Dog Bites

"A dog is the only thing on earth that loves you more than he loves himself." - Josh Billings

Quite clearly, this statement is untrue, if the incidence of dog bites is anything to go by. A provoking factor can, however, be found in many cases. Dogs resent being disturbed whilst eating, will attack if they feel threatened, if they believe their territory is being invaded, or if they become jealous of the attention paid to other family members.¹

Most reviews suggest that larger dogs such as German shepherds, pit bull terriers and Rottweilers are the most likely to bite, but all dogs should be considered potentially dangerous.² Knowing the breed of dog is important, as a bite from a larger dog is more prone to damage deeper structures such as tendons and bones.³

Common bacteria include:

• Staphylococcus
• Streptococcus
• Eikenella
• Pasteurella
• Proteus
• Klebsiella
• Haemophilus
• Enterobacter
• Capnocytophaga canimorsus (formerly known as DF-2)
• Bacteroides

Owners can be prosecuted by the police under the Dangerous Dogs Act 1991, which makes ownership of certain breeds illegal.⁴ A civil claim can also be made against the owners for damages under the Animal Act 1991.⁵

An accurate estimate of incidence is impossible, as dog bites are frequently unreported. One study of paediatric patients suggested that less than 50% of dog bites were reported to the police or to healthcare workers.⁶ UK estimates suggest that 740 people per 100 000 population are bitten by dogs annually. Overall, 2.6/100 000 population need hospital admission.⁶ A recent telephone survey of 1184 Belgian families found that the annual incidence of bites in children aged under 15 years was 22/1000.⁷ Most children are under ten, with the highest incidence at age 1 year.⁶ Very young children tend to be bitten at home, but there is a subset of children with an average age of 9 who are bitten in public places.⁸ In the case of children, most dogs are known to the victim and a provoking factor can be identified.⁶

Risk factors^3,6

• Male dogs more likely to bite than female dogs
• Men more likely to be bitten than women
• Likely circumstances include:
  • Playing with/near dog
  • Passing the dog (walking)
  • Cuddling the dog
  • Feeding the dog
  • Passing the dog (cycling)
  • Disturbance of dog while eating
  • Surprising the dog
  • Pulling the dog's tail
  • Interfering during dog fight

History

It may not be possible to obtain a full history in all cases, but the following information should be sought:

• Breed of dog
• Health status of the animal
• Time and location of the event (with particular reference to travellers bitten in a country in which rabies is prevalent)
• Circumstances of the bite (provoked or unprovoked)
• Location of the animal now
• Any pre-hospital treatment
• Any factors likely to compromise immunity - splenectomy, HIV, steroid therapy
• Any recent antibiotics (the presence of infection in patients already taking antibiotics could suggest a resistant organism)

Examination

The extent of examination will depend on the history and it will usually be evident on brief initial assessment whether one is dealing with a serious situation which needs full resuscitative measures or minor trauma. If the injury appears serious, not too much time should be wasted in examining the patient in the community.

• Carefully examine the wound, and make diagrams or take photographs if possible. These wounds may be quite complex as they often involve shearing forces as the dog embeds its teeth into the skin, which then tears as the person pulls away from it.
• Note the size, depth, degree of crush injury, the presence of any devitalised tissue, any tendon damage, and involvement of bones and joints.
• Check very deep wounds for visceral injury.
• Debridement under local or general anaesthetic may be necessary to make a full evaluation of the wound. Exclude the presence of foreign bodies such as teeth.
• Check reflexes, sensation and circulation to exclude neurological or vascular damage.

The diagnosis will usually be obvious from the history, but where a history is not available (e.g. comatose patients), the following need to be excluded:

• Human bites
• Cellulitis
• Cervical spine fractures
• Hand Infections
• Neck trauma
• Osteomyelitis
• Rabies
• Tetanus

• Wound Swab This is unlikely to be contributory in a fresh wound, but is indicated in older wounds which appear infected.
• Full blood count and blood cultures These should be considered if the patient appears systemically unwell and generalised sepsis is suspected.
• Imaging Patients may require x-rays or scanning to determine the presence of occult fractures, osteomyelitis, injury to tendons or to exclude the presence of foreign bodies. This is particularly essential for children with head bites who should have plain films or CT scan to exclude bony penetration and cervical injury.

Emergency trauma evaluation

Patients with facial or cranial bites may need neck immobilisation until neck injuries can be excluded.

Irrigation

The wound should also be cleaned by irrigating copiously with tap water or normal saline. A 19-gauge needle attached to a 35 ml syringe may be necessary to access all areas of the wound and provide sufficient pressure to provide sufficient pressure for cleansing.

Debridement

The wound should be debrided if necessary to remove devitalised tissue, clots and any foreign bodies.

Primary suturing

This may be considered if the wound appears clean or has been cleaned adequately. Primary closure is particularly suitable for facial wounds due to the excellent blood supply. In situations in which infection is likely, closure should be delayed. Factors predisposing to a high risk of infection include:

• Alcoholism (increased susceptibility to Pasteurella infection)
• Cirrhosis, asplenia (increased risk of Capnocytophaga)
• Steroid therapy, rheumatoid arthritis, diabetes mellitus, and lymphoedema after radiotherapy (all increase risk of Pasteurella infection
• Wounds more than 6 hours old
• Devitalised tissue
• Previously sutured wounds
• Full thickness wounds involving tendons, ligaments, and joints
• Bites on limbs, especially hands

Limb elevation

This should be instituted if swelling has occurred or is likely to occur.

Prophylactic antibiotics¹

The literature concerning prophylactic antibiotics is controversial, and it is generally considered that wound debridement and cleansing is more important than medication. .The consensus however is that antibiotics are useful in the following high risk scenarios:

• All bite wounds after primary closure
• Puncture wounds
• Bites to hand and wrist
• Crush wounds with devitalised tissue
• Dog bite injuries to the genitals
• High risk patients (diabetes mellitus, immunosuppression, splenectomy, cirrhosis, post-mastectomy, rheumatoid arthritis, prosthetic joints)

Co-amoxiclav is considered first-line and will cover most potential infections.

Antibiotics for established infections¹

Wounds sufficiently severe to require antibiotic treatment will normally need hospital admission. The antibiotic regime needs to cover Pasteurella, anaerobes, and staphylococci. Intravenous treatment may be needed in the initial stages. Imipenem with cilastatin and clindamycin are used for very severe infections empirically until culture results are available. Intravenous ciprofloxacin plus metronidazole are used for patients allergic to penicillins. The antibiotic regime may need to be modified according to culture results. Conversion to oral treatment can occur when the C-reactive protein level falls below 50 mg/l.

Tetanus prophylaxis

Tetanus is rare after a dog bite, but all guidelines recommend prophylaxis with immunoglobulin and toxoid for patients with a history of two or fewer immunisations.

Assessment of rabies risk

If the patient has sustained a dog bite , however minor, in a country in which rabies is known to occur, contact the Health Protection Agency Centre for Infection or Health Protection Scotland.^9,10 To assess the need for prophylaxis, staff will enquire about the following:

• Previous vaccination status
• Country where bitten
• Site and date of bite
• Provoked or unprovoked bite
• Domestic or feral dog
• Current health of animal if known

If required, prophylaxis is with intramuscular rabies vaccine and human rabies immunoglobulin, obtainable from the centres.

Prognosis is usually excellent, providing adequate, timely and appropriate treatment is given.

Public health campaigns advising about appropriate behaviour when around dogs, wound care after sustaining a bite, and signs that might indicate infection, have proved helpful.