Rat Health

This page is written not from the view point of a scholar or vet, but from one of a pet owner. I offer here only experience and suggestions. Nothing on this page should be considered expert advice, but rather simply a layman's take on health in a format that hopefully you can understand.

This page covers only very common--actually almost inevitable--health issues in daily rat life. Please look at other resources for help with accidents and serious health problems (like cancer).

If your rat is sick, take him to a rat-savy vet (not all vets are rat-savy, and I have had some bad advice and wrong diagnoses, so take heed). Also, check out these links to valuable and more expert rat health articles.

Staying Healthy

The American health care system has always held more to healing the sick than maintaining the healthy, which explains why health care is so outrageously expensive! Pet owners, working with their own budgets, are beginning to realize that the real key to avoiding high bills and maintaining a good quality of life for their pets is through preventative medicine. What does that mean? Well, cat and dog owners can, should, and usually do practice several forms of preventative medicine, which ensure long and healthy lives for their pets. These include a healthy diet, safe and secure housing, a good grooming regime, spaying and neutering at a young age (preventing pregnancy, tumors, and potentially life-threatening infections), regular vaccines against a wide scope of contageous diseases, and year round flea, tick, and worm prevention. Without these things, cats and dogs would be at much higher risks for health problems--and steep vet bills!

Ah, but these are rats, not cats or dogs. As much as rat owners want to keep there animals healthy, there are many preventative procedures practiced with cats and dogs that are either not available or not practical for our rodent pets. Rat owners have had to develop practices to counteract this lack of availability, but don't worry! There are many measures you can take to ensure your rats' continued health. I will discuss this important preventative measures as well as other health issues that might concern you.


I knew about quarantine. I knew it was important. But there were a few things I wasn't told, and when I found out it was too late. My rats got SDA, and I spent several nightmarish weeks of heavy vet bills, sleepless nights keeping very sick animals warm and giving them fluids, watching some die despite my efforts, and hoping the ones that hadn't shown symptoms wouldn't... and then four more months with my rattery carefully "locked up" with no litters, no new rats, and I didn't even enter a building with another rat in it. The SDA passed, but it left a couple rats dead, and a few others with some lung damage. Thankfully, I knew how to do a full quarantine at the time, so the disease did not spread to anyone else. However, the whole thing could have been prevented. Quarantine needs to be done completely and correctly--every time--even if your new rats appear healthy--even if they are from a reputable source. Trust me, learning from experience is not a good option.

This alone is the most important weapon we have against deadly contageous (I'm talking between rats--not to people) disease. Quarantining rats is equivalent to vaccinating cats and dogs. However, it must be done correctly to be effective. Although many people know they should quarantine, a lot of them either don't do it, or don't do it properly--often because they do not know how. ALL NEW RATS MUST BE QUARANTINED from any other rodents in your household.

The nature of diseases can vary, but the most dangerous rat diseases are viruses, which cannot be cured by any medicine (symptoms can be controlled, though) and must be allowed to run their course. They can be airborne. They can live for a while (it is believed up to two hours) outside a host on surfaces or in a person's mucus (nose, mouth). Animals can carry them without symptoms for some time (usually quoted as up to two weeks) and can carry and shed them (infect other animals) without ever having symptoms. After a rat has had the virus, he is immune to that strain for a fair amount of time, so he can't be reinfected, and the virus can run its course through a colony and be gone.

Because of the airborne nature of these viruses, rats need to be quarantined in a place with a separate air supply--that means another building. This might not always be possible, so a typical pet owner needs to keep their new rats as far from their others, on another floor if they can. Breeders and owners of many rats really do need a separate building (like a rodentless friend's house). If they don't, then they should not get a new rat, and probably should not be breeding.

Besides the location of quarantine, all the animal's supplies should be kept separate too. It is best if the person caring for the new rat is not the same as the one caring for the other animals. Why? (This is where I made my folly and brought SDA into my colony...) Because if you come in contact with the new rat or their supplies, you can bring the virus to your others. The viruses can live for some time outside their host. Showering and changing clothes is not enough. You might be carrying the virus in your nose or on your hands, and soap alone cannot kill it. If you MUST be the caretaker of both groups, you should wait several hours--even a day--before you enter the room/building with the other one. This problem seems tricky, but it can be remedied. You simply need a rodentless friend who can take care of your new rat in their home for the quarantine period. (My parents take care of mine.)

