Fleas

Fleas are parasites of many animals including cats, dogs, rodents, birds and bats. The cat flea (Ctenocephalides felis) is the most common flea that infests homes and attacks humans and pets.

How to identify fleas

Adult fleas

• Dark brown to black, less than 1/8 inch long.
• Wingless; body is flattened from side to side.
• Large hind legs for jumping.

Larvae

• About 3/16 inch long.
• Whitish; resemble tiny worms.

Dark, pepper-like dried blood and dark reddish-brown or black flea excrement (called “flea dirt”) may be found on pets or their bedding.

Biology of fleas

Adult fleas

• Feed on blood and spend almost their entire lives on their hosts.
• Their favorite hosts are cats and dogs, but they also feed on wildlife, including raccoons, opossums, skunks and foxes.
• Fleas can bite people but females require a blood meal from a non-human host to produce eggs.
• Female fleas lay 4 to 8 eggs at a time and can lay as many 500 eggs in their lifetime.
• Adults may survive for weeks without a blood meal.

Flea eggs

• Nonsticky and typically fall to the ground.
• After 2 to 5 days, eggs hatch into small, white, worm-like insects.
• Larvae feed on flea feces (commonly referred to as flea dirt), which is largely composed of undigested blood.
• Larvae normally take about 7 to 15 days to finish their development.
• They avoid light and require humidity above 75%.
• Eggs can take up to six months to develop into larvae if temperatures and humidity are unfavorable.

Larvae

• Larvae make cocoons where they become pupae and remain for weeks or months.
• Pupae can take 12 months or longer to develop into adults if temperatures and humidity are unfavorable.
• Adult fleas emerge when cocoons are stimulated by warmth, carbon dioxide (breath), and pressure or vibrations (someone walking or vacuuming).
• Adult fleas live for 1 to 12 months.

How fleas are harmful

Fleas are generally pests of animals, and dogs and cats serve as their primary hosts in homes. Adult fleas readily bite pets for a blood meal.

Pets

• Can experience dermatitis as a result of flea bites.
• Biting causes itching, reddening of the skin and further skin irritation.
• Fur loss can also occur and in extreme cases, animals may become anemic.
• Speak to your veterinarian about any animal health concerns associated with pets.

Humans

• Adult fleas bite and feed on blood.
• Often it results in raised, red bumps that itch.
• Symptoms may persist for five days or more.
• Bites typically occur in clusters on lower legs.

Some people do not react to flea bites and may not notice their presence. Other people may experience flea bite allergic dermatitis, resulting in more intense itching, hair loss and reddening. Scratching these areas may result in secondary infections. Speak to your physician about any health concerns associated with flea bites.

Caution: It is very challenging to diagnose flea bites only from lesions as other causes can look similar. The best method for verifying fleas is to find adult fleas on pets or in the home.

While fleas can technically transmit several diseases to people, like plague and murine typhus, cases of these diseases have not been found in Minnesota. Fleas are known to transmit tapeworms to dogs and cats in Minnesota.

How to control fleas

It is important to control fleas on your pets at the same time as in your home. Use a combination of nonchemical methods and insecticides to control fleas in your home.

You can have a flea problem even if you don't have pets. Wild animals such as raccoons, opossums or squirrels nesting in the attic, fireplace or crawlspace, can bring them in. Treat these areas, seal holes or other possible entryways so animals can't get back in, and remove wild animal hosts to control fleas in these situations.

Fleas are rarely found in lawns or other outdoors sites on your property in Minnesota, as they do not survive winter temperatures.

Treating pets

• It is very important to treat pets at the same time the home is treated. 
• Be sure to consult your veterinarian for help in selecting a specific product to treat your pet. 
• Different breeds of cats and dogs can also have different tolerances to particular active ingredients.
• It is critical to follow all product directions to ensure effectiveness and safety. 

Preventing fleas on pets

Preventing fleas on pets is easier than treating infested animals. It can take several months to eliminate moderate to severe flea problems on pets. 

The most effective preventive medications are topical spot-ons and oral chewable tablets. These products are very effective and long-lasting (one to three months depending on the product).

Products used for prevention can also be used for treating existing problems.

Topical spot-ons

Effective topical spot-ons contain one of the following active ingredients:

• Fipronil (e.g. Frontline®)
• Imidacloprid (e.g. Advantage II®)
• Selamectin (e.g. Revolution)
• Indoxacarb (e.g. Activyl®)
• Permethrin is usually combined with imidacloprid or dinotefuran (e.g. Vectra 3D®)

Oral medications

Effective oral medications contain one of the following active ingredients:

• Fluralaner (e.g. Bravecto®)
• Afoxolaner (e.g. Nexgard®)
• Nitenpyram (e.g. Capstar®)
• Spinosad (e.g. Comfortis®)
• Sentinel® Flavor tabs® (Lufenuron)
• Sarolaner (e.g. Simparica®)

Insect growth regulators (IGRs)

There are both topical spot-ons and oral medications that use insect growth regulators (IGRs). An IGR is an insecticide that mimics naturally occurring hormones. It interferes with the fleas' normal development, preventing flea larvae from turning into adults. IGRs do not kill adult fleas.

