Introduction
Background
Because many animal bites are never reported, determining the exact incidence of animal bite wounds in the United States, let alone the world, is difficult. An estimated 74.8 million dogs lived in the United States in 2007; these account for an estimated 5 million dog bites per year, of which 800,000 require medical attention1 . Substantially more dog bites occur than cat bites. These two species account for the majority of (nonhuman) animal bite wounds encountered in the emergency department (ED).
Pathophysiology
Dog bites typically cause a crushing-type wound because of their rounded teeth and strong jaws. An adult dog can exert 200 pounds per square inch (psi) of pressure, with some large dogs able to exert 450 psi.2 Such extreme pressure may damage deeper structures such as bones, vessels, tendons, muscle, and nerves.
A bite from a pit bull is shown below.
Wounds to the left arm inflicted during a pit bull attack. This young patient was also bitten once on the left side of his face.
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The sharp pointed teeth of cats usually cause puncture wounds and lacerations that may inoculate bacteria into deep tissues. Infections caused by cat bites generally develop faster than those of dogs.3,4
Limited literature is available on other animal bites. Monkey bites have a notorious reputation based largely on anecdotal reports. Several cases of unprovoked attacks on young children and infants by domesticated ferrets have been documented. The bites of foxes, raccoons, skunks, bats, dogs, and cats have been clearly linked to rabies exposure. Bites from large herbivores generally have a significant crush element because of the force involved.
Bites of the hand generally have a high risk for infection because of the relatively poor blood supply of many structures in the hand and anatomic considerations that make adequate cleansing of the wound difficult. In general, the better the vascular supply and the easier the wound is to clean (ie, laceration vs puncture), the lower the risk of infection.
A major concern in all bite wounds is subsequent infection. Infections can be caused by nearly any group of pathogens (bacteria, viruses, rickettsia, spirochetes, fungi). At least 64 species of bacteria are found in the canine mouth, causing nearly all infections to be mixed.5,6,7 Common bacteria involved in bite wound infections include the following:
- Dog bites
- Staphylococcus species
- Streptococcus species
- Eikenella species
- Pasteurella species
- Proteus species
- Klebsiella species
- Haemophilus species
- Enterobacter species
- DF-2 or Capnocytophaga canimorsus
- Bacteroides species
- Moraxella species
- Corynebacterium species
- Neisseria species
- Fusobacterium species
- Prevotella species
- Porphyromonas species
- Cat bites
- Pasteurella species
- Actinomyces species
- Propionibacterium species
- Bacteroides species
- Fusobacterium species
- Clostridium species
- Wolinella species
- Peptostreptococcus species
- Staphylococcus species
- Streptococcus species
- Herbivore bites
- Actinobacillus lignieresii
- Actinobacillus suis
- Pasteurella multocida
- Pasteurella caballi
- Staphylococcus hyicus subsp hyicus
- Swine bites
- Pasteurella aerogenes
- Pasteurella multocida
- Bacteroides species
- Proteus species
- Actinobacillus suis
- Streptococcus species
- Flavobacterium species
- Mycoplasma species
- Rodent bites - Rat-bite fever
- Streptobacillus moniliformis
- Spirillum minus
- Primates
- Bacteroides species
- Fusobacterium species
- Eikenella corrodens
- Streptococcus species
- Enterococcus species
- Staphylococcus species
- Enterobacteriaceae
- Simian herpes virus
- Large reptiles (crocodiles, alligators)
- Aeromonas hydrophila
- Pseudomonas pseudomallei
- Pseudomonas aeruginosa
- Proteus species
- Enterococcus species
- Clostridium species
Frequency
United States
Of an estimated 3-6 million animal bites per year in the United States,8 approximately 80-90% are from dogs, 5-15% are from cats, and 2-5% are from rodents, with the balance from other small animals (eg, rabbits, ferrets), farm animals, monkeys, reptiles, and others. Some estimate that 1% of emergency visits are for dog bite wounds. Approximately 1% of dog bite wounds and 6% of cat bite wounds require hospitalization.1,9
International
The lack of standard reporting in many countries makes accurate estimates of animal bite incidence difficult to determine. Depending on locale, the range of animals inflicting bites is wide and includes large cats (tigers, lions, leopards), wild dogs, hyenas, wolves (Eurasia), crocodiles, and other reptiles. As in the United States, most bites, however, are from domestic dogs. In developing countries, animal bites (especially bites by dogs, cats, foxes, skunks, and raccoons) carry a high risk of rabies infection.
