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Guideline review – human and animal bites: antimicrobial prescribing
  1. Peter Fielding,
  2. Shrouk Messahel
  1. Paediatric Emergency Department, Alder Hey Children's NHS Foundation Trust, Liverpool, UK
  1. Correspondence to Dr Peter Fielding, Paediatric Emergency Department, Alder Hey Children's NHS Foundation Trust, Liverpool L12 2AP, UK; fielding.peter2{at}gmail.com

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Background

An estimated 1%–2% of all new presentations to emergency departments in the UK are caused by animal bites.1 It is reported that roughly 50% of people sustain animal bites in their lifetime, with more than 90% of those from domestic animals.2 Dog bites are the most common presenting bite injury, followed by cat and human bites, respectively.3 4 It is difficult to define the incidence of human and animal bite injuries in the wider population, as many people do not report them, nor do they seek medical attention for them.3

Information about the guideline

This guideline was produced by the National Institute for Health and Care Excellence (NICE) in 2020. There are no former guidelines to which this is an amendment or addition.

The guideline covers the assessment and management of human and common domestic animal bites in adults, young people and children. Its overall aim is to rationalise the use of antibiotics in bite injuries, and to prevent antimicrobial resistance.

Topics covered include distinguishing between infected and non-infected wounds, when to offer antibiotic prophylaxis for non-infected bite wounds and how to treat bites which are suspected to be infected.

Only the paediatric guidance is summarised here. It sits alongside broader NICE guidance on other sources of bites and stings (box 1).

Box 1

Link to the guideline

Human and Animal Bites: Antimicrobial Prescribing: https://www.nice.org.uk/guidance/ng184.

  • NHS, National Health Service; NICE, National Institute for Health and Care Excellence.

Key issues

Assessing a bite wound

Assess and document:

  • Whether the bite is from a human or animal (and from which type of animal).

  • All parts of the anatomy which have sustained a bite wound.

  • The depth of the wound.

  • The risk of tetanus, rabies and bloodborne viral infections, and take appropriate action (beyond the scope of this guideline).

  • Irrigation, cleansing and debridement of the wound as required.

  • Any safeguarding concerns, and the action taken.

Refer children for hospital admission if they have:

  • Symptoms or signs suggestive of serious illness, such as sepsis, severe cellulitis, abscess, osteomyelitis, septic arthritis or necrotising fasciitis.

  • A penetrating wound involving arteries, joints, nerves, muscles, tendons, bones or the central nervous system.

The severity of the wound

Infection

Signs of an infected wound include signs of inflammation (swelling, redness and warmth) local to the wound, fever, discharge or an unpleasant smell, and disproportionate levels of pain.

Any penetrating, deep, puncture or crush wound, or a bite which has caused significant tissue damage or which is visibly contaminated, should raise concern for infection.

All children who become systemically unwell after a bite wound (feverish, tachycardic, tachypnoeic, evidence of poor perfusion or end organ dysfunction), or who have evidence of cellulitis, abscess, osteomyelitis, septic arthritis or necrotising fasciitis, should be treated for infection.

High-risk anatomical areas

The following areas are high risk for bite injuries: hands, feet, face, genitals, skin overlying cartilage or areas of poor circulation. The hands and feet are high risk as they have multiple small compartments and many joints.

Comorbidity

Always consider whether your patient has any comorbidity which makes them more susceptible to serious infection. This includes, but is not limited to: diabetes, immunosuppression, asplenia or decompensated liver disease.

Antibiotic prophylaxis for uninfected bites

Figure 1A–C below outlines when to offer antibiotic prophylaxis for bites which do not appear to be infected.

Figure 1

(A) Non-infected human bite; (B) non-infected cat bite; (C) non-infected dog (or other traditional pet) bite.

Cat bites are dealt with as a separate entity, as the sharp teeth create deep, narrow puncture wounds which are difficult to irrigate and assess.

Advice for dog bites extends to traditionally kept pets, such as rabbits and hamsters.

Specialist advice should be sought for bites from wild or exotic animals, and any non-traditional pets. This would include birds, snakes, lizards, monkeys and bats, farmyard animals and also any pets you are not familiar with. This is because the spectrum of bacteria from such animals’ bites is different than that found with more traditional pets, and there may be additional risks of non-bacterial infection.

The antibiotic of choice for prophylaxis is the same as that used in the treatment of infected wounds, and is covered below. The duration of prophylactic antibiotics is 3 days.

Infected bites

Always take a microbiology swab for culture and sensitivity in any bite wound which has discharge, whether purulent or non-purulent.

A treatment course of antibiotics for an infected wound is 5 days.

