There are two main parasites that use the rat as a host to the extent that they pose a real threat to our pet rats' health. These are the Spined Rat Louse and the Rat Fur Mite. Many other parasites do trouble our rats from time to time such as fleas, worms and sarcoptic mange, but these are all much less common.
For this reason it is advisable to check your rats regularly for signs of mites and lice. Unfortunately, no matter how clean we keep our cages, any rat can suddenly show signs of infestation. A lot of vets, and owners, believe that these parasites (particularly mites) are actually endemic (present within the population at all times), but only become a problem for the rat at times of ill health, when the rat is stressed etc. For example, one rat, out of a cage of six, may appear to have mites while the rest do not. A number of rat owners have also reported finding lice on rats that are close to death, but not on their cagemates. This suggests that the rat's own natural defences (immune system) are generally excellent at keeping these parasites under control, and that populations only 'explode' when the immune system becomes depressed. However, it’s always worth checking all of your rats regularly.
At 2mm long lice are just visible to the naked eye and if an infested rat is examined closely the lice can be seen moving on the skin at the base of the fur. They are often described as orange/tan or deep red (colour depends on how recently they have fed).
Rat lice are species specific so will not feed from other animals or humans. Within the species they also tend to show a high degree of host specifity, prefering to remain on and feed from only one individual of the species. This might explain why one rat in a group might be heavily infested whilst others appear to have no lice at all.
The eggs of the louse are glued firmly to the hair shaft and can be seen (empty) as the hair grows as tiny silver dots attached to a single hair. Unlike small skin flakes they will not easily brush off. Eggs cannot survive for more than a day or two off the host, so re-infestations from cages and furniture are unlikely in a treated rat. Hatching takes place after a period of about 4-10 days depending on the environment (temperature etc). The nymphs then live on and feed from the host through four moults (each taking between 3 and 12 days) until they reach adulthood. As mature adults they can then reproduce, and will generally live for a period of about a month. Treament will kill hatched lice but not eggs. Therefore at least two treatment cycles, about 10 days apart are generally needed to get rid of an infestation.
Lice can, and will, spread to other rats, and around different cages if you don’t treat soon enough. The nits and lice can hitch a lift on your clothes, and before you know it, all of your rats are infested. Lice are feeding on the blood of your rats and without prompt treatment they can become anæmic.
To check your rat for lice sift through the fur in the wrong direction beginning at the base of the tail. Look closely for white specks on the hair shafts and darker, reddish or orange specks on the skin. Sometimes these red/orange specks will move - they are lice! White specks on the hair shaft can be nits or dandruff. If the specks brush away easily then it is simply dandruff, nits tend to be stuck fast to the hairs.
The common fur mite that affects rats is not visible to the naked eye. You will see the symptoms of a mite infestation - but not the mite itself. Symptoms usually begin with small scabs and lesions under the chin, then entending around the neck and shoulders. Severely affected animals may have lesions all over their bodies, with the coat taking on a rather ragged appearance and there can be hair loss in places. All of these symptoms are self inflicted by the rat due to excessive scratching. It is not uncommon for inexperienced owners and vets to assume the rat has been fighting, or has an allergy (often protein is quoted) or underlying skin problem. Tests for mites are unreliable - often giving false negative results. It is better to treat for mites and only look for an alternative diagnosis if Ivermectin treatment and a nail clip isn't successful.
Mites generally only affect one animal in a group and only the affected animal really needs treatment. Mites usually respond to just one dose of Ivermectin.
- Excessive scratching
- Scratches to the chin and back of the neck/shoulder area
- In more severe cases, the sides of the body may also be scratched.
- Hair loss
- Dermatitis and infected lesions
Other types of parasite
Sarcoptic mange mites – leave crusty lesions on the outer edge of the ear, the nose, tail, and also feet and genital area. The ears are usually affected first. Can be persistent and is very contageous. Treatment is Ivermectin and three doses, 10 days apart will generally be required.
Fleas – there is a flea (the European Rat Flea) that specifically affects rats but it is uncommon in pet rats and it is much more likely that your rats may be bitten by fleas from other household pets. Treating cats and dogs with preventative flea control is to be recommended.
The vet will examine your rat, including weighing and give a spot on treatment. There are various products your vet may use, after calculating the suitable dose. Ivomec, Stronghold, Revolution, Advantage, Panomec may all be used depending on the type of parasite involved. Ivermectin may not be the best treatment for fleas. You will then be asked to return a week to ten days later for a second dose, and then again for a third dose if needed.
Mites – it is usually sufficient just to treat the affected animal.
Lice – it is advisable to treat all of your rats simultaneously.
Until recently pet shop treatments were largely ineffective. However, there are now various products available, which contain ivermectin, and these have had good reviews.
See here for more information about Ivermectin dosage and use.
Author: Vicki Anderson and Alison Campbell