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    Medically important venomous snake species of Sri Lanka.

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    Algorithm differentiating venomous, medically important snake species of Sri Lanka by clinical syndrome.

  • 1

    Baldaeus P, 1672. Naauwkeurige beschryvinge van Malabar en Choromandel, der zelver aangrenzende ryken, en het machtige eyland Ceylon. Amsterdam: JJ van Waesberge and J van Someren.

  • 2

    Sawai Y, Toriba M, Itokawa H, De Silva A, Perera GLS, Kottegoda MB, 1984. Study on deaths due to snakebite in Anuradhapura District, Sri Lanka. The Snake 16 :7–15.

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  • 3

    Fox S, Rathuwithana AC, Kasturiratne A, Lalloo DG, de Silva HJ, 2006. Underestimation of snakebite mortality by hospital statistics in the Monaragala District of Sri Lanka. Trans R Soc Trop Med Hyg 100 :693–695.

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  • 4

    de Silva A, 1990. Colour Guide to the Snakes of Sri Lanka. Portishead, United Kingdom: R & A Publishing Ltd.

  • 5

    Ranasinghe L, Uragoda CG, 1983. Symposium: medically important snakes and snake-bite in Sri Lanka. Ceylon Med J 28 :107–201.

  • 6

    Theakston RD, Reid HA, 1977. Micro-ELISA for detecting and assaying snake venom and venom antibody. Lancet ii :639–641.

  • 7

    Virivan C, Veeravat U, Warrell MJ, Theakston RD, Warrell DA, 1986. ELISA confirmation of acute and past envenoming by the monocellate Thai cobra (Naja kaouthia). Am J Trop Med Hyg 35 :173–181.

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  • 8

    Ho M, Warrell MJ, Warrell DA, Bidwell D, Voller A, 1986. A critical reappraisal of the use of enzyme-linked immunosorbent assays in the study of snake bite. Toxicon 24 :211–221.

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  • 9

    Phillips RE, Theakston RD, Warrell DA, Galagedera Y, Abeysekera DT, Dissanayake P, Hutton RA, Aloysius DJ, 1988. Paralysis, rhabdomyolysis and haemolysis caused by bites of Russell’s viper (Vipera russelli pulchella) in Sri Lanka: failure of Haffkine antivenom. Q J Med 68 :691–716.

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  • 10

    Dong le V, Selvanayagam ZE, Gopalakrishnakone P, Eng KH, 2002. A new avidin-biotin optical immunoassay for the detection of beta-bungarotoxin and application in diagnosis of experimental snake envenomation. J Immunol Methods 260 :125–136.

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  • 11

    Chandler HM, Hurrell JG, 1982. A new enzyme immunoassay system suitable for field use and its application in a snake venom detection kit. Clin Chim Acta 21 :225–230.

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  • 12

    Viravan C, Looareesuwan S, Kosakarn W, Wuthiekanun V, McCarthy CJ, Stimson AF, Bunnag D, Harinasuta T, Warrell DA, 1992. A national hospital-based survey of snakes responsible for bites in Thailand. Trans R Soc Trop Med Hyg 86 :100–106.

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  • 13

    Warrell DA, Davidson NMcD, Greenwood BM, Ormerod LD, Pope HM, Watkins BJ, Prentice CR, 1977. Poisoning by bites of the saw-scaled viper (Echis carinatus) in Nigeria. Q J Med 46 :33–62.

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  • 14

    Sano-Martins IS, Fan HW, Castro SC, Tomy SC, Franca FO, Jorge MT, Kamiguti AS, Warrell DA, Theakston RD, 1994. Reliability of the 20 minute whole blood clotting test (WBCT20) as an indicator of low plasma fibrinogen concentration in patients envenomed by Bothrops snakes, Butantan Institute Antivenom Study Group. Toxicon 32 :1045–1050.

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  • 15

    Ariaratnam CA, Thuraisingam V, Kularatne SA, Sheriff MH, Theakston RD, de Silva A, Warrell DA, 2008. Frequent and potentially fatal envenoming by hump-nosed pit vipers (Hypnale hypnale and H. nepa) in Sri Lanka: lack of effective antivenom. Trans R Soc Trop Med Hyg 102 :1120–1126.

