Lice are insects that can be seen with the naked eye. They are flattened and possess no wings. They are very host-specific and do not tend to leave their preferred animal. Lice spend their entire life cycle on the pet. Lice (singular: louse) are insects belonging to either the Mallophaga for chewing lice and Anoplura for sucking lice. There are about 460 species of sucking lice and 3,000 species of chewing lice.

Transmission of lice is by direct contact with an infested pet. Unlike fleas and ticks, lice do not persist or travel in the environment. Grooming instruments may, however, serve as a source of transmission. Lice lay eggs (termed nits) on the hair shafts. The life cycle takes about 21 days to complete.


The most noted sign of a louse infestation is a scruffy, dry hair coat. Hair loss may occur and the animal may itch, at times severely. In very heavy infestations of blood-sucking lice (biting), one may detect anaemia, especially in puppies and kittens. A diagnosis can usually be acco mplished with the naked eye. Nits tend to be more visible than the actual louse, but both can be seen.

Lice are highly host-specific. Lice do not survive long if they are removed from their host, so they live on the host all the time.

Common chewing (biting) lice affecting animals

Host Animals Common Name Louse Species
Cat Cat biting louse Felicola substrata
Dog Dog Biting louse Trichodectes canis,
Heterodxus spiniger
Horse Horse biting louse Bovicola equi

Common sucking lice affecting animals

Host Animals Common Name Louse Species
Dog Dog sucking louse Linognathus setsus
Horse Horse sucking louse Haematopinus asini
Mallophaga - Biting Lice or Chewing Lice

Biting lice have mouthparts designed for chewing; not sucking and they feed on feathers, hair and skin scales. They live on mammals and birds. An infestation of lice is called pediculosis.

Chewing lice (Mallophaga) represent the larger of the two traditional suborders of lice (sucking lice).

Mallophaga is divided into three separate suborders:


The Amblycera are a large suborder of lice, parasitic on both birds and mammals. The Amblycera are considered the most primitive suborder of lice. They roam freely over the surface of their host and, unlike other lice, do not form permanent attachments. They feed by chewing soft areas of skin, causing an area of localized bleeding from which they drink. The Amblycera are the most generalized and least host specific.

The Amblycera are divided into six families:

  • Boopidae
  • Gyropidae
  • Laemobothriidae
  • Menoponidae
  • Ricinidae
  • Trimenoponidae

The Ischnocera is a large suborder of lice mostly parasitic on birds but including a large family (the Trichodectidae) parasitic on mammals. The genus Trichophilopterus is also found on mammals (lemurs) and represents a host switch from birds to mammals. Many of the avian Ischnocera have evolved an elongated body shape. This allows them to conceal themselves between the feather shafts and avoid being dislodged during preening or flight. The Ischnocera are the most specialized.

The families are:

  • Heptapsogasteridae
  • Goniodidae
  • Philopteridae
  • Trichodectidae

The genus Haematomyzus includes two species of lice that are different from all other lice that they have been placed in a suborder of their own. These unusual lice are ectoparasites of elephants and warthogs. Their mouthparts are elongated to form a drill-like structure that allows them to penetrate the thick skin of their host.

Anoplura - Sucking Lice

Sucking lice feed solely on blood and have mouthparts designed for sucking. Their mouthparts penetrate the skin and actually fit into a blood vessel from which the blood meal is drawn. Sucking lice only occur on mammals. Blood sucking lice causes severe irritation because they penetrate the skin of your pet in order to feed.

Sucking lice (Anoplura) have around 460 species and represent the smaller of the two traditional suborders of lice. The Anoplura are all blood-feeding ectoparasites of mammals. They can cause localised skin irritations and are vectors of several blood-borne diseases.

Infestations with lice are not life threatening, unless the lice carry some sort of disease organisms. The lice normally cause red papules and cause severe itching which can lead to dermatitis and secondary infection


Treatment is very simple. Both biting and chewing lice are easily killed with flea and tick products. We prefer to bathe weekly with a pyrethrin shampoo. Once the pet is dry, powder heavily with a flea and tick powder. Repeat this process weekly for four weeks. It usually is not necessary to treat the environment, but flea and tick foggers may help, especially in severe cases. Keep all grooming utensils clean.


A single animal may be infested with thousands of lice. Their feeding activity results in hair or feather loss, blood loss, skin irritation and secondary infection. Lousy animals may be weak and susceptible to other infestations or diseases. Infested animals will scratch frequently, worsening the condition. However, grooming by the host animal may remove lice and help lessen the effects of lice activity. Also, an animal's immune system may affect lice and reduce their numbers. Some animals may be infested with lice and show no ill effects.