The course length can be increased to 7 days (with review) based on clinical assessment of the wound. If there is significant tissue destruction, or penetration of tendon or vascular structure, a 7-day course would be advised. Septic arthritis or osteomyelitis requires a longer course of treatment, with antibiotics extended to 3–4 weeks with infectious disease team advice.

Reassessment

Animal or human bites should be reassessed if:

  • Symptoms or signs of infection develop or rapidly worsen, or do not start to improve within 24–48 hours of treatment.

  • Child becomes systemically unwell.

  • Child has significant pain which is out of proportion to the wound or local infection.

Chase up any microbiology swabs which have been sent, and if a change in antibiotic treatment is indicated based on sensitivity results, aim to use an antibiotic which is as narrow in spectrum as possible.

At review, the following situations should prompt referral to general paediatric inpatient teams for assessment and management:

  • Children who have symptoms or signs of infection after taking prophylactic antibiotics.

  • Children with lymphangitis.

  • Children who cannot take oral antibiotics.

  • Infected bites which are not responding to oral antibiotics.

  • Bites in areas of poor circulation, such as a limb or part of the body with pre-existing venous or lymphatic stasis.

Recommended antibiotic choice (table 1)

Table 1

Antibiotic choice (3-day course for prophylaxis, 5-day course for treatment)

Give oral antibiotics if the child is able to take oral medication, and the severity of their condition is not deemed to require intravenous antibiotics.

Advice on dosing of the above medications can be found in the full guideline (link in box 1) and in the BNF for Children, which also contains advice for dose adjustment in renal or hepatic impairment, or during pregnancy/breast feeding.

Underlying evidence base

Evidence was only available for managing bites from humans, dogs and cats.

The guideline committee agreed it was reasonable to extrapolate evidence from human, dog and cat bites to other traditionally kept pets, such as rabbits and hamsters.

Aggregate evidence on human bites suggests that prophylactic antibiotics are more effective than placebo at reducing the incidence of infection.5 6

In human bites that broke the epidermis but did not draw blood, and in anatomical areas not at high risk, studies show rates of infection to be low.5

A small study of cat bites (n=11)6 did not show a statistically significant difference between antibiotic prophylaxis versus placebo in terms of reducing the incidence of infection in cat bites.

Evidence from dog bites did not show a statistically significant difference between antibiotic prophylaxis and placebo for reducing the incidence of infection after a dog bite.6 7

There was no evidence on the treatment of human or animal bites.

The guideline committee used expert opinion, collective experience and current practice in producing this guideline. The advice for dog bites was extrapolated to other traditional domesticated pets by consensus opinion.

There was also no evidence base to inform antibiotic choice. The committee based their antibiotic recommendations on the need to cover the most common aerobic and anaerobic organisms isolated from human, cat and dog bites, and on knowledge of antimicrobial resistance in these organisms.

What do I need to know?

What should I start doing?

For non-infected bites, use the flow charts to determine whether prophylactic antibiotics are required.

Prophylactic antibiotics should be prescribed for 3 days. Oral co-amoxiclav is the first-line recommendation in most cases.

If a wound shows evidence of infection, take a microbiology swab for culture and sensitivity.

Antibiotics for treatment of infection should be prescribed for 5 days. Oral co-amoxiclav is the first-line recommendation in most cases.

Bites from exotic, non-traditional pets, farmyard animals or animals you are not familiar with should be discussed with a microbiologist.

What should I continue doing?

Seek specialist advice and consider referral and admission to hospital for more complex injuries involving at-risk body areas or wounds demonstrating significant tissue damage.

Consider comorbidity in determining whether a person is more at risk of serious infection to inform management choices.

Consider safeguarding of children presenting with any form of bite injury—involve safeguarding team and act accordingly.

Critical review

This guideline outlines antibiotic treatment recommendations for human and animal bites in children.

The evidence base behind the recommendations is limited and involves studies with small sample sizes. The guideline acknowledges that the quality of the evidence in most areas is poor. As a result of this, consensus opinion is used from a multiprofessional committee to mitigate risk of infection from bite injuries in the absence of a robust evidence base. The rationale outlined in the guideline for their choices appears sound.

Ongoing monitoring of antimicrobial resistance patterns and the types of organism cultured from such bites is likely to inform any further changes to practise in the future.

Take home messages

  • The main factors determining management are the location, depth of the bite, whether inflicted by a human or animal, and the species of the animal.

  • Co-amoxiclav is the antibiotic of choice for prophylaxis and treatment, unless contraindicated.

  • Antibiotic prophylaxis is a 3-day course, treatment is a 5-day course.

Ethics statements

Patient consent for publication

References

Footnotes

  • Contributors PF prepared and authored the manuscript, along with all figures and tables (first author). SM reviewed and edited the manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Commissioned; externally peer reviewed.