When Life Bites: Dealing with Mammal Bites in the Backcountry

Stop To set the scene, imagine you are out hiking on a beautiful spring day, when all of a sudden you hear a scream come from off the trail.  You run in to find a woman cradling her arm which you see is dripping blood and she tells you “I’ve been bit!”.  Gulp!  Now imagine its a parent holding his child who was just bit…double gulp!  In the back country we are ‘invading’ the habitats of many animals, and when threatened, some will defend their territory and attack.

So how exactly do we deal with these bites?  ALWAYS, ALWAYS, ALWAYS (and this is without exception if the hint wasn’t strong enough), evaluate your scene FIRST for safety.  If the animal is still present and aggressive, figure out a way to separate the animal from the victim.  Getting yourself killed by rushing in isn’t going to help anyone.  Also, although it would be ideal to have the ability to observe a wild animal for behavior that would suggest rabies, getting yourself bit while trying to capture the animal is not worth it.

Irrigate

Once you have the victim in a safe location, the next step is to ask three questions: Are they stable?  Where is the bite?  What bit them?  The basic CAB’s (circulation, airway, breathing) should always be evaluated first, and controlling significant hemorrhage is vital.  Once you have run through these, your top priority is to irrigate.  High pressure irrigation with clean water (using filtered water is preferable) can be achieved using a large syringe and 18 gauge needle, however if you do not have these with you you can also puncture a small hole into a plastic bag filled with water to create a high pressure stream.  If the plastic of the bag is thin, use a small diameter pin to create a few holes close together.  If the plastic is thick (such as on a platypus bag), use the screwdriver or blade of a swiss army knife to make one larger hole.  If you have povidone-iodine or benzlakonium chloride solution on hand and rabies is of concern, you can use it to clean the wound as they have some virucidal properties.1,2 Otherwise use only water, as cleaning with alcohol, iodine or hydrogen peroxide can interfere with wound healing. Debride any obviously crushed tissue and remove any dirt or debris seen in the wound.  Now onto the specifics:

Dog Bites

Dog aggressiveDog bites are the most commonly bite seen in the front country, but can be seen in the back country from both domestic dog companions and wild dogs. If you come upon a scene where the animal is still present, you should try to remain calm, keep a non-threatening stance with your front always facing the dog, do not stare into its eyes but always be watching its movements and do not make any threatening gestures.2  If you are on the receiving end of an attack, do no fight back but curl into a ball and act dead until the dog loses interest and leaves.2  Not altogether surprisingly, bites on most older kids and adults are seen in the upper extremities (defensive wounds most likely) and lower extremities, whereas younger kids have more bites to the face and head.3,4  The initial damage can be devastating as their jaws are able to exert >300lbs of force and their teeth are blunted.1,5  Wounds should be examined for both underlying broken bones and crush injuries, and bites to the neck should be evaluated for airway penetration and compromise.  Also, check the wound for any foreign bodies as teeth may break off in the struggle and create a nidus for infection later on.  Most commonly, fatalities from dog bites are related to bites to the neck that lead to exsanguination, so control any hemorrhage with direct pressure.6  These polymicrobial bites commonly include pasturella, steptococcus, staphylococcus, fusobacterium and others.  Traditionally, following irrigation, these bites were left open to close secondarily.  However, recent studies have shown improved cosmetic appearance and no increased risk of infection with primary closure.1,7  Since these are considered contaminated wounds, absorbable subcutaneous sutures are not recommended.  Instead, primary closure using simple interrupted, non-absorbable sutures is recommended.1  This will also help prevent further wound contamination while in the back country.   If the wound is not deep, significantly debilitating, occurring to the hand, foot, face or over a joint, and doesn’t show signs of infection, it may not be necessary to evacuate the victim from the back country under emergent circumstances.  However, watch the wound closely for any swelling, erythema or warmth.