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  • 16

    Ariaratnam CA, Sheriff MH, Theakston RD, Warrell DA, 2008. Distinctive epidemiologic and clinical features of common krait (Bungarus caeruleus) bites in Sri Lanka. Am J Trop Med Hyg 79 :458–462.

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  • 17

    Amarasekera N, Jayawardena A, Ariyaratnam A, Hewage UC, De Silva A, 1994. Bites of a sea snake (Hydrophis spiralis): a case report from Sri Lanka. Am J Trop Med Hyg 97 :195–198.

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  • 18

    Senanayake MP, Ariaratnam CA, Abeywickrema S, Belligaswatte A, 2005. Two Sri Lankan cases of identified sea snake bites without envenoming. Toxicon 45 :861–863.

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  • 19

    Warrell DA, 1994. Sea snake bites in the Asia-Pacific Region. Gopalakrishnakone P, ed. Sea Snake Toxinology. Singapore: Singapore University Press, 1–36.

  • 20

    Gnanathasan CA, Rodrigo PC, Peranantharajah S, Anitha Coonghe, Pieris P, 2008. A Case Series of Envenoming by Saw-Scaled Viper (Echis carinatus) in Sri Lanka. Global Issues in Clinical Toxinology, Melbourne. Available at: http://www.snakebiteinitiative.org/files/GICT%20Conference%202008/Session%204/Dr%20Ariaranee%20Gnanathasan.ppt. Accessed July 12, 2009.

  • 21

    Pathmeswaran A, Kasturiratne A, Fonseka M, Nandasena S, Lalloo DG, de Silva HJ, 2006. Identifying the biting species in snakebite by clinical features: an epidemiological tool for community surveys. Trans R Soc Trop Med Hyg 100 :874–878.

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  • 22

    Sellahewa KH, Gunawardena G, Kumararatne MP, 1995. Efficacy of antivenom in the treatment of severe local envenomation by the hump-nosed viper (Hypnale hypnale). Am J Trop Med Hyg 53 :260–262.

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  • 23

    Seneviratne SL, Opanayake CJ, Ratnayake NS, Sarath Kumara KE, Sugathadasa AM, Weerasooriya N, Wickrema WA, Gunatilake SB, de Silva HJ, 2000. Use of antivenom serum in snake bite: a prospective study of hospital practice in the Gampaha district. Ceylon Med J 45 :65–68.

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  • 24

    Premawardhena AP, de Silva CE, Fonseka MM, Gunatilake SB, de Silva HJ, 1999. Low dose subcutaneous adrenaline to prevent acute adverse reactions to antivenom serum in people bitten by snakes: randomised placebo controlled trial. BMJ 318 :730–733.

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Syndromic Approach to Treatment of Snake Bite in Sri Lanka Based on Results of a Prospective National Hospital-Based Survey of Patients Envenomed by Identified Snakes

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  • 1 Department of Clinical Medicine and Department of Community Medicine, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka; Liverpool School of Tropical Medicine, Liverpool, United Kingdom; Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom

Of 860 snakes brought to 10 hospitals in Sri Lanka with the patients they had bitten, 762 (89%) were venomous. Russell’s vipers (Daboia russelii) and hump-nosed pit vipers (Hypnale hypnale) were the most numerous and H. hypnale was the most widely distributed. Fifty-one (6%) were misidentified by hospital staff, causing inappropriate antivenom treatment of 13 patients. Distinctive clinical syndromes were identified to aid species diagnosis in most cases of snake bite in Sri Lanka where the biting species is unknown. Diagnostic sensitivities and specificities of these syndromes for envenoming were 78% and 96% by Naja naja, 66% and 100% by Bungarus caeruleus, 14% and 100% by Daboia russelii, and 10% and 97% by Hypnale hypnale, respectively. Although only polyspecific antivenoms are used in Sri Lanka, species diagnosis remains important to anticipate life-threatening complications such as local necrosis, hemorrhage and renal and respiratory failure and to identify likely victims of envenoming by H. hypnale who will not benefit from existing antivenoms. The technique of hospital-based collection, labeling and preservation of dead snakes brought by bitten patients is recommended for rapid assessment of a country’s medically-important herpetofauna.

