Animal or Human Bites in Adults - Prevention of Infection

Publication: 01/07/2009  --
Last review: 27/04/2018  
Next review: 27/04/2021  
Clinical Guideline
ID: 1752 
Approved By: Improving Antimicrobial Prescribing Group 
Copyright© Leeds Teaching Hospitals NHS Trust 2018  


This Clinical Guideline is intended for use by healthcare professionals within Leeds unless otherwise stated.
For healthcare professionals in other trusts, please ensure that you consult relevant local and national guidance.

Guideline for the Prevention of Infection Following Animal or Human Bites (including antimicrobial prophylaxis) in Adults

Animal or Human Bites in Adults - Prevention of Infection

Diagnostic criteria
Guidelines apply to any mammalian bite (including human).

No microbiology investigations required if no signs of infection.
X-ray: if suspicion of bony injury or penetrating joint injury or suspicion of retained radio-opaque foreign body (e.g. tooth).


Specialist referral
Consider referral to hand / plastic surgeons if extensive wound or complex structures involved or if cosmetic concerns e.g. facial wounds.  If there is doubt consult with a senior Emergency Department Clinician

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Two hundred thousand dog bites have been reported to occur in Britain each year (Smith et al., 2003). 0.5-1% of Emergency department visits are due to animal bites (Smith et al., 2003).  Bites may become infected or transmit infectious agents (e.g. rabies, hepatitis B, HIV).  About 9% of dog bites become infected (Smith et al., 2003) but a meta-analysis of trials revealed only one study that showed a significant benefit for antimicrobial prophylaxis – there is general agreement that routine antimicrobial prophylaxis is not required and that initial wound care is key.

Bite wounds generally contain polymicrobial flora that reflects the microbiology of the skin of the victim, the oral flora of the biter and the environment. The predominant cause of bites wound infection varies with the type of animal but broad antimicrobial cover is generally required because of the polymicrobial nature of infections. Important bacterial causes include: Pasteurella, Staphylococcus aureus, Staphylococcus intermedius, Streptococci, Capnocytophaga canimorsus and anaerobes.

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Clinical Diagnosis

If cellulitis is already present see Guidelines for cellulitis and necrotizing fasciitis for antimicrobial and treatment recommendations

Initial clinical assessment should include documenting the timing, nature and location of the bite, the animal involved and where the bite took place. Documentation should include any initial treatment, subsequent potential contamination.  In addition any immunosuppression and known allergies to antimicrobials should be established. Standard procedures should be followed relating to protection of children and vulnerable adults.
NB patients may not volunteer that a human bite has occurred – specific questioning may be required to elicit this history.

Check tetanus vaccination status.  In human bites check Hepatitis B vaccination status.

The depth of the wound should be assessed.

The wound and adjacent structures should be examined for signs of infection, foreign bodies (e.g. teeth especially in deep or crush wounds) damage to blood vessels, nerves, tendons, joints, or bones and lymphadenopathy.

Categorise wound risk according to box 1.

Wound is HIGH RISK if the dermis has been penetrated and any of the following are present

Human bites

Open fracture secondary to bite

Puncture wound (deep injury with small skin wound, e.g. cat bites)

Tendons, joint, bone, vessels involved

Hands, face, feet, genitals involved

Delayed presentation >8 hours

Alcoholic liver disease


Splenectomy and functional hyposplenism


Box 1. Categorisation of high-risk wounds (based on (Dendle & Looke, 2008; Moore, 1997))

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If there is no clinical evidence of infection at the time of presentation no microbiological investigations are required.

X-ray if bite is over a joint, wound is to/through periosteum, unable to determine depth of wound (as well as speciality referral), suspected foreign body (including tooth fragments) and suspicion of retained radio-opaque foreign body. 
Rarely tooth fragments may remain in bite wounds, particularly when high forces such as punch injuries or some dog bite injury occur.  In the presence of deep or extensive bite injuries soft tissue x-rays may be required to exclude retained foreign body.

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Antibacterial prophylaxis

Routine antimicrobial prophylaxis is not recommended for dog bites (Cummings, 1994; Smith et al., 2003). [Evidence level A].

There is general agreement that antimicrobial prophylaxis should be confined to high risk wounds (Cummings, 1994; Dendle & Looke, 2008; Smith et al., 2003) [Evidence level C]

For prophylaxis in the penicillin allergic patient, there is no evidence though Doxycycline Description: electronic Medicines Compendium information on Doxycycline has traditionally been used in many countries. The microbiological data from animal bites suggest second generation fluoroquinolones and Azithromycin Description: electronic Medicines Compendium information on Azithromycin have good activity against most of the common pathogens. Azithromycin Description: electronic Medicines Compendium information on Azithromycin is not effective against Staphylococcus intermedis (but this is uncommon). Azithromycin Description: electronic Medicines Compendium information on Azithromycin has better activity against Pasteurella and Eikenella than Clarithromycin Description: electronic Medicines Compendium information on Clarithromycin and Erythromycin Description: electronic Medicines Compendium information on Erythromycin.  Azithromycin Description: electronic Medicines Compendium information on Azithromycin also seems to have good tissue penetration, is a once daily regimen and is well tolerated. Compliance with a combination of Metronidazole Description: electronic Medicines Compendium information on Metronidazole and Doxycycline Description: electronic Medicines Compendium information on Doxycycline likely to be less compared with the more simple regimen of once daily Azithromycin Description: electronic Medicines Compendium information on Azithromycin – which also has a better safety profile.