Dog bite

Signs of infection necessitate immediate evacuation for proper antibiotic and/or surgical treatment.  Prophylactic antibiotic use is still controversial, with some studies showing decreased rates of infection and others showing no benefit.1,8,9,10  Augmentin (amoxicillin-clavulanate) is used for dog bites (as well as other bites and cellulitis) and is a good antibiotic to carry with you in your back country med pack.  Doxycycline, trimethoprim-sulfamethoxazole and cefuroxime are also acceptable alternatives in a penicillin allergic patient.5  One study did find lower rates of infection with prophylactic antibiotics specifically related to wounds that were closed primarily or puncture-like.9  More importantly, a recent meta analysis showed that when used in victims with bites to the hands, prophylactic antibiotics significantly reduced infection rates (28% vs. 2%).10  Due to the controversial benefit outside of hand bites, it is not an emergent trip ending need if you do not have this antibiotic, but if you have it with you there is little downside to giving it and avoiding infection in the back country can improve morbidity greatly.  Again to emphasize, hand bites have higher rates of infection and higher morbidity, and should be evacuated with prophylactic antibiotics started in the back country if possible.  Decompensation of the victim including shock, gangrene or dermatologic lesions require immediate evacuation and should evoke the thought of Capnocytophaga canimorsus infection (seen in dog bites).   The mortality rate is very high with this infection and requires intravenous antibiotics and supportive care.11

Coyote and wolf bites should be treated the same as dog bites with respect to closure and initial management.  Many of these victims are children, so pay special attention (just as in dog attacks) to scalp lacerations, as they may have an underlying depressed skull fracture from the pressure of the bite.  Foxes have smaller teeth and cause more puncture-like bites, leading to higher rates of infection, and initial management will mimic more a cat bite.  They also have high rates of rabies infection, so prophylaxis should be sought.2

Cat Bites

Cat angryNot often acquired in the back country, cat bites and scratches are commonly ignored by pet owners in the front country and can be seen more often as a result of a lack of treatment.  This is because the bites and scratches themselves are often small and puncture-like, going deep into the tissue but leaving little if any trace on the surface.1,2  The infection rate is twice that of dog bites and delayed treatment can result in surgical repair and/or permanent impairment.  Infection can lead to cellulitis, tenosynovitis, septic arthritis and osteomyelitis.  These polymycrobial bites include pasteurella (multocida and septica), streptococcus, staphylococcus, fusobacterium and others.1  The wounds are typically not amenable to irrigation, and due to the high risk of infection may need to be opened and even enlarged to allow high pressure irrigation.  If the wound occurs on the hand, especially in a closed area such as the terminus of a digit, around a joint space, or in the palm or thenar area, get them to a medical facility as quick as possible as infection of these areas may require surgical debridement or intravenous antibiotics.  It is best to allow these wounds to remain open and close secondarily, as long as they are not disfiguring.12

Cat bite

Like dog bite, prophylactic antibiotic use is controversial, but studies have shown decreased rates of infection with  Augmentin (or one of the alternatives listed previously) use as prophylaxis in cat bites.  The appearance of any vesicles around the bite or scratch site, or lymphadenopathy and/or painful lymph nodes may be evidence of cat scratch disease caused by Bartonella henselae.  Though usually self limited, systemic symptoms including aching and malaise can debilitate the patient, and serious complications can also arise from this infection.1,13  Immediate evacuation to a medical facility for antibiotic treatment is highly recommended.

Human Bites

More often than not, these injuries occur during altercations.  These can occur as occlusion bites, which occur when the teeth sink into the skin during a purposeful bite, or a closed-fist bite from strikes to the face that result in cuts to the knuckles from the teeth.  Closed-fist bites are particularly dangerous because the joint capsule is commonly penetrated during the strike but seals when the hand relaxes, creating a bacterial growth chamber within the joint itself.5  On average, half of all human bites get infected, with closed-fist injuries being more likely.  These polymicrobial bites include streptococcus, staphylococcus and eikenella, along with other anaerobes.5,14   Occlusion bites often don’t require anything more than high pressure irrigation, and can be left open to heal secondarily if not disfiguring.  Closed-fist injuries should also be copiously irrigated, but should be evacuated more urgently as infection of the hand requires surgical debridement and intravenous antibiotics.  Leave these wounds open and monitor closely for signs of infection.  Prophylactic antibiotics have been shown to be unnecessary for human bites that are superficial and on areas other than the hands or feet.15,16  Deep bites (penetrating the dermis) or those on the hands and feet should be treatment with Augmentin.5,14,16

Bat

Bat Bites

Outside of the already stressed high pressure irrigation of the wound, there is little different to do for bat bites.  However, they are considered especially dangerous because of their high association with rabies.  Discussed further below, a patient who has been bitten by a bat (or even just had contact or near-contact without any skin penetration or skin-to-skin contact) should be evacuated immediately to the nearest hospital to receive rabies prophylaxis.1,2

