Animal bites are added under "INFECTIOUS DISEASES" because the major difficulty with bites, besides the trauma, which can be minor or major, is the likelihood of infection to skin and soft tissues. With many parts of the hand (tendon sheaths, bones, ligaments, etc.) and legs compartmentalized, they are areas very vulnerable to the rapid spread of infection via tissue spaces and lymphatics. Also, since some infectious diseases (such as rabies) attack the central nervous system faster, the closer the bite is to the brain, facial bites increase dramatically in importance for immediate care.

 

Epidemiology

• Cat bites: more common in women than men.
• Dog bites: more common in men than women.
• ALL BITES: more common in children than adults.

INFECTIOUS AGENTS ASSOCIATED WITH BITES: The predominant pathogens in animal bite wounds are the oral flora of the biting animal and human skin flora.

• Animal flora: About 85% of bites harbor potential pathogens, and the average wound yields five types of bacterial isolates; 60% have mixed aerobic and anaerobic bacteria.

• Pasteurella species are isolated from 50% of dog bite wounds and 75% of cat bite wounds.
• Capnocytophaga canimorsus can cause bacteremia and fatal sepsis after animal bites, especially in patients without spleens or those with liver disease.
• Anaerobes isolated from dog and cat bite wounds include
  • Bacteroides,
  • Fusobacteria,
  • Porphyromonas,
  • Prevotella,
  • Cutibacteria (formerly propionibacteria), and
  • Peptostreptococci.

• Human flora: Skin flora such as staphylococci and streptococci, including MRSA, are isolated in about 40% of bites.

 

Signs and Symptoms

• Fever,
• erythema,
• swelling,
• tenderness,
• purulent drainage and
• lymphangitis.

 

Complications

• Subcutaneous abscesses,
• osteomyelitis,
• septic arthritis,
• tendonitis,
• bacteremia.

And when involving cats,

• Cat scratch fever is an infectious disease typically characterized by self-limited regional lymphadenopathy, although it can become complicated by visceral organ, neurologic, and ocular involvement.

Besides from scratch or bite from an infected cat, it can also spread by exposure to cat fleas, contact with cat saliva through broken skin or mucosal surfaces (e.g., mouth and eyes), and even from exposure to dogs via flea bites.

• Rabies: Rabies is endemic in some animals, such as bats. (Any bat bite from one that gets away mandates rabies post-exposure therapy. Any unknown animal bite or bite from an animal known to carry rabies mandates a rabies prevention protocol consisting of serial immunoglobulin injections, tetanus coverage, and possibly IM corticosteroids. It is noteworthy that exposure to rabies can occur from the droppings of bats and other animals.

Animal bites considered suspect:

• Any unknown or feral dogs and cats.
• Raccoons.
• Skunks.
• Foxes.
• Woodchucks.
• Beavers. 
• Coyotes.
• Bobcats.
• Mountain lions.
• Wolves.
• Bears (although rabies prophylaxis is the least of your troubles!).

If the wound is superficial, rabies prophylaxis can be delayed briefly if the animal is available for rabies testing.

Animal bites not considered suspect:

• Squirrels.
• Chipmunks.
• Rats.
• Hamsters.
• Gerbils.
• Guinea gigs.
• Mice.
• Rabbits/hares. 
• Livestock.

 

Management

First, copious irrigation, preferably with sterile saline, and removal of visible debris.

Then:

• Prophylactic antibiotics, specifically amoxicillin-clavulanate.
• Tetanus immune globulin and tetanus toxoid to everyone with < 3 prior immunizations.
• Possible rabies prophylaxis if indicated.

If the infection has progressed to deep layers or severe infection, IV antibiotics should be used.

Infected wounds and deep punctures should be left open to drain and eventually heal spontaneously. Roofing over a deep deposit of bacteria is a frequent and calamitous mistake.

In the field, your response is limited to

• copious irrigation,
• containing blood loss and
• transport for ER evaluation and for antibiotic coverage.

Since children are the most common victims, reassurance in a calm setting and informative communication with the parent(s) is a hallmark of transport. As in any transport, attention is prioritized for maintenance of ABC (airway, breathing, circulation), especially with bites to the throat and neck or deep punctures to the chest area. Pain management or even sedation (with children) may be necessary.

Also, involve the proper authorities in identifying and securing the biting animal. This is important forensically to rule out rabies, which is uniformly fatal if untreated.