The Rat Fan Club

A Zoonotic Fungus Infection

by Debbie Ducommun

I have heard from three rat owners who have experienced unusual skin lesions that were just like fungus lesions I have had several times. As it seems that most physicians are not familiar with this fungus, I thought it would be helpful to write an article about it.

The scientific name of the fungus is Trichophyton mentagraphytes. When you look it up online you will see that it is usually passed to humans from animals. The animals usually don’t have any symptoms. All four times I have had the skin lesions I had both guinea pigs and rats, so I don’t know which I got it from. I suspect that at this point I might be carrying the fungus dormant in my skin as the last 2 lesions have been on the same area of my hand.

The lesion starts out as a tiny sore red bump that looks much like the beginning of a pimple. Within just a day or two, it becomes a blister, and then over the next day or two a cluster of blisters, and then one big blister. The blisters don’t itch or hurt on their own, but they are very tender and if you rub or bump them they hurt. Like most blisters, they eventually break open and weep. The first time I had the fungus was several years ago on my forearm. I thought it was a spider bite and the blisters only got about a half inch across. After a few weeks the lesion went away on its own. About 3 years later I got it on my hand and this time I went to the doctor. I ended up going to two dermatologists, and the second one finally did a biopsy, which told us it was the fungus.

If you don’t know what the lesion is, then it can get pretty bad before you start the right treatment. Once I got it on my upper lip, and didn’t recognize it quickly enough, and that was awful! It spread pretty quickly and I had a miserable few days. Now I recognize the beginning signs of the lesion right away and if you treat it right away by applying a topical anti-fungal ointment it tends to clear up pretty well. However, the last lesion I had was persistent and it didn’t go away completely until I also took oral grapefruit seed extract capsules which is a great anti-fungal, for about 2 weeks. Back when the fungus was diagnosed by the dermatologist I took an oral anti-fungal medication but that didn’t seem to help much.

As for treating your rats, your only option is an oral treatment medication since you won’t see any skin lesions on them (I never saw anything on my rats or guinea pigs). I don’t know if an oral anti-fungal would actually eliminate the fungus on them since it didn’t work for me. You could try giving your rats the grapefruit seed extract. Once you know what the lesion is, if you get one you can treat it right away with the topical anti-fungal ointment and oral grapefruit seed extract capsules and it should go away quickly. By treating it right away it is only a minor nuisance. It’s probably not worth treating your rats, and is certainly not a reason to get rid of your pets.

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