Mortality/Morbidity
Dog attacks kill approximately 10-20 people annually in the United States.8,10 Most of these fatalities, unfortunately, are young children. While local infection and cellulitis are the leading causes of morbidity, sepsis is a potential complication of bite wounds, particularly C canimorsus (DF-2) sepsis in immunocompromised individuals. Pasteurella multocida infection (the most common pathogen contracted from cat bites) also may be complicated by sepsis. Meningitis, osteomyelitis, tenosynovitis, abscesses, pneumonia, endocarditis, and septic arthritis are additional concerns in bite wounds. When rabies occurs, it is almost uniformly fatal.
Sex
Women are more frequently bitten by cats, whereas men are more often bitten by dogs (despite being man's best friend).11
Age
Peak incidence of animal bites occurs among children aged 5-9 years.9,8,10
Clinical
History
History for animal bites should include the following:
- Time and location of event
- Type of animal and its status (ie, health, rabies vaccination history, behavior, whereabouts)
- Circumstances surrounding the bite (ie, provoked or defensive bite versus unprovoked bite)
- Location of bites (most commonly on the upper extremities and face)
- Prehospital treatment
- Patient’s medical history (immunocompromise, peripheral vascular disease, diabetes, tetanus and rabies vaccination history)
Physical
Major resuscitation rarely is required. Because patients typically are children, reassurance and parental presence may facilitate examination. Where applicable, consider the following:
- Distal neurovascular status
- Tendon or tendon sheath involvement
- Bone injury, particularly of the skull in infants and young children
- Joint space violation
- Visceral injury
- Foreign bodies (eg, teeth) in the wound
Significant damage due to bites is shown in the images below.
The devastating damage sustained by a preadolescent male during a pit bull attack. Almost lost in this photograph is the soft tissue damage to this victim's thigh. This patient required 2 units of O- blood and several liters of isotonic crystalloid. Repair of these wounds required a pediatric surgeon, an experienced orthopedic surgeon, and a plastic surgeon. Attacks such as these have caused a movement in some areas of the country to ban pit bulls.
Massive soft tissue damage of the right leg caused by a pit bull attack. This patient was transferred to a level one pediatric trauma center for care. At times, staff members may need counseling after caring for savagely mauled patients.
Causes
Bite wounds from cats and dogs can occur without provocation, but provoked bites, such as disturbing animals while they are eating, are more common. Older animals often are less tolerant of disturbances, especially by children. Most dog bites involve a dog that belongs to the family or friend of the victim and approximately half occur on the pet owner's property.10
Certainly, unprovoked bites by wild or sick-appearing animals (most notably by dogs, cats, raccoons, foxes, skunks, and bats) further raise underlying concerns about likelihood of rabies exposure.
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References
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Chambers GH, Payne JF. Treatment of dog bite wounds. Minn Med. 1969;52:427-430. [Medline].
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Moscati RM, Mayrose J, Reardon RF, Janicke DM, Jehle DV. A multicenter comparison of tap water versus sterile saline for wound irrigation. Academic Emergency Medicine. May 2007;14 (5):404-9. [Medline].
Oehler RL, Velez AP, Mizrachi M, Lamarche J, Gompf S. Bite-related and septic syndromes caused by cats and dogs. Lancet Infect Dis. Jul 2009;9(7):439-47.
Cummings P. Antibiotics to prevent infection in patients with dog bite wounds: a meta-analysis of randomized trials. Ann Emerg Med. Mar 1994;23(3):535-40. [Medline].
Gilbert DN, Moellering RC, Eliopoulos FM, Sande MA, eds. Bites. In: The Sanford Guide to Antimicrobial Therapy. 37th ed. 2007:46,47,140.
Guy RJ, Zook EG. Successful treatment of acute head and neck dog bite wounds without antibiotics. Ann Plast Surg. Jul 1986;17(1):45-8. [Medline].
Trott A. Bite wounds. In: Wounds and Lacerations Emergency Care and Closure. 2nd ed. St Louis, Mo: Mosby-Year Book Inc; 1997:265-84.
Weber EJ. Mammalian bites. In: Marx JA, Hockberger RS, Walls RM, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 6th ed. Mosby; 2006:906-21.
Further Reading
Keywords
animal bites, animal bite management, wound management, animal bite treatment, animal bite infection, bite wound, animal bite wound, dog bite, cat bite, pet bite, wild animal bite, bite wound infection, bite-related infection, mammal bites, rodent bites, ferret bites, rabbit bites, pit bull bite, cellulitis, rabies, septic arthritis, Staphylococcus, Streptococcus, Pasteurella, Bacteroides, Capnocytophaga canimorsus, Eikenella, Enterobacter, Proteus, Haemophilus, Klebsiella, Actinomyces, Fusobacterium, Peptostreptococcus, Clostridium, Wolinella, Propionibacterium, osteomyelitis
