Often the first signs of lice are the observation of cattle rubbing and, in more severe infestations, loss of patches of hair. As the numbers of lice increase, the hair in infested areas often takes on a ‘scurfy’ or dandruff like appearance and sometimes eggs or exoskeletons from moulted lice can be seen in the hair coat.
However, rubbing due to other causes can be mistaken for a lice infestation. Other causes include:
When diagnosing a lice infestation it is important to actually see the live lice on the skin or in the hair, whether they be biting or sucking lice (see signs of lice). Don’t assume that lice are present just because cattle are rubbing.
When looking for lice the main areas to inspect are the on the head, neck and face and along the backline, particularly in areas where the hair coat is longer and where cattle can’t reach to lick. Lice are also commonly seen on the sides of the neck and dewlap, the tail head and the tail switch. These are areas where chemical concentrations can be low and lice can survive to re-establish the infestation if treatments aren’t carefully applied according to label instructions.
Biting (also referred to as chewing) lice can often be seen moving away from the light when the hair is parted, whereas sucking lice don’t move as much when disturbed during inspection. Some species of sucking lice are commonly found on the bare skin around the anus and vulva and sometimes around the eyes or nostrils of cattle. These may appear as dark patches or blotches on the skin until closely examined. On close examination (wear your reading glasses!) these blotches can be seen to be clumps of sucking lice.
Cattle lice are very difficult to detect when in low numbers, particularly during summer. New louse outbreaks can commence from undetected infestations of lice that have carried over summer on one or a few animals.
Remember, the most common louse species are quite small and can be difficult to see if you have failing eyesight. Remember, if you need glasses to read a phone book, use your glasses when inspecting for lice.