Bites by non-native venomous snakes in the United States

Transcription

1 Wilderness and Environmental Medicine, 4, (1996) ORGNAL ARTCLE Bites by non-native venomous snakes in the United States SHERMAN A. MNTON* Department ofmicrobiology and mmunology, ndiana University School ofmedicine. ndianapolis. N USA Fifty-four consultations regarding bites by venomous snakes not native to the United States are summarized. These are from a database of 164 consultations during the period At least 9 non-native snake species were involved with cobras making up -40% of the group. There was one fatality. A high percentage of venomous snakebites in the United States involve deliberate interaction with snakes. The proportion of bites by non-native species seems to be increasing. Some of the snake species involved are discussed, and some principles for management of these bites are given. Key words: snakebite epidemiology, exotic snakebites, cobra bites, antivenoms ntroduction n most nations, snakebite is a disease of the rural agricultural population, and the reptiles involved are part of the free-living native herpetofauna. However, in the United States, Australia, and some European nations a significant number of snakebites are caused by snakes kept in captivity that often are non-native species. n the United States, this is largely a development of the past 30 years and can be attributed to the increasing popularity of herpetoculture as an avocation and a money-making business. A great majority of herpetoculturists work only with nonvenomous species, but a few specialize in keeping and breeding venomous species, and others do so occasionally. n a 1959 survey of US hospitals and physicians, Parrish [1] reported that only 7 of 6680 venomous snakebites were inflicted by non-native species. Five cases were persons bitten by snakes in zoos, pet shops, and private collections; two were workers bitten by snakes imported in bananas. During the period, Parrish reported three fatalities from bites of exotic snakes. Russell [] reported that 13% of snakebites in his series of 650 cases were inflicted by non-native species of at least 19 genera. There have been no other extensive surveys in recent years, although there have been a number of individual case reports [3-7]. This report summarizes information on 54 bites by non-native venomous snakes in the United States during a 17-year period. Materials and methods The database for this paper is 164 consultations concerning reptile bites between 1977 and 1995 excluding 1980, a year the author spent mostly outside the United States. Requests for *Address for correspondence: Department of Microbiology and mmunology, ndiana University School of Medicine, 635 Barnhill Drive, ndianapolis, N , USA Chapman & Hall

2 98 Minton information came from hospital emergency departments, poison information centers, physicians in private practice, zoos, serpentaria, and the patients themselves. They originated from 3 states, the majority from ndiana, Florida, and Texas. The great majority of consultations were by telephone; however, several patients were seen in hospital setting or where the bite occurred. All consultations were within 7 hours or less of the bite; incidents reported to me weeks or months afterward are not included. The author almost always attempted to get follow-up information following the initial consultation, but this was forthcoming in less than half of the incidents. Fifty-four instances of envenoming by snakes not native to North America are the substance of this report and make up 33% of the total. Omitted are two cases of envenoming by the Mexican beaded lizard (Heloderma horridum) and two cases of bites by large pythons where the concern was infection and trauma. Snakes of at least 9 species were involved (Table 1). Only rarely was the author able to verify the identification of the snake personally; however, identifications by competent herpetologists on the site were accepted. Fifty-three of the bites were inflicted by snakes in captivity. One involved a herpetologist bitten by a coral snake in the field in Mexico where he was initially treated before being evacuated to the United States. This case is reported in more detail elsewhere [8]. There were 106 bites by native North American reptiles (l05 snakes, 1 lizard). n some, the snake was not identified, and not all bites resulted in envenomation. Results n addition to 58 bites by exotic reptiles, 5 of the 106 bites by native species in this series were inflicted by animals in captivity. This leaves only 80 of 164 bites inflicted by free-living reptiles, and a substantial number of these bites resulted from individuals attempting to capture snakes. Clearly, keepers and hunters of venomous reptiles make up a well-defined high-risk group. Ofthe 51 individuals in this series bitten by non-native snakes, 47 were adult males and 4 adult females. The youngest was age 16 years. Three individuals were bitten twice by exotic snakes during a -year period; one of them sustained a third bite by a native snake. Cobras accounted for 3 of the bites by non-native venomous snakes and for the only fatality. Twenty-two of the bites were by cobras of the genus Naja and one by the king cobra (Ophiophagus hannah). Because cobras represent to most of the public the quintessential deadly snake, they are almost obligatory in a zoo reptile house and are popular with snake showmen and some amateur snake keepers. Moreover, they are readily available in the animal trade. fhealthy when acquired, they do well in captivity. Seven bites were ascribed to the monocellate cobra here identified as Naja kaouthia (Figure 1), although the monocle hood mark may be seen in other Asian Naja, and not all kaouthia show it in typical form. The monocellate cobra appears to be the species most generally available in the United States. Two other Asian species, N. atra and N. oxiana were each identified as the cause of one bite. Six bites including the fatality were ascribed to ndian or Asian cobras not identified to species. The African ringed cobra (Naja haje annulifera) accounted for three bites, two inflicted by the same snake on the same individual about 3 months apart. The African Cape cobra (Naja nivea) accounted for one bite, and an African spitting cobra not identified to species accounted for one. n two cases, the snake was identified only as a cobra. On the basis of information available, seven of the non-fatal cases showed serious systemic symptoms and might have been placed in a "life-threatening" category. Seven showed only local symptoms, but two of these individuals had significant necrosis. The remaining cases could not be categorized on the available information, but all apparently recovered. The king cobra bite is discussed in detail [9]. African vipers of the genus Bitis accounted for six bites, three by the puff adder (B. arietans),

