Many kinds of bacteria (germs) called Capnocytophaga live in the mouths of dogs and cats. These germs do not make dogs or cats sick.

Rarely, Capnocytophaga germs can spread to people through bites, scratches, or close contact from a dog or cat and may cause illness, including sepsis. Most people who have contact with a dog or cat do not become sick. People with a weakened immune systems who have difficulty fighting off infections (for example, people with cancer or those taking certain medications such as steroids) are at greater risk of becoming ill.

Many Capnocytophaga germs are normal bacteria commonly found in the mouths of people, dogs, and cats. These germs sometimes cause opportunistic infections, which means under the right conditions they can cause an infection, such as in a person with a weakened immune system.

People with weakened immune systems include those who:

• Drink alcohol excessively
• Have had their spleens removed
• Have HIV infection or cancer

People with these conditions should speak with their doctors about how to safely interact with cats and dogs.

The Capnocytophaga germs that are common in dogs and cats can be spread to people through a bite or after close contact with dogs or cats. Infections are more often linked to dog bites or dog contact.

See the Preventing Dog Bites page for information on how to prevent dog bites and what to do if you are bitten, regardless of your health status.

Other Capnocytophaga germs can also be found in human mouths and can cause illness in some people who have the bacteria in their own mouth. People who have weak immune systems get this type of infection more often than healthy people.

Most reported infections occur in tissues connected to the mouth and throat, including:

• Periodontal (gum) disease
• Respiratory tract infections (infections of the mouth, nose, throat, and lungs)
• Eye infections

In both types of infections—those that spread from animals or from oneself—the bacteria can enter the blood stream, which can lead to infection in various parts of the body. Infection can also cause the following:

• Septicemia (blood infection)
• Endocarditis (inflammation of the lining of the heart)
• Abscesses (collections of pus in the tissue that cause redness and swelling) in various body tissues
• Inflammation of the eyes, face, lymph nodes, or brain membranes

Most contact with dogs and cats does not lead to a Capnocytophaga infection or any illness, even after a bite. But, you should take precautions if you have contact with animals, especially if you have a condition that puts you at higher risk of infection.

People who are infected with Capnocytophaga can have a range of signs and symptoms such as:

• Blisters around the bite wound within hours of the bite
• Redness, swelling, draining pus, or pain at the bite wound
• Fever
• Diarrhea and/or stomach pain
• Vomiting
• Headache and/or confusion
• Muscle or joint pain

After being bitten, most people who become ill will show symptoms within 3 to 5 days, but this can range anywhere from 1 to 14 days.

Most Capnocytophaga infections usually occur with dog or cat bites. But some people who develop a Capnocytophaga infection have not been bitten. People may be infected after close contact with a dog or cat, especially after contact with the animal’s saliva (spit).

Capnocytophaga infection can cause serious complications, including heart attack, kidney failure, and gangrene. Some people may need to have fingers, toes, or even limbs amputated because of complications from severe infection.

About 3 in 10 people who develop a severe infection die. Some infections can progress very quickly, result in sepsis, and lead to death within 24 to 72 hours after symptoms start.

If you have been bitten by a dog or cat, wash the bite area right away with soap and water, and call your doctor, even if you don’t feel sick. This is because dog and cat bites can pose a risk for rabies, as well as Capnocytophaga.

People with certain health conditions are at greater risk of infection, but anyone could become sick from Capnocytophaga bacteria.

You may have a higher risk of infection if you:

• Use alcohol excessively
• Do not have a spleen (asplenic)
• Have an immuno-compromising conditions, including but not limited to:
  • Cancer
  • Diabetes
  • HIV infection
• Are taking drugs that are toxic to cells (such as chemotherapy)

Most Capnocytophaga infections occur in adults over 40 years of age. However, cases have also been diagnosed in young children.

Capnocytophaga germs can cause serious illness in pregnant women and their unborn babies. Infection during the last few weeks of pregnancy can lead to inflammation of the membranes that surround the baby in the womb, a condition known as chorioamnionitis. In the newborn, it can also cause low birth weight, and it can lead to serious infection of the bloodstream or body tissues, known as sepsis.

If you have any of these conditions and have contact with dogs or cats, see the Prevention and Pets pages for more information. If you are bitten by a dog or cat, call your doctor immediately and describe your animal contact.

Capnocytophaga infection can be treated with prescription medicine called antibiotics. Antibiotics kill bacterial germs like Capnocytophaga. It is important to call your doctor if you have been bitten by a dog or cat or believe that you might be infected with Capnocytophaga germs.

Different kinds of antibiotics can be used to treat Capnocytophaga infection. You may need to take more than one antibiotic to help you get better.

Learn how to prevent dog bites and what to do if you are bitten by a dog or cat. If you are at a higher risk of infection with Capnocytophaga germs, it is important to seek medical care promptly.

If you start having symptoms within 14 days of being bitten, get medical care immediately. Tell your health care provider that you were recently bitten by an animal.

About 3 in 10 people (30%) who develop serious infections with Capnocytophaga germs die. Some infections can lead to death within 24 to 72 hours after symptoms start.

If you have been bitten by a dog or cat, wash the bite area right away with soap and water, and call your doctor, even if you don’t feel sick. This is because dog and cat bites can pose a risk for rabies, as well as Capnocytophaga.

People may be infected after close contact with a dog or cat without being bitten. If you are at higher risk of infection, speak with your doctor about how to protect yourself when you have contact with pets. Also, see the Pets page for information about safer contact with pets.

Most dogs and many cats have Capnocytophaga and other germs in their mouths (oral flora). These germs do not make the animals sick. Animals can be tested to see if they have Capnocytophaga germs, but a negative result may not mean the animal will always be negative – and the same is true for a positive result. Although animals could be given medicine to get rid of the germs in the short term, they will likely get them again after contact with other animals.

Having pets like dogs and cats has many benefits. Most contact with dogs and cats does not lead to a Capnocytophaga infection or any illness, even after a bite. But, you should take precautions if you have contact with animals, especially if you have a condition that puts you at higher risk of infection.