Human and Animal Bites

Introduction | Aetiology and Types of Bites | Clinical Presentation | Diagnosis | Management and Treatment | Prevention | When to Refer | 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, or livestock can pose risks of specific infections, including rabies and tetanus. The management of these bites depends on the type of animal and the circumstances of the bite.

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, 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.
• Systemic Symptoms: In cases of severe infection or sepsis, the patient may present with systemic symptoms such as fever, chills, tachycardia, and hypotension.

Diagnosis

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

• History: A detailed history of the bite, including the type of animal, circumstances of the bite, time elapsed since the bite, and the patient’s tetanus immunisation status, is essential.
• Clinical Examination: Assess the extent of the wound, signs of infection, and any involvement of deeper structures. Look for evidence of neurovascular compromise or other complications.
• Imaging: X-rays may be necessary to assess for foreign bodies, fractures, or involvement of bones and joints, particularly in deep or severe bites.
• Laboratory Tests:
  • Full Blood Count (FBC): May show signs of infection, such as elevated white blood cell count.
  • C-Reactive Protein (CRP): Elevated CRP levels can indicate the presence of infection or inflammation.
  • Wound Culture: A swab for bacterial culture and sensitivity can help guide antibiotic therapy, especially in infected wounds.

Management and Treatment

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

1. Wound Care

• Cleaning: Thoroughly clean the wound with saline or clean water. Avoid using antiseptics like hydrogen peroxide or iodine directly on deep wounds as they can delay healing.
• Debridement: Remove any devitalised tissue or foreign material to reduce the risk of infection.
• Closure: Primary closure of the wound is generally avoided in bites due to the high risk of infection, especially for puncture wounds, bites to the hands, or bites older than 6 hours. Delayed closure or healing by secondary intention is often preferred.
• Dressing: Apply a sterile dressing to the wound to protect it from further contamination and to absorb any exudate.

2. Antibiotic Therapy

• Prophylactic Antibiotics: Prophylactic antibiotics are recommended for bites at high risk of infection, such as cat bites, deep puncture wounds, bites to the hands or face, or bites in immunocompromised patients.
  • Co-amoxiclav: First-line prophylactic antibiotic for most bites, covering a broad spectrum of pathogens including Pasteurella and anaerobes. Typically prescribed for 5-7 days.
  • Doxycycline and Metronidazole: For patients allergic to penicillin, a combination of doxycycline (for Pasteurella) and metronidazole (for anaerobes) can be used.
• Treatment of Infected Bites: If the wound is already infected, a full course of antibiotics should be initiated based on the severity of the infection and culture results, if available.

3. Tetanus Prophylaxis

• Tetanus Immunisation: Assess the patient’s tetanus immunisation status. If the patient is not up to date with tetanus vaccination, administer a tetanus booster. For deep or dirty wounds, tetanus immunoglobulin may also be required.

4. Rabies Prophylaxis

• Rabies Vaccination: Rabies vaccination should be considered for bites from animals suspected of being rabid, particularly in areas where rabies is endemic. Post-exposure prophylaxis (PEP) with rabies immunoglobulin and a series of rabies vaccinations may be required.

5. Pain Management

• Analgesics: Over-the-counter pain relief such as paracetamol or ibuprofen can be used to manage pain and inflammation.

Prevention

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

• Animal Handling: Educate patients on safe handling of pets and animals, especially dogs, to prevent bites.
• Supervision of Children: Children should be supervised around animals to prevent bites, and they should be taught not to provoke animals.
• Prompt Wound Care: Immediate and thorough cleaning of any bite wound can reduce the risk of infection.

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 bites resulting in significant tissue damage may require surgical consultation.
• Infected Bites: Bites that develop significant infection, particularly if there is concern for abscess formation, osteomyelitis, or septic arthritis, should be referred for further management.
• Suspected Rabies Exposure: Any bite with a high risk of rabies exposure should be referred for rabies post-exposure prophylaxis and specialist advice.
• Immunocompromised Patients: Patients with compromised immune systems may require more aggressive management and specialist input.

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).