Bite

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Alejandro Lemor, M.D. [2]

Overview

A bite is a wound received from the mouth (and in particular, the teeth) of an animal or person. Most animal bites are from dogs or cats, and the pathogens in the wound are composed by the normal oral flora of the biting animal and human skin flora.

Animals may bite in self-defense, in an attempt to predate food, as well as part of normal interactions. Other bite attacks may be apparently unprovoked, especially in the case of bites committed by psychologically or emotionally disturbed humans. Some disorders such as Lesch-Nyhan syndrome may cause people to bite themselves.

Bite wounds can be very complex and it is important to address the following aspects:

• Generalized tissue damage due to tearing and scratching.
• Serious hemorrhage if major blood vessels are pierced.
• Infection by bacteria or other pathogens, including rabies.
• Introduction of venom into the wound by venomous animals such as some snakes.
• Introduction of other irritants into the wound, causing inflammation and itching.

Common Pathogens

Almost every bite will have a polimicrobial contamination and some bites have characteristic pathogens associated to the oral flora of the animal that bit.

Most common pathogens according to the type of bite

Bite	Most Common Pathogens
Human	Viridans streptococci, S. epidermidis, Corynebacterium, S. aureus, Eikenella, Bacteroides, Peptostreptococci
Dog	Pasteurella canis,Pasteurella multocida, S. aureus , Streptococci , Anaerobes (Bacteroides spp, Fusobacterium, Prevotella heparinolytica, Proprionibacteria, and Peptostreptococci)
Cat	Pasteurella multocida, S. aureus, Streptococci , Anaerobes (Bacteroides spp, Fusobacterium, Prevotella heparinolytica, Proprionibacteria, and Peptostreptococci)
Pig	Pasteurella spp, Gram-negative bacilli, Gram-positive cocci, Anaerobes
Monkey	Herpesvirus simiae (B Virus)
Rat	Spirillum minus, Streptobacillus moniliformis
Seal	Mycoplasma spp
Camel	S. aureus, S. epidermidis, Moraxella catarrhalis, Klebsiella pneumoniae, S. pyogenes,E. coli, Pseudomonas aeruginosa, Bacillus spp.

Treatment

• All bite wounds should be cleaned profusely with iodide soap and water.

• Bites are contaminated by a polimicrobial flora and antibiotic prophylaxis treatment is recommended to avoid subsequent infection.

• The route of administration depends on the depth and severity of the wound, as well as the time that has passed since the bite.

Antibiotic TherapyAdapted from Guidelines for Skin and Soft-Tissue Infections CID 2005

▸ Click on the following categories to expand treatment regimens.

Antibiotic Prophylaxis   ▸  Any Type of Bite Specific Therapy   ▸  Bat Bite   ▸  Camel Bite   ▸  Cat Bite   ▸  Dog Bite   ▸  Human Bite   ▸  Monkey / Primate Bite   ▸  Pig (Swine) Bite   ▸  Racoon Bite   ▸  Rat Bite   ▸  Seal Bite   ▸  Skunk Bite

Antibiotic Prophylaxis Preferred Regimen ▸ Amoxicillin-clavulanate 500-875/125 PO q8-12h Alternative Regimen ▸ Clindamycin 300 mg q8h OR ▸ Metronidazole 500 mg PO q8h PLUS ▸ Doxycycline 100 mg q12h OR ▸ TMP-SMX 160/800 mg PO q12h OR ▸ Penicillin VK 500 mg PO q6h OR ▸ Cefuroxime 500 mg PO q12h OR ▸ Moxifloxacin 400 mg PO q24h Human Bite Preferred Regimen ▸ Ampicillin sulbactam 1.5 g IV q6h OR ▸ Cefoxitin 2 gm IV q8h OR ▸ Ticarcillin clavulanate 3.1 g IV q6h OR ▸ Piperacillin-tazobactam 3.375 g IV q6-8h Alternative Regimen (beta-lactam allergy) ▸ Clindamycin 300 mg PO q8h PLUS ▸ Ciprofloxacin 500-750 mg IV q12h OR ▸ Moxifloxacin 400 mg IV q24h OR ▸ TMP-SMX 160/800 mg q12h Dog Bite Preferred Regimen ▸ Amoxicillin-clavulanate 500-875/125 PO q8-12h Alternative Regimen (beta-lactam allergy) ▸ Clindamycin 300 mg PO q8h PLUS ▸ Ciprofloxacin 500-750 mg IV q12h OR ▸ Moxifloxacin 400 mg IV q24h OR ▸ Gatifloxacin 400 mg q24h Cat Bite Preferred Regimen ▸ Amoxicillin-clavulanate 500-875/125 PO q8-12h Alternative Regimen (beta-lactam allergy) ▸ Cefuroxime 500 mg q12h OR ▸ Doxycycline 100 mg q12h Pig (Swine) Bite Preferred Regimen ▸ Amoxicillin-clavulanate 875/125 mg PO q12h Alternative Regimen ▸ Ampicillin sulbactam 1.5 to 3 g IV q6-8h OR ▸ Imipenem cilastatin 1 g IV q6-8h OR ▸ Ceftriaxone 1 g q12 h OR ▸ Cefotaxime 2 g q6 h OR ▸ Ticarcillin clavulanate 3.1 g IV q6hr Monkey / Primate Bite Profilaxis ▸ Valacyclovir 1 g PO q8h x 14 days OR ▸ Acyclovir 800 mg PO 5 times/day Preferred Regimen (without CNS symptoms) ▸ Acyclovir 12.5–15 mg per kg IV q8h OR ▸ Ganciclovir 5 mg per kg IV q12h Preferred Regimen (with CNS symptoms) ▸ Ganciclovir 5 mg per kg IV q12h Adapted from Prevention of and Therapy for B Virus Exposure • CID 2002:35 Uncomplicated Rat Bite Preferred Regimen ▸ Amoxicillin-clavulanate 875/125 mg orally q12h Alternative Regimen (beta-lactam allergy) ▸ Doxycycline 100 mg orally q12h Rat Bite Fever Preferred Regimen ▸ Penicillin G 400,000 - 600,000 IU/day IV x 10-14 days (dose should be increased to 1.2 M if no clinical response) Alternative Regimen ▸ Streptomycin 15 mg/kg/day IM divided q12-24h x 10-14 days OR ▸ Tetracycline 250 to 500 mg orally q6h Adapted from Clin. Microbiol. Rev. January 2007 vol.20 no.1 13-22 Seal Bite Preferred Regimen ▸ Tetracycline 1.5 g 1 dose, then 0.5 g q6h x 4-6 weeks Alternative Regimen ▸ Doxycycline 100 mg q12h x 4-6 weeks Adapted from Journal of Infection (2002) 45: 71±75 Camel Bite Preferred Regimen ▸ Dicloxacillin 250–500 mg PO q6h PLUS ▸ Ciprofloxacin 750 mg PO q12h Alternative Regimen ▸ Cephalexin 500 mg PO q6h PLUS ▸ Ciprofloxacin 750 mg PO q12h Adapted from Eur J Clin Microbiol Infect Dis. 1999;18(12):918-9. Bat Bite Preferred Regimen ▸ Amoxicillin-clavulanate 875/125 mg orally q12h Alternative Regimen ▸ Doxycycline 100 mg orally q12h Racoon Bite Preferred Regimen ▸ Amoxicillin-clavulanate 875/125 mg orally q12h Alternative Regimen ▸ Doxycycline 100 mg orally q12h Skunk Bite Preferred Regimen ▸ Amoxicillin-clavulanate 875/125 mg orally q12h Alternative Regimen ▸ Doxycycline 100 mg orally q12h

