Rat-Bite Fever

What is rat-bite fever?

Rat-bite fever (RBF) is a rare bacterial disease that most commonly spreads through the bite of infected rats. RBF can also spread if an infected rat scratches you or if you come into contact with rat saliva (spit), feces (poop) or urine (pee).

RBF can be a serious and even deadly infection. Talk to a healthcare provider right away if you have symptoms of RBF after coming into contact with a rat.

What are the types of rat-bite fever?

Two types of bacteria can cause rat-bite fever:

• Streptobacillus moniliformis (S. moniliformis). This type most commonly occurs in the United States. Other names for this type of RBF include streptobacillary rat-bite fever or Haverhill fever (if you ingest unpasteurized milk that has the bacteria).
• Spirillum minus (S. minus). This type most commonly occurs in Asia. You can’t get a Spirillum minus infection by ingesting the bacteria through food or drinks. Other names for this type of RBF include spirillary rat-bite fever and sodoku.

These bacteria exist in the mouths and upper respiratory tracts of rats and other animals.

Can other animals spread rat-bite fever?

Yes, other animals may carry the bacteria that cause rat-bite fever. These include:

• Mice.
• Squirrels.
• Gerbils.
• Guinea pigs.

There may also be a rare association between RBF and:

• Dogs.
• Cats.
• Cattle (such as cows, bulls or oxen).
• Pigs.
• Ferrets.
• Turkeys.
• Weasels.
• Nonhuman primates (such as gorillas, apes and chimpanzees).

But there isn’t much research on the possible association between RBF and these animals.

How common is rat-bite fever?

Rat-bite fever is rare. There are about 20,000 to 40,000 rat bites each year in the United States. You have up to a 10% chance of getting RBF from a rat bite. There are roughly 2,000 to 4,000 cases of RBF each year in the U.S.

But RBF isn’t a reportable condition in the U.S. That means that healthcare providers don’t consider it a major threat to public health and don’t have to report occurrences. RBF occurrences may be higher than the estimates.

What are the first symptoms of rat-bite fever?

Streptobacillary rat-bite fever and spirillary rat-bite fever share many symptoms. But there are some differences.

Streptobacillary rat-bite fever

• Headache.
• Fever.
• Nausea and vomiting.
• Skin rash, usually around your hands and feet.
• Joint pain.
• Muscle pain.

Symptoms usually appear three to 10 days after exposure to S. moniliformis bacteria.

Spirillary rat-bite fever

• Fever that goes away and comes back (recurrent fever).
• Skin lesions and/or swelling around the bite.
• Swollen lymph nodes.
• Skin rash.

Symptoms usually appear seven to 21 days after exposure to S. minus bacteria.

What causes rat-bite fever?

The S. moniliformis and S. minus bacteria that some rats and other animals carry cause rat-bite fever. The animals are just the hosts of the bacteria. In most cases, they don’t show any symptoms of being sick if they have the bacteria.

How is rat-bite fever transmitted to humans?

In most cases, people get rat-bite fever from the bite or scratch of an infected rat or other animal. However, S. moniliformis and S. minus bacteria can also spread by:

• Touching a surface contaminated with infected rat or animal secretions (spit, pee or poop) and then touching an open wound or your mouth, nose or eyes.
• Ingesting food or drinks that contain the bacteria, usually from infected animal secretions.

RBF isn’t contagious among people.

Who does rat-bite fever affect?

Rat-bite fever can affect anyone who interacts with an infected rat or other animal. This may occur from a bite or contact with infected pee, poop or spit. Cases most commonly occur in the U.S. and Asia.

You may be at a higher risk of RBF if you:

• Have pet rats or other rodents, including mice and guinea pigs.
• Keep rats to use as food for other animals, such as snakes.
• Spend time in areas with rat or rodent infestations.
• Regularly interact with rats, rodents or other animals, such as a pet store or during animal research.
• Have a weak immune system.

What are the complications of rat-bite fever?

S. moniliformis and S. minus bacteria can cause serious infections that spread to other areas of your body, including your:

• Brain and spinal cord (meningitis).
• Heart (endocarditis, myocarditis and pericarditis).
• Kidneys (nephritis).
• Liver (hepatitis).
• Lungs (pneumonia).

RBF can also be fatal without proper treatment. Streptobacillary RBF is fatal in about 10% of infected people.

