Reduce risks of infection with animal bites

When a patient presents with an animal bite, there is an extremely high risk of infection, says Timothy Erickson, MD, FACEP, director for the emergency medicine residency program and division of clinical toxicology at the University of Illinois at Chicago Medical Center. "As a result of the high infection rate and potential limb loss with more severe bites, the patient should be managed in an aggressive fashion," he stresses. Here are some ways to reduce risks of infection:

Assess for crush injury. "Regardless of the type of animal bite, domestic or wild, the key is to assess for tendon, nerve, and vascular injury," says Erickson. "Large mammal bites can result in severe crush injuries."

Know risks of suturing. "If the bite involves the extremities, suturing the wound is discouraged since they are very prone to infection," says Erickson. "Tight suturing of an extremity wound will invite infections to develop."

If the wounds to the extremities are large, deep, and jagged, loose approximation of the wound borders may be acceptable, but this is controversial, says Erickson. "Bites to the face can be sutured if necessary for cosmetic reasons, since the vascular supply is much more plentiful than with the extremities."

Reduce risks of infection. "Most types of bites, particularly cats, cause deep puncture wounds and are a set-up for wound infections and cellulitis," says Erickson. Debride crushed and devitalized tissue if possible, he advises.

Assess for foreign body by wound exploration and/or radiograph, says Erickson. "A retained foreign body is a common cause of wound infection," he stresses. "Antibiotics are indicated for larger, deep bite wounds, particularly to the extremities. The type of antibiotic depends on the type and source of the bite."

Most clinicians prescribe augmentin (amoxicillin plus clavulinic acid) or dicloxicillin for dog and cat bites, says Erickson. "For penicillin-allergic patients, clindamycin and TMP-SMX are generally recommended," he notes.

"Dog bites to the face do not usually require antibiotics as long as the wound is small and wound follow-up in 24-28 hours can be assured," he notes.

Pasturella multicida, a common pathogen in cat bites, is resistant to dicloxacillin, notes Edward Otten, MD, professor of emergency medicine at the University of Cincinnati and president of the Wilderness Medical Society, based in Indianapolis. "Instead, use augmentin or cefuroxime," he recommends.

Provide prevention information. Remind campers not to pet animals, and don't leave food out around a campsite, says Otten. "Do not feed any wild animal. This includes chipmunks and bison," he stresses. "Keep food out of tents and wash hands after cleaning fish, cooking, and eating."

If camping in bear country, banging pots and pans together or speaking in loud voices is recommended while hiking, to give the animals a chance to hide, says Erickson. "If surprised, these and other larger mammals will bite in self defense," he adds. "If a human slowly backs away from the animal without making sudden or threatening gestures, usually no harm will come."

Don't miss rabies. Dog bites in the United States rarely result in rabies. "However, if a patient has been traveling in a developing country, dog bites may transmit rabies since immunizations are not routinely administered," says Erickson.

Check with local public health officials to determine if rabies is common in your area. "In this area, raccoons, bats, and skunks commonly carry rabies, but cats and dogs rarely if ever have it, so we normally don't worry about it," says Otten. "But dogs along the Texas-Mexico border commonly carry rabies, so you'd have to worry there."

Regardless, public health officials need to be notified about any bite so the animal can be quarantined for a 10-day period to see if it shows signs of illness. "If a stray dog bites you and takes off, then it's a difficult decision to make. But if there is any question, then I would go ahead and give the rabies prophylaxis," says Otten. "Rabies is a universally fatal disease and if you can prevent it, you definitely want to do that."

Other animal bites prone to rabies in the United States include skunks, bats, foxes, and raccoons. "Contrary to popular belief, rat and other rodents, such as squirrels, do not transmit rabies," says Erickson. "However, they are prone to wound infection."

Irrigate thoroughly. "Copious wound irrigation with 0.9 normal saline is the cornerstone of wound management," says Erickson.

Don't miss dirt. "If you have dirt in a bite wound, the number of bacteria you need for infection goes way down," says Otten. "You are much more likely to get infection if there is foreign material in the wound, such as dirt, or a piece of rock or twig."

Don't soak bite wounds. "Soaking things is worthless," says Otten. "Often, if somebody comes in with a cut on their foot, nurses will give them a pan of betadyne to soak their foot in. That doesn't get any dirt out."

Soaking can actually be harmful. "Anything other than hibicleanse, water, and 1% betadyne isn't good for the wound," says Otten. "Peroxide, soap, and detergent really aren't good for the wound. Peroxide kills off white blood cells, so you are actually doing harm when you pour it over a wound. You are better off picking out big pieces of dirt and irrigating with a syringe with an 18 or 19 gauge catheter."

Ensure tetanus immunization is up to date. "Make sure tetanus is up to date with any kind of a bite. Nurses are more prone to keep an eye on that information than physicians are," says Otten. "If the patient is unsure, I give it to them, because all bites are tetanus prone wounds."