American Fancy Rat & Mouse Association

This article is from the WSSF 2005 AFRMA Rat & Mouse Tales news-magazine.


No Pep/Sneezing/Humping Rat

By Carmen Jane Booth, D.V.M., Ph.D.

Char Gagnon, Lowell, IN
Q I am a first time rat owner. I bought my first female rat a couple months ago and then read how they like companionship, so now I have two.

I did get them from a pet shop so I took them to the vet. One was sneezing (the Albino, Abby) and was put on antibiotics for 10 days. I would have bought from a breeder but didn’t really research—just saw the cute rat and bought her—too late, I love them both.

Anyway, my question is, the Albino rat, Abby, doesn’t have as much “pep” (lays around a lot more) then Lilly, the Hooded rat. Also, she still sneezes quite often. Is this just a difference in the two kinds? My vet said the Albino one will be smaller and it could just be the way her sub-species acts. Can anyone help me??

Also, the Hooded rat “humps” the Albino a lot (they’re both female) and now she wants to “hump” my hand sometimes.

If you have any info on this, I would sure appreciate it.

A Both rats are the same species Rattus norvegicus and the albino (Abby) may be from one of the laboratory strains. Rats just like other species (dog, cats, horses, etc.) can have different personalities and activity levels based on their breed or strain. I have four female Sprague-Dawley albino rats, and they are all very different. Two are slugs who basically sit around and eat, and two are much more active. You didn’t say how old Abby and Lily are. Older rats can have lower activity levels than younger ones. It’s hard to know without knowing or seeing the rats in person if her level of activity is abnormal.

The most common cause of sneezing in pet store rats is the bacteria, Mycoplasma pulmonis. Unfortunately, even with long term antibiotic treatment, this bacteria persists and the rat never completely clears the infection. There are many antibiotics that can help. My preference is Baytril (Enrofloxacin) at 5 mg/kg once a day for 2–4 weeks to calm things down, and then switch to an antibiotic you can put in the water for chronic therapy. Long term antibiotics are not without their complications and you and your veterinarian have to decide what is the best course for your rats.

M. pulmonis is not the only organism that can cause respiratory symptoms. There are other bacteria and viruses that can have sneezing as a clinical sign. If you keep their cage cleaner by more frequent changes to reduce the level of ammonia (converted from their urine by bacteria in the environment), and keep them away from cool air drafts, you can help decrease the trauma to their respiratory tracts that exacerbate the damage by M. pulmonis. Although my rats do not have M. pulmonis, I keep them in the warmest room in my house (65–70°F) (the rest of the house is at 60°F). This room has no drafts and their cage is changed 2–3 times a week. Individual animals can vary in their response to any disease, and having two rats with different severity of symptoms is not uncommon. I will suggest radiographs in pets rats with unrelenting symptoms despite antibiotic therapy to try to access the degree of lung damage and determine the prognosis and next course of action.

As far as the mounting (humping) behavior. This is normal behavior in male and female rats. I wish you the best with Abby and Lily. *

Updated March 19, 2014