3 Non-native venomous snakebites in the United States Table 1. Venomous bites by non-native snakes Species 99 Bites (n) Family Elapidae Eastern green mamba Dendroaspis angusticeps Balsan coral snake Micrurus laticollaris Chinese cobra Naja atra African ringed cobra Naja haje annulifera Monocellate cobra Naja kaouthia Oxus cobra Naja oxiana Cape cobra Naja nivea King cobra Ophiophagus hannah Cobra, species uncertain Collett's snake Pseudechis colletti Family Viperidae Puff adder Bitis arietans Gaboon viper Bitis gabonica Rhinoceros viper Bitis nasicornis Desert horned viper Cerastes cerastes Russell's viper Daboia russelli Sindhi saw-scale viper Echis carinatus Painted saw-scale viper Echis coloratus Baluch sand viper Eristicophis macmahoni Nose-horn viper Vipera ammodytes European viper Vipera berus Cantil Agkistrodon bilineatus Eyelash viper Bothriechis schlegeli Tropical rattlesnake Crotalus durissus Uracoan rattlesnake Crotalus vegrandis Green tree vipers Trimeresurus spp. Family Atractaspididae South African burrowing asp Atractaspis bibroni Family Colubridae Mangrove snake Boiga dendrophila Boomslang Dispholidus typus Malagasy hognose snake Leioheterodon madagascariensis Southeast Asian garter snake Rhabdophis sp one by the Gaboon viper (B. gabonica; Figure ), and two by the rhinoceros viper (B. nasicornis). These are large, very heavy snakes, and the Gaboon and rhinoceros vipers have bizarre and colorful patterns, all factors that make them popular with zoos and snake hobbyists. Only one of these bites resulted in serious envenomation; four were by small juvenile snakes. However, in 1964 a zoo director died from the bite of a puff adder, the only snakebite fatality at a major U.S. zoo in recent times. Two bites were by the small but very dangerous saw-scaled vipers of the genus Echis, one E. carinatus from Pakistan, the other E. coloratus of unknown origin. The carinatus case involved severe envenoming of an individual who had had 145 previous snakebites. t is reported in detail

4 300 Minton... '~., #1 ~., - '~!'_.'~ ~ )<'ig. 1. Monocellate cobra (Naja kaouthia). This southeast Asian cobra is the species most available to zoos and private collectors in the United States. elsewhere [3,10]. The coloratus bite was one of moderate envenoming. Two bites by the very dangerous Russell's viper (Daboia russelli) at serpentaria did not result in serious envenomation. Arboreal vipers are a group commonly maintained in captivity by both amateurs and professionals, for they are beautifully colored, pose attractively on branches and vines, and some have curious head ornamentation. Species of the Asian genus Trimeresurus, Latin American Bothriechis and Bothriopsis, and African Atheris are involved. n my series, one bite was inflicted by the eyelash viper (Bothriechis schlegeli, Figure 3) and two by green Trimeresurus. A very recent (1996) consultation involved a bite by the African green bush viper (Atheris chlorechis). Species identification of tree vipers can be difficult even for experienced herpetologists. These vipers are an important cause of snakebites in Latin America and tropical Asia, but fatalities are rare. The bites in my series were not serious. The Family Colubridae includes most of the world's snakes with species whose bites range from potentially lethal to completely innocuous. Minton [11] discusses venomous bites by snakes of this family. Bites of four non-native colubrid species are included in this report. One by an Asian snake of the genus Rhabdophis was accompanied by coagulopathy, indicative of systemic envenomation. Discussion The series of incidents reported here strongly suggests that snakebite in the United States is frequently related to deliberate interaction between humans and venomous snakes. n a

