Human and Animal Bites

Introduction | Aetiology and Types of Bites | Clinical Presentation | Diagnosis | Management and Treatment | Legal and Ethical Considerations | Prevention | When to Refer | Patient Education and Support | References

Introduction

Human and animal bites are common injuries that can lead to significant morbidity due to the risk of infection, tissue damage, and potential complications. These bites often require prompt medical attention to prevent infections and ensure proper wound management. The management of bites varies depending on the species of the biting animal, the severity of the injury, and the risk of infection, particularly rabies in the case of animal bites.

Aetiology and Types of Bites

Bites can be classified based on the source of the injury, with specific considerations for each type:

• Human Bites: Human bites can be either intentional (e.g., during a fight) or accidental (e.g., a child biting another). These bites are particularly concerning due to the high bacterial load in the human mouth, including Streptococcus, Staphylococcus aureus, and anaerobes like Eikenella corrodens. Human bites are prone to infection and can lead to severe complications if not managed properly.
• Dog Bites: Dog bites are the most common animal bites and can vary in severity from superficial wounds to deep lacerations or crushing injuries. The bacterial flora in dog bites often include Pasteurella multocida, Staphylococcus, Streptococcus, and anaerobes.
• Cat Bites: Cat bites tend to cause puncture wounds that can penetrate deeply, leading to a higher risk of infection. Pasteurella multocida is a common pathogen in cat bites, which can cause rapidly progressing infections.
• Other Animal Bites: Bites from other animals such as rodents, bats, monkeys, or livestock can pose risks of specific infections, including rabies, tetanus, and other zoonotic diseases. The management of these bites depends on the type of animal and the circumstances of the bite.
• Exotic Animal Bites: Bites from exotic pets like snakes, spiders, or lizards may introduce unusual pathogens or venom, requiring specific management.

Clinical Presentation

The clinical presentation of a bite injury varies depending on the severity of the bite and the organism involved:

• Wound Appearance: Bites may present as puncture wounds, lacerations, abrasions, avulsions, or crushing injuries. The wound may appear erythematous, swollen, and tender.
• Signs of Infection: Redness, warmth, swelling, and purulent discharge are common signs of infection. Fever, lymphadenopathy, and malaise may also be present in more severe infections.
• Deep Tissue Damage: Severe bites may involve damage to underlying structures such as tendons, muscles, nerves, and bones, leading to functional impairment.
• Systemic Symptoms: In cases of severe infection or sepsis, the patient may present with systemic symptoms such as fever, chills, tachycardia, hypotension, and altered mental status.
• Allergic Reactions: Some patients may experience allergic reactions to animal saliva, ranging from localised urticaria to anaphylaxis.
• Psychological Impact: Bites can cause significant psychological distress, including fear, anxiety, or post-traumatic stress disorder, especially in children.

Diagnosis

Diagnosis is based on a thorough history and clinical examination, with additional investigations as needed:

• History: A detailed history of the bite, including:
  • Type of animal and its vaccination status, if known.
  • Circumstances of the bite (provoked or unprovoked).
  • Time elapsed since the bite.
  • Previous medical history, including immunocompromised status and allergies.
  • Tetanus and rabies immunisation status.
• Clinical Examination: Assess the extent of the wound, signs of infection, and any involvement of deeper structures. Look for evidence of neurovascular compromise, tendon damage, or fractures.
• Imaging:
  • X-rays: May be necessary to assess for foreign bodies (e.g., teeth fragments), fractures, or involvement of bones and joints.
  • Ultrasound or MRI: Consider if soft tissue involvement or abscess formation is suspected.
• Laboratory Tests:
  • Full Blood Count (FBC): May show leukocytosis indicating infection.
  • C-Reactive Protein (CRP) and Erythrocyte Sedimentation Rate (ESR): Elevated levels can indicate the presence of infection or inflammation.
  • Blood Cultures: In cases of suspected sepsis.
  • Wound Culture: A swab for bacterial culture and sensitivity can help guide antibiotic therapy, especially in infected wounds.
  • Rabies Testing: In rare cases, testing the animal or patient for rabies may be considered.

Management and Treatment

Management of human and animal bites involves wound care, infection prevention, and consideration of prophylactic measures:

1. Wound Care

• Immediate Cleaning: Encourage bleeding by gently squeezing the wound. Thoroughly irrigate the wound with copious amounts of saline or clean water to remove contaminants and reduce bacterial load.
• Debridement: Remove any devitalised tissue or foreign material to reduce the risk of infection and promote healing.
• Wound Closure:
  • Primary Closure: Generally avoided in bites due to high infection risk. Consider primary closure for facial wounds for cosmetic reasons, after thorough cleaning and debridement.
  • Delayed Closure: Wounds may be left open initially and closed later if no signs of infection develop.
  • Secondary Intention: Allowing the wound to heal naturally without closure may be appropriate for heavily contaminated wounds.
• Dressing: Apply a sterile, non-adherent dressing to protect the wound and absorb exudate. Change dressings regularly and monitor for signs of infection.