INTRODUCTION

Snake bite is an important public health problem in Sri Lanka first revealed to the outside world by Baldaeus in 1672: “The most venomous ones are Cobres Capellos of whose bite I know many persons died at Jafnapatan.”1 According to the Epidemiology Unit, Ministry of Health, reported snake bite numbers increased from 12,175 per year in 1991 to 37,244 in 2002 and 36,861 in 2005. Deaths peaked at 194 in 2000; there were 134 in 2005. However, these data, based on hospital records, underestimate the true extent of the problem. 2,3

More than 100 terrestrial snake species inhabit Sri Lanka, but only six are medically important: Indian cobra (Naja naja), common and Sri Lankan kraits (Bungarus caeruleus and B. ceylonicus), Russell’s viper (Daboia russelii), saw-scaled viper (Echis carinatus), and hump-nosed pit viper (Hypnale hypnale).4,5 Three other vipers, H. nepa, H. walli, and Trimeresurus trigonocephalus, bite rarely and with negligible consequences as do some mildly venomous colubrids.5 Some 15 species and 8 genera of venomous sea snakes (Elapidae) have been recorded in Sri Lankan waters. Hundreds of clinical reports of snake bites have been published in the Sri Lankan and international medical literature over the past century. In most cases, these are based only on the presumptive identification of the species involved.

Accurate snake identification is important for optimal management of the patient and for determining epidemiology of bites. Species identification depends mainly on interpretation by doctors of descriptions of the snake provided by victims or witnesses. This method is unreliable because most bites occur at night or in undergrowth and few people are trained to identify snakes. Even if the snake is seen, its markings may be obscured or misrecorded and there may be a reluctance to capture or kill the animal because of fear or superstition. Evolutionary mimicry of venomous by non-venomous species further complicates accurate identification. For example, in Sri Lanka, several harmless colubrid snakes are frequently confused with kraits, e.g., Lycodon aulicus (banded form) and Dryocalamus nympha with B. caeruleus and Cercaspis carinatus with B. ceylonicus.4

Laboratory diagnostic techniques, notably enzyme immunoassays, have been developed to detect venom antigens in blood, wound swabs, wound aspirate, and other body fluids,610 but commercial venom detection kits are marketed only in Australia. 11 An alternative approach is to identify distinctive clinical syndromes associated with bites by individual species. This type of syndromic classification of snake bites will enable identification of snake bites without relying solely on the live or killed snake or victim’s description of the snake. First, a reliable data base of clinical cases must be developed in which the biting species has been established beyond doubt. We adopted the technique of Viravan and others, who established the distribution and relative medical importance of 16 taxa of venomous snakes in Thailand by collecting dead snakes brought to hospitals with bitten patients. 12

METHODS

This was a collaborative study between the Universities of Oxford and Colombo conducted from August 1993 through July 1997. We visited 10 hospitals in Sri Lanka (3 in Colombo and 1 each in Negombo, Panadura, Wathupitiwela, Chilaw, Matale, Polonnaruwa, and Anuradhapura). These hospitals were selected because of their high snake bite admissions and their locations in different climatic zones of Sri Lanka. The study protocol was discussed with doctors and nurses in the medical wards and intensive and emergency care units. Ethical clearance was provided by the Ethics Review Committee, Faculty of Medicine, University of Colombo.

Snakes responsible for bites.

Patients were selected for the study if they had a history of snake bite and had brought with them to hospital the snake responsible. Snakes were labeled with the patient’s name, hospital number, date and time of bite, hospital and district, and the name of the snake in Sinhala, Tamil, or English. Dead snakes were immersed in formaldehyde and their body cavities were opened by a ventral incision before immersion in the case of large specimens. Smaller snakes were injected with preservative every 2 cm along the length of the body. Live snakes were transported to the National Zoological Garden in Colombo. Every 3–6 months, the principal investigator visited the hospitals to check adherence to the protocol and to collect the dead snakes. These were identified, measured, and their sexes were determined at the Faculty of Medicine in Colombo with the assistance of the late Hiasinth Molligoda, an experienced herpetologist.