• Pyriproxfen is used in some topical spot-on products; it is usually combined with fipronil, imidacloprid, etofenprox or permethrin (e.g. Effipro Plus®).
• Methoprene is also used in some topical spot-on products; it is sometimes combined with fipronil (e.g. FleaStroy™).
• Lufenuron is used as oral medication (e.g. Sentinel® Spectrum®).

Flea collars

Some flea collars are very effective in preventing flea problems. Particularly, effective is Seresto®, containing flumethrin and imidacloprid. However, longevity of Seresto® decreases if your dog spends a lot of time in the water.

Sprays, dips or shampoos

Sprays, dips or shampoos can sometimes effectively eliminate a flea infestation but they do not last as long as the above topical spot-ons and oral medications.

They are not effective in preventing fleas.

Active ingredients include permethrin and bifenthrin. A few of these products contain methoprene, an IGR.

Some products contain pyrethrins. This insecticide is derived from the chrysanthemum flower. However, pyrethrins have a very short residual, generally lasting only a few hours. They can't provide any long-term protection for pets against fleas.

Essential oils

The use of essential oils, like thyme oil, peppermint oil, clove oil, rosemary oil and cedarwood oil is not recommended.

There is a lack of research data to support their effectiveness.

There is also concern that the ingestion of these oils by dogs and cats could be harmful.

CAUTION: Before using any flea or tick treatment on a pet, consult with your veterinarian to discuss the most appropriate product(s). Using the incorrect product could pose medical concerns to your pet.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Be sure that the area you wish to treat is listed on the label of the pesticide you intend to use. Remember, the label is the law.

Treating fleas in homes

Open all  |  Close all

Detection

Determine where fleas are most common and target these areas for treatment.

• This is usually where your pet sleeps or spends a lot of time.
• For dogs this is often a few particular spots, but for cats it can include tucked-away locations.
• This happens because flea eggs don't stick to animals but drop off.
• For cats, look in areas where they typically jump off furniture to land on the floor. This is often an important area for fleas because of the shedding of dander and dried flea feces as the pet lands on the floor.

Test for the presence of fleas

• Use the white socks test.
  • Walk through your home wearing white socks.
  • The fleas, attracted by the warmth and movement, will jump to your feet and ankles.
  • It is easy to see their dark-colored bodies against the white background of the socks.
• Use a shallow pan with warm water.
  • Add a couple of drops of liquid soap to prevent the fleas from jumping back out. 
  • Add an Alka-seltzer tablet; the carbon dioxide helps draw nearby fleas into the pan.
• There are also a variety of manufactured traps you can buy in stores or online to help detect fleas.
  • Flea traps help detect fleas but they don't get rid of them.

Nonchemical methods

• Vacuum daily, especially where fleas have been found.
  • Vacuuming removes flea feces, an important food source for the larvae.
  • The motion and vibrations from vacuuming with a beater-bar (or powerhead) attachment can also stimulate adult fleas to emerge from cocoons.
  • Frequent daily vacuuming can help remove and kill fleas.
  • Throw away vacuum cleaner bags after they have been used to prevent any captured fleas from escaping.
  • If practical, freeze bags for several days then reuse.
• A steam extraction carpet cleaner is effective in killing all stages of fleas.
• Wash any pet bedding in hot water. Wash any human bedding if it becomes infested with fleas.
• Ultrasonic and other sound emitting devices are not effective in controlling fleas.

Insect growth regulators

An insect growth regulator (IGR) is an insecticide that mimics naturally occurring hormones. It interferes with the fleas' normal development, preventing flea larvae from turning into adults. 

• IGRs are very effective against immature fleas but do not kill adult fleas.
• They are often combined with a residual insecticide (e.g. permethrin) which kills adult fleas.
• IGRs are a very low risk to people and animals.
• Pyriproxyfen (Nylar) is a commonly available IGR for treating homes.

Residual insecticides

There are several products available to treat homes containing insecticides, such as permethrin, β-cyfluthrin, and deltamethrin. Treat areas where fleas are found which could include under and around furniture and areas where pets sleep or play.

Products containing pyrethrins are of minimal value. They only last a few hours.

Total release aerosols, or bug bombs, are not very effective. These products disperse product into the air which falls randomly to the floor. They can not place insecticide to specific locations where fleas occur.

Professional pest management companies

You may also want to consider an experienced pest control service to treat your home for fleas. Their knowledge and experience plus a larger assortment of products allow pest management companies to control fleas more effectively. 

If your flea problem is due to wild animals in your home, contact a wildlife pest management company to get rid of them.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Be sure that the area you wish to treat is listed on the label of the pesticide you intend to use. Remember, the label is the law.

Authors: Jeff Hahn, Extension entomologist, and P.J. Liesch, entomologist, University of Wisconsin