How is rat-bite fever diagnosed?

A healthcare provider can diagnose rat-bite fever after reviewing your medical history, asking about your symptoms and conducting a physical examination.

If the provider suspects you have RBF, they may conduct a blood test or take a fluid sample from your joints. They’ll send the samples to a laboratory to check for the presence of S. moniliformis or S. minus bacteria.

Is rat-bite fever curable?

Yes, rat-bite fever is curable, especially with early diagnosis from a healthcare provider. Talk to a provider if you have RBF symptoms after close contact with a rat or another animal.

How do you treat rat-bite fever?

If a rat, rodent or other animal bites or scratches you, you should first wash out the wound with clean water and antibacterial soap. You may also want to clean it with hydrogen peroxide. Pat the wound dry with a clean towel, apply a skincare ointment such as Neosporin® or Aquaphor® and cover it with a bandage.

Then, reach out to a healthcare provider. They’ll likely prescribe antibiotics to help clear the infection. You may have to take antibiotics for up to two weeks. These may include:

• Penicillin.
• Ceftriaxone.
• Ampicillin.
• Amoxicillin.
• Doxycycline.

You may take these antibiotics orally (as a pill with water) or intravenously (through a needle in a vein). You must take your full course of antibiotics, even if you start to feel better. If you don’t, rat-bite fever can return and be more difficult to treat.

How soon after treatment will I feel better?

Most people feel better a few days after starting treatment for rat-bite fever.

Can rat-bite fever be prevented?

You can help lower your risk of developing rat-bite fever with the following tips:

• Stay away from rats and rodents. Avoid areas where they pee or poop.
• Wear rubber gloves, goggles and a mask that covers your nose and mouth if you must clean up rat or rodent droppings.
• Use disinfectant to sanitize areas that contain rat or rodent pee or poop.
• Seal holes in and around your home so rats and other rodents can’t enter.
• Set rat traps around your home to help decrease the population.
• Avoid leaving food out in your home or while camping. Easily accessible food sources draw rats and other rodents.

What is the outlook for rat-bite fever?

Most people with rat-bite fever fully recover without lasting effects after treatment.

What is the mortality rate for rat-bite fever?

The mortality rate for rat-bite fever is about 10%. You can help improve your chances by seeing a healthcare provider right away after a rat bite or scratch.

How do I take care of myself if I have rat-bite fever?

The following tips can help you take care of yourself if you have rat-bite fever:

• Keep your wound clean. Wash it with soap and water and cover it with a clean bandage.
• Take your antibiotics exactly as directed by a healthcare provider. Set an alarm on your cell phone or another device to help you remember when to take them.
• Stay hydrated. Drinking plenty of water can help your body clear infections.

When should I see a healthcare provider?

Rat-bite fever can quickly become serious, especially if you have a weakened immune system. Contact a healthcare provider right away if a rat, rodent or other animal bites you and you have signs of RBF.

You should also contact a provider if you have RBF and your symptoms don’t improve after treatment.

What questions should I ask a healthcare provider?

• How did I get rat-bite fever?
• If I don’t have rat-bite fever, what other condition might I have?
• What treatment do you recommend?
• What should I do if I forget to take a dose of my antibiotic?
• Are there any signs I should look for that indicate rat-bite fever is getting worse?

Can my pet rat have rat-bite fever?

It’s possible for pet rats to have rat-bite fever. Rats, rodents and other pets don’t usually have clear symptoms if they have S. moniliformis and S. minus bacteria. The bacteria can spread through direct contact with other infected rats or from contaminated food or water.

Though rare, other pets can spread the bacteria if they interact with infected rats. These may include dogs and cats that hunt or eat rats.

A note from Cleveland Clinic

Rats and other rodents can be cute, sweet and affectionate animals. Many people choose to adopt them as pets for these reasons. But they can also carry bacteria that make you sick. Two of these bacteria include Streptobacillus moniliformis and Spirillum minus, which cause rat-bite fever. Rat-bite fever is a rare but serious disease that develops after close contact with an infected animal. It can be deadly without proper treatment.

If you develop RBF symptoms after a rat or other animal scratch or bite, or after being in an area where rats live, see a healthcare provider immediately. The faster you get treatment, the greater your chance of making a full recovery without any complications.