 

Large Cat Attacks

Although rare, large cat attacks tend to be very lethal.  If you arrive on a scene and the animal is still present, do not run but raise your arms and bring your jacket above your head to make yourself look as big as possible.  Unlike dogs, if they do attack, fighting back may make them abandon the fight.2 They tend to attack the head and neck, and many with either attempt to damage the spinal cord by getting their teeth between the vertebrae, or attempt to strangle the victim but biting and applying pressure to the front of the neck.17  The puncture wounds from these animals should be treated like their smaller counter parts.  Due to the number of vital structures in the targeted region, controlling hemorrhage from the nearby major vessels and securing the airway are of utmost importance.  Protect the cervical spine if possible (difficult to impossible if you are controlling hemorrhage from a nearby major vessel), as both the bites and jarring motions from the attack can lead to cervical spinal damage.  Irrigation and prophylactic antibiotic treatment would follow similarly to small cat bites.1,2

Wild SwineWild Swine

Texas especially is seeing an explosion in the population of wild swine that are roaming the countryside.  There are many reports of attacks on humans, and the number is increasing.  The wounds are typically due to goring injuries from their tusks, which can be puncture-like in nature but can leave large, gaping wounds due to the thrashing motion of their heads.  These wounds are considered very contaminated and should be treated with broad spectrum antibiotics (possibly parenteral) as soon as possible.2  The wounds should not be closed in the field, and the focus should be on hemorrhage control and evacuation.

Raccoon

Raccoon Bites

Raccoons are particularly known for the association with rabies, but they have a few other disease associations such as leptospirosis, listeriosus, tetanus and tuliremia.  Due to their small teeth and puncture-like bites, the initial management should resemble that of a cat bite, but they should be taken to a medical facility immediately for prophylaxis for both rabies and bacterial infections.2

PorcupinePorcupines

While they do not typically bite during their attack, it is worth mentioning briefly how to deal with a porcupine quill.  The quills themselves cannot be projected from the porcupine’s body, but if they become embedded in the skin they are very difficult to remove (due to their barbs) and can migrate up to 10 inches under the skin.  Their cores are spongy and they can absorb body fluid, causing them to expand and inflict additional damage if not removed immediately.   Quills should be removed as soon as possible, especially if there is any chance they may migrate into the thoracic or peritoneal area and damage internal organs.  High pressure irrigation of the puncture hole should be performed, but the quills have some antiseptic properties and infection rates are very small, making prophylactic antibiotic treatment unnecessary.2  Closure of the wound via a bandage is sufficient and if there is no concern of damage to underlying structures, immediate evacuation is not necessary.

 

General Wild Animal Bite Precautions 

In general, make sure to get a good medical history including any conditions or medications they are on which may place them in an immunocompromised state.  Also, make sure to check on their immunization status, with particular importance to their last tetanus vaccination.  If >5yrs since their last tetanus vaccine, they require a booster.  If this is a child who hasn’t completed their full set of tetanus vaccinations (or an adult who is not sure that they received them), they require a tetanus vaccination and tetanus immune globulin.

When evaluating for rabies transmission, the type of animal that bit the patient is the most important information to collect.  Domestic animal bites have a low risk, and if you are able to watch the animal for 10 days you can definitively rule out the need for rabies prophylaxis.  The risk from wild animals is very high, and the ability to capture and watch them is minimal.  While capturing the animal live is ideal, if you are able to kill it without damaging its brain, you can transport the freshly dead animal to a medical facility with the patient for analysis of the brain tissue for the rabies virus.  SkunkThe majority of human rabies cases in North America have been tied to bat bites or exposure18,19, but raccoons and skunks are well known to carry rabies.  There is flux in the current recommendation for rabies prophylaxis and bat exposure due to finding of aerosolized transmission of rabies in an animal model.1  The CDC recommends that unless the victim can be absolutely, 100% sure that they did not have ANY direct contact with the bat in question, they should receive prophylaxis.20  If the bite is from an animal that is domesticated or captured, the animal may be either sacrificed to directly test for rabies tissue samples from the brain, or observed for 10 days for any abnormal behavior.  In this case post-exposure prophylaxis (PEP) does not need to be given as long as the animal tests negative for rabies or remains healthy and behaves normally.  If the bite is from a wild animal that could not be captured, the current recommendation is to give PEP if the bite was from a raccoon, skunk, fox or coyote.  Small rodents such as squirrels, chipmunks, rats, mice and rabbits have never been found to be infected with rabies, and most likely do not need PEP as long as their behavior during the bite was not grossly abnormal.20  However, almost any wild animal bite received in the back country should be evacuated in a timely manner to be evaluated for the need for rabies prophylaxis, as it will be too late if the person begins to show signs of infection.20

 

REFERENCES

1. Edens, M.A., Michel, J.A., & Jones, N. (2016). Mammalian Bites in the Emergency Department: Recommendations For Wound Closure, Antibiotics, and Postexposure Prophylaxis.  EB Medicine, 18(4).

