American Fancy Rat & Mouse Association

This article is from the WSSF 2004 AFRMA Rat & Mouse Tales news-magazine.


More Misc. Questions

By Carmen Jane Booth, D.V.M.

Rat with Dislocated Jaw

From our files
Q Last night I could have sworn my rat broke his jaw. His mouth was crooked and it was hanging funny.Well, I freaked out and gave him a carrot to see if he could eat it (this is a rat who will gobble anything in sight). At first he was having problems eating and would just softly nibble the carrot. Then finally he started chowing down on it. After he was done, I picked him up and his jaw looked fine—I mean it was normal again. Is it possible for rats to dislocate their jaw and fix it themselves? I’d really like to know what happened to my rat.

A It is possible (and likely) that your rat dislocated its jaw and then it resolved spontaneously. My concern is why or how did it happen in the first place. If it happened once, it may happen again if there was damage to the jaw. I would want to make sure that there were no fractures.

I would suggest that you (or your veterinarian) look over your rat very carefully while eating some soft and hard food and drinking water. I would also gently palpate the jaw and surrounding structures for detection of any abnormalities. If there is nothing obvious and the rat has no further problems, then I would not worry. If it happens again, I would suggest getting a radiograph of the rat using an enlarging technique to check for an underlying problem.

Dosage for Liquid Tylan

Lorryta Bowker, Arkansas
Q I have access to liquid Tylan out here, any idea what the dosage per 8 or 16 oz. of water would be?

A I do not have my formulary here at work. What is the dose used with the powder? I would need to know the concentration of the Tylan powder and the Tylan liquid to do the math myself. You can do this yourself by plugging in the numbers:

X mg of Tylan powder (formula weight or mg Tylan/mg powder) in Y ml water.

This gives you the dosage (Z Tylan mg/ml water) per unit volume of water that you have been using.

If you take the information on the bottle of liquid Tylan, it should give you it in mg Tylan/ml of solution (lets call this R mg/ml). Then it is just a matter of basic math:

Assume a 1 L (1000 ml) Total Final Volume of Diluted Tylan for use.

You know the final desired concentration Z mg/ml, and you know the initial concentration of the liquid Tylan R mg/ml. Here’s the equation:

Volumefinal x Concentrationfinal = Volumeinitial x Concentrationinital

1000 ml x Z mg/ml = Vi x R mg/ml; solve for Vi in ml

Vi is the amount of the concentrated Tylan to add enough water to bring the total volume to 1 L. Note: all the units must be the same, i.e. in mg and ml for everything to work.

Foot Joint Sores

Katalin Schrott, Austria
Q I have two rats (father and son), and they both have at the foot joints a sore that looks like an abscess. The place sometimes bleeds and swells quite large. I went to the veterinary surgeon; however, he could not determine which illness the symptoms corresponded to and only gave cortisone shots. I am very anxious because the older rat was a feeder rat that I saved along with a female. I kept the only son to live with the father. The poor small son was so weak and wouldn’t eat and became so thin. I do not want to lose him as the older rat needs him. By the way, the older rat is okay and doesn’t worry about the sore. After the shots, the rats were better for weeks; however, now the small rat feels bad again, very bad. I cannot pay the veterinary surgeon at the moment. My questions are:

  1. What is this illness and what is the cause?
  2. Is it perhaps a symptom of another illness?
  3. What would the best treatment be?

All pieces of advice are very highly appreciated. I hope that someone can please help me.

Abscesses, Bumble Foot

Q I’ve seen some information written about abscesses, but I’d really like to know more about them. What if there never was a scratch or sore? What would make them develop? If it’s only under the skin, should the muscle be cut to make sure it isn’t any deeper? Also, I’ve just learned about a disease/infection called “bumble foot.” It causes sores on the undersides of the back feet. Can you tell me anything about this?

Pain Medicine for Rats?

Q Is there any kind of pain medicine that is safe to give to rats? If so, in what dose.

A Answer to Foot Joint Sores, Abscesses, Bumble Foot, and Pain Medicine questions by Carmen Jane Booth, D.V.M.


An abscess is defined as a localized collection of pus buried in tissues, organs, or confined spaces. Most of the time we see them as a bump or soft swelling under the skin. Pus is basically made up of neutrophils (one of the five white blood cells circulating throughout our body) and dead (necrotic) cellular debris. One of a neutrophils main function is to kill bacteria. A skin abscess is formed when bacteria or a foreign body (splinter, etc.) penetrate the skin through a puncture, abrasion, bite, or scratch. In many cases, the skin wound has healed by the time an abscess is seen.

Each different type of bacteria has a minimum time (lag phase) before they can replicate into two bacteria. As soon as neutrophils find bacteria, they recruit more neutrophils and other white blood cells by releasing special substances called chemoattractants. In the process of killing the bacteria, many neutrophils die and this results in the release of many other biologically active products that result in swelling, redness, etc. Additionally, many of the products that the bacteria release cause tissue damage as well. As the number of white blood cells increase along with the influx of fluid and damage to the tissue, then the area swells and you now have a visible abscess.

In mice, abscesses are more common in males than females because they fight more.

In dogs and cats in California, fox tails are the leading cause of abscesses.

Bumble Foot

Bumble foot is just the lay person’s term for abscesses seen on the bottom foot of mice or rats. Bacteria are everywhere in the environment and if the surface that the animal walks on is too rough, then foot abscesses occur. This is a big problem in rabbits and guinea pigs.

