American Fancy Rat & Mouse Association

This article is from the WSSF 2009 AFRMA Rat & Mouse Tales news-magazine.


Sniffling Mice; Growths on Rat
Sniffling Mice

Rita, e-mail
Q I recently purchased some mice at a pet store and found that some of them were occasionally sniffling and sneezing. I waited to see if it was an allergy but apparently it’s not. The pet store recommended that I treat them with Tetracycline for 10 days. My concern is that the medicine they gave me came straight from the fish department. It is Tetracycline Hydrochloride in 250 mg capsules. I am to mix one capsule per 8 oz water per day and mix in a teaspoon of sugar for taste. I’m entering the second day of treatment and all the mice seem fine so far. Also, one of the mice appears to be pregnant. Her stomach is swollen as if she is 1 to 1.5 weeks from giving birth. All the mice are kept together in the same cage so they are all being treated together, regardless of whether they were sneezing or not. Should I be concerned about the pregnant mouse or any of the others? I will discontinue treatment if it’s not safe. The pet store owner seemed knowledgeable about mice and I don’t think she would have given me this treatment unless it’s proven to be safe and effective.

A This question is whether to treat sniffling in the mice or not with tetracycline antibiotics as suggested by a pet store employee.

Respiratory issues in mice are not usually caused by allergies, but by bacterial or viral infection. The most common cause is Mycoplasma pulmonis. There are a variety of antibiotic regimes that can help reduce the clinical symptoms. Mycoplasma do not have a cell wall so they are killed by the penicillin or cephalosporin antibiotics. Although fluroquinilones (Enrofloxacin, Ciprofloxacin) and tetracycline antibiotic can transiently eliminate the bacteria, reinfection or persistent infection is the usual outcome. Other antibiotics such as aminoglycosides (Gentamicin) can be used; however, they can cause kidney damage or deafness in some cases. Immune compromised mice (nude mice) and older mice with additional health problems can have a decreased response to the antibiotic therapy. In persistent infections, mice are often treated with repeated courses of antibiotic. Fluroquinilones are reported to cause damage to developing cartilages and are therefore discouraged for use in pregnant or neonatal mice. In the case of a respiratory viral nfection, antibiotics are of little use for clearing the virus. However, they may be used for treating secondary bacterial infections that occur as a result of the viral infection. Lastly, although I believe that many pet store employees are knowledgeable and have good intentions, to diagnose and then prescribe an antibiotic treatment for other people’s animals requires a degree in veterinary medicine. There are other factors that can impact in the decision on how best to treat a particular group of animals that mis-diagnosis and incorrect treatment can result in harm. Carmen Jane Booth, D.V.M., Ph.D.

Growths on Rat

James Ashforth, e-mail
Q I had to have my rat put down on Saturday due to what I believe was a cancerous growth. The symptoms were that she wasn’t eating and was growing thinner by the day. I have had rats before this and in two other cases the same thing has happened.

I asked the vet what causes the growths and he said that no one knows for certain.

I would like to get another rat, but am concerned about the occurrence repeating itself. Have you got any recommendations about diet, bedding, etc?

Answer by Carmen Jane Booth, D.V.M., Ph.D.
A Without knowing the specific type of growth, it is difficult to answer this question with any certainty. My suspicion is that this rat had mammary tumors. Mammary tumors are relatively common in older female rats. The majority (80–90%) are benign fibroadenomas and the remainder are malignant and usually classified as carcinomas. There are strain differences due to genetic variation; however, dietary and environmental factors may also play a role. Mammary fibroadenomas also occur periodically in male rats.

The other common tumors in older rats include pituitary adenomas, histocytic sarcoma, lymphoma, testicular interstitial cell tumors, mesotheliomas, and Zymbal’s gland tumors. However, rats as other species can develop the cancer in just about every tissue.

Answer by Karen Robbins
A We had an article in the WSSF 2008 newsletter on “Diet and Tumors in Rats” (also online at Diet should be a high quality lab block with treats of healthy low/no sugar cereals, fresh washed veggies and fruits, healthy table scraps, etc. As far as bedding, use a paper or aspen product. We have many articles and information on bedding on our web site *

Updated March 19, 2014