How long to quarantine is not as complicated an issue. Since viruses can live in a seemingly healthy rat for up to two weeks, any healthy new rat you get from a reliable source (good breeder) should be quarantined for at least two weeks. If the source is questionable, quarantine at least three or four weeks. If the animal is sick or gets sick, you shouldn't start counting weeks until after all the symptoms are cleared up. If you get a disease in your colony (like I did), quarantine them (getting no new animals, having no litters, and not coming in contact with other rodents) for at least three or four months after all the symptoms are gone (it takes a good bit longer for the virus to run its course through a group).

Be cautious about pet stores, vets, and shows! If you go to any of these or other places that might have rats or rodents around, make sure you wait several hours and wash thouroughly before coming in conact with your rats. You need to do this even if you do not touch any animals (airborne viruses, remember?).

In some parts of the world, certain viruses, particularly SDA and Sendai, are more prevalent than others. It seems most acute in the United States in places where rats are very popular or where they are shown or traded often. However, even if you are not from a "risky" area, you should quarantine your rats with as much dilligence as a cat/dog owner gets his pet regular vaccines.


There are a great deal of misconceptions about this thing we call "myco." It is very important that you, as a rat owner, know what this is and what it does. "Myco" is short for mycoplasmosis, a condition caused by a bacteria. Some of the symptoms myco can cause are infections in the ears and sinuses, congested lungs, excessive poryphin (the red stuff around eyes and noses that people mistake for blood), and infections in the reproductive tract. While I called it a "disease," myco bacteria is usually carried asymptomatically. I will get into that in a moment.

Myco is highly contageous. Aaa! That's a scary statement. Now after saying that, let me add that you do not need to worry about your rats "catching myco." What? Yeah, you read right. The truth is that myco is so contageous, that nearly all rats not raised in a sterile lab setting probably already carry this bacteria. It is very much a part of rats in the pet trade, passing from rat to rat by sharing a waterbottle, grooming, short-distance aerosol, and from mother to offspring through nursing. In short, all those healthy rats you see have myco bacteria in their bodies.

Myco is a bacteria, so in theory, it can be cured right? Well, not really. Even if it was cured, the rat would be reinfected right away. The issue with myco is not in curing it or getting rid of it. Instead, rats simply adapted to it. Some lines of rats (usually those bred specifically for health) have adapted so well to the bacteria that they will never show any symptoms in their whole lives--and why fear an organism that doesn't actually cause disease? To these lines, myco isn't even a pathogen. Laboratory lines, however, have been raised without the presence of the bacteria, so they have not adapted. People who adopt lab rats with the hopes of a healthy animal are in for a shock. If those rats ever come in contact with one from a pet, feeder, or show line, they will quickly get sick and likely die from myco. They have no tolerance for the disease because they were never exposed to it. Keep this in mind if a breeder says their rats are "myco-free." Either the breeder is lying (maybe unintentionally) or their lines are as frail as lab rats.

Let's get on to the pathology of this bacteria. While rats most of the time are asymptomatic, this disease can make rats sick and does kill. There are three ways a myco infection can affect a rat

Asymptomatic: The rat is healthy. It might have no symptoms at all or the myco might sometimes cause minor things like a stuffy nose in colder weather or some sneezing when the rat is in a new home or otherwise stressed. Minor myco symptoms should not cause alarm, but watch the rat in case it progresses to something more serious.

Acute: Myco "flares up" and causes a sudden (usually severe) onset of illness. This can include an upper respiratory infection (excessive poryphin, ear infection, coughing, head tilt), a lower respiratory infection (wheezing, heavy breathing, gasping, pneumonia), and/or reproductive infection (dischange, swelling, fever). Onset can be extremely sudden. Watch for any behavior changes. Swift treatment is crucial. Once a rat recovers, it can often resume complete health.

Chronic: The animal can have severe or minor symptoms. Usually this takes the form of slowly degenerating health (in old age). The rat breathes heavier over time and often loses weight and appetite. In more advanced stages, the rat might have gasping attacks.