Rat with “Bumble Foot.” Owned by Nichole Royer. Photo by Craig Robbins.

Treatment, in general, consists of systemic antibiotics (usually orally), and cleaning out the wound. In many cases, simply hot packing the abscess with a warm wash cloth and soaking with dilute betadine solution while the animal is on antibiotics will cause the abscess to rupture so that the body can heal properly. If there is extensive tissue damage, then the animal has to be anesthetized and the area debrided (all the necrotic tissue removed) and sutured. Foot abscesses are problematic in rodents because there is not much tissue to work with. In these cases, antibiotics and cleaning the feet has to suffice.

Pain Medicine

Cortisone is an anti-inflammatory steroid and has been reported to give a feeling of well-being in humans at high doses where it causes immune suppression necessary in certain diseases. When inflammation is the cause of pain or discomfort, then anti- inflammatory steroids may help alleviate pain by reducing the amount of inflammation. Steroids have no direct pain relieving properties.

There are no non-prescription pain-relieving products that would be effective in rodents. Many of the lectures that I have attended at different meetings suggest that with the high metabolic rate of rodents, most pain relieving drugs are metabolized so quickly that the frequency of dosing required makes it difficult to provide sustained relief.

Wheezing Rat

Rochelle, e-mail
Q I found your web site searching for some answers after our newest fancy rat died yesterday morning. She became ill literally over night and died in my hands unable to take a breath. Our other rat is constantly sneezing, even when she is not digging or moving around. I’ve heard rats can carry an organism that makes them do this but doesn’t affect all rats, while others, it may kill. If this is the case, can it be contagious? I’m afraid to buy another friend for her until I can determine if her wheezing is contagious, and I need to treat her with an antibiotic.

A There are a number of different organisms that can cause respiratory problems in rats. The most common one is Mycoplasma pulmonis. This is highly contagious to other rats and is almost always present in pet rats that come from pet stores, etc. It cannot be cured, but a variety of antibiotic therapies can help decrease the symptoms. It must be remembered that the symptoms are only alleviated while on antibiotic therapy and will resume when it is stopped.

Husbandry is very important in helping to minimize respiratory difficulty, i.e. frequent cage changes to keep the ammonia levels down, appropriate temperature and humidity, etc. It is impossible without doing a necropsy, serology, or bacterial culture to know what is the exact causative agent.

Since most rats have this organism, they usually do not succumb until they are stressed by other bacteria, viruses, environmental conditions, or other underlying problems such as cancer.

Neutering and Aggression

Phone call to Karen Robbins
Q I just got off the phone with someone who had to have their aggressive male rat neutered last week because he kept fighting/wounding his male cagemate and had even bit the owner a couple times (they had been bought at the same time when they were babies so had grown up together and were now just coming up to 1 year of age). She was concerned because he was still biting the cagemate even though he was neutered a week ago. She now has them separate but they are miserable because they are separate. She had bought them at the pet store so can’t go back to the breeder and let them know about the problem.

Some questions on neutering:

  • When to neuter male rats (best age—wait to see if they are aggressive or neuter them when young and at what age when young).
  • How long before the testosterone wears off in their system so they don’t have the aggression.
  • The best procedure for the vet to use when they neuter (abdomen vs. scrotum).
  • What happens if they never get over their aggression (I’ve heard of two cases where this happened).
  • Is aggression hereditary—passed down from fathers who show aggression or from mothers out of males who show aggression or both.

Of course I have my opinions and observations over the years, but a lot of people don’t have the same policy as I do about these matters. I figure that we are promoting rats as pets and we tell people they don’t bite, then to have people breed rats that show aggression and now I hear of/see more and more male rats showing aggression, it just goes against everything we are trying to do. Sigh . . .

A Behavior just like everything else is highly heritable. Mean animals have a higher probability of producing mean progeny. Behavior is inherited from both parents although it can only take one aggressive parent to result in aggressive pups. This is true for all species that I have dealt with. If an aggressive male is neutered, the testosterone is usually out of their system within a month. I don’t know the exact period. However, if after a month the rat is still aggressive, than the behavior is not related to testosterone. Aggression can be learned or innate and neutering does not help.

I prefer the abdominal rather than the scrotal approach for neutering rats. Males raised together since birth usually get along. Once a pair or group of rats have a problem, then they may have to be separated permanently even if one or more are neutered. One may just be more dominant and nothing is going to change the dynamics in the pair or group.

There is no ideal age to neuter rats. It just depends upon how comfortable the person is doing the surgery. The only thing I can think of that might be a problem, is that the younger they are, the smaller they will be as adults since there is no testosterone.

My philosophy is that all pet animals that are dangerous or so aggressive that they can’t be handled, should not be bred. I think that unless someone is prepared to keep their other rodents and all people including children who could come in contact with such an animal protected, the animal should be euthanized for humane reasons. Society in general has a poor regard for rodents, let alone as pets. One highly public incidence with an aggressive rat and a child could undermine all the good work of AFRMA to promote rats and mice as pets. I think that rats and mice make excellent pets and there is no place for aggressive animals in breeding. All one has to do is read the paper about aggressive dogs and what is possible to get passed as legislation. We do not need rats and mice banned as pets. *

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Updated February 13, 2015