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What Are the Most Common Rat Diseases?

By Eddie Chevrel


Updated on

Rats and mice make fun pocket pets yet they are also prone to certain illnesses that we can now fully understand. After you read this short guide, you will know everything about the most common pet rat diseases, whether some of them are transmittable to humans, and whether it is dangerous or not to own a fancy rat.

The Most Common Diseases In Pet Rats

Your average fancy rat is not likely to get sick so easily since they have been bred to be free from disease and illness. Throughout hundreds of thousands of successfully bred rats that are meant for the pet industry, only a handful of actual illnesses and ailments are usually ever seen. This list tells you what signs to look for if you suspect your fancy rat is getting sick. Some of these problems can be treated, while others are simply genetics due to their short lifespan.

1. Respiratory infections

Rats and mice are not so lucky when it comes to dust and spores that can get into their little lungs. The first sign that your rodent is showing a mild case of respiratory infection is coming from its breathing. They can be wheezing, coughing, or breathing from their mouth.

You will also see eye and nose discharge that is showing they are affected by something in their habitat. One of the most common problems is called Mycoplasma and will cause them to show signs of breathing discomfort. This is typically caused by a cage that is dirty or has bedding that contains cedar shavings. It can also be caused by high levels of ammonia from bedding that has soaked up this urine.

Don’t use cedar shavings as they contain aromatic phenols and microscopic dust from the shavings that get into your rat’s lungs. Use alternative wood shavings such as aspen, which is better for rats and mice.

2. Gastrointestinal disease

This is another problem that can occur in your rat if they have been exposed to bacteria or parasites. Rats that were raised and bred in conditions that are similar to pet mills will have this problem. They will show signs of diarrhea and will not be eating as they should. It can also develop if you don’t clean their cage or remove any kind of meat or vegetables that have gone bad.

Another reason for Gastrointestinal disease is if you put a water bowl into their cage. They will end up getting ‘Wet Tail’ which causes more internal stomach problems if their feces get into that water supply. These problems can be treated at the vet with antibiotics. If your rat is not eating enough, it will need to be fed fluids by the vet.

3. Dental problems

All rodents have teeth that will grow continually, which is why they need things to gnaw on all the time. If you don’t give your rat the right chewing supplies, its teeth will become overgrown pretty quickly and you will see that your rat drool more often and have a wet chin. This is because their front incisors don’t fit all the way down and they can’t close their mouth properly.

To avoid this, be sure to include in your rat cage setup a set of chewing toys, chewing sticks, a pumice stone, and plenty of pellets that allow them to naturally gnaw their teeth down to size. If you don’t provide these items, it will cause them pain and will be a costly trip to the vet to have their teeth trimmed. Because of this, they will also not be able to groom themselves properly and will have fur that looks shabby.

4. Tumors

Rats and mice are most likely to form tumors that grow on their chest. They will all form differently but luckily most of these are not cancerous. They also grow very quickly and it is often a sign they could become sick if the conditions in their habitat aren’t so clean.

These tumors can be removed surgically if they are caught in time. These are expensive vet visits that might not be worth the expense for most owners. Most vets will tell you they won’t have much longer if they grow too large. At best you can expect a rat that has a tumor to live another 6 months before it becomes cancerous for them. Sadly the best thing to do is give them enough care until they are too sick to carry on.

5. Staphylococcal infections

This is a common problem with fancy rats which is caused by rodents that are fighting or biting each other. The wounds or scratches can become infected with sore or even abscesses that have Staph germs preventing the wound from healing. These can be remedied by using antibacterial ointments, and antibiotics, and keeping your rat’s nails properly trimmed.

Because they will be in contact with their droppings, Staph germs can be on their feet or on their nails. Once it gets into the skin they get a Staph infection. It’s not life-threatening unless you don’t get them treated. You can easily buy these antibacterial creams from the pet store or from your vet. Either way, if you have rats that fight and end up getting these infections, you might want to remove them from the cage until they heal properly.

