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Case report of a coyote attack in Yellowstone National Park
Wilderness and Environmental Medicine, 2, 170-172 (1996)
CASE REPORT
Case report of a coyote attack in Yellowstone National Park SAMUEL S. HSUI and LUANNE F. HALLAGANI,2 I Departmell1
of Surgery, Division of Emergency Medicine, University ofMaryland; 2 Yellowstone Park Medical Services
We report the case of an unprovoked coyote attack on a human visitor to Yellowstone National Park. Although the patient suffered only soft tissue injuries, unprovoked attacks are rarely reported in the medical literature. This case and plans on how to manage coyote attacks are discussed.
Key words: coyote, attack
Introduction Although there have been anecdotal reports of coyote attacks on humans, the literature that documents such cases is sparse and we were unable to find any medical literature on how to manage such attacks. With the increasing popularity of vacations in wilderness settings, we can expect a rise in human encounters with, and potential attacks by, coyotes. We present the case of a coyote attack and its treatment in Yellowstone National Park.
Case report A 57-year-old man from Germany had been hiking through Yellowstone Park when he stopped to rest in a field, removed his shoes, and fell asleep. He awoke with a pain in his right foot to find that he had been bitten by a coyote. The animal was described as sickly in appearance and it circled the patient and his companion for a moment before running away. The patient drove a private vehicle to Lake Hospital and was examined within an hour of the injury. The patient had no significant past medical history. Upon examination, multiple linear lacerations 5-10 mm were seen circumferentially around the distal right foot (Fig. I). The wounds were superficial and did not penetrate the subdermal tissue. Neurovascular examination of the foot was normal. The wounds were irrigated, dressed with Polysporin ointment and sterile gauze, and left to heal by secondary intent. The patient was treated with prophylactic rabies immunization (rabies immune globulin and human diploid cell vaccine). At the time of a follow-up visit the wounds had healed without complication. The suspect coyote was observed in the wild and while under surveillance it attempted to attack a ranger. The animal was captured and destroyed; laboratory studies were negative for rabies and canine distemper. Postmortem studies of the animal did not reveal a known pathologic explanation for its unusual behavior and appearance.
Discussion Coyotes are not normally aggressive animals. Like most undomesticated animals, they will shy away from human contact if given the opportunity although some can attack if provoked. Carbyn 1080-6032 © 1996 Chapman & Hall
Coyote attack in Yellowstone National Park
171
compiled anecdotal reports of coyote attacks in various Canadian national parks and in Yellowstone [I). The four cases presented occurred between 1960 and 1988 and involved apparent predatory attacks on small children less than 4 years old. The author surmised that these animals had become habituated to human contact due to feedings from tourists. Furthermore, these animals all attacked during times of food shortage. It was believed that the coyotes regarded the children as potential food sources. Although these attacking coyotes were thought to be healthy, they were not captured for testing. In our case report, the coyote's aggressive behavior was believed to arise from disease. Although rabies has never been reported in Yellowstone Park (personal communication) the ill appearance and bizarre behavior of this coyote made rabies our first concern. Rabies in coyotes has been reported: Clarke et al. reported an epizootic of canine rabies in Texas from 1988-1993 that involved 158 coyotes and 180 dogs [2]. There were no reports of human attacks by these animals. Another possible infectious source of this coyote's aggression was canine distemper virus, an airborne pathogen that can cause a spectrum of illness that ranges from asymptomatic infection to multisystem failure and death. In its more severe form an infected animal can resemble a rabid animal with fever, vomiting, and central nervous system dysfunction [3]. Fortunately, distemper is not a human pathogen. Data are scarce on the medical management of coyote bites. Treatment practice must therefore be extrapolated from the more familiar cases of domestic canine bites. Generally animal bites can be categorized as either crush/avulsion injuries, such as those inflicted by dogs or coyote, or puncture wounds, such as those inflicted by cats. The incidence of wound infection varies according to wound characteristics: crush/avulsion wounds are amenable to irrigation and debridement and have a lower risk for infection; puncture wounds frequently involve the innoculation of deep tissues and are difficult to clean, making them more prone to infection. The most common bacterial pathogens cultured from infected animal bites are Staphylococcus aureus, Streptococcus spp, and Pasturella multocida. A wider range of gram-negative and gram-positive organisms have been recovered from bite wound cultures but they are not frequent pathogens [4]. Although no documentation exists of the pathogenic flora obtained from coyotes, we