Confused now? I know I just said rats always have myco, but they are only sometimes sick. Why? What triggers it? Myco is opportunistic. If the immune system weakens, myco flares up. Acute disease is often brought on by the presence of other pathogens, including the SDA or Sendai viruses. In fact, when a rat gets these diseases, it is the myco that kills them--not the virus. Stress, extreme temperature change, and other factors could bring on an attack too. Chronic myco is usually caused by aging. As rats get older, their immune systems weaken and can allow a disease like myco to get the upper hand. Rats that die from "old age" often die from myco.

Because myco is a bacteria, it is treated fairly easily with antibiotics. It is futile and inadvisable to treat rats with minor or no symptoms (like any other animal, rats can build a resistance to medicine, making it less effective if given to long or often). If a rat gets pneumonia, even if it was triggered by a virus, it can be controlled with antibiotics to kill off the myco bacteria More info about this can be found on the Health Links page.


Lice, mites, and fleas are the most common cause of scabs and sores on rats. People, even vets, often mistake such sores for allergies or fungal infections because these parasites are sometimes not obvious, and even a thorough search or test will show up negative. It has been my experience, however, that sores on the neck, shoulders, butt, back, or even face are usually the result of parasites. It only takes one flea to cause a severe reaction in many rats... -- Also, keep in mind that sores indicate only an allergy to the bug bites. Many rats can be heavily infested with no noticable symptoms! So, if one rat has parasites, treat them all!

Ivermectin is the usual vet tratment for parasites. I do not use it myself though. It is considered relatively harmless even at fairly high doses, but overdose is deadly, and I've read several accounts of it, so I choose to play it safe. What is safe? Well, first you should remember that safe also means less effective, but it can offer your pets some relief, and will work if you are dilligent. The safest treatment is with a spray made especially for rodent pets or birds (they are the same stuff, but the bird spray might be easier to find). You can buy this in any pet store. Another method is by use of a kitten flea shampoo (NEVER use dog producs). This stuff is a little stonger, so take care with it and rinse very well. Whatever method you choose, you must keep the treatment up for at least a month, because these things kill only adult fleas--not eggs or larvae, and that is the only way to get rid of the problem.

When treating your rats, make sure to treat their cage and litter too. If using a spray, you can spray everything directly (keep away from food and water). Otherwise, change the litter often, and bleach the cage and accessories.

Prevention is important here to avoid annoyances and those nasty sores. Parasites can be brought in on either other rodents or an accessories. While a new rat is in quarantine, check it thouroughly for parasites. Actually, you might as well just treat for parasites as a precaution. Buying your supplies from a source that doesn't carry any animals (like an online store or department store) can reduce the risk of bringing in parasites. You can also put new litter in the over or freeze it to kill parasites. When I clean cages, I always spray the new litter and clean cage with bird lice killer as a precaution.


Like people, rats can be allergic to things. Anything from food, litter, smoke, etc. can cause an allergic reaction. Allergy symptoms can be sores (for food or bedding ellegies) or a stuffy nose, wheezing, and/or poryphin (again, the red stuff people mistake for blood).

Food allergies are the same in rats as they are in people. Dairy products and certain grains (wheat, corn, etc.) are the biggest culprits. Males are also prone to "protein sores," alergies caused by a diet too high in fat and protein. If you suspect your rat has a food allergy, switch to a special diet. One thing I have found to be very effective is feeding allergic rats a diet made solely of Nutro Natural Choice Lite dog food or Sensible Choice Lamb and Rice Reduced Calorie dog food. Both are low in fat and protein, based on lamb protein and rice filler, and contain no corn and little or no wheat. Some rat lab blocks are similar and can be used instead or in addition.

As for litter, you might be thinking "So and so, a reputable rat person told me ____ litter was safe, but my rat sneezes terribly!" First, it is important to note, that "safe" in terms of litter refers to three things; 1)the litter is nontoxic if ingested; 2)the litter will not cause injuries or impaction from living on or eating it; 3)the litter does not contain aromatic oils--the things in pine and cedar that cause liver damage. "Safe" has nothing to do with dust or allergies. Safe litters can include a wide spectrum from aspen shavings to CareFresh or pelleted paper or wood litter. Don't let anyone tell you differently, no litter is perfect! Rats can be allergic to anything or very sensitive to dust in some litters. For example, I have known many rats that had breathing problems from the dust in paper litters like CareFresh and Healthy Pet, and some of my rats would get sores from laying in it. I once has a rat allergic to aspen. For a long time, I thought his stuffyness was just minor myco, but it went away completely when I changed to a different kind of litter. Changing what kind of litter you use can make a big difference.