Patients were admitted to the hospital for at least 24 hours. Informed consent was obtained before they were recruited into the study. Medical history was recorded on a standard proforma, including demographic data, results of clinical examinations and investigations, and the medical staff’s identification of the snake. Venom-induced consumption coagulopathy was detected using the 20-minute whole blood clotting test. 13,14

Statistical analysis.

Proportions and percentages were used to describe the clinical characteristics of snake bites. Validity of the syndromic classification of snake bites as a screening test in identifying specific snake bites was assessed using sensitivity (i.e., ability of a test to identify those who have a condition/ disease) and specificity (i.e., ability of a test to identify those who do not have a condition/disease).

RESULTS

Identified snakes.

The dead or living snake responsible was brought to the hospital by 860 bitten patients. Seven hundred sixty-two specimens (89%) comprised 7 venomous species (Table 1). Russell’s vipers (38%) and hump-nosed pit vipers (35%) were the most numerous and the most widely distributed (in all 10 hospitals). Ninety-eight specimens (11% of the total) comprised 9 non-venomous species (Colubridae: 48 wolf snakes [15 Lycodon striatus sinhalayus and 33 L. aulicus], 10 green vine snakes [Ahaetulla nasuta], 14 cat snakes [8 Boiga forstenii, 4 B. trigonata trigonata, and 2 B. ceylonensis], 11 rat snakes [Ptyas mucosus], 6 kukri snakes [Oligodon arnensis], 1 trinket snake [Elaphe helena], 3 checkered keelbacks [Xenochrophis piscator], 1 flying snake [Chrysopelea ornata ornata]; Uropeltidae: 1 pipe snake [Cyllindrophis maculatus], 1 keelback water snake [Atretium schistosum]; and Boidae: 2 pythons [Python molurus molurus]).

Misidentification of snakes by hospital staff.

Snakes were misidentified by the hospital staff on 51 occasions; this misidentification resulted in unnecessary use of antivenom. Hump-nosed pit vipers were misidentified as Russell’s vipers on 36 occasions; cat snakes (Boiga ceylonensis and B. trigonata trigonata) were misidentified as hump-nosed pit vipers twice, as Russell’s vipers three times, and as a saw-scaled viper once; pythons were misidentified as Russell’s vipers twice; wolf snakes (L. aulicus), banded phase, and L. striatus sinhalayus) were misidentified as common kraits 5 times and rat snakes as cobras twice. Antivenom was given inappropriately on 13 occasions because a non-venomous species or a hump-nosed viper had been mistaken for one of the four species covered by Indian polyspecific antivenom.

Epidemiology.

The 860 patients who brought the snake responsible for the bite comprised 25% of the 3,411 snake-bitten patients admitted to the 10 participating hospitals during the 4-year study period. Six hundred twelve (71%) patients were male and 248 (29%) were female (M:F ratio = 2.5:1). Most were 20–30 years of age. All but one of the common krait bites occurred while victims were sleeping at night on the floors of their homes, whereas only 2% of Russell’s viper and hump-nosed pit viper bites occurred under similar circumstances. Fifty-six percent of cobra and Russell’s viper bites occurred during the day (40% of D. russelii bites occurred between 6:00 pm and midnight). Fifty percent of hump-nosed pit viper bites occurred after 6:00 pm (during the hours of darkness).

Most bites (52%) occurred during September–November, in the rainy season (northeast monsoon), which included 56% of Russell’s viper bites that occurred during this period. The main activities of victims associated with snake bites were sleeping, farming, walking, working, and gardening. Sixty-nine percent of Russell’s viper bites were associated with agricultural activities such as harvesting, weeding, and cutting grass in paddy fields, and 19% occurred while the victim was walking on rural roads or narrow foot paths, jungle tracks, and paddy fields. Seventy-eight percent of hump-nosed pit viper bites occurred while the victims were walking in the dark along roads or foot paths, were in their compounds or engaged in activities such as gardening, collecting firewood, or playing.

Anatomic sites of bites.

Ninety-two percent of D. russelii bites and 81% of H. hypnale bites occurred on the lower limbs. Krait bites occurred anywhere on the body (35% on the upper limbs, 25% on the lower limbs, 19% on the trunk, 3% on the genitalia, and 2% on the scalp).