6. Chronic progressive nephrosis (glomerulonephrosis)

This is an illness that affects older rats only. It is seen more often with male rats than with females and is causing inflammation in the kidneys. It is directly linked to their diet, so it may or may not occur if your feed them correctly. It also has something to do with their breed type, so not all rats will suffer from this. The warning sign is when your rat tends to drink water more often and urinate a lot more too.

Sadly, this is a disorder that cannot be treated and will result in a rat that is lazy and begins to slowly lose weight, which will lead to death. All you can do is give them as much comfort as possible and dietary recommendations from your vet.

Are some of these diseases transmittable to humans?

There are only three known problems that most fancy rats or mice may carry in their system. Most of the time these will never affect people if they’ve been bred in clean environments. Except for Salmonellosis, this is only caused if your rat has contracted this from their stool.

1. Rat bite fever

Rat-bite fever is caused by bacteria that are carried in the saliva of your rat. Most people will not be affected by this type of bacteria, and less than 10% of anyone who is scratched or bitten by a rat will show any signs of sickness at all.

2. Salmonellosis

Salmonellosis is transmitted by rats that come into contact with their poop and it gets onto your skin. This is why you need to keep their cage nice and clean. You need to wash your hands if you’ve been handling your rats- regardless of their cleanliness.

3. Leptospirosis

This is not so common with fancy rats that are bred in the western world but it has been a problem in tropical or temperate areas. It can affect some people while others have no symptoms at all. It might be transmitted through contact with your rats’ urine.

How can I prevent rat germs and viruses to be caught by humans?

The golden rule to handling rats or mice is to wash your hands before and after picking them up, which is a practice that goes with owning rodents. You don’t know if they were stomping around on some turd in their cage, so you want to avoid getting Staph poisoning by accident.

Having clean hands before and after is a habit you want to have when it comes to handling rodents. Besides that, rats have very poor eyesight so if you were touching any food, they might mistake your finger for a snack. It’s not very common unless you don’t wash your hands to remove these leftover scents.

Is it dangerous to own a fancy rat?

It is no more dangerous to own a fancy rat than it is to own a dog or a cat. However, rats are a lot smaller and you need to be gentle with them as they will bite if they feel mistreated. You need to be patient with your rat and let them learn to appreciate your company. After that, they will be as affectionate as you allow them to be.

Just look for the signs that will tell you that your rat is not in a playful mood. They can become irritated for various reasons ranging from excessive dog barking to your pet cat jumping in front of their cage suddenly.

Trying to tame a wild rat is truly dangerous and is not recommended at all. They can be carrying illnesses that can make you sick if they bite you or scratch you.

What should I do to prevent my rat from being sick?

Pay attention to their dietary needs. Learn the right kinds of foods that will give them all the vitamins and minerals they can handle. Stay away from sugary snacks or heavily salted food like potato or corn chips.

The next thing you want to do is keep their cage as clean as you can. Weekly cage cleaning is what we recommend the most since unclean cages are the leading cause of most health problems for fancy rats.

The only sad part is that rats will likely develop tumors on their chest or stomach. In male rats, it’s usually testicle tumors that are equally unsightly. In this case, you can take them to the vet to have surgery performed. It will cost money like anything else, but won’t be 100% that these tumors will appear elsewhere on their body later in time.

Can I kiss my pet rat?

Aside from your rat being gentle and affectionate, you should not allow your rat to come in contact with your mouth. They do have illnesses that they carry that could be transmitted to you. The problem that comes with any rat that you kiss is that they could potentially bite you and that can lead to an infection. They will also be confused by the smell from your mouth or anything you happened to eat. Since they have such bad eyesight, the smell of your breath could trigger them to think there is food nearby.

Handling them is perfectly fine since you can wash your hands afterward, but if they’re on your shoulder, try to avoid letting them get too close to your mouth. Once in a while, you get a ratty nose in your ear – it is rarely going to be a problem, but always be on your guard even if your rat is tame.

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About Eddie Chevrel

Eddie Chevrel is an animal journalist and the founder of ThePetSavvy. He's very passionate about exotic pets and spends most of his free time doing research, meeting, and interviewing people working with animals. Learn more about The Pet Savvy's Editorial Process.