Adult fleas are biting insects that feed on warm-blooded animals. Worldwide, approximately 2,500 species of fleas have been identified, seven of which can affect human health.
Adult fleas are small brown insects that are flattened from the sides, making them tall and skinny (under magnification; with the naked eye they look like black specks). They have powerful jumping legs that allow them to hop from the ground onto passing hosts. Because of this, one way to survey for fleas in the home is to walk through the problem area with light-colored pants and socks pulled up over the cuffs. Fleas that jump onto your pants will be easily observed.
Fleas on pets are often seen where hair is sparse (groin and belly) or where it is difficult for the animal to reach (hind quarters). Unlike ticks that attach for long periods of time to feed, fleas are often observed moving on the host and can jump (ticks cannot). Combing the hair against the grain (toward the animal’s head or up) can help you spot fleas as they hide amongst the fur.
When fleas have infested an animal, you may observe “flea dirt” in the animal’s fur or where they sleep. These black flecks are actually flea feces, made of processed blood from the host. Flea dirt and white eggs can be found in pet resting areas, giving a salt and pepper appearance. Adult flea feces are food for the developing larvae. Larval fleas are found in pet resting areas, are cream colored to white worms with a black head capsule. Flea pupae (1/8 inch or 3 mm long), the transition stage between larvae and adults, are silky white cocoons that attract dust and debris, making them blend in with the environment.
Adult fleas are ectoparasites that feed on animal blood. Most infestations start when fleas enter a building on pets such as cats and dogs. However, fleas can hitch a ride on other animals living in the structure, such as squirrels, raccoons, opossums, and even rodents. Flea species can be identified to determine what host brought in the flea, but a microscope will be needed to distinguish the various flea species using pictorial keys.
The most common pest flea found inside homes and kennels is the cat flea, which has a large host range and can infest many animals including dogs and cats. The other common fleas are host specific, meaning they cannot reproduce by feeding on a different type of host. In other words, a rat flea cannot survive to reproduce by feeding on a dog, and will not infest a person. However, this does not prevent them from biting and feeding on other warm-blooded hosts.
Fleas are biting, blood-feeding insects that leave itchy welts on people. Because of their blood-feeding habit, fleas can transmit pathogens to people if they previously fed on an infected animal. Thankfully, the pathogens that cause plague and flea-borne typhus are rare in New York. Cat scratch disease is more common.
Pets can be infested with fleas, causing distress and irritation of the skin (flea allergy). Fleas can transmit pathogens to pets too, and are the source of parasites such as tapeworms that infect companion animals. Because of these concerns, fleas are considered a medically important pest. Steps should be taken to prevent infestations on pets and to quickly address problems identified in the home.
Based on the lifecycle of fleas, a multifaceted approach is needed for their management.
Find the Source
The first and most important step is to identify the source of fleas: were they brought in on a pet or introduced by wildlife living somewhere in the building?
Dogs and cats should be protected from fleas year-round. This includes protective treatments even in winter (that may also protect your pet against ticks). The current research suggests that flea problems are most often caused by failure of pet owners to treat their pet in a timely and consistent manner. There are multiple options for treating pets against fleas, including flea and tick collars, spot-on (topical) and oral treatments. You should discuss the option that is best for you and your pet with your veterinarian. Keep in mind that over-the-counter products are not as effective as those prescribed by a veterinarian. Note that hired pest professionals (exterminators) are not qualified to treat pets.
In addition to chemical treatments for flea control, use of a flea comb can help reduce the number of adult fleas and flea dirt in the fur. Flea combs are a special type of comb that have a very small spacing between the tines of the comb. When used to groom your pet, adult fleas and flea dirt get trapped between the tines. It is a good idea to have a vial or dish of rubbing alcohol or soapy water and a pair of tweezers nearby when combing pets for fleas. Any intercepted fleas can be removed with the tweezers and placed in the alcohol to immediately kill them. Combing should focus on areas that are prone to fleas, such as the groin and hind quarters, but should cover the rest of the body as well.
In some cases, flea problems are not eliminated even when the proper steps are followed. A possible explanation for these rare cases is that the fleas are coming from a wildlife host living in the basement, crawl space, attic, walls or other inaccessible part of the home. For example, the pest problem may be due to squirrel fleas or northern rat fleas. A certified wildlife professional should be consulted to determine if there is a pest problem, and how to effectively remove and prevent future problems through exclusion.
Clean Pet Sleeping Areas
After the host animal has been identified and treated (if it’s a pet), the next step is to eliminate larval feeding sites in pet resting areas. Homeowners are responsible for putting pet bedding, blankets and toys through the laundry to kill fleas. Areas surrounding pet resting locations should be vacuumed on a daily basis using a vacuum with a beater bar or other agitator. This is important because the pupal stage of fleas can remain dormant until host cues are detected, which includes vibration.
Note that hardwood floors with gaps between boards and spaces at the floor/wall junction present a challenge for flea management. Larvae, pupae, flea dirt and animal dander can collect in these spaces, providing protection against vacuuming and pest management treatments. Crack and crevice tips on vacuums can be used here, as well as compressed air or steam to blow out or kill flea life stages, respectively.
Steam can also be used on thick carpets to kill larvae living at the base of the carpet that might be protected from vacuuming. When using compressed air, caution is needed to not blow fleas out of one secluded area to another location.
Treat Pet Sleeping Areas
Pesticide treatments can be used in combination with vacuuming, steaming and laundering to kill flea larvae. Unfortunately, pupae can be difficult to kill because of the silky cocoon and debris that attaches to this life stage making it less susceptible to chemical control.
In addition to indoor pet resting areas, consider outdoor areas that may contain fleas. For example, if pets rest under porches, under bushes or another shady and cool location with minimal vegetation and powdery soil, fleas can develop in these areas and should be treated by a professional.
Pest management professionals have a number of products at their fingertips to control fleas. One class of chemicals are called Insect Growth Regulators, or IGRs. These materials stop normal development of insects and can prevent reproduction. Because they are based on insect hormones, they pose low risk to humans and other mammals.
Monitor to Confirm Success
Monitoring for fleas is as simple as walking in the room with light-colored pants and socks. However, a flea trap can also be constructed using a desk lamp over a pan of soapy water to detect fleas at night. See our factsheet for more details: Flightless Leaping Ectoparasitic Arthropods = FLEAs.