New infestations of lice in a herd nearly always begin from lice-infested cattle that enter the herd by way of purchases, strays or agisted stock. Cattle that have missed muster or have had louse treatments poorly applied are also a common source of lice. Some cattle appear to be particularly susceptible to lice. These cattle consistently have the highest numbers of lice in the herd and are most likely to be the cattle on which lice persist through summer.
The main species of lice that infest cattle do not live on other animals. Buffaloes and camels may carry some of the less common northern louse species.
Lice do not survive more than a few days away from cattle, so indirect transfer, for example from pastures, fences or feed bunks, or from other animal species, is unlikely to be a source of new infestations.
Every property should have a biosecurity plan in place. Although these plans generally address more damaging diseases or parasites, such as ticks and worms, cattle should also be checked for lice and adding lice to the plan will help to prevent new infestations. Elements of a good biosecurity plan include:
Cattle lice are very difficult to detect when in low numbers, particularly during summer. New louse outbreaks in winter can commence from undetected infestations of lice. When conditions become suitable, or treatments wear off, lice can be transferred from infested animals to other cattle in the herd. Special care should be taken in finding and treating these animals. In some overseas situations it has been suggested that susceptible animals be culled, but under Australian conditions this is rarely likely to be justified.