2. Antibiotic Therapy

• Prophylactic Antibiotics: Recommended for:
  • All cat bites and human bites.
  • Dog bites involving the hands, face, or genitals.
  • Deep puncture wounds or crush injuries.
  • Immunocompromised patients or those with diabetes.
• First-Line Antibiotics:
  • Co-amoxiclav: Provides broad-spectrum coverage against common bite pathogens.
  • Doxycycline with Metronidazole: For penicillin-allergic patients.
• Treatment Duration: Typically 5-7 days for prophylaxis; longer courses may be required for established infections.
• Manage Established Infections: Adjust antibiotics based on culture results and clinical response. Hospital admission may be necessary for intravenous antibiotics in severe cases.

3. Tetanus and Rabies Prophylaxis

• Tetanus Immunisation:
  • Verify immunisation status.
  • Administer tetanus booster if indicated (last dose more than 10 years ago or uncertain history).
  • Tetanus immunoglobulin may be required for high-risk wounds in non-immunised individuals.
• Rabies Prophylaxis:
  • Assess risk based on animal type, behaviour, and local rabies prevalence.
  • Administer rabies vaccine and immunoglobulin as per national guidelines.
  • Report suspected rabies exposures to public health authorities.

4. Pain Management

• Analgesics:
  • Paracetamol: For mild to moderate pain.
  • NSAIDs: Ibuprofen for additional anti-inflammatory effects, unless contraindicated.
• Severe Pain: May require stronger analgesics; assess for underlying complications like infection or deep tissue damage.

5. Follow-Up and Monitoring

• Wound Review: Arrange follow-up to assess healing and detect any signs of infection or complications.
• Remove Sutures: If wound closure was performed, remove sutures as appropriate (usually within 3-5 days for facial wounds).
• Monitor for Systemic Symptoms: Advise the patient to seek immediate medical attention if systemic symptoms develop.

Legal and Ethical Considerations

Certain bites may have legal implications or require reporting:

• Mandatory Reporting: Some jurisdictions require reporting of animal bites, especially if rabies is suspected.
• Animal Control Notification: Inform animal control authorities about aggressive animals to prevent further incidents.
• Confidentiality: Maintain patient confidentiality, especially in cases of human bites or bites involving known individuals.
• Consent for Testing: Obtain consent before testing the patient or source animal for transmissible diseases.
• Safeguarding: Consider the possibility of abuse or neglect in cases involving children or vulnerable adults, and follow appropriate safeguarding protocols.

Prevention

Preventive measures can help reduce the risk of bites and their complications:

• Education on Animal Behaviour: Teach individuals, especially children, how to interact safely with animals.
• Responsible Pet Ownership: Encourage vaccination, training, and proper care of pets to reduce aggression and disease transmission.
• Public Health Measures: Support efforts to control stray animal populations and rabies vaccination programmes.
• Workplace Safety: Provide training and protective equipment for professionals who work with animals.
• Personal Protective Equipment (PPE): Use appropriate PPE when handling animals known to be aggressive or in high-risk settings.

When to Refer

Referral to a specialist or hospital may be necessary in the following situations:

• Severe Bites: Deep wounds, bites involving vital structures, or significant tissue loss may require surgical intervention.
• Infected Bites: Signs of spreading infection, systemic illness, or failure to respond to initial antibiotic therapy.
• Suspected Rabies Exposure: Immediate referral for assessment and initiation of post-exposure prophylaxis.
• Complex Wounds: Involvement of joints, tendons, nerves, or bones necessitates specialist management.
• Immunocompromised Patients: Higher risk of complications may require specialist input.
• Psychological Support: Patients exhibiting significant distress may benefit from mental health services.
• Allergic Reactions: Severe allergic responses require emergency care and possible referral to an allergist.

Patient Education and Support

Providing patients with information and support is crucial for recovery and prevention of future incidents:

• Wound Care Instructions: Educate on keeping the wound clean, recognising infection signs, and when to seek further care.
• Medication Adherence: Emphasise the importance of completing antibiotic courses and proper use of analgesics.
• Recognising Complications: Advise on symptoms of infection, allergic reactions, or systemic illness that require prompt attention.
• Preventive Measures: Discuss strategies to avoid future bites, including safe animal interactions and supervision of children.
• Vaccination Information: Provide details on tetanus and rabies vaccinations, including schedules and importance.
• Mental Health Support: Offer resources for coping with anxiety or trauma related to the bite incident.
• Follow-Up Appointments: Encourage attendance at scheduled reviews for wound assessment and management.

References

1. British Association of Dermatologists (2024) Guidelines for the Management of Human and Animal Bites. Available at: https://www.bad.org.uk (Accessed: 26 August 2024).
2. National Institute for Health and Care Excellence (2024) Management of Bites: Diagnosis and Treatment. Available at: https://www.nice.org.uk/guidance/ng109 (Accessed: 26 August 2024).
3. British National Formulary (2024) Antibiotic Prophylaxis for Bites. Available at: https://bnf.nice.org.uk/ (Accessed: 26 August 2024).