Delay before admission to a hospital.

Because their bites occurred at night when transport was scarce, only 20% of B. caeruleus bite victims reached hospital within an hour of the bite, compared with 44% of H. hypnale bite victims and 25% of D. russelii viper bite victims.

Clinical features.

The clinical features recorded in the 762 patients bitten by 7 species of identified venomous snakes are shown in Table 2. Based on these observations and some additional data (see below), distinctive clinical syndromes were recognized (Table 3 and Figure 1).

For Russell’s viper (D. russelii) bites (319 cases), local swelling and regional lymphadenopathy developed in 307 (96%) patients. Incoagulable blood (20-minute whole blood clotting test) occurred in 244 (76%). There was persistent bleeding from bite (46%) or venipuncture (38%) sites. Spontaneous bleeding manifested as hematuria (47%), gum bleeding (34%), hematemesis (34%), vaginal or rectal bleeding (2%), and ecchymosis and bruising (11%). Acute renal failure that required peritoneal or hemodialysis developed in 60 (19%) patients. Fifty-seven percent showed neurotoxic signs, 24% showed generalized myalgia, and 2% showed respiratory failure that required mechanical ventilation.

For hump-nosed pit viper (H. hypnale) (302 cases), 15 276 (91%) patients had local swelling and 186 (62%) had blistering. Incoagulable blood and spontaneous bleeding occurred in 117 patients (39%). Acute renal failure that required dialysis developed in 30 (10%) patients. None had neurotoxic signs.

For saw-scaled viper (E. carinatus) (1 case), local bleeding, swelling, incoagulable blood, and spontaneous bleeding developed in one patient. He did not develop acute renal failure or neurotoxicity.

For cobra (N. naja) (45 cases), these patients often had severe neurotoxic signs and/or local envenoming (swelling, pain, blistering, necrosis). Local swelling developed in 91% of patients, blistering in 84%, and necrosis in 67%. Thirty-four patients (76%) required wound debridement and 16 (36%) needed skin grafting. Eight (18%) required amputation of limbs, fingers, or toes. Thirty-six (80%) developed neurotoxic signs, of which 35 (78%) had ptosis, 29 (64%) had ophthalmoplegia, 6 (13%) had dysphagia, and 9% had respiratory failure that required mechanical ventilation. No patient developed spontaneous bleeding, incoagulable blood, or acute renal failure.

For common krait (B. caeruleus) (88 cases), 16 symptoms or signs of local envenoming (minimal swelling, pain, paraesthesiae) were recorded in 9% of the patients. Typical neurotoxic signs, such as partial or complete ptosis, external ophthalmoplegia, and difficulty in breathing, which were identical to those observed in cobra bite victims, developed in 84 (95%) patients and respiratory failure that required mechanical ventilation developed in 64%. Abdominal pain and/or vomiting were reported in 80 (91%). No patient had spontaneous bleeding or incoagulable blood.

For sea snake (Hydrophis spiralis) (1 case), 17 one bite victim had no signs of local envenoming. Multiple fang marks were observed at the site of bite. He had severe myalgia, muscle tenderness, and neurotoxic signs but did not develop respiratory failure or acute renal failure.

For green pit viper (Trimeresurus trigonocephalus) (6 cases), four patients (67%) had local swelling. One complained of abdominal pain and vomiting. None had signs of systemic envenoming.

The clinical spectrum of local and systemic envenoming is shown in Tables 3 and 4. This spectrum formed the basis for development of a syndromic approach to the treatment of envenoming in Sri Lanka.

Sensitivity and specificity of clinical syndromes.

The sensitivity (i.e., ability of a test to identify true positive results) and specificity (i.e., ability of a test to identify true negative results) of clinical syndromes as a screening test for identifying which species of snake was responsible for envenoming is shown in Table 5. Specificities were high for all syndromes (< 95%). None of the patients bitten by N. naja, B. caeruleus, or H. hypnale showed the D. russelii envenoming syndrome (specificity = 100%). Sensitivities varied considerably (Table 5) because of wide variation in the extent of envenoming, especially by the two viperine species.

Antivenom treatment.

