enter the pupal stage by weaving cocoons. The fleas are largely immune to insecticides for days or weeks until the adult fleas are ready to emerge from the cocoons.
The adult fleas do not emerge until they sense nearby movement or body heat, indicated a blood meal is available in the area. Upon hatching, the adult females latch onto a warm-blooded host to secure a meal—this is the time when pets often pick up outdoor fleas and bring them indoors. After feeding, the adult fleas seek mates and begin a new cycle. An entire generation can be completed in a matter of days when conditions are favorable, but it can take years if no blood host is immediately available.
How Should I Treat Flea Bites?
In most instances, flea bites can be treated with a 1 percent hydrocortisone cream and/or an antihistamine to reduce itchiness. Some individuals are much more reactive to flea bites, exhibiting swelling and severe itching. A flea bite that gets badly swollen or warm to the touch calls for a doctor's attention, as does any other sign of infection. The goal of anti-itch medications is to prevent breaking the skin through scratching, which makes make secondary infection more likely.
Which Fleas Spread Disease?
Fleas are among the most serious carriers of disease in all of recorded history. The Black Death or Bubonic Plague that wiped out a large percentage of the world's population during several waves during the Middle Ages was caused by fleas that picked up the bacteria from infected rats and transmitted it by biting humans.
Plague is still sometimes spread by fleas, though it is no longer the same deadly disease, thanks to modern antibiotics. But as blood-feasting insects, fleas can also spread a variety of other diseases, including typhus. Of the 2,500 species of fleas found worldwide, there are roughly 300 that can be found in North America, and of these, four species are possible spreaders of disease:
- Cat fleas (Ctenocephalides felis) can transmit some types of typhus and cat-scratch disease (CSD). It commonly infests all types of warm-blooded domestic animals, not just cats. Rarely, it has been found to carry plague bacteria. This is the pest that most often infests pets in North America and the one that most often bites humans.
- Dog fleas (Ctenocephalides canis) are a prime carrier of the Dipylidium caninum tapeworm, which can infest dogs, cats, and even humans. Despite the name, it's not very common as a pest for dogs.
- Ground squirrel fleas (Oropsylla montana) are associated with ground squirrels and are known to be a factor in the spread of plague bacteria in North America.
- Oriental rat fleas (Xenopsylla cheopis) are common spreaders of plague and typhus.
Some diseases are spread indirectly when a victim scratches bites, which then opens up the skin to bacteria found in flea feces or other sources. Other diseases, such as typhus, and parasites such as tapeworms, are transmitted directly by bites from fleas that have picked up pathogens from other sources, such as rodents or wild animals.
Fleaborne Diseases of the United States. Centers for Disease Control and Prevention.