Lice Affecting Animal Health

Importance

  • There are over 3,000 species of lice worldwide. A small number of species can affect people and domestic animals.
  • Animals with lice infestations may be intensely itchy. Affected animals may rub against fences or other objects and rub off hair or fur. Lice can also cause anemia and reduced productivity in severe infestations. Some pathogens may be transmitted by lice.
  • 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 lice-related FADs may include:
    • Unusual louse appearance or large infestations
    • Large number of sick or dead animals
    • Unusual signs of illness (like fever, anemia, and severe skin lesions)

About Lice

  • Lice are tiny, wingless insects that live their entire life parasitizing animals.
  • There are two main groups of lice.
    • Sucking lice feed on the blood of animals. These types of lice are generally better vectors of pathogens.
    • Chewing or biting lice feed on skin cells, exudates, fur, feathers, and sometimes blood.
  • Lice complete all life stages on an animal host and usually live for about four weeks.
  • Most lice are host-specific, only feeding on one animal species (or a few closely related species).
    • Lice usually do not live longer than a few days off an animal host.
  • The adult female lays eggs (nits). Once the egg hatches, the louse undergoes a series of nymph stages before becoming an adult.
    • Lice burdens on animals usually increase during winter and spring months.
    • Lice are transmitted from one animal to another through direct contact or fomites (such as bedding and grooming tools).
A lice life cycle highlighting the three stages of egg, nymph and adult.

Identification of Lice

  • Lice are tiny but may be seen with the naked eye. Many can be identified by their appearance and animal host, including their location on the host.
    • Determining the species may be difficult or impossible without the help of a dissecting microscope or trained entomologist.
  • Adult lice have flattened bodies, an elongated abdomen, and six clawed legs used for grasping hair shafts or feathers of hosts.
    • Sucking lice usually have broad heads and move quickly through the hair.
    • Chewing or biting lice usually have narrow, pointed heads and move slowly.
  • Nymphs resemble small adults.
  • Louse eggs (nits) are glued to hairs near the skin surface and appear oval in shape and pale in color.
  • Identification keys and lice experts can be consulted for further details.
Diagram of major structures of louse anatomy including the head, elongated abdomen, and six legs with claws.

Lice of Animal Health Concern

The lice listed below are examples of common species in the United States. In certain areas, these lice 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. Foreign diseases listed are highly contagious and reportable diseases in animals. Learn more about recognizing and reporting FADs at CFSPH: FAD Prevention.

Close-up photograph of a brown hog louse on pig skin.

Hubert Szczygieł, iNaturalist, CC BY-NC 4.0

Name: Haematopinus suis (hog louse)

Characteristics: Sucking louse affecting swine worldwide; large (up to 6mm long) and brown; eggs are 1-2mm long and light cream to gray in color.

Endemic Diseases:

Swinepox

Swine eperythrozoonosis (Mycoplasma suis)

Foreign Diseases:

African swine fever

Microscope view of long-nosed cattle louse on white background.

Alan R Walker, Wikimedia, CC-BY-SA-3.0

Name: Linognathus vituli (long-nosed cattle louse)

Characteristics: Sucking louse affecting cattle worldwide; small (2-3mm) with bluish-black coloring and slender “nose”; eggs are 1mm long and cream-colored.

Endemic Diseases:

Bovine anaplasmosis

Dermatomycosis (ringworm)
Theileriosis (Theileria orientalis Ikeda)

Foreign Diseases:

Theileriosis (other types than Theileria orientalis Ikeda)

Microscopic view of canine chewing louse on white background.

Daniel J Drew, Wikimedia, public domain

Name: Trichodectes canis (canine chewing louse)

Characteristics: Chewing louse affecting dogs worldwide; prefers the head, neck, and tail of its host; small (1-2mm long) and tan in color.

Endemic Diseases:
Tapeworm (Dipylidium caninum)

Foreign Diseases:

None

Microscope icon

Collection and Submission of Lice

  • To check an animal for lice, 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 louse.
  • History and clinical signs can be helpful for presumptive diagnosis. However, lice of concern should be collected for identification to ensure effective control measures are used.
    • Lice may be collected from affected areas with forceps, superficial skin scrapes, or hair samples collected with a fine-toothed comb or brush.
    • Lice 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.
    • Always label specimens with host, location collected from the body, and date of collection.
  • 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 Lice

  • Lice populations can be managed by disrupting their life cycle on the host(s).
    • For prompt detection and control, continuously monitor animals for lice infestations and frequently inspect animal bedding and grooming tools for lice.
    • Promote good animal husbandry (including proper nutrition and low stress environments) and avoid crowded living conditions to maintain animal health and resist severe lice infestations.
  • A variety of lice control products are available for animals, including injectables and topical pour-ons and sprays. Be sure to choose a product with an EPA registration number (topicals) or FDA (A)NADA number (injectables).
    • Read the product label carefully to make sure it is effective for the species of lice and safe for the species and age of animal to be treated.
    • Systemic treatments generally work better for sucking lice than chewing lice.
    • Louse eggs are not susceptible to insecticides, so repeat treatments are often needed for complete control.
    • Common flea and tick preventatives and parasite control medications may also control lice.
  • Promptly treat animals with any diseases or secondary infections. Isolation of the animal may be needed.
  • Avoid moving lice from one site to another.
    • Check animals closely for lice 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 lice, their impacts on animals, and control can be found below.

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.