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Animal bite infection in Adult
Other Resources UpToDate PubMed

Animal bite infection in Adult

Contributors: Wesley G. Willeford MD, Ricardo M. La Hoz MD, Zaw Min MD, FACP
Other Resources UpToDate PubMed


Animal bite wounds and associated infections represent approximately 1% of all patient visits to emergency departments each year. In the United States alone between 2001 and 2003, there were an estimated 4 521 300 mammalian animal bites resulting in 855 000 medical visits per annum. Infection occurs through direct inoculation with the oral flora, and 3%-18% of animal bites go on to become infected. Generally, dog bites represent about 60% of animal bites, and 10%-20% are accounted for by felines.

Dog bites are more common in the summer months. In adults, the bites tend to be on the extremities. In children under the age of 10 years, bites are more commonly on the face and thus tend to be more serious in nature. Cat bites are more common in women and elderly individuals. Infection tends to develop approximately 8 hours postinjury.

While canine and feline bites represent the majority of such injuries, patients may present with a human bite or injuries caused by human teeth. This warrants a slightly different approach to management. These injuries typically occur during a brawl and may result from one party punching another in the face. This is distressing for both parties. Injuries typically affect the metacarpophalangeal joints, and there is a high likelihood of involvement of the tendons. Given the relative tightness of the hand compartments, immediate attention is required. See human bite hand injury.

Typical symptoms and exam findings of any bite seen at presentation include pain, cellulitis, and purulent discharge at the site of the injury. There can be regional adenopathy and fever, and tenosynovitis or osteomyelitis can develop if the wound is in close proximity to deeper structures.

Immunocompromised Patient Considerations:
Patients undergoing chemotherapy or who have any form of immunosuppression have a higher likelihood of a more complicated clinical course. Patients with immunocompromised state, asplenia, or chronic liver disease are at higher risk of developing severe infections with encapsulated organisms (Staphylococcus pneumoniae, Haemophilus influenza, and Neisseria meningitides), Babesia, Ehrlichia, and Capnocytophaga canimorsus. Such patients require immediate emergent attention.


W55.81XA – Bitten by other mammals, initial encounter

399907009 – Animal bite wound

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Differential Diagnosis & Pitfalls

Differential diagnosis is narrow in the setting of a known animal or human bite.

The infecting organism varies by animal type, but in general the organisms are a mix of aerobes and anaerobes. Microbial profiles are available from animals ranging from bears to Tasmanian devils.

Cat bite organisms:
  • Pasteurella multocida (most common)
  • Streptococcus spp.
  • Staphylococcus spp. (including MRSA)
  • Fusobacterium spp.
  • Bacteroides spp.
  • Porphyromonas spp.
  • Moraxella
Dog bite organisms:
Note: In the event of a human bite, organisms include:
  • Streptococcus anginosus
  • Staphylococcus aureus
  • Prevotella spp.
  • Peptostreptococcus spp.
  • Fusobacterium nucleatum
  • Haemophilus spp.
  • Eikenella corrodens
  • Potential for transmission of hepatitis B/C and HIV

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Last Updated:03/23/2021
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Animal bite infection in Adult
A medical illustration showing key findings of Animal bite infection : Fever, Lymphangitis, Regional lymphadenopathy, Wound
Clinical image of Animal bite infection - imageId=6112227. Click to open in gallery.  caption: '<span>Pasteurella multocida infection;</span> 24 hours post cat bite.<br />'
Pasteurella multocida infection; 24 hours post cat bite.
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