Rats have sensitive respiratory tracts. Here are some other things that can irritate them: dust, dry air, perfume, air freshener, smoke (remember cigarette smoke can also cause cancer), hairspray, paint, animal dander (yes, I have known rats that were allergic to cats), pollen, etc. As you can see, they really are not much different from us in many of their health issues.

Lumps and Bumps

People are too quick to panic about lumps on rats, probably because there is a lot of hype about the occurence of tumors in rats. A lump is no reason to panic! You simply need to make yourself aware of what the problem could be and what the best solution is. Most lumps in/on rats are not tumors. They could be a cyst, abcess, or a "pimple." Also, keep in mind that not all tumors are malignant and not all are inoperable or "incurable." Also many do not cause any pain or discomfort and grow very slowly. I have had experience with many kinds of lumps, so I will try to give you an idea of how to identify them and how to make choices about treatment. ~~Remember, when in doubt, consult your vet!~~

Abcess: An abcess is a pocket of infection. It can be anywhere on the body. It is usually round or slightly flattened and is in or just under the skin. Abcesses are the most common lumps on rats. They can be caused by a splinter or any accidental scratch (even from play). Treating an abcess is very simple; it should be lanced to drain or allowed to drain on it's own. (Do not squeeze an abcess or it can rupture internally and could cause the blood to become septic.) You can bring the infection to the surface using a warm compress. Abcesses are full of white to even greenish fluid and often have a foul odor. After they are drained, rats usually do a good job of keeping them clean, but they might reform and need draining again.

Cyst: Cysts are also lumps in the skin, but unlike abcesses and pimples, they occur almost always on the back and mostly in males. Cysts (or sebaceous cysts) are the result of clogs or overproduction of the sebaceous glands. Cysts usually feel very hard and cannot or should not be lanced or removed except by a vet. They don't grow very fast and do not bother the rat.

Tumor: Tumors are lumps that are lower down below the skin. They are solid masses (some are firm and defined, while others are soft and less defined) connected in the tissue. Tumors are the result of excess or out of control cell growth (often triggered by hormonal changes in older females). Most tumors are mammary gland or lymph node derived and only occur in the underside of rats, especially around the armpits. Tumors are far more common in female rats over the age of 18 months. Most mammary tumors can be easily and successfully treated as long as they are caught early on. Treatment is surgical and can only be done by a vet. Experienced vets remove the tumor and a good bit of surrounding tissue (to get the "roots") or the entire gland. It has been my experience that rats recover quickly from surgery and usually go for many months or their whole lives without a reoccurence of tumors. When deciding on treatment, you should keep the animal's general health (regardless of age) in mind. Any healthy animal should have no problem getting through surgery as long as it is done by an experienced vet. If tumors reoccur soon after surgery, I usually will not opt for another surgery, because it would likely be fruitless. Rats can live quite happily with a small tumor for many months, depending on the tumor's location. If surgery is not done, watch your rat's activty levels and apetite for signs of loss of quality of life. (If you suspect a tumor but don't want to opt for surgery, see the vet anyway for an appointment, because it might be a harmless and easily treatable abcess...) There is some evidence that certain supplements can slow or prevent tumor growth. Spaying a female under 2 years old reduces the risk of tumors tremendously and might be worth considering, especially if your rat is from a line prone to tumors.

Old Age

It's inevitable; rats age. With age comes, at least at some point, poor health, and rats are very mortal creatures. They live short lives, and old age will be upon them quickly. Some rats start "getting old" early, around 18 months; other remain vibrant and "young" well into their second year of life--or longer if they are lucky. The way I figure the "rat age calculator" is about 3 rat years per real month of life, so a rat that is 2 years old is physically like a 70 year old. Just as in people you have both healthy and frail 70-somethings, you see the same differences in rats.

Instead of telling you how to deal with elderly rat (which other articles by other people cover pretty well), I'd like to share a story. Don't worry, it's better than my SDA story.

