American Fancy Rat & Mouse Association

This article is from the WSSF 2011 AFRMA Rat & Mouse Tales news-magazine.


Multimammate Rat With Lumps [a.k.a. Multimammate Mouse/Natal Rat/African Soft-Furred Rat/Common African Rat]

Melissa De Santis, Italy/London, England, e-mail
QSorry to bother with my e-mail but I think I need the help of one of your specialists. I believe, as I received part of the answer, that my rat (multimammate rat/Praomys [Mastomys] natalensis) has the papilloma wart virus as she has three warts growing on her chest. I found a photo on a website which shows exactly what she has (the rat in the picture has much more warts than mine). I have two multimammates who I thought had some mammary tumors but now I’m not so sure. One is a female (I don’t know exactly the age, I rescued her) but should be 1 year old, and she has three external lumps now similar to a crust or wart (in the beginning I thought it was a small infection to the breast as she had babies twice)—one under the forearm and the other two on the belly; the other is a male (8 months) and he has a small pink lump under the forearm. Do you think you can help me? What do they have? I really do care about them!!

Could you please tell me if I have to take the rat to the vet and remove the warts or they are going to drop off in few weeks? I found some different opinions on the matter so I would like to know what to do. I had many bad experiences with vets and this kind of pets. I’m now living in London and contacted a clinic which should have experience with rats. I would like to go to the vet knowing what they have; I need to be sure they are going to treat them properly

Many thanks for your help!!

Answer from Karen Robbins
AThe multimammate/natal rats are illegal in California so we don’t have any experience with them. We have an article on Papilloma Wart Virus or Rat Pox Virus in regards to domestic rats and mice in which they normally only get one of these growths at a time, not multiple ones like in the photo example you sent. In there it says the papilloma virus is historical in the African soft-furred rat. Your rat needs to be seen by a vet as I can’t answer your question on whether the warts should be removed or will drop off in time.

Answer from Carmen Jane Booth, D.V.M., Ph.D.
AYou should take your rodents to a veterinarian where you live who is experienced with rodents. If there is a Veterinary School in the region, take your rats there. They at least will have veterinarians trained in rodents.

Your rats probably have the papiplloma virus, but I cannot be sure. Or it could be fungal, or could be mites . . . .

QUpdate: I found only one page on the Papilloma Virus and there are no details on what a person should do to cure it. My vet in Italy told me that there isn’t any cure against the Papilloma Virus and usually they put the rats to sleep but first I need to separate them from the others as it’s really contagious. I don’t want to put them to sleep—is it really necessary?

Anyway I’m trying to contact as many vets as possible here in London (though it seems there’s no one here knowing so much about that kind of problem), and I have found a vet that said that if the warts are two or three, there’s no need to put the rat to sleep as long as she is fine, eating, and playing. Anyway, I made an appointment to have her looked at.

The rat hasn’t any symptoms apart from the warts—she is eating and playing. I can’t even think to put her to sleep. I’m very thankful for your help!

APlease contact your veterinarian as he/she is correct. There is a lot of information available on rodent papilloma virus available on the web. Look up papilloma virus in general for humans to find out about the virus. Look at the dog and mouse literature.

There is no cure. The virus incorporates into the DNA. Some develop an immune response that keeps the virus subclinical. Some progress to cancer. There is not much known on Mastomys species.

As for euthanasia, all your rats have likely been exposed, so I see no benefit. Time will tell. You will have to decide what you want to do or not.

I am sorry that I cannot help you directly but I am not licensed where you live and it violates my veterinary license. Carmen Jane Booth, D.V.M., Ph.D. *

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July 7, 2015