As with most "pocket pets," guinea pigs don’t get a lot of attention in the scientific literature. As a result, we are limited in what we know about certain diseases in this species, and we tend to rely a lot on personal experience, small case studies and extrapolation from other species. It’s not that these sources of information are bad, they’re just not a replacement for larger, more controlled studies.

A recent study in the journal Mycoses (Kraemer et al. 2012) provides a rather comprehensive overview of ringworm (dermatophytosis) in these little fuzzy critters. The authors surveyed 74 owners of guinea pigs with ringworm and veterinarians. Here are some highlights from the results:

  • 97% of ringworm infections were caused by Trichophyton mentagrophytes. Ringworm can be caused by a few different species of fungi, with a different organism, Microsporum canis, being most common in dogs and cats.
  • 43% of the time, a new guinea pig was introduced into the household in the weeks preceding the onset of disease, and around one-third of affected guinea pigs had been in the household for less than 3 months. That’s not too surprising, since new animals are often a prime source of infectious diseases. It shows the importance of ensuring that new pets are examined carefully and are healthy before they are brought into the household. It’s certainly no guarantee that there won’t be problems, since healthy-appearing animals can be shedding various infectious agents, but it helps reduce the risk.
  • Ringworm lesions were most common around the head. Hair loss was the most common sign, with scaling and crusting also common.
  • Signs of ringworm were also present in other guinea pigs in the household in over one-third of cases.
  • Various treatments were used and some animals weren’t specifically treated.  In fact, 7/8 of the guinea pigs that did not receive specific anti-fungal therapy got better. It’s known that ringworm can be self-limiting (meaning the animal will get better on its own over time). However, treatment can speed the process up and decrease the likelihood of transmission to other animals or people.
  • In 24% of cases, people in the household also had signs of ringworm, on the head, neck and arms. Children were most commonly involved. That’s not too surprising since kids probably had more contact and closer contact with the animals than their parents.

While not a severe disease, ringworm is a problem because it’s highly transmissible. It can easily and quickly spread between animals, and between animals and people, and elimination of ringworm from a highly contamination household can be a major hassle. Presumably the risk of widespread environmental contamination is less with guinea pigs compared to dogs and cats because of their smaller size and tendency to be kept confined to cages most of the time.

Ringworm should be considered in any guinea pig that develops hair loss or other skin/hair problems. This is particularly true if it’s a new acquisition or if a new guinea pig has been introduced to the household recently.

If ringworm is suspected, a prompt visit to the veterinarian is in order. The guinea pig should be handled sparingly (or ideally, not at all) until the cause of the skin disease is identified. Close attention should be paid to hand hygiene, and even the use of gloves could be considered, although gloves aren’t a cure-all and people sometimes misuse gloves to such an extent that they actually increase the risk of spreading disease.

If a new guinea pig is obtained, it’s ideal to have it examined by a veterinarian before it comes into the household. I’m a realist and realize this is unlikely, but it’s ideal. In lieu of that, it’s important to get a guinea pig from a reputable source, to ensure that other guinea pigs from the same source don’t have skin disease, and to carefully examine the animal for skin lesions before it gets home. It’s also ideal to keep any new guinea pig in its own cage for a couple weeks to act as a quarantine period and allow for identification of any incubating diseases.

If owners of an infected guinea pig develop skin lesions, they should be examined by their physician, and make sure the physician knows they have been in contact with an infected animal.

(click image for source)