Lice Of Cattle

Lice are a major problem in cattle operations worldwide. Domestic cattle are parasitized by six species of lice: three species of Haematopinus, one of Linognathus, one of Solenopotes, and one of Bovicola. Domestic Asiatic buffalo are typically parasitized by H. tuberculatus (Tables I and II).

Females of the cosmopolitan cattle biting louse (Bovicola bovis) lay an average of 0.7 eggs per day, which hatch 7—10 days later. Each nymphal instar lasts 5—6 days, and adult longevity can be as long as 10 weeks. Preferred host sites for this louse are the base of the tail, the shoulders, and the top line of the back, but lice may also populate the pollard in severe infestations.

The longnosed cattle louse (L. vituli) (Fig. 4.7H) also is a worldwide pest. Females deposit about one egg per day, and the life cycle is completed in about 21 days. This louse is most common on calves and dairy stock; it rarely occurs in large numbers on mature cattle. Preferred infestation sites are the dewlap and shoulders; declining spring populations are often confined to the shoulders.

The little blue cattle louse (Solenopotes capillatus) (Fig. 4.7F) also has a worldwide distribution. Females lay one or two eggs per day; oviposition typically causes the hairs on which eggs are laid to bend. Eggs hatch after about 10 days, and adulthood is reached about 11 days later. Clusters of S. capillatus typically occur on the muzzle, dewlap, and neck of mature cattle. Aggregations of this louse may surround the eyes in severely infested animals, giving a spectacled appearance to the host.

The cosmopolitan shortnosed cattle louse (H. euryster-nus) is the largest louse found on North American cattle; adults measure 3.5—4.7 mm in length. Females lay one to four eggs per day for about 2 weeks, nymphs reach adulthood in about 14 days, and adult longevity is 10—15 days. This louse is more common on mature cattle than on young animals. Preferred infestation sites are the top of the neck, the dewlap, and brisket. However, in severe infestations, the entire region from the base of the horns to the base of the tail can be infested. In North America, H. eurysternus is most prevalent in the Great Plains and Rocky Mountain regions.

The cattle tail louse (H. quadripertusus) parasitizes cattle in the warmer regions of the world. It was inadvertently introduced into the United States, where it now occurs in the Gulf Coast states. Females of this louse oviposit on the tail hairs, which become matted with eggs in severe infestations. Infested tail heads may be shed under these circumstances. Eggs hatch after 9—25 days, depending on the season. Under optimal conditions, the entire life cycle can be as short as 25 days. Nymphs migrate over the host body surface, but adults are typically confined to the tail head. Unlike other cattle lice, H. quadripertusus is most abundant during the summer.

Except for H. quadripertusus, cattle lice increase in numbers during the winter and early spring in temperate regions. During summer, lice persist on 1 —2% of the members of a herd; these chronically infested animals typically reinfest other herd members during the winter. Bulls and older cows often serve as reservoirs of lice. Bulls have longer, thicker hair and massive shoulders and neck that compromise self-grooming. During summer, a small number of lice can survive on the cooler ear tips, where lethal temperatures are rarely reached.

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