Fleas Affecting Animal Health

Importance

  • There are over 2,000 species of fleas found worldwide. Only about 20 species affect people or domestic animals.
  • Animals with flea infestations may be intensely itchy. Fleas can also cause hair loss, flea allergy dermatitis, anemia, and death in severe cases (particularly in young animals). Fleas may be vectors of highly contagious, foreign, or reportable diseases.
  • Foreign vectors and foreign animal diseases (FADs) are not found in the United States and can threaten human and animal health. FADs can be introduced to the United States, so animal owners and veterinary personnel have a key role in recognizing and reporting FADs to animal and public health officials. Early signs of flea-related FADs may include:
    • Unusual flea appearance or large infestations
    • Large number of sick or dead animals
    • Unusual signs of illness (like fever, enlarged lymph nodes, and sudden death)

About Fleas

  • Fleas are tiny, wingless insects that live their entire life parasitizing animals.
  • Fleas have four life stages.
    • Adults feed on blood, mate, and lay eggs on a host
    • Eggs may fall off the host and into the environment.
    • Larvae and pupae develop indoors or in protected outdoor sites away from direct sunlight.
  • Fleas usually live for about two or three months.
    • Adults live most of their lives on a host.
    • Immature stages contaminate the surrounding environment and can survive for months.
  • Some fleas are host-specific and prefer to feed on one type of animal. Other fleas will feed on a wide range of hosts, including people.
  • Flea activity is highest in summer months, but can be year-round in warmer climates.
  • Fleas are transmitted from one animal to another through direct contact or fomites (such as bedding and grooming tools).
Life cycle of the flea includes egg, larva, pupa, and adult.

Identification of Fleas

  • Fleas are tiny but may be seen with the naked eye. Many can be identified by their appearance and animal host.
    • Determining the species may be difficult or impossible without the help of a dissecting microscope or trained entomologist.
  • Adult fleas have hard, narrow bodies with large hind legs for jumping large distances.
    • The shape of the head varies by species.
    • The number and appearance of combs (dark, comb-like bristles) also varies by species. The genal comb is located below the eye, like a moustache. The pronotal comb is located behind the head, like a collar.
  • Pupae are sticky, like cocoons, and may be white or brown depending on their stage of development.
  • Larvae are slender, worm-like, and pale in color.
  • Eggs are white and oval, similar to grains of salt, and may be sticky after they are laid.
  • Identification keys and flea experts can be consulted for further details.
Illustration of a flea showing the major body parts including head, eye, mouthparts, genal comb, and pronotal comb.

Fleas of Animal Health Concern

The fleas listed below are common species in the United States. In certain areas, these fleas may transmit pathogens. Some examples of diseases are listed as well. Endemic diseases in animals may or may not be reportable, depending on the jurisdiction. Learn more about recognizing and reporting highly contagious, foreign, and reportable diseases at CFSPH: FAD Prevention.

Microscopic view of cat flea.

crispychris28, iNaturalist, CC BY-NC-4.0

Name: Ctenocephalides felis (Cat Flea)

Characteristics: Genal and pronotal combs present, head length twice its height.

Hosts and Distribution: Primarily cats, but other animals (including humans) may be hosts; worldwide distribution.

Endemic Diseases:

Bartonellosis

Flea-borne spotted fever

Murine typhus

Mycoplasmosis
Tapeworm (Dipylidium caninum)

Microscopic view of human flea.

Katja ZSM, Wikimedia, CC BY-SA 3.0

Name: Pulex irritans (Human Flea)

Characteristics: Genal and pronotal combs absent, rounded head, ocular bristle below eye.

Hosts and Distribution: Primarily humans, but other animals may be hosts; worldwide distribution.

Endemic Diseases:

Flea-borne spotted fever
Murine typhus
Plague

Microscopic view of Oriental Rat Flea.

Olha Schedrina/The Natural History Museum, Wikimedia, CC BY 4.0

Name: Xenopsylla cheopis (Oriental Rat Flea)

Characteristics: Genal and pronotal combs absent, rounded head, ocular bristle behind eye.

Hosts and Distribution: Primarily rodents but other animals (including humans) may be hosts; worldwide distribution.

Endemic Diseases:

Murine typhus
Plague

Microscope icon

Collection and Submission of Fleas

  • To check an animal for fleas, restrain the animal and part its hair to look for eggs or adults near the skin. Preferred sites vary by animal species and type of flea.
    • Flea dirt (excreted blood) may be visible on an animal’s haircoat or skin.
    • A fine-toothed comb and damp towel may be useful to reveal fleas and “flea dirt” as water will turn black debris into reddish-brown specks.
  • History and clinical signs can be helpful for presumptive diagnosis. However, fleas of concern should be collected for identification to ensure effective control measures are used.
    • Fleas can be placed in a labeled, sealed, leak-proof container with 70-90% ethanol. Rubbing alcohol, hand sanitizer, or clear cocktail alcohol (80 proof or higher) will also work, if needed.
  • Laboratories and shipping companies may have specific instructions for you to follow.

For additional tips, visit How to Submit Vectors for Identification.

Restriction sign icon

Control and Prevention of Fleas

  • Flea populations can be managed by disrupting their life cycle and habitat.
    • For prompt detection and control, continuously monitor animals for flea infestations and frequently inspect animal bedding and grooming tools for fleas and flea dirt.
  • A variety of flea control products are available for animals, including oral medications, topical pour-ons, and sprays/dips. Be sure to choose a product with an EPA registration number (topicals) or FDA (A)NADA number (orals).
    • Read the product label carefully to make sure it is effective against fleas and safe for the species and age of animal to be treated.
    • Treat all affected animals for at least two to three consecutive months to kill newly hatched fleas from the environment.
  • Environmental measures are an important step in controlling flea infestations.
    • Vacuum affected areas daily and dispose of any vacuum cleaner bag promptly.
    • Wash and dry affected animal bedding, rugs, and washable items.
    • Consider using diatomaceous earth to dehydrate immature fleas. Be sure to follow the product label closely to avoid harm to people and animals.
  • Promptly treat animals with any diseases or secondary infections. Isolation of the animal may be needed.
  • Avoid moving fleas from one site to another.
    • Check animals closely for fleas and flea dirt before movement.
    • Quarantine, inspect, and monitor new and returning animals in a separate area.
    • Clean and disinfect contaminated bedding, grooming tools, vehicles, and other equipment before movement.

For additional guidance, visit Considerations When Managing Vectors.

Learn More

Additional information on fleas, their impacts on animals, and control can be found below.

Fleas and flea control

Important diseases spread by fleas

Note: This webpage shows some of the most significant vectors of concern to domestic animals in the United States. It is not meant to be a complete resource of all arthropods, their associated diseases and conditions, or used as a diagnostic tool. Veterinary consultation is advised for clinical cases.