Fast Five Quiz: Dog and Cat Bites

1)Pasteurella multocida infection is the most common infection contracted from cat bites. It may also be complicated by sepsis. Wound infections associated with animal bites usually have a polymicrobial etiology. Complications include rapidly progressive cellulitis, abscesses, tenosynovitis, osteomyelitis, and septic arthritis. The latter two are particularly common after cat bites because cats have small, sharp, penetrative teeth.

2)Dog bites often cause a crushing-type wound because of their rounded teeth and strong jaws. The sharp pointed teeth of cats usually cause puncture wounds and lacerations that may inoculate bacteria into deep tissues. An adult dog can exert 200 pounds per square inch (psi) of pressure, with some large dogs able to exert 450 psi. Such extreme pressure may damage deeper structures, such as bones, blood vessels, tendons, muscle, and nerves.

3)Most cases of human rabies acquired from dogs manifest as "furious rabies." Patients develop agitation, hyperactivity, restlessness, thrashing, biting, confusion, or hallucinations. After several hours to days, this becomes episodic and interspersed with calm, cooperative, lucid periods. Furious episodes last less than 5 minutes. Episodes may be triggered by visual, auditory, or tactile stimuli or may be spontaneous. Seizures may occur. This phase may end in cardiorespiratory arrest or may progress to paralysis.

A minority of patients develop paralytic rabies, also known as "dumb rabies" or "apathetic rabies," because the patient is relatively quiet compared with a person with the furious form. Paralysis occurs from the outset, and fever and headache are prominent. Paralytic rabies may initially mimic Guillain-Barré syndrome (GBS), with ascending lower motor-neuron weakness unpreceded by classic "mad" signs, and rabies should be considered in the differential diagnosis of GBS.

According to the World Health Organization (WHO), dogs are the main source of human rabies deaths, contributing to as many as 99% of all cases. The WHO also states that the incubation period for rabies is 2-3 months but can vary from 1 week to 1 year, depending on such aspects as the location of virus entry and the viral load.

Recommendations from the Centers for Disease Control and Prevention (CDC) state that if a dog or cat appeared healthy at the time of the bite, and if the animal can be held in quarantine for 10 days, no antirabies prophylaxis is needed.

4)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 anatomical 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 versus puncture), the lower the risk for infection. In addition to the hand, bites on the feet, major joints, scalp, and face are also associated with increased risk for infection.

5)According to AAFP recommendations, although bite wounds may be closed if cosmetically desirable, wounds at high risk for infection should be left open. Antibiotic prophylaxis is recommended in high-risk bite wounds and should be considered for average-risk wounds. All cat bites are considered high risk for infection because they tend to be deep puncture wounds.

The AAFP recommends amoxicillin-clavulanate as first-line antibiotic prophylaxis in children and adults with animal bites. Alternative medications in adults include clindamycin, doxycycline, penicillin VK, a fluoroquinolone, trimethoprim-sulfamethoxazole, or cefuroxime plus either metronidazole or clindamycin. Azithromycin is recommended in pregnant women who are allergic to penicillin. Tetanus vaccination is recommended after an animal bite if it has been longer than 5 years since the patient has been immunized.