Vet's corner: treating itchy cattle

Most, if not all, cattle are now housed throughout the country, so treating cattle for lice is on the minds of many farmers.

Last week, I got a call that I seem to be getting more frequently. This call was to examine some cows that were scratching and it looked more than just lice. This was a dairy herd, with cows that were housed about three weeks.

On examination, you could see where cows were licking and also rubbing their necks and backs. Around a lot of the tail heads, there was hair loss and irritation, as well as around the necks of two of the cows.

I clinically examined them and could see no obvious signs of lice, so I took skin scrapes from several cows and we diagnosed a mange mite called chorioptic mange. These irritable external parasites burrow into the skin, causing extreme itching and scratching, resulting in reduced appetite and dry matter intake, which decreases production.

It seems over the last number of years there is an increase in cases of mange in cattle, in my opinion. At this time of year, because cattle have been housed and there is much more contact between animals, these parasites are spread much easier. The fact that at this time of year cattle are much hairier helps with the life cycle of the parasite. The main things that will cause scratching in cattle are lice and mange at this time of year. So I’m going to deal with some of the common agents and describe how you can control them.

Both mange and lice are external parasites that affect the skin. There are three types of mange: sarcoptic, chorioptic and psoroptic mange. The only one I have personally diagnosed has been chorioptic mange, which causes the lesions I described in the previous herd.

The main thing, where they are thought to be present, is to perform skin scrapes of affected animals and once a diagnosis has been made, treat all animals affected and in contact with them. In beef cattle, there are numerous options around which you can treat. However, due to withdrawal issues, we are more likely to only be able to use eprimectin in dairy cows. Your own vet will advise on specific treatments if a diagnosis is made of mange mites.

Far more commonly seen in our herds is lice (pediculosis) and these are often treated with routine pour-ons (synthetic pyrethroids). There are two types of lice – biting lice and sucking lice.

Biting lice seem to be much more common, but again, I find looking at skin scrapes or hair plucks can be hugely beneficial when deciding what treatment to use.

With biting lice, you will see a lot of scratching, rubbing and licking. In advanced cases, it can cause hair loss and skin damage. Early treatment is essential for successful control. It is worth noting when heavy burdens present that two treatments two weeks apart are useful to kill any lice eggs that have hatched in the two weeks after the initial dose.

I often recommend a multivitamin to cattle that are more severely affected to help them recover.

Often with lice and mange, we will also see more ringworm issues and this can be due to the fact that the immunity in the skin is impaired, allowing for spread of ring worm more easily and quickly.

So, it is not uncommon in my experience to have ringworm compounding underlying issues with mange and lice. Also, because a new disease called besnoithiosis has been discovered in Ireland that can have similar skin symptoms to mange or lice, a more thorough investigation should be carried out if initial treatments aren’t having the desired effect. In some of these cases, I recommend taking skin biopsies to send to the lab for more accurate diagnosis.

There are many effective pour-ons available. Just ensure they are licensed and appropriate for the skin parasites you are trying to treat, especially in dairy cows where we are limited with the products we can use, especially when treating mange.