Rat-bite fever (RBF) is an infectious disease caused by two different bacteria:

• Streptobacillus moniliformis, the only reported bacteria that causes RBF in North America (streptobacillary RBF)
• Spirillum minus, common in Asia (spirillary RBF, also known as sodoku)

People typically become infected with these bacteria after contact with rodents carrying the bacteria. A person can also get infected through consumption of food or water contaminated with the urine and droppings of rodents carrying the bacteria. This is known as Haverhill fever.

If not treated, RBF can be a serious or even fatal disease.

There are several ways that people can get RBF:

• Through bites or scratches from rodents carrying the bacteria. The bacteria can enter the body directly through a bite wound, open skin, or mucous membranes such as in the eyes, nose, or mouth
• When handling rodents carrying the bacteria or through contact with their saliva, urine, or droppings
• Through contact with surfaces that are contaminated with the bacteria. The bacteria can enter the body through open skin, such as cuts or scrapes, or mucous membranes such as in the eyes, nose, or mouth
• Consuming food or drinks that have been contaminated with droppings or urine from a rodent carrying the bacteria

RBF is not spread from one person to another.

RBF can be a serious or even fatal disease. See your doctor right away if you have any of the signs or symptoms of RBF.

In addition to RBF, rodents can spread other diseases to people.

Without early diagnosis and appropriate treatment, RBF can cause severe disease and death. In addition to RBF, contact with rodents can result in several other illnesses.

The early symptoms of RBF can be similar to the symptoms of other medical conditions. Symptoms of RBF are often different for the two types of disease: streptobacillary RBF and spirillary RBF (sodoku).

Symptoms and signs of streptobacillary RBF include:

• Fever
• Vomiting
• Headache
• Muscle pain
• Joint pain or swelling (about 5 in 10 people with RBF have this)
• Rash (occurs in about 3 out of 4 people with RBF)

Symptoms usually begin 3 to 10 days after contact with the bacteria, but can be delayed as long as 3 weeks. By this time, any rodent bite or scratch wound that caused the infection has usually healed.

Within 2 to 4 days after fever begins, a rash may appear on the hands and feet. This rash looks like flat, reddened areas with small bumps. One or more joints may then become swollen, red, or painful.

The symptoms that develop with Haverhill Fever (the type of infection that can follow after consuming contaminated food or water) are similar to Streptobacillary RBF, but may include more severe vomiting and sore throat.

Complications of streptobacillary RBF can include:

• Abscesses (pockets of infected fluid) inside of the body, like in the belly (abdominal cavity)
• Infections of the liver (hepatitis) and kidneys (nephritis)
• Infections involving the lung (pneumonia)
• Infections involving the brain and nervous system (meningitis)
• Infections involving the heart (endocarditis, myocarditis, or pericarditis)

About 1 in 10 people who have streptobacillary RBF infection die.

Symptoms and signs of spirillary RBF (sodoku) can vary and often include:

• Fever (that may come and go or occur repeatedly)
• Swelling or formation of an ulcer at the bite wound (if present)

• Swollen lymph nodes (small glands that filter lymph, the clear fluid that circulates through the lymphatic system, and help fight infections)
• Rash (about 5 in 10 people with sodoku have this) that can appear all over the body or only near the area of the bite wound (if present)

These symptoms usually occur 7-21 days after exposure to an animal carrying the bacteria.

If you have any of the symptoms of RBF after contact with rats or other rodents, immediately see your health care provider. Make sure to tell your provider about your contact with rodents.

Any person who comes into contact with the bacteria that cause RBF is at risk for becoming sick with the disease. Remember, without early diagnosis and appropriate treatment, RBF can cause severe disease and death. People who may be at greater risk for RBF infection include:

• Those who have pet rats or other rodents in their home
• People who have live or frozen feeder rats or other rodents in their home
• People who have been bitten or scratched by a rat or other rodent
• Those who work with rats or other rodents, such as at animal research laboratories or pet stores
• People who live or spend time in areas with rodent infestations
• Children who have contact with rodents
  • Children 5 years old or younger are at higher risk for infection with RBF because their immune systems may still be developing. Additionally, they are less likely to know how often they need to wash their hands, and how to properly do so. Infants and young children may place unclean fingers in their mouths or contaminate common household objects.
• Adults ages 65 and older, women who are pregnant, or those with weakened immune systems who have difficulty fighting off infections (for example, people with cancer, HIV/AIDS, organ implants, or those taking certain medications such as steroids).

If you develop any of the signs and symptoms of RBF after coming in contact with rats or other rodents, immediately contact a health care provider. Make sure to tell your provider about your contact with rodents.

If your provider suspects that you have RBF, he or she will treat you with antibiotics. Antibiotics can be highly effective at curing the disease if treatment is started soon after you become sick. It is important that you follow your doctor’s instructions on how to take your antibiotics, and that you take all of the medicine that your doctor prescribes to you, even if you start to feel better.

Without early diagnosis and appropriate treatment, RBF can cause severe disease and death.

You can lower your risk of becoming infected with RBF and other rodent diseases by avoiding direct contact with rodents, places with rodent infestations, or other areas where rodents may be present.

