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Man's best friend? Treating dog and cat bites

Penny Keith
BA BSc RGN DN
Nurse Practitioner
Meadowell Centre
Watford
Nurse Practitioner Mentor
London South Bank University
E:penny.keith@nhs.net

Bites by mammals are quite common, making up about 1% of urgent presentations.(1) The most common bites are by dogs and cats, and people are usually bitten by their own pet. Over half of those bitten are school-age children.(2)
Patients are usually very aware that they have been bitten but may be unsure as to whether they need to be seen by a health professional. Without treatment bite wounds can become infected and there is a risk of functional impairment. Good assessment and prompt treatment can prevent most complications.(3) For the health professional, treatment for the immediate effects of the bite are required but consideration also needs to be given to the risk of infection, the role of prophylactic antibiotics, achieving satisfactory wound healing, and the need for tetanus.
Dogs have large teeth that can cause tearing and crushing of tissue, leading to lacerations in 30-45% of presentations, puncture wounds in 13-34% and superficial abrasions in 30-43%.(2,4) Cats have fine, sharp teeth that cause a weaker bite but are capable of penetrating bone and joint capsules.(5) Puncture wounds occur in 57-86% of presentations, lacerations in 5-17% and superficial abrasions in 9-25%.(4) Some 30-50% of cat bite wounds become infected, compared with 15-30% of dog bites.(2,4) Dog bites are the most common mammalian bite - about 200,000 are reported every year in the UK.(4)
Care must always be taken to rule out nonaccidental injury, particularly if the presentation does not seem to fit with the history given. Likewise, consideration must be given to parenting ability and supervision if an animal has bitten a child.

Initial management
Control bleeding - apply pressure, and if bleeding does not stop or there is heavy blood loss refer to accident and emergency (A&E). Generally bites do not result in major bleeding.
Take a swab - if infection is suspected.
Irrigate wound (using sodium chloride 0.9%) - this removes dirt and bacteria and minimises the risk of infection. There is some debate about the required ­pressure for irrigation. Although it is recognised that high pressure is more effective at reducing bacterial wound counts, care must be taken not to further tissue damage. High-pressure irrigation can be achieved using a 30-60ml syringe and 16-19 gauge needle, with care being taken to prevent sprayback.(6,7) In some situations this degree of force can damage tissue, so if it is felt more appropriate the wound can be irrigated with a syringe without a needle using a saline-filled canister or water.(6)
Antiseptic cleaners have been shown to damage tissue and delay wound healing.(8) If debridement is required this must be done using a local anaesthetic, such as lidocaine, and may need referring on. Puncture wounds should not be debrided.(5)

Assessment
After initial management the wound should be fully assessed recording the number of wounds, location, size (accurately measured and drawn or mapped as appropriate) and type, alongside the history and nature of the injury and when it occurred. Photographing the wound may be considered, particularly if there is a risk of disfigurement or litigation.(2) Wounds older than six hours are more prone to infection.(9) A thorough history must be taken to assess:

  • The patient's risk of wound infection.
  • The general health of the animal (and, if the bite occurred abroad, the risk of rabies).
  • Whether the animal was provoked.
  • Whether the time of the injury was recorded.

Assess for damage to arteries, nerves, muscles and tendons, paying close attention to puncture wounds, which can be much deeper than they appear. Signs of infection should be recorded - redness, tenderness, swelling, heat and discharge.
Any items of jewellery should be removed from the affected areas.
The patient should be asked about past medical history - particularly concerning chronic illness, immunocompromising conditions, immunosuppression therapy, presence of prosthetic valves or joints,(2) current and past medications, and allergies to drugs and dressings.

