Capnocytophaga Infections

This rare but deadly bacteria lives in your dog’s mouth, but the chance of you contracting a disease from it is slim.


Capnocytophaga infections in people are rare, but they get big press because they can be fatal and because the source may be your pet.

Capnocytophaga canimorus is part of the normal bacteria population in your dog’s mouth. Many capnocytophaga species are normal microflora in people and other animals as well.

To get a capnocytophaga infection from your dog, you need direct contact with the bacteria, such as through a bite, and in most cases, a weakened immune system. People at risk of this infection tend to be elderly, very young, or have chronic health conditions that lower their immunity. Most infections are adults over 40 with health problems, including diabetes.


Some people will have gastrointestinal signs, muscle pain, and a headache or confusion, but the usual symptoms of capnocytophaga infections include:

  • Fever
  • Blister-type swelling
  • Severe pain
  • Redness around the bite
  • Pus/discharge


A bite is the most common way this infection is transmitted between a dog and a person, but, even then, it’s rare. What is important is that it can be a deadly infection.

If you are bitten by a dog, even if by accident, immediately clean the wound carefully, flushing it thoroughly with an antiseptic bacterial wash like chlorhexidine, if available, but even water will help if that’s all there is.

Contact your physician immediately. Go to urgent care if directed by your health-care provider or if you cannot be seen by your health-care provider. Most people who develop serious infections will show signs in three to five days, rarely as soon as one day or as late as two weeks. If you have any concerns, get medical attention.


Capnocytophaga infections respond to antibiotics, but treatment needs to be started early before sepsis starts. Mortality is high (up to 30%) in susceptible people.

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Deb M. Eldredge, DVM, is a graduate of Cornell University’s College of Veterinary Medicine and the first recipient of the vet school’s coveted Gentle Doctor Award. Currently retired from clinics, Dr. Eldredge is an award-winning writer and the technical editor of Cornell’s DogWatch. She and her daughter own the Coyote Run Belgian Tervuren kennel. Dr. Eldredge actively competes her dogs in all dog sports and breed shows.