What I Learned About Rats After I Graduated From Vet School

From respiratory disease to mammary tumors and more, a vet shares how knowledge about rat health problems has progressed in the past couple of decades.

Written by
Only a few decades ago, not much information was available about pet rat health issues. Gina Cioli/Lumina Media
Dr. Jerry Murray

When I was in the College of Veterinary Medicine at Texas A&M University, I had a short “everything you need to know about pet rats” lecture. Obviously the professor could only cover a few topics in his 50-minute presentation, and it was clearly not everything I needed to know about pet rats. His talk was more about lab animal rats and not really aimed at pet rats. Unfortunately there were very few articles on pet rats in the veterinary journals back then, and the only textbook at that time was The Biology and Medicine of Rabbits and Rodents, which also focused mainly on lab animal rats. It would be another six years before the first edition of the “pink book” (Ferrets, Rabbits and Rodents: Clinical Medicine and Surgery) would come out. This was a giant step forward for pet rats.

Respiratory Disease

One of the most common problems of pet rats involves the respiratory system. Rats are prone to chronic respiratory disease (CRD) and bacterial pneumonia. This very common malady was only briefly covered during my studies. The professor mentioned that high ammonia levels from urine combined with bacteria and viruses can cause respiratory disease. Boy, this was a big understatement. Now I know most cases are from a very difficult-to-treat bacterium called Mycoplasma pulmonis. Mycoplasma infections are not common in lab animal rats, but they are very common in pet rats.

Clinical signs of this respiratory infection include snuffling, nasal discharge, weight loss, ruffled coat and red tears. The bacterium causes a chronic bronchitis and inflammation in the lungs. Mycoplasma can be treated with the antibiotic doxycycline or with the antibiotic enrofloxacin, but it is hard to actually cure the rat even with long-term use of an antibiotic. Bronchodilators (albuterol) can help some and cortisone can help reduce some of the inflammation in the lungs. Most rats can live for two to three years with CRD.

Bacterial pneumonia is usually caused by a Streptococcus bacterium; typically there is also a coronavirus and mycoplasma involved in the infection. Young rats seem to be at higher risk for this infection and frequently die from it. Treatment has to be aggressive and potent antibiotics like amoxicillin with clavulanic acid and enrofloxacin are frequently required.

Mammary Tumors

The other very common problem for pet rats is mammary cancer. I do not think this was even covered in school. Rats have mammary tissue covering almost their entire body, so mammary tumors can show up anywhere from the head to the tail. Because this is so common, I automatically assume any tumor on a rat is from mammary tissue unless a pathologist verifies another type of cancer.

Some of these tumors can become very large and can eventually become fatal. Surgery is the treatment of choice for the small to medium tumors; however, some tumors are just too large to remove. I have tried using anti-hormone therapy with melatonin and leuprorelin to try to slow down the growth of these large tumors. Surprisingly this has actually caused some of these tumors to become smaller. Melatonin and leuprorelin were not even used for dogs and cats back when I was in school.

Dental Problems

I do not recall dental problems of rats being covered in school, but it is something that I see frequently. Long incisor teeth are common in pet rats, almost as common as overgrown teeth in rabbits. Luckily rat teeth are easy for a veterinarian to trim, and most owners are able to examine the front teeth frequently.


I do remember covering the tropical rat mite while in school, but I have yet to see one of those since I graduated. I have seen a few cases of rat lice. These are species-specific, so people will not get lice from their pet rats. The lice spend their entire life on the rat, which makes treating the rat with ivermectin or selamectin easy. I have never seen lice on a hairless rat. Of course they did not actually cover hairless rats in school.

The other common parasite problem that I see is fleas. It is usually a case of the pet rat getting fleas from the cat or the dog, so it is not actually the rodent flea on the rat. The modern flea products were not around when I was in school, but there are many great flea products now that can be used on the cats and dogs. Some of these are safe enough to use on rats, so talk to your veterinarian about which flea product to use on your rat and what to use to treat all of the other pets in the house.

Red Tears 

Red tears are common in rats, and this was briefly mentioned in school. When it occurs, it really looks like the rat is bleeding from the eye. Fortunately, it is just a normal red pigment in the tears. This is frequently a sign of stress or a respiratory disease in the rat, so it is a good to have your rat checked for illness and look at the husbandry if he has red tears.


This is another topic that was covered in school, but I have yet to see it in practice. Ringtail happens when young rats are kept in low humidity rooms. They will often lose blood supply to the distal tail and slough the distal tail off or need part of the tail to be amputated. I guess Texas, where I practice, is humid enough to prevent this from happening, or maybe it is just not common in pet rats.

I have learned a lot about pet rats and their unique diseases since I graduated from vet school. Most pet rats are quite friendly, entertaining, and make good pets. Needless to say, pet rats are nothing like Willard and Ben, the rats from famous horror movies.

Like this article? Please share it, and check out:
One Rat Health Issue You Can’t Ignore
10 Common Rat Behaviors

15 Rat Facts That Prove They Are Amazing Pets
Life With Your First Pet Rat

See all rat and mouse health Q&A
See all rat behavior Q&A

Article Categories:
Critters · Mice and Rats