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LOUSE INFESTATION This usually presents as a chronic, generally mild dermatitis. AETIOLOGY The sucking lice of cattle belong to the genera Haematopinus, Linognathus and Solenopotes; the only biting species is Damalimia bovis. PREVALENCE Louse infestation is extremely common. SIGNIFICANCE Louse infestation can cause direct losses through hide damage and indirect losses through loss of production. CLINICAL SIGNS Skin irritation is evident, with rubbing and licking of the affected areas. Any part of the body may be affected. Most cases are mild and not associated with loss of hair, but in severe cases some hair is lost in an irregular pattern and there may be superficial abrasions and skin scaling. Bareness of the necks of cattle tied in stalls. In wintertime is sometimes associated with the presence of lice. Very heavy infestations of sucking lice can occasionally cause an anaemia. PATHOGENESIS Local irritation caused by the feeding of both sucking and biting lice is often followed by mechanical abrasion due to licking and rubbing. With heavy infestations of sucking lice, blood loss anaemia occasionally develops. EPIDEMIOLOGY Infection is mainly by direct contact of animal to animal since all stages of the life cycle occur on the host and heavy louse burdens are generally seen in groups of cattle during the winter when the hair coat is long. DIAGNOSIS By careful examination and recognition of the insects or their eggs (‘nits*) stuck on the hairs. Cattle lice are small and dark and move so little that they may appear inanimate and are only recognised by very close inspection. TREATMENT AND CONTROL Various pyrethroid and organophosphorus insecticides and amitraz are effective against lice. Both ivermectin and doramectin are highly effective against the sucking lice of cattle. Although it is difficult to eliminate lice completely treatment of groups of cattle at housing in the autumn will help to reduce louse populations during winter. |
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