2. Auerbach, P. S. (2011). Wilderness & Environmental Medicine, 22(2).

3. Weiss, H. B. (1998). Incidence of Dog Bite Injuries Treated in Emergency Departments. Jama,279(1), 51.

4. Abubakar, S., & Bakari, A. (2012). Incidence of dog bite injuries and clinical rabies in a tertiary health care institution: A 10-year retrospective study. Ann Afr Med Annals of African Medicine, 11(2), 108.

5. Kennedy, S. A., Stoll, L. E., & Lauder, A. S. (2015). Human and Other Mammalian Bite Injuries of the Hand. Journal of the American Academy of Orthopaedic Surgeons, 23(1), 47-57.

6. Sacks, J. J., Sinclair, L., Gilchrist, J., Golab, G. C., & Lockwood, R. (2000). Breeds of dogs involved in fatal human attacks in the United States between 1979 and 1998. Journal of the American Veterinary Medical Association, 217(6), 836-840.

7. Paschos, N. K., Makris, E. A., Gantsos, A., & Georgoulis, A. D. (2014). Primary closure versus non-closure of dog bite wounds. A randomised controlled trial. Injury, 45(1), 237-240.

8. Moscona, R. (1996). Antibiotics to prevent infection in patients with dog bite wounds: A meta-analysis of randomized trials. Plastic & Reconstructive Surgery, 98(1), 191.

9.  Tabaka, M. E., Quinn, J. V., Kohn, M. A., & Polevoi, S. K. (2015). Predictors of infection from dog bite wounds: Which patients may benefit from prophylactic antibiotics? Emergency Medicine Journal Emerg Med J, 32(11), 860-863.

10. Henton, J., & Jain, A. (2012). Cochrane corner: Antibiotic prophylaxis for mammalian bites (intervention review). Journal of Hand Surgery (European Volume), 37(8), 804-806.

11.  Butler, T. (2015). Capnocytophaga canimorsus: An emerging cause of sepsis, meningitis, and post-splenectomy infection after dog bites. Eur J Clin Microbiol Infect Dis European Journal of Clinical Microbiology & Infectious Diseases, 34(7), 1271-1280.

12. Schwartz, D. A. (2006). Dog and Cat Bites to the Hand: Treatment and Cost Assessment.Journal of Hand Therapy, 19(3), 371.

13. Dendle, C. & Looke, D. (2009).  Management of Mammalian Bites.  Aust Fam Phys, 38(11).

14. Malahias, M., Jordan, D., Hughes, O., Khan, W. S., & Hindocha, S. (2014). Bite Injuries to the Hand: Microbiology, Virology and Management. The Open Orthopaedics Journal TOORTHJ,8(1), 157-161.

15. Broder, J., Jerrard, D., Olshaker, J., & Witting, M. (2004). Low risk of infection in selected human bites treated without antibiotics. The American Journal of Emergency Medicine, 22(1), 10-13.

16. Pauls, S. W. (1991). Management of early human bites of the hand: A prospective randomized study. Annals of Emergency Medicine, 20(11), 1273.

17. Wolf, B.C. & Harding B.E. (2014). Fatalities due to indigenous and exotic species in Florida. J Forensic Sci, 59(1).

18. Blanton, J. D., Hanlon, C. A., & Rupprecht, C. E. (2007). Rabies surveillance in the United States during 2006. Journal of the American Veterinary Medical Association, 231(4), 540-556.

19. Blanton, J. D., Palmer, D., & Rupprecht, C. E. (2010). Rabies surveillance in the United States during 2009. Journal of the American Veterinary Medical Association, 237(6), 646-657.

20. Other Wild Animals. (2016, March 23). Retrieved April 02, 2016, from http://www.cdc.gov/rabies/exposure/animals/other.html

 

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