Causative Agent
  • Lice are small, flattened, wingless insects that are external parasites of mammals and birds.
  • Lice are of two general types:
    • those that chew on fur, feathers and skin debris;
    • those that suck on blood.
Click on images to enlarge.
Lice Lice - Arctic Fox Lice - Mule Deer
Photomicrograph of a chewing louse. Lice within the fur of an Arctic fox. Mule deer from Washington state showing hair loss due to infestation with exotic lice.
  • Found throughout the world.
  • Recently, cases have been reported of deer (Cervidae) in the western United States and British Columbia experiencing mild to severe hair loss due to infestations with exotic louse species brought to North America on non-native introduced or exotic species of deer.
  • Lice populations undergo seasonal fluctuations that vary according to the biology of the louse and affected host.
  • Found at higher numbers on affected animals in winter and early spring, and are generally absent or extremely rare in summer and autumn.
Hosts, Transmission and Life Cycle
  • Birds and mammals.
  • Chewing lice are more often found on birds.
  • Sucking lice are exclusively found on mammals.
Transmission and Life Cycle:
  • Lice vary from 0.3 to 10 mm long; chewing lice have a head that is broader than the rest of the body while the head of sucking lice is narrower than the rest of the body.
  • The entire life cycle of lice occurs on the host.
  • Lice lay eggs directly onto fur or feathers.
  • Transfer of lice between hosts occurs from physical contact.
  • Lice are very well adapted to a particular host species and even to specific areas on a host’s body; lice will not survive on other host species.
  • Lice may serve as vectors for other wildlife diseases such as Lyme disease, brucellosis, hemobartonella, ringworm, salmonellosis and certain tapeworms.
  • A generation of lice usually lasts 45 days.
Signs and Symptoms
  • Small infestations of lice are commonplace on animals, and do not often cause harm to the host.
  • Large numbers of lice may be found on older or young animals, animals in poor condition, those suffering from a concurrent illness, or those that are inefficient at grooming.
  • Lice leave the host 1-2 days following death of the host.
  • Animals may become immune to the effects of lice infestation resulting in reduced survival of eggs, fewer eggs being produced, and a reduction in feeding on host tissues.
  • Lice may cause the following in animals:
    • anemia;
    • itching;
    • inflammation of the skin;
    • skin sensitivity;
    • allergic reactions;
    • intense grooming;
    • fur mats;
    • loss of hair;
    • secondary infections at the location of bites;
    • reduced survival in winter due to hair loss.
  • Death may result from heavy infestations in young animals or those in poor condition from other disease conditions.
Meat Edible?
  • Meat quality is not affected by lice infestation.
Human Health Concerns and Risk Reduction
  • Rubber gloves and protective clothing should be worn when handling wildlife with skin conditions.
  • Although lice from animals cannot be transferred to humans, lice may initially crawl onto humans when infected animals are handled. This may cause a minor irritation, but the lice do not remain for long.
Samples for Diagnosis
  • Collection of a whole louse placed in 70% ethanol is sufficient for identification.
Similar Diseases
  • Ticks and mites are also external parasites but are very different in appearance.
Further Reading
Return to Manual Home Page Disease List - Body Region Affected Disease List - Causative Agent or Risk Factor Disease Surveillance Form Glossary Contact Information
Return to Manual Home Page Return to Disease List - Body Region Affected Return to Disease List - Causative Agent or Risk Factor Disease Surveillance Form Download Glossary Contact Information