Overview
The most common bites are associated with dogs, cats, and humans. Human bites can include:
- Occlusal injuries – injuries from biting
- Clenched-fist injuries (‘fight bites’) – when a fist hits someone’s teeth in a fight
Most human bites occur on the hand, often due to fights. Dog bites usually have puncture wounds which can cause deep cuts, crush wounds, bone damage, and soft tissue avulsion. Cats have fine and sharp teeth and cause narrow, deep puncture wounds that can penetrate bone, joints, and tendons. They tend to also inoculate saliva, which can increase the risk of abscesses and osteomyelitis.
Infective Agents
Animal bites
Animal bites are polymicrobial, however, the most commonly isolated organism is Pasteurella multocida.
Human bites
Human bites tend to be from aggressive behaviour and can be more serious. They are also polymicrobial, however, commonly isolated organisms include Streptococci, Staphylococci, Eikenella, and Fusobacterium species.
Human bites may potentially transmit viral infections including Hepatitis B and C, and HIV.
Management
Management involves removal of any bodies, encouraging the wound to bleed unless it is already bleeding, irrigation, and considering debridement. People should also be offered prophylactic antibiotics:
- Animal and human bites: co-amoxiclav or doxycycline + metronidazole if allergic
Complications
Structural damage – including scarring, disfigurement, the need for amputation, and fractures.
Bacterial infection – skin and soft tissue infections are the most common complication following bites. Other infective complications can include cellulitis, abscesses, tenosynovitis, septic arthritis, osteomyelitis, and necrotising fasciitis. Infections can also spread, causing distal infections including infective endocarditis, meningitis, and sepsis. The longer an infected bite wound is left, the higher the risk of these complications. The infection risks may include:
- Human bites – 10-50%
- Cat bites – 30-50%
- Dogs – 5-25%
- Viral infections
Viral infections (including HIV) – the risk is generally low, but they are still possible. The risk depends on the depth of the bite and whether there was any blood in the biter’s saliva. The risk of HIV transmission from someone with known HIV and not taking antiretroviral therapy is <1 in 10,000.
Tetanus – this may occur following a bite, especially if wounds contain devitalised tissue, dirt, or foreign bodies. Tetanus from a human bite is very rare.
Cat scratch disease – due to Bartonella henselae and can occur following a bite/scratch from a cat or dog. It can present with a raised inflammatory nodule at the scratch site with fever and lymphadenopathy.
Rabies – causes encephalomyelitis and is almost always fatal. Usually seen when bitten by a dog in an endemic area. In the UK, the risk is very low. The very few cases of rabies in the UK have mostly been from people who have been bitten in a country where rabies circulates.