speculated that it is similar to that of domestic dogs and managed the wound as if it were a dog bite. Current management guidelines for dog bites begin with copious irrigation with high pressure saline and debridement of devitalized tissue. If the patient presents early and the wound can be thoroughly cleaned, the wound can often be closed primarily and the patient discharged with close follow-up but without prophylactic antibiotics. Patients who require more rigorous treatment (prophylactic antibiotics and close observation) include patients with diabetes, immunosuppression, and the elderly. When prophylaxis is indicated amoxacillin-clavulanate, dicloxacillin, or cephalexin provide reasonable coverage for canine oral pathogens. Bites to the hand are potentially high risk for infection because of relatively poor blood supply, so delayed closure, prophylactic antibiotics, and surgical consultation [4] should be considered. High-risk cases must be assessed individually since management styles may differ. If indicated, tetanus toxoid should be administered as part of the management of all wounds. Depending on the circumstances of attack rabies prophylaxis should be considered. For domestic animals, initiation of rabies prophylaxis can be delayed up to 10 days while the animal is quarantined and the suspicion for rabies by history is low. However, wild animals are not easily captured or positively identified in most cases. Since ruling out rabies transmission by observation or laboratory study of the animal is often not possible, the Centers for Disease Control
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Hsu and Hallagan
recommend initiation of rabies prophylaxis for all wild animal bites except for rodents and lagamorphs [5]. Conclusion
Multiple factors may contribute to a coyote attack, the strongest factors being habituation to human contact and food shortage. Few guidelines exist for the management of coyote bites due to the paucity of documented cases. However, management practices can be derived from guidelines for dog bites. Meticulous wound care, consideration of prophylactic antibiotics for high-risk cases, and attention to tetanus and rabies prophylaxis form a firm basis for management. References 1. Carbyn, L. Coyote attacks on children in Western North America. Wild/. Soc. Bull. 1989; 17,444-446. 2. Clarke, K.A., Neill, S.U., Smith, J.S., et al. Epizootic canine rabies transmitted by coyotes in south Texas. JAm Vet Med Assoc 1994; 204(4), 479--484. 3. Appel, G. Canine Distemper Virus. Virology Micrographs, Vol. II. New York: Springer-Verlag, 1972: 54-55. 4. Doan-Wiggins, L. Animal bites and rabies. In: Rosen, P., Barkin, R.M., eds. Emergency Medicine: Concepts and Clinical Practice, 3rd edition. St. Louis: c.Y. Mosby, 1992: 864-866. 5. Centers for Disease Control. Rabies Prevention-United States. Recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR 40INo RR-3: I, 1991.
CASE REPORT
Case report of a coyote attack in Yellowstone National Park SAMUEL S. HSUI and LUANNE F. HALLAGANI,2 I Departmell1
of Surgery, Division of Emergency Medicine, University ofMaryland; 2 Yellowstone Park Medical Services
We report the case of an unprovoked coyote attack on a human visitor to Yellowstone National Park. Although the patient suffered only soft tissue injuries, unprovoked attacks are rarely reported in the medical literature. This case and plans on how to manage coyote attacks are discussed.
Key words: coyote, attack
Introduction Although there have been anecdotal reports of coyote attacks on humans, the literature that documents such cases is sparse and we were unable to find any medical literature on how to manage such attacks. With the increasing popularity of vacations in wilderness settings, we can expect a rise in human encounters with, and potential attacks by, coyotes. We present the case of a coyote attack and its treatment in Yellowstone National Park.
Case report A 57-year-old man from Germany had been hiking through Yellowstone Park when he stopped to rest in a field, removed his shoes, and fell asleep. He awoke with a pain in his right foot to find that he had been bitten by a coyote. The animal was described as sickly in appearance and it circled the patient and his companion for a moment before running away. The patient drove a private vehicle to Lake Hospital and was examined within an hour of the injury. The patient had no significant past medical history. Upon examination, multiple linear lacerations 5-10 mm were seen circumferentially around the distal right foot (Fig. I). The wounds were superficial and did not penetrate the subdermal tissue. Neurovascular examination of the foot was normal. The wounds were irrigated, dressed with Polysporin ointment and sterile gauze, and left to heal by secondary intent. The patient was treated with prophylactic rabies immunization (rabies immune globulin and human diploid cell vaccine). At the time of a follow-up visit the wounds had healed without complication. The suspect coyote was observed in the wild and while under surveillance it attempted to attack a ranger. The animal was captured and destroyed; laboratory studies were negative for rabies and canine distemper. Postmortem studies of the animal did not reveal a known pathologic explanation for its unusual behavior and appearance.
