1. Cat and Dog Bites “Women and cats will do as they please, and men and dogs should relax and get used to the idea” — Robert Heinlen

2. Prevalence While most cat and dog bites are minor, they do account for as many as 1% of ER visits. Pit bulls account for most of the deaths due to dog bites in the US, although there is only one death for every 16,000 ER visits (10- 20 per year total). These bites occur most commonly on the upper extremities. In adults, most bites are work-related.

3. Presentation Wounds should be searched for signs of infection such as localized cellulitis, purulent discharge, or joint penetration. Infection usually manifests as cellulitis at the site of injury. In one study, cat bites led to infection in about 12 hours, compared to dog bites, which took 24 hours.

4. Microbiology Pasteurella multocida is a Gram negative coccobacillus that is classically associated with cat bite wound infections, although it is also present in 20-50% of dog bite wound infections. Other species of Pasteurella can also occur (canis for dog, multocida and septica for cats). Cultures have grown multiple organisms, including Staph, Strep, anaerobes, and Gram negatives. Over half of animal bite infections are mixed anaerobe and aerobes. Wound cultures immediately after bites are generally unhelpful as isolates do not correlate with risk of infection or pathogens after infection becomes apparent. However, cultures may be helpful if infection is clinically apparent.

5. Treatment Prophylactic antibiotics have been used to prevent infection, with several trials showing no significant benefit and one showing a statistically significant benefit to those treated at least 9 hours after the bite with amoxicillin/clavulanate. A metaanalysis showed a NNT of 14 to prevent one infection. Cipro/clinda may be used for those with PCN allergy, while TMP-SMX/clinda may be used in children. Risk factors used to help guide the decision on whether to initiate prophylactic antibiotics include: - Wounds on hand, head, or neck - Deep puncture wounds (most cat bites given slender and sharp teeth) - Wounds requiring surgical debridement - Elderly patients - Immunocompromise - Wound in extremity with prosthetic joint - Wound in extremity with venous or lymphatic compromise

6. Treatment (cont.) Besides antibiotics for prophylaxis, or treatment if infection is present, management includes washing with soap and water. Plain radiographs should be obtained for bite wounds that appear infected. Wound closure should not be performed if the wound is on the hand or is a puncture wound such as a cat bite. Tetanus toxoid booster should be given if the patient has not received this in the past 5 years. PTSD can develop in children after dog bite, and they should be assessed for this as well.

7. Rabies Prophylaxis Due to immunization programs in the US, rabies has been essentially eliminated from domesticated animals and most cases of rabies in this country are from wild animals such as bats, raccoons, skunks, foxes, coyotes, woodchucks, and beavers. No documented human cases of rabies have come from animals as small as squirrels. Rabies has been found in bats in all of the 49 continental states.

8. Rabies Prophylaxis (cont.) Rabies accounts for 50,000 deaths worldwide yearly, with 90% of these cases from dogs. However, there were only 36 cases of rabies in the US between 1980 and 2000. 12 of these were due to exposure to foreign dogs and 21 were due to bat exposures. Rabies can be transmitted through bites, mucous membrane exposure, or even organ donation from infected individuals. Rabies cannot be transmitted through blood, feces, guano, urine, or from non-mammals. Cleaning the wound reduces risk of rabies transmission by 90%.

9. Rabies Prophylaxis (cont.) Incubation of rabies can be as fast as 4 days, particularly with bites close to the CNS (neck). Alternatively, there may be a latency period of several years. Anyone with potential rabies exposure should receive the rabies vaccine series (to promote active response within 7-10 days) as well as rabies immune globulin (passive response) injected at the site of the bite. If the animal is alive after 10 days, it did not have rabies and the treatment can be stopped. The animal can also be euthanized and tested for rabies. Veterinarians and others who have previously received rabies vaccination need only the vaccine after an exposure and not the immune globulin. The vaccine has been administered to pregnant women without complications.

10. References 1. Fleisher, GR. The management of bite wounds. N Engl J Med 1999; 340:138. 2. Talan DA, Citron DM, et al. Bacteriologic analysis of infected dog and cat bites. Emergency Medicine Animal Bite Infection Study Group. N Engl J Med 1999;340:85-92. 3. Raj, N., Nayar, R., et al. Once bitten, twice shy!. Ann Rheum Dis 2000; 59: 684-687 4. Brakenbury PH, Muwanga C. A comparative double blind study of amoxycillin/clavulanate vs placebo in the prevention of infection after animal bites. Arch Emerg Med 1989;6:251-256 5. Cummings P. Antibiotics to prevent infection in patients with dog bite wounds: a meta-analysis of randomized trials. Ann Emerg Med 1994;23:535-540 6. Dire DJ; Hogan DE; Riggs MW. A prospective evaluation of risk factors for infections from dog-bite wounds. Acad Emerg Med 1994 May- Jun;1(3):258-66. 7. United States, 1999. Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Morb Mortal Wkly Rep 1999; 44(RR-1). 8. Investigation of rabies infections in organ donor and transplant recipients-- Alabama, Arkansas, Oklahoma, and Texas, 2004. MMWR Morb Mortal Wkly Rep 2004 Jul 9;53(26):586-9. 9. UpToDate, Online version 13.1, 2005.