Vaccination

Tetanus Prophylaxis

The need for active immunization, with or without passive immunization, depends on the condition of the wound and the patient’s immunization history. The following table summarizes the indications for tetanus prophylaxis.

Vaccination History	Clean, minor wounds		All other wounds
	Td†	Tetanus immune globulin (TIG)	Td†	Tetanus immune globulin (TIG)
Unknown or less than 3 doses	YES	NO	YES	YES
3 or more doses
If > 10 yrs since last dose	YES	NO	YES	NO
If > 5 yrs since last dose	NO	NO	YES	NO
†Tdap may be substituted for Td if the person has not previously received Tdap and is 10 years or older
Table adapted from CDC Vaccines and Immunizations - Tetanus

Rabies Prophylaxis Adapted from CDC - ACIP Recommendations for postexposure prophylaxis (PEP) to prevent human rabies.

Animal bites inflicted by carnivores (except rodents) are considered possible cases of rabies. The animal is caught alive or dead with its head preserved, so the head can later be analyzed to detect the disease.

If the animal lives for ten days and does not develop rabies, then it is probable that no rabies infection has occurred.

If the animal is gone, prophylactic rabies treatment is recommended.

Signs of animal rabies include:

• Foaming at the mouth
• Self-mutilation
• Growling
• Jerky behavior
• Red eyes.

Indications for rabies prophylaxis

Animal Type	Evaluation of the Animal	Prophylaxis Recommendation
Dog, cat, ferret	Healthy and available for observation for 10 days	Prophylaxis should not be started unless the animal develops symptoms If rabies symptoms develop, immediately begin rabies prophylaxis
	Confirmed or suspected rabies infection	Immediately begin rabies prophylaxis
	Unknown	Immediately begin rabies prophylaxis
Skunk, raccoon, bat, fox, coyote, other carnivores	Considered as rabies infection	Immediately begin rabies prophylaxis
Livestock, rodents, rabbit, squirrels, hamster, guinea pig, gerbil, chipmunk, rat, mouse, woodchuck		Almost never require anti-rabies prophylaxis, but consult public health officials

▸ Click on the following categories to expand prophylactic regimens.

Rabies Prophylaxis   ▸  Patient Not Previously Vaccinated   ▸  Patient Previously Vaccinated

Patient Not Previously Vaccinated Prophylactic Regimen ▸ Wound cleansing PLUS ▸ Human rabies immune globulin† (HRIG) 20 IU/kg If anatomically feasible, the full dose should be infiltrated around and into the wound, and any remaining volume should be administered IM PLUS ▸ Human diploid cell vaccine (HDCV) 1.0 mL IM OR ▸ Purified chick embryo cell vaccine (PCECV) 1.0 mL IM Administer 4 doses in total; on days 0, 3, 7 and 14¶ †HRIG should not be administered in the same syringe as vaccine. ¶ For suppressed patients administer an additional dose on day 28 Patient Previously Vaccinated Prophylactic Regimen ▸ Wound cleansing PLUS ▸ Human diploid cell vaccine (HDCV) 1.0 mL IM OR ▸ Purified chick embryo cell vaccine (PCECV) 1.0 mL IM Administer 2 doses in total; on days 0 and 3 HRIG should not be administered.

See Also

• Snakebite
• Spider bite
• Wilderness first aid
• Insect bites and stings

External links

• Treating human bites