Discussion Coyotes are not normally aggressive animals. Like most undomesticated animals, they will shy away from human contact if given the opportunity although some can attack if provoked. Carbyn 1080-6032 © 1996 Chapman & Hall
Coyote attack in Yellowstone National Park
171
compiled anecdotal reports of coyote attacks in various Canadian national parks and in Yellowstone [I). The four cases presented occurred between 1960 and 1988 and involved apparent predatory attacks on small children less than 4 years old. The author surmised that these animals had become habituated to human contact due to feedings from tourists. Furthermore, these animals all attacked during times of food shortage. It was believed that the coyotes regarded the children as potential food sources. Although these attacking coyotes were thought to be healthy, they were not captured for testing. In our case report, the coyote's aggressive behavior was believed to arise from disease. Although rabies has never been reported in Yellowstone Park (personal communication) the ill appearance and bizarre behavior of this coyote made rabies our first concern. Rabies in coyotes has been reported: Clarke et al. reported an epizootic of canine rabies in Texas from 1988-1993 that involved 158 coyotes and 180 dogs [2]. There were no reports of human attacks by these animals. Another possible infectious source of this coyote's aggression was canine distemper virus, an airborne pathogen that can cause a spectrum of illness that ranges from asymptomatic infection to multisystem failure and death. In its more severe form an infected animal can resemble a rabid animal with fever, vomiting, and central nervous system dysfunction [3]. Fortunately, distemper is not a human pathogen. Data are scarce on the medical management of coyote bites. Treatment practice must therefore be extrapolated from the more familiar cases of domestic canine bites. Generally animal bites can be categorized as either crush/avulsion injuries, such as those inflicted by dogs or coyote, or puncture wounds, such as those inflicted by cats. The incidence of wound infection varies according to wound characteristics: crush/avulsion wounds are amenable to irrigation and debridement and have a lower risk for infection; puncture wounds frequently involve the innoculation of deep tissues and are difficult to clean, making them more prone to infection. The most common bacterial pathogens cultured from infected animal bites are Staphylococcus aureus, Streptococcus spp, and Pasturella multocida. A wider range of gram-negative and gram-positive organisms have been recovered from bite wound cultures but they are not frequent pathogens [4]. Although no documentation exists of the pathogenic flora obtained from coyotes, we speculated that it is similar to that of domestic dogs and managed the wound as if it were a dog bite. Current management guidelines for dog bites begin with copious irrigation with high pressure saline and debridement of devitalized tissue. If the patient presents early and the wound can be thoroughly cleaned, the wound can often be closed primarily and the patient discharged with close follow-up but without prophylactic antibiotics. Patients who require more rigorous treatment (prophylactic antibiotics and close observation) include patients with diabetes, immunosuppression, and the elderly. When prophylaxis is indicated amoxacillin-clavulanate, dicloxacillin, or cephalexin provide reasonable coverage for canine oral pathogens. Bites to the hand are potentially high risk for infection because of relatively poor blood supply, so delayed closure, prophylactic antibiotics, and surgical consultation [4] should be considered. High-risk cases must be assessed individually since management styles may differ. If indicated, tetanus toxoid should be administered as part of the management of all wounds. Depending on the circumstances of attack rabies prophylaxis should be considered. For domestic animals, initiation of rabies prophylaxis can be delayed up to 10 days while the animal is quarantined and the suspicion for rabies by history is low. However, wild animals are not easily captured or positively identified in most cases. Since ruling out rabies transmission by observation or laboratory study of the animal is often not possible, the Centers for Disease Control
172
Hsu and Hallagan
recommend initiation of rabies prophylaxis for all wild animal bites except for rodents and lagamorphs [5]. Conclusion
Multiple factors may contribute to a coyote attack, the strongest factors being habituation to human contact and food shortage. Few guidelines exist for the management of coyote bites due to the paucity of documented cases. However, management practices can be derived from guidelines for dog bites. Meticulous wound care, consideration of prophylactic antibiotics for high-risk cases, and attention to tetanus and rabies prophylaxis form a firm basis for management. References 1. Carbyn, L. Coyote attacks on children in Western North America. Wild/. Soc. Bull. 1989; 17,444-446. 2. Clarke, K.A., Neill, S.U., Smith, J.S., et al. Epizootic canine rabies transmitted by coyotes in south Texas. JAm Vet Med Assoc 1994; 204(4), 479--484. 3. Appel, G. Canine Distemper Virus. Virology Micrographs, Vol. II. New York: Springer-Verlag, 1972: 54-55. 4. Doan-Wiggins, L. Animal bites and rabies. In: Rosen, P., Barkin, R.M., eds. Emergency Medicine: Concepts and Clinical Practice, 3rd edition. St. Louis: c.Y. Mosby, 1992: 864-866. 5. Centers for Disease Control. Rabies Prevention-United States. Recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR 40INo RR-3: I, 1991.