Antivenom was used in 77% of bites by Russell’s viper, 78% of bites by cobras, 95% of bites by the common krait, 19% of bites by hump-nosed vipers, and all bites by green pit vipers.

DISCUSSION

An algorithm has been developed that will help medical personnel in Sri Lanka determine the species of snake responsible for a bite based on the circumstances of the accident and the clinical syndromes that were identified (Figure 2). This algorithm was based largely on a survey of 762 patients in 10 hospitals in Sri Lanka who brought the snake responsible for biting them to the hospital. This technique, which was used in Thailand, 12 is recommended as a simple means of obtaining information about the relative importance of different species of venomous snakes in a particular geographic region and the effects of envenoming. Dead snakes brought to hospitals are usually discarded by the medical staff after cursory inspection. However, in our study, we asked the nursing and medical staff to label dead snakes and drop them into a bucket of formalin kept near in the ward. Time spent in explaining the study in the participating hospitals was amply rewarded by the resulting enthusiastic cooperation and interest.

Because only those patients who were able to bring the snake responsible (dead or alive) were included in this study, bites by more sluggishly moving vipers are likely to be over-represented, compared with faster and more agile elapids. Snakes that habitually bite at night while the patient is sleeping, such as B. caeruleus, are also less likely to be seen and caught. Because only one case each of envenoming by E. carinatus and sea snake (H. spiralis) and only six cases of envenoming by T. trigonocephalus were represented in our series, further case reports and reviews were considered when defining the clinical pattern of envenoming by these species. 5,1820

Recently, Pathmeswaran and others published a clinical scoring system for identification of the snake species responsible for bites in Sri Lanka. 21 However, rather than using actual snake bite data, the authors resorted to an artificial data set based, somewhat arbitrarily, on “published literature and our knowledge from extensive clinical experience of snakebite.” This set enabled them to create “as many different artificial circumstantial and clinical scenarios as possible that were both typical and atypical for bites of different species, far more than would have been possible in a real life.” Their system was validated prospectively in 134 snake bite cases in which the living or dead snake had been identified, not by a herpetologist, but by the attending physician, a system known to be unreliable. For individual species, sensitivity and specificity were, respectively, N. naja, 76% and 99%; Bungarus spp., 85% and 99%; and D. russelii, 70% and 99%. The score had a low sensitivity and specificity for identifying envenoming by H. hypnale and E. carinatus.

In comparison, our syndromes, based on real cases, demonstrated sensitivities and specificities of 78% and 96% for N. naja, 66% and 100% for B. caeruleus, 14% and 100% for D. russelii, and 10% and 97% for H. hypnale, respectively (Table 5). Because of the high specificity of the syndromes, there is a probability > 95% that patients positive for envenoming by a particular species according to this screening test have been envenomed by the species indicated. However, despite the high specificity, only a small proportion (< 15%) of patients with D. russelii and H. hypnale envenoming was identified by the syndromic classification, which indicated its low sensitivity. Thus, in patients negative for viper bite envenoming according to the screening test, this diagnosis is not excluded conclusively.

The syndromic approach is important, as in many other diseases, because species diagnosis is required for optimal clinical management. The snake is brought as definitive evidence of the diagnosis in only a minority of cases, 25% in the present study and, even when available, it must be correctly identified. In our study, hospital staff misidentified the snake brought by the victim on 51 occasions, leading to the unnecessary, potentially dangerous, expensive, and wasteful use of antivenom on 13 occasions. Enzyme immunoassays can accurately identify the species responsible for envenoming, but they are unlikely to become available in the developing world because of their cost and they provided results too slowly to guide emergency management. However, such tests may be useful for retrospective diagnosis in epidemiologic surveys and to help develop treatment algorithms. Epidemiologic clues may help species diagnosis. 5,15,16 Bites inflicted at night when victims are sleeping are highly likely to be have been caused by B. caeruleus.16 Although clinical features of H. hypnale and D. russelii envenoming may be similar, H. hypnale is found mainly in urban or semi-urban areas during dusk throughout the year, whereas D. russelii bites are associated primarily with agricultural activities.

