Pediculosis

Introduction

Pediculosis is an infestation of lice. Lice are host-specific, permanent parasites of animals, which are most prevalent in cooler conditions when the animals coat is longer.

Lice are mostly spread by direct contact, as they can only survive off the host for up to one week. The eggs of lice are found on the host 'cemented' to the hair and the whole lifecycle takes around 2- 3 weeks to complete.

There are two types of lice; chewing and sucking lice. In severe cases, pediculosis can cause anaemia (sucking lice), weakness, discomfort and damage to hair or wool.

Clinical Signs

Clinical signs are species specific to some extent, but all usually include self-trauma causing hair loss and abrasions on the skin, which is due to variable degrees of pruritus caused by the lice.

Discomfort and pruritus may also interfere with normal feeding, causing weight loss and anorexia. This may also exacerbate any existing lameness.

Severe cases occasionally may cause anaemia.

Diagnosis

Clinical signs and history, such as indoor housing for farm animals can be indicative of the disease.

Definitive diagnosis can be achieved by identification of the lice and eggs in skin scrape, hair pluck or coat brushing sample under the microscope.

Treatment and Control

Few insecticides will kill lice eggs on the animal therefore two treatments at two week intervals are needed to kill nymphs emerging from eggs at the time of the initial treatment and those that will emerge 2-3 weeks later. Alternatively, a product with a two week residual activity can be used.

Sucking lice are more susceptible to systemic insecticide treatment than chewing lice.

Pour-on and injectable formulations are available.

Test yourself with the Lice Flashcards

Lice Flashcards

References

Andrews, A.H, Blowey, R.W, Boyd, H and Eddy, R.G. (2004) Bovine Medicine (Second edition), Blackwell Publishing

Blood, D.C. and Studdert, V. P. (1999) Saunders Comprehensive Veterinary Dictionary (2nd Edition), Elsevier Science

Cowart, R.P. and Casteel, S.W. (2001) An Outline of Swine diseases: a handbook, Wiley-Blackwell

Foster, A, and Foll, C. (2003) BSAVA small animal dermatology (second edition), British Small Animal Veterinary Association

Fox, M and Jacobs, D. (2007) Parasitology Study Guide Part 1: Ectoparasites, Royal Veterinary College