Rats are sometimes affected by infestations of external parasites such as fur mites. Clinical signs of infestation include bald patches, thinning of hair, excess scurf (small dry flakes) on the skin, and self-induced trauma as the affected rats scratch or chew themselves.
Many of these parasites are too small to be seen with the naked eye, so a trip to the veterinarian will usually be required. Your veterinarian may need to look at hair samples and skin scrapings under the microscope to be able to tell you what is affecting your rat.
Treatment with appropriate topical ‘spot-on’ treatments is very successful. Talk to your veterinarian about this and what products are appropriate and safe to use. Avoid treatments such as washing with flea shampoos as this is very distressing to the rat, and the new smell after washing could lead to social isolation.
Symptomatic pathogenic infections of internal parasites are not common in rats, although asymptomatic infections may be more common, especially with pinworms. Symptomatic infections usually occur in unhygienic, overcrowded conditions, which lead to a build-up of worm eggs and parasite cysts building up in the enclosure to the extent where all the rats become infected – and then re-infected time after time – as they eat infected droppings. If rats have a symptomatic internal parasite infection, they may show signs such as weight loss, diarrhoea, or other gastrointestinal disturbances. Rats showing any of these signs or who are not eating well should be taken to the veterinarian promptly for diagnosis and treatment. If your rats have been diagnosed with pinworms, it is very important to deep clean and disinfect the environment thoroughly under the direction of your veterinarian as well as treating the affected animals, as pinworm eggs have been shown to persist in the environment and could cause reinfection.
As symptomatic infections with internal parasites are not common in rats, regular routine worming for your rats is not generally necessary, unless recommended by your veterinarian.
Frohlich J (2020) Rats and mice. In: Quesenberry KE, Orcutt CJ, Mans C, Carpenter JW (eds) Ferrets, rabbits and rodents, 4th ed. W.B. Saunders, pp 345–367