Complications

Wound infection
This occurs in some 15-30% of dog and 30-50% of cat bites.(2,4)

Risk of infection
This is raised in puncture wounds, hand injuries, full-thickness wounds and those involving joints, tendons, ligaments or fractures.(4,5,10)

Less frequent complications
These include tetanus, rabies, septicaemia, septic arthritis, tenosynovitis (inflammation of a tendon sheath), tendonitis, fractures, osteomyelitis, peritonitis, endocarditis, endophthalmitis (inflammation of the inside of the eye), meningitis and disfigurement.(5,10)

Cat-scratch disease
This is caused by the bacteria Bartonella henselae and can occur after a dog or cat bite or scratch. It presents with a primary erythematous papule 3-10 days after injury, followed by lymphadenopathy and fever. The condition is generally self-limiting and resolves within two months.(3,5)

Capnocytophaga canimorsus
This bacteria is found in canine oral flora and also occasionally isolated in cat bite wounds. It has been associated with severe infections in patients who are immunocompromised, and can lead to meningitis, endocarditis, renal failure and septicaemia.(5)

Referral
Consider referral to A&E or plastics for:

  • Bites involving arteries, nerves, muscle, tendons or bones.
  • Penetrating bites to the hands and feet.
  • Facial wounds.
  • Presence of a foreign body (such as a tooth).
  • Wounds that would benefit from closure.
  • Cases where extensive debridement is needed.
  • Cases where there is accompanying systemic ­illness.
  • Severe cellulitis.
  • Asplenic patients and those who are ­immunosuppressed.

Children are at particular risk, especially when the injuries are to the face and neck, and these should be referred.(11) Appropriate early referral is vital to prevent long-term complications.(12)

Wound closure
Suturing is not usually recommended for nonfacial bite wounds, deep punctures, bites to the hand or clinically infected wounds, due to the increased risk of infection.(7) Sterile skin closure strips may be used, but delayed closure is usually more beneficial and should be used for wounds more than six hours old.(4)
Facial wounds and larger lacerations may require suturing to prevent scarring and aid healing.(11) The wound should be covered with a sterile, nonadhesive dressing.

Antibiotic prophylaxis
A Cochrane systematic review found evidence that antibiotic prophylaxis significantly reduces ­infection after bites to the hand, but confirmatory research is required.(1) There are insufficient data to determine whether prophylactic antibiotics are effective for dog or cat bites.(1)
Antibiotic prophylaxis is generally recommended for:(4,13)

  • High-risk animal bite wounds - that is, to the hand, foot and face.
  • Puncture wounds, especially cat bites.
  • Wounds requiring surgical debridement.
  • Wounds involving joints, tendons, ligaments or ­suspected fractures.

Moore advises prophylactic cover following primary suturing along with thorough wound cleansing.(11) Antibiotic prophylaxis is also recommended for those with diabetes, cirrhosis, asplenia or immunosuppression.(9)
If the wound is more than two days old and there is no evidence of infection antibiotics are not required.
Whether an antibiotic is prescribed or not, cleansing remains a vital part of the treatment.(6)

Treatment of infection
If clinical infection is evident the wound should be swabbed and tested for culture and sensitivity and therapy reviewed in light of the results.
All clinically infected bites should be treated with systemic antibiotics.(12) There is usually polymicrobial colonisation in:

  • Infected dog bites - often Pasteurella canis, Pasteurella multocida, Staphylococcus aureus and other staphylococci, streptococci and anaerobic bacteria.
  • Infected cat bites - often P multocida, ­staphylococci, streptococci and anaerobes.

Co-amoxiclav, a broad-spectrum antibiotic, is recommended as first-line treatment for mild-to-moderate infections following a dog or cat bite managed in primary care (see Table 1).(5,10,14) Erythromycin can also be used but is the least effective drug available.(11)

[[NIP22_table1_51]]

If the patient is allergic to penicillin, first-line treatment is based on wound type and most probable infecting organism - for dog and cat bites this is generally oxytetracycline or doxycycline plus metronidazole. Advice must be given to avoid exposure to sunlight or sunlamps to reduce the risk of photosensitivity reactions when taking tetracyclines, and not to take within two to three hours of food, iron, calcium, zinc or antacids.
If the patient cannot be given a tetracycline (under 12 years, pregnant, breastfeeding), advice should be obtained from the local microbiologist.
Anyone presenting with a severe infection or ­systemically unwell should be referred to A&E for assessment for intravenous antibiotic therapy.

