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Treating Animals Bites in a wilderness setting by Dr Sean Hudson

Treating Animal Bites

Animal bites are fortunately uncommon occurrences on expedition; wild animals rarely have contact with humans unless the expeditions purpose is game capture. Dogs inflict the most common animal bites.

There are four fundamental problems associated with animal bites

  1. Infection
  2. Wound closure
  3. Tetanus
  4. Rabies

The pathogens in the mouth of animals are varied and can be difficult to treat. If left untreated with antibiotics there is a high probability an unpleasant infection will develop. Different antibiotics are recommended for a variety of animals. Co-amoxiclav is predominantly used for dog bites worldwide.

The wound inflicted by an animal bite normally involves a combination of crush, tear and puncture. The wound is often difficult to close neatly as tissue has been severely disrupted. Puncture wounds may be left open to heal by secondary intention, other wounds can be treated with a combination of sutures and steristrips. If as a non-medical professional you feel unhappy with closing a wound it is entirely acceptable to leave the wound unclosed, but be extremely thorough with hygiene and dressing until medical attention can be sort.

Any wound needs to be cleaned, scrub with soap and sterile water, then immerse in >40% alcohol, or iodine, which act as bactericidal and virucidal agents. Time spent cleaning a wound is always well spent. Warn the patient that it must be done thoroughly and will hurt if you have no local anaesthetic. You must be happy there are no foreign bodies (for example pieces of clothing or dirt) in the wound and that it looks clean.

Daily antibacterial impregnated gauze dressings are recommended. This allows you to observe the wound and react to any signs of infection, (increasing pain, discharge or inflammation). This can be extremely difficult on expedition but imperative. If you have no impregnated dressing, clean the wound with iodine or alcohol daily and cover with a dry dressing.

Tetanus should not be an issue since everyone should be adequately covered before going on an expedition. If however an individual as escaped the vaccination programme, they will need immunisation and tetanus immunoglobulin soon. The incubation period for tetanus is 7-10 days, but this is variable. The time period between the first symptom, which is normally stiffness of the masseters, and spasms of other muscle groups, can be as short as 1 day. Spasm of opposing muscles results in rigidity and can lead to ineffective breathing, and laryngeal spasm to anoxia. Death is normally due to respiratory failure.

Rabies is a viral disease of mammals, usually but not exclusively transmitted by dogs. Other mammals, including cats, small mammals and bats have also been identified as vectors. Rabies encephalitis has virtually a 100% mortality, only 6 people worldwide are recorded as having survived episodes.

If the expedition is operating in an area in which rabies is endemic all the team should be immunised. Avoid contact with stray or wild animals. If a member of the team is bitten, or has a wound licked by a suspected rabid animal, clean the wound thoroughly, scrub with soap and wash under running water for 5 minutes or more. Then apply a virucidal agent, such as 40% alcohol or a solution of iodine. The decision whether to then proceed to vaccination is difficult. It is useful to know the behaviour of the suspected infectious animal, and if rabies is endemic in the area. If in doubt casevac to vaccinate, and do not delay this decision. Immunisation should be administered within 24 hours of exposure if possible, and rabies immunoglobulin infiltrated around the wound (anaphylaxis is common with equine rabies immunoglobulin). Vaccination within days of exposure is 100% effective in preventing the progression of the infection to encephalitis.
The older Semple vaccine, which has been used most widely in the developing world, is itself capable of inducing encephalitis. The sheep CNS components left in the vaccine can produce severe CNS disease with a 3% mortality. Efforts have been made to make the newer tissue culture-grown vaccine more affordable, tests on smaller doses being given intradermally have shown good results, and currently a 2-site intradermal regime giving 0.1ml-0.2ml at each of two sites (deltoids) on days 0,3,7 and at one site (deltoid) on days 28 and 90, is recommended. Those previously immunised still need post exposure immunisation. (Two booster injections of vaccine). They receive the vaccine but not the immunoglobulin. It is prudent to also send the suspected animal, at least its head for investigation. The treatment can be stopped if tests on the animal prove negative.
http://www.expeditionmedicine.co.uk/index.php/resources_fathomit/resource_form/7/c-000,50.html
Avoid being bitten by not interacting with stray dogs and ensure all your vaccinations are up to date. If you are bitten be cautious and assume the animal is a reservoir of the above diseases and seek medical attention.

Dr Sean Hudson, Medical Director Expedition & Wilderness Medicine

 

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