Recommended prophylaxis for high risk wounds: Co-Amoxiclav (Amoxicillin-Clavulanate) Description: electronic Medicines Compendium information on Co-Amoxiclav (Amoxicillin-Clavulanate) 625mg three times daily for 3 days, stop if no evidence of infection at 3 day review.
[Evidence level D]

Recommended prophylaxis for high risk wounds and genuine penicillin allergy: Azithromycin Description: electronic Medicines Compendium information on Azithromycin 500mg daily for 3 days.
[Evidence level D]

If uncommon or unusual animals are involved seek expert advice (Microbiology/Infectious Diseases).

Prevention of Tetanus
A tetanus toxoid booster should be administered for patients whose immunization schedule is not up to date, or whose immune status is unknown, and further doses given to complete the five-dose schedule.

Link to guidance for tetanus prophylaxis and management of tetanus prone wounds
Link to notes for use of tetanus guidance

In human bites consider hepatitis B transmission risk
Link to Hepatitis B PGD

In human bites consider HIV transmission risk
Link to Infection control needle stick policy
Link to infection control needle stick/splash/bite injury flow chart

Rabies: animal bites
There is no risk from bites acquired in the United Kingdom. Bites acquired overseas require a risk assessment. Always seek advice from infectious diseases for patients with animal bites acquired from overseas.

Rabies: bats
Advice should be sought from PHE, Virus Reference Department (VRD), Colindale, London (Tel: 020 8327 6017).

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Non-Antimicrobial Treatment

Wound Management

  • Immediate irrigation with copious amounts (at least 250ml) of sodium chloride 0.9% or water (Dendle & Looke, 2008; Smith et al., 2003). Visible contamination should be removed with forceps or scrubbing. [Evidence level B].
  • If debridement is likely to result in a significant tissue deficit which will compromise wound closure or cosmetic outcome referral should be made to plastic surgery.
  • Primary wound closure should not routinely performed except for bite wounds on the face.  Rigorous cleansing and appropriate debridement must occur prior to any primary closure. Delayed primary closure should be considered at review at 48-72 hours. The presence of cellulitis or other obvious wound infection is a contraindication to delayed primary closure at that time.

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Treatment Failure
Please contact Microbiology if the patient is not responding to the recommended antimicrobial regimens.

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Record: 1752
  • To guide the initial management of patients presenting with animal and human bites to reduce the likelihood of subsequent complications – particularly infection.
  • To provide evidence-based recommendations for appropriate antimicrobial prophylaxis of animal and human bites
  • To recommend appropriate dose, route of administration and duration of antimicrobial agents.
  • To advise in the event of antimicrobial allergy.
  • To set out criteria for referral for surgery or specialist input.
  • To standardise the initial management of animal and human bites.
Clinical condition: Animal or human bites in adults
Target patient group: Adult
Target professional group(s): Pharmacists
Secondary Care Doctors
Secondary Care Nurses
Adapted from:

Evidence base

  • Cummings, P. (1994). Antibiotics to prevent infection in patients with dog bite wounds: a meta-analysis of randomized trials. Ann Emerg Med 23, 535-540.
  • Dendle, C. & Looke, D. (2008). Review article: Animal bites: an update for management with a focus on infections. Emerg Med Australas 20, 458-467.
  • Goldstein, E. J. C., Citron, D. M., Gerardo, S. H., Hudspeth, M, & Merriam, C.V. (1998). Activities of HMR 3004 (RU 64004) and HMR 3647 (RU 66647) Compared to Those of Erythromycin, Azithromycin, Clarithromycin, Roxithromycin, and Eight Other Antimicrobial Agents against Unusual Aerobic and Anaerobic Human and Animal Bite Pathogens Isolated from Skin and Soft Tissue Infections in Humans. Antimicrob. Agents Chemother. 42: 1127-1132.
  • Griego, R. D., Rosen, T., Orengo, I. F. & Wolf J. E. (1995). Dog, cat and human bites: a review. J Am Acad Dermatol 33, 1019-1029.
  • Health Protection Agency North West (2007). Guidelines for the management of human bite injuries.
  • Medeiros, I. & Saconato, H. (2001). Antibiotic prophylaxis for mammalian bites. Cochrane Database Syst Rev (2), CD001738.
  • Moore, F. (1997). "I've just been bitten by a dog". Bmj 314, 88-90.
  • Morgan, M. & Palmer, J. (2007). Dog bites. British Medical Journal 334, 413-417.
  • NHS Clinical Knowledge summaries. Bites - human and animal. Assessed 12th November 2008.
  • Smith, M. R., Walker, A. & Brenchley, J. (2003). Barking up the wrong tree? A survey of dog bite wound management. Emerg Med J 20, 253-255.
  • Smith, P. F., Meadowcroft, A. M. & May D. B. (2000). Treating mammalian bite wounds. Journal of Clinical Pharmacy and Therapeutics 25, 85-99.
  • Talan, D. A., Citron, D. C., Abrahamian, F. M., Moran, G. J., & Goldstein, E. J. C. (1999). Bacteriologic analysis of infected dog and cat bites. New England Journal of Medicine 340, 85-92.

Evidence levels:
A. Meta-analyses, randomised controlled trials/systematic reviews of RCTs
B. Robust experimental or observational studies
C. Expert consensus.

Approved By

Improving Antimicrobial Prescribing Group

Document history

LHP version 1.0

Related information

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