If you handle rats in a pet store setting:

• Wear protective gear, such as gloves.
• Avoid touching your mouth and face after handling rodents.
• Wash your hands with soap and warm water for at least 20 seconds after handling rodents, their cages, bedding, urine, or droppings.

If you handle rats in a laboratory or animal research setting:

• Wear proper protective laboratory gear, including gloves, and follow appropriate safety precautions.
• Avoid touching your mouth and face after handling rodents.
• Wash your hands with soap and warm water for at least 20 seconds after handling rodents, their cages, bedding, urine, or droppings.

What to do if you’re bitten or develop RBF signs and symptoms

If you are bitten or scratched, immediately clean the wound with soap and warm water. Then, contact a health care provider and tell the provider about your recent injury. If you were bitten at work, make sure to document the bite and report the incident to your supervisor. Remember, without early diagnosis and appropriate treatment, RBF can cause severe disease and death.

If you develop any of the signs and symptoms of RBF, even if you have not had a bite or scratch, immediately contact a health care provider and tell the provider about your contact with rodents.

Additional recommendations

Rodents may not be suitable to keep as pets or feeder animals in your home, classroom, or child care center. This is particularly true if your home or establishment has infants, young children, pregnant women, or people with weakened immune systems. People with weakened immune systems include the elderly and people with illnesses such as diabetes, HIV/AIDS, or cancer.

There are currently no laboratory tests that can accurately tell whether or not an animal is infected with S. moniliformis or S. minus. There is also no data to support the use of antibiotics to get rid of either S. moniliformis or S. minus in animals carrying these bacteria.

Isolated cases and outbreaks of Haverhill Fever can occur after people consume food or drinks that have been contaminated with rodent droppings or urine that contain the bacteria. It is important to remember that contaminated food and drink sources may look and smell normal. To prevent contamination, take steps to avoid rat infestations and keep domestic rodents out of kitchens and other areas where food and drink are prepared, served, or consumed.

Rats can carry the bacteria that cause RBF without showing signs of illness. In addition to RBF, contact with rodents can result in several other illnesses.

Do your research before adopting a small pet

Have you thought about getting a small pet like a hamster, gerbil, or guinea pig? You may think small pets will make a good “starter” pet for your child, or that they’re less of a commitment than other pets like cats and dogs. Despite their small size, owning one of these pets is a big responsibility! Just like larger pets, small pets need exercise, attention, and veterinary care to stay healthy and happy.

It’s also important to remember that rodents and other small mammals are more likely than other pets to spread germs like Salmonella. These germs are especially risky for young children and can make them very sick. If you have a child under 5, consider another pet.

Before Choosing a Small Pet

• Consider if this pet is right for your family. Children under 5 years old, adults 65 and older, and people with weakened immune systems are more likely to have severe illness from germs rodents and other small mammals can carry.
• Research and learn how to care for your pet. Small pets need special habitats, toys, and supplies. Some small pets are social animals that shouldn’t be kept alone.
• Choose a pet that matches your lifestyle. Think about the pet’s attitude, size, and activity level and how much time you can spend with your pet. For example, some small pets are shy, while others enjoy being handled.

Keep Your Small Pet Healthy

• Keep your pet in a habitat that can be closed and locked.
• Watch your pet for any changes in activity level, appetite, or overall health.
• Take your pet for regular checkups with an exotic animal veterinarian. Small pets often require specialized care that all veterinarians may not provide.

Keep Yourself Healthy

• Wash your hands after handling your pet or its supplies.
• Keep your pet and its supplies away from anywhere food is stored, prepared, or eaten.
• Don’t let small pets roam freely around the house. They could get injured, and they can also contaminate surfaces with germs.
• Don’t kiss, snuggle, or hold your pet close to your face.
• Learn how to handle your pet properly. Small pets may bite or scratch when scared or startled.

The primary hosts of Streptobacillary RBF are rats, both the black rat (Rattus rattus) and the Norwegian rat (Rattus norvegicus), kept as pets and used in animal research. These animals can carry and spread the bacteria throughout their lives without showing signs of illness. Other rodents can also carry and spread the bacteria.

The bacteria live in the upper respiratory tract of rats and other rodents. Studies have shown that many domestic rats and over half of wild rats carry S. moniliformis.

Other rodents that can carry the bacteria are:

• Mice, guinea pigs, gerbils, and squirrels
• Infrequently, dogs, cats, ferrets, weasels, cattle, pigs, koalas, non-human primates, and turkeys, but this is not well documented

The bacteria may spread to these animals after they consume contaminated food or water, or after direct contact with rats. These animals may or may not show signs of illness.

People can become infected with the bacteria after being bitten or having contact with an animal carrying the bacteria. One study showed that dogs that had been in close contact with wild rats had S. moniliformis DNA in their mouths. Additionally, a human case of RBF occurred after the patient was bitten by a dog known to eat rats.

There are currently no laboratory tests that can accurately tell whether or not an animal is infected with S. moniliformis or S. minus. The bacteria can sporadically be in an animal’s saliva, urine, and feces, so a negative test might not mean the animal is actually free of the bacteria. There is also no data to support the use of antibiotics to get rid of S. moniliformis or S. minus in animals carrying these bacteria.