Mites and lice

There are two common parasites that affect rats, the rat fur mite and the spined rat louse. Many other parasites may occasionally affect rats but are uncommon. If you are unsure please seek veterinary advice.

The rat fur mite

Microscopic fur mites are probably endemic in the rat population, that is, all rats probably have them most of the time. They are too small to be visible to the naked eye and are only noticeable by the symptoms they cause. It is thought that when a rat is fully fit and unstressed their immune system prevents the mites from getting out of control, and the rat doesn’t develop symptoms. However, whenever a rat is stressed or ill it is possible for the mites to gain the upper hand and the rat will develop symptoms (excessive scratching leading to small scabs around the chin, neck and shoulders).

The spined rat louse

Lice are just visible to the naked eye. They are tiny, orange, cigar shaped parasites, which can often be seen by parting the rat’s fur around its rump. It is easy to mistake buck grease for lice – the difference being that lice will move if you touch them with a fingernail! lice are easily transferred from rat to rat and have a life cycle that involves the louse laying an egg (nit) that it glues to the base of a hair shaft. Even once the young louse has hatched out the egg case will remain visible attached to the hair - moving further away form the skin as the hair grows. Egg cases will often remain until a hair moults out, so a treated rat can have empty egg cases in its fur and be free of the infestation. A rat with lice will scratch excessively.

Untreated infestations can lead to the rat looking out of condition, with a raggy or thin coat, or patches of hair loss.

Treatment

Treatment for both mites and lice is topical Ivermectin which can be obtained from your vet. One drop is placed behind the rat’s ear, once every 7 to 10 days for three consecutive treatments. Do not let your vet inject Ivermectin as this is unnecessary and in a few sensitive rats been linked to rapid neurological deterioration and death. Some vets will prescribe other ‘spot-on’ medications which if prescribed should be suitable. Most over the counter preparations from pet shops are not effective and in many cases are not suitable for animals like rats that groom heavily. However, Beaphar make a small animal Ivermectin preparation that is available from petshops or online shops such as The Rat Warehouse.

It is a good idea to thoroughly clean out your cage when you treat you rats, but lice eggs can only survive off the host for a couple of days at the most, so re-infestation from the cage or furniture is unlikely in a treated rat (the treatment effects are thought to last for a period of weeks).

Your rats will also benefit from having their nails cut as this will prevent them from damaging their skin when scratching.

Unless your rats regularly attend shows it is not necessary to treat them unless they have an infestation. If you only have a few rats and you need to treat one of them it is probably wise to treat them all so as to iradicate the parasites from within your group for a period of time.

Rat mites and lice are species specific and will not live on humans or other pets.