Tetanus prophylaxis
A total of five doses of vaccine, administered at appropriate intervals, is considered to give lifelong immunity.(16)
If a patient is fully immunised but there is a high risk of infection, human tetanus immunoglobulin may be given. This can be obtained from the Blood Transfusion Service in general practice,(7) but it would generally be more expedient to send the patient to A&E.
If primary immunisation is complete but boosters are incomplete but up to date, a booster is not needed but may be given if it is due. Human tetanus immunoglobulin may be given for wounds with a high risk of infection.
If primary immunisation is incomplete or boosters are not up to date, a tetanus booster should be given and further doses as needed to complete the schedule, adding human tetanus immunoglobulin at a different site if the wound is high risk.
If an individual has a tetanus-prone injury and requires a tetanus, then low-dose diphtheria, tetanus and inactivated poliomyelitis vaccine should be given (only for adults and children over 10 years of age) (Revaxis 0.5ml prefilled syringe; Aventis Pasteur MSD).
If the bite was obtained abroad the risk of rabies must be assessed and rabies prophylaxis may be required.

Other medications
Advice regarding the use of OTC analgesics or prescribed analgesics may be appropriate, such as paracetamol or ibuprofen (if suitable).

Follow-up advice
Patient information leaflets are available to download from the Department of Health website (www.dh.gov.uk).(7) The patient should be informed of the signs of infection and the need to return for review if these occur.
If the wound is infected it should be reviewed after 24 hours and after 48 hours to ensure the infection is responding to treatment. If there is no response to firstline therapy a wound swab should be sent for culture and sensitivity. It may be appropriate to give some simple preventive information to patients, such as:(2)

  • Avoiding animals while they are eating.
  • Exercising caution around unfamiliar animals.
  • Never trying to separate fighting animals.
  • Reminding parents not to leave young children alone with a pet regardless of its perceived ­disposition.

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References

  1. Medeiros I, Saconato H. Antibiotic ­prophylaxis for mammalian bites. Cochrane Database Syst Rev 2001;2.
  2. Lewis K, Stiles M. Am Fam Phys 1995;52:479-85.
  3. Bower MG. Nurse Practitioner Am J Primary Health Care 2001;26(4):36-47.
  4. Dire DJ. Emerg Med Clin North Am 1992;10:719-36.
  5. Smith PF, Meadowcroft AM, May DB. J Clin Pharm Ther 2000;25(2):85-99.
  6. Cole E. Nurs Stand 2003;17(46): 45-52.
  7. DH. Bites - human and animal. Prodigy guidance. London: DH; 2004.
  8. Hollander JE, Singer AJ. Ann Emerg Med 1999;34:356-67.
  9. Moulton C, Yates D. Lecture notes on emergency ­medicine. Oxford: Blackwell Science; 1999.
  10. Monteiro JA.Eur J Int Med 1995;6:209-15.
  11. Moore F. BNF 314 1997;88-9.
  12. Mitnovetski S, Kimble F.Aust NZ J Surg 2004;74:859-62.
  13. Chaudhry MA. Eur J Emerg Med 2004;11:313-17.
  14. Nurse Prescribers' Formulary/BNF 46. London: RPSGB; 2003.
  15. DH. List of ­medicines available to extended ­formulary nurse prescribers. London:?DH; 2004.
  16. DH. Immunisation against infectious disease. London: HMSO; 1996.

Further information
Do you need to alert any ­authorities in the event of an animal bite?
There are no actual guidelines or policies on this. A&E take the line that if there's any civil action required by the patient then they are to contact the police. The RSPCA say they are to be contacted only if the animal is sick or injured, ­otherwise the local police should be contacted or the dog warden if there is one locally. Public health say that it is not normally an issue for them unless the animal has rabies, and to date all cases of rabies have been acquired abroad.
Any other concerns would be addressed to environmental health.
A useful website for more ­information is:Health Protection Agency
W:www.hpa.org.uk