Two months after Belldandy's second birthday, I noticed a change in her. The change crept up on me, and it seemed slow. At first I attributed it to "just aging." Belldandy had lost a lot of weight. She wasn't staying clean any more. Her face and forearms were completely stained with poryphin. I noticed that she stumbled when taking steps. I gave her a yogurt drop one day and then saw she would not hold the treat with her paws. Instead she tried to bite into it and it would scrape into crumbs. If she got a piece into her mouth, she would try to chew it, but crumbs would fall out. She seemed to be trying to grab her mouth but couldn't lift her hands. Afraid she was choking, I lifted her up and looked in her mouth. One bottom incisor was twice as long as the other! Suddenly I felt very guilty, like I had been starving my rat to death because of not noticing a "broken tooth." My sister helped me trim the long one. But a few days later her teeth were uneven again.

Belldandy didn't have a dental problem. She had had a stroke. Her whole sense of balance and coordination was thrown off, so she was "eating crooked" whenever she did. (I suspect any teeth-wearing she did was bruxing though, because she wouldn't touch solid food.) The poryphin, it turned out, was not due to illness, but just the accumulation over the night--because she couldn't wash her face. Anyway, she seemed so determined to try and be a normal rat, despite being unable to eat and having no coordination with her hands. She was not in pain nor was she "sick" (healthiest set of lungs a rat could have!), and seemed to be really trying. At first, I decided I would just do what I could to keep her alive and comfortable until she died. I was certain she didn't have long. I even postponed my return to college a whole week, expecting Belldandy would die, and I should bury her before leaving. But she kept, in my mind, "lingering."

Every few days, I trimmed her teeth and she flopped in my hands (not able to put up a really good fight). I let her sleep in my bed with me, for fear she'd fall and hurt herself in the cage. I would give her Nutri-cal everyday, and I had to give her water to lap, because she wouldn't use the waterbottle. I washed her hands and face for her, and gave her a bath now and then. I bought a can of wet dog food and mixed into it crushed yogurt drops, Nutri-cal, milk, and other soft things I had. I would put her face into the bowl, and she would eat for ten minutes non-stop. Then, she would turn away, and I'd wash her face. She seemed to be an invalid, and I felt at first, irritated that she wouldn't simply allow herself to die. Then I felt guilty for thinking that about my beloved pet and then guilty for not having her euthanised in light of her dismal life. And for all the guilt, I would treat Belldandy with a seedless grape, one thing she could hold on to--at least loosely, and enjoyed scraping into her mouth.

I'm not sure when I noticed or how it happened, but something was changing. One day, I went to cut her tooth, and I saw that they were almost the same length, and a couple days later, she fought me so hard I couldn't even check. I put her in the cage with the other rats, and she went to the water bottle and drank. One day, after she had eaten her meal, she stood back and cleaned her face. Overjoyed, I ran to my sister and told her Belldandy cleaned herself. I probably sounded like a nut, but I didn't care! A few days later I gave Belldandy a yogurt drop, and she ate it without making a pile of crumbs. That night was the first night she didn't sleep with me in over three weeks. The reason was that she was running around and even to the end of the bed where, in her younger years, she had plotted and carried out clever escapes (from spelunking between my bed and the wall to sliding down my curtains or using my clothes pile as stairsteps). She had that mischeivous gleam in her eyes, so I put her back in the cage for the night...

That is one of my "old rat" stories. I have many others, but most are bittersweet, because old rats do die, and all we can do is make sure are pets are comfortable and live good lives--no matter how short or long. As pet owners, we have to make decisions for our animals. We have to discern if they are suffering or if they want to live. Recovery is not a guarantee, often chances are slim, but I believe if you can really be observant and in sync with your pets, you will be able to make the right decisions. When dealing with pets, the issue of euthanasia is very real. It is a difficult choice to make--I have had to make that decision a few times, but it is never a selfish one. It is hard to face such a decision, and no one can really say what you should do, but your pets will let you know, and you should never feel guilty for the choices you make--as long as they are based on love.

A Vital Resource

In my opinion, all rat and mouse (mice have very similar health issues to rats) owners should own a copy of Debbie Ducommun's Rat Health Care booklet. You can order it from her site for $5. For me, it has been the most valuable book I have ever owned, because with it, you can make big decisions with far more confidence. You have a better idea of your rat's chances when something bad happens (like cancer) and you will be able to decide when you need to see a vet, when surgery is or isn't worth it, and how to prevent your rats from getting sick or injured.

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