5 Non-native venomous snakebites in the United States 301 Fig.. Gaboon viper (Bitis gabonica). These large, heavy African snakes are popular in zoos and private collections. significant number of cases, the snakes are not native species. This is associated with some potential problems. Although zoos and research institutions that keep venomous snakes almost always have emergency plans that involve briefing emergency physicians and providing appropriate antivenoms, this is rarely the case with amateur snake keepers. Some are irresponsible individuals; others may be violating state or city laws by keeping venomous or legally protected reptile species. This may make them reluctant to seek help when bitten and to give full information. An accurate identification of the snake, including scientific name is important. Names such as "golden cobra" or "black-and-white cobra" are not terribly helpful. "Mangrove snake" to most herpetologists is a large arboreal southeast Asian colubrid, but have heard the name applied to an Asian pit viper and an innocous Florida water snake. t is not the intent of this paper to discuss clinical management of snakebite on a global basis. This is adequately done in several recent books and papers [1-14]. However, a few principles are worth mentioning. Most individuals and institutions that maintain collections of venomous snakes are located in or near large cities, so the emergency department of a large urban hospital may be the first medical facility contacted by a snakebite victim. This may be a totally unfamiliar situation for the medical personnel, and there may be a tendency to over-react. There is nearly always time to seek advice from poison information centers and other sources. Remember also that even the most dangerous snakes, such as the king cobra and black mamba, may bite and inject no venom. Although there are unique aspects to snake envenomation, many serious manifestations, such as hypovolemic shock, respiratory failure, and renal shutdown, respond to well-known general supportive procedures.

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7 Non-native venomous snakebites in the United States 303 Antivenoms are not available for a fair number of snakes, including the burrowing asps (Atractaspis), bush vipers (Atheris), dwarf cobras (Aspidelaps) nearly all colubrids, and a variety of rare species. Unfortunately, these novelties are often sought by snake keepers, and their bites can present difficult decisions in management. A recent example was a bite by Collett's snake, (Pseudechis colletti) a large Australian reptile, rare and poorly known even to Australian experts. An assumption that its venom was similar to that of its better known relative, the king brown snake (P. australis), luckily proved to be correct. Many snake species are disappearing worldwide with the wilderness, but others persist in new and unexpected roles. Snakebites in the United States no longer occur almost exclusively in rural and wilderness environments and no longer are inflicted almost exclusively by native reptiles. References 1. Parrish, H.M. Poisonous Snakebites in the United States. Vantage Press, New York: Russell, F.E. Snake Venom Poisoning. J.B. Lippincott, Philadelphia: Plowman, D.M., Reynolds, T.M., and Joyce, S.M. Poisonous snakebite in Utah. West J Med 1995, 163, Stueven, H., et al. Cobra envenomation: an uncommon emergency. Ann Emerg Med 1983, 1, Tiger, M.E., Brecher, E., Bevan, D. Cobra bite in Philadelphia. Penn Med 1975; 87, Trestrail, J.H. The "undergroundzoo"-the problem of exotic venomous snakes in private possession in the United States. Vet Human Toxicol (Suppl) 198; 4, Gold, B.S. Neostigmine for treatment ofneurotoxicity following envenomation by the Asian cobra. Ann Emerg Med 1996; 8, Pettigrew, L.C., Glass, J.e. Neurologic complications of a coral snake bite. Neurology 1985; 35, Wetzel, WW., Christy, N.P. A king cobra bite in New York City. Toxicon 1989; 7, Weis, lr., et al. Prolonged hypofibrinogenemia after envenomation by the exotic snake Echis carinatus. Venom Res Lab Veterans Affairs Med Ctr Salt Lake City, Minton, S.A. Venomous bites by nonvenomous snakes: an annotated bibliography of colubrid envenomation. J Wilderness Med 1990; 1, Junghanss, T., Bodio, M. Notfall-Handbuch Gifttiere. Georg Thieme, Stuttgart: Meier, J., White, J. Clinical Toxicology ofanimal Venoms and Poisons. CRC Press, Boca Raton, FL: Minton, S.A., Norris, R.L. Non-North American venomous reptile bites. n: Auerbach, P.S., ed. Wilderness Medicine, Mosby-Year Book, St. Louis: 1995: Theakston, R.D.G., Warrell, D.A. Antivenoms: a list of hyperimmune sera currently available for the treatment of envenoming by bites and stings. Toxicon 1991; 9,