Lice: parasite affecting cattle especially at housing

Cattle lice only affect cattle and cannot survive for long periods off the host (seven days).

Cause

Lice infestation is a disease of the wintertime in Ireland due to lower skin and hair temperatures, overcrowding and poor nutrition. High skin temperatures in the summer kill off lice. Most disease will be seen in younger animals and those in the poorest condition. Transmission of lice between animals is by direct contact for the most part or by an intermediate object such as scratching brushes/posts, feed railings or other such objects.

Symptoms

Affected animals suffer from skin irritation / dermatitis caused by biting lice, a roughened hair coat, hair loss and anaemia (thinning of the blood due to blood sucking by sucking lice). Lice related dermatitis may occur over the entire body in heavy infestations but are more common over the back, neck, brisket, tail-head, and any long-haired part of the body.

Treatment

Both synthetic pyrethroids (eg cypermethrin, deltamethrin) are effective therapeutic agents against sucking and biting lice. Pyrethroid pour-ons are the most commonly used therapeutic agents against lice in this country.

Timing of treatment is crucial. When animals are in close proximity, lice can transfer quickly and easily from one animal to another. The life cycle of lice takes just over 34 days, so fast replication can be an issue.

Treatment for lice will only kill hatched lice, not the eggs. For that reason, many pharmaceutical products to treat lice are recommended to be used twice, the second treatment to eliminate the lice which may have matured since the initial treatment. It is advised that animals are treated for lice at housing to keep them under control. All animals in a group should be treated for lice as they may be harbouring these parasites without yet showing clinical signs of disease. Essentially, all the cattle in a shed should be treated on the same day, and any animals which added to the shed afterwards should be treated on entry. Where lice are not treated at housing, more severe issues can occur in November and December as lice populations grow quickly.

Prevention and control

The use of pyrethroid pour-ons or other therapeutic agents following housing will give protection for eight to 10 weeks in most cases and will often prevent a severe outbreak of disease from occurring. The environment should be kept clean and animal stocking rates should be decreased.