The only antivenoms available in Sri Lanka are polyspecific, covering four species (N. naja, B. caeruleus, D. russelii, and E. carinatus). In the case of hump-nosed viper (H. hypnale) bites, administration of such antivenoms carries the usual high risk of early anaphylactic reactions 2224 without any possible benefit because the venom of this species is not neutralised. 15 The same is true for the mild envenoming caused by T. trigonocephalus. However, in our series, all patients bitten by this species and 13 bitten by H. hypnale or non-venomous species that had been misidentified as D. russelii were treated unnecessarily and ineffectively with polyspecific antivenom from India. Another compelling reason for species diagnosis in the treatment of snake bite is to anticipate and prevent complications associated with envenoming by different species. Thus, in the case of cobra bites, there is a high risk of local necrosis (67% in the present series), which justifies early antivenom treatment, especially where digits are involved. Similarly, H. hypnale and particularly D. russelii bites carry a risk of acute renal failure, which might be mitigated by maintaining high urine flow. Fatal hemorrhagic or thrombotic complications of viper bites must also be prevented by timely and adequate antivenom treatment, or, in the case of H. hypnale envenoming, by use of clotting factors or platelets.

Table 1

Numbers, total lengths, and sex ratios of 762 venomous snakes collected at 10 hosptials in Sri Lanka, August 1993–July 1997

Table 1
Table 2

Clinical features of envenoming in 762 patients bitten by 7 identified species of venomous snakes, Sri Lanka, August 1993–July 1997

Table 2
Table 3

Clinical syndromes of snake bite in Sri Lanka, August 1993–July 1997

Table 3
Table 4

Clinical spectrum of syndromes of snake bites, Sri Lanka, August 1993–July 1997

Table 4
Table 5

Sensitivity and specificity of clinical syndromes as a screening test in identifying snake bites, Sri Lanka, August 1993–July 1997

Table 5
Figure 1.
Figure 1.

Medically important venomous snake species of Sri Lanka.

Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 81, 4; 10.4269/ajtmh.2009.09-0225

Figure 2.
Figure 2.

Algorithm differentiating venomous, medically important snake species of Sri Lanka by clinical syndrome.

Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 81, 4; 10.4269/ajtmh.2009.09-0225

*

Address correspondence to Christeine A. Ariaratnam, Department of Clinical Medicine, Faculty of Medicine, University of Colombo, No 25, Kynsy Road, Colombo 08, Sri Lanka. E-mail: ariaranee2000@yahoo.com

Authors’ addresses: Christeine A. Ariaratnam, Mohamed H. Rezvi Sheriff, and Carukshi Arambepola, Faculty of Medicine, University of Colombo, 25 Kynsey Road, Colombo 08, Sri Lanka, E-mails: Aria ranee2000@yahoo.com, rsheriff@emed.lk and rezvi.sheriff@gmail.com, and carukshi@yahoo.com. R. David G. Theakston, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom, E-mail: r.d.g.theakston@liverpool.ac.uk. David A. Warrell, Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom, E-mail: david.warrell@ndm.ox.ac.uk.

Acknowledgments: We thank the medical and nursing staff of the 10 hospitals, especially consultants in charge of the units and medical officers, for assistance, especially with collection of data and help with the care of the patients; the late Haisinth Molligoda, Premasiri Peiris, Sunil Fernando Silva for help with handling live snakes; and Gamini Wasantha Perera and Somasiri Sripala for their help in transferring the specimens to the main centre in Colombo. ASTMH assisted with publication expenses.

REFERENCES

  • 1

    Baldaeus P, 1672. Naauwkeurige beschryvinge van Malabar en Choromandel, der zelver aangrenzende ryken, en het machtige eyland Ceylon. Amsterdam: JJ van Waesberge and J van Someren.

  • 2

    Sawai Y, Toriba M, Itokawa H, De Silva A, Perera GLS, Kottegoda MB, 1984. Study on deaths due to snakebite in Anuradhapura District, Sri Lanka. The Snake 16 :7–15.

    • Search Google Scholar
    • Export Citation
  • 3

    Fox S, Rathuwithana AC, Kasturiratne A, Lalloo DG, de Silva HJ, 2006. Underestimation of snakebite mortality by hospital statistics in the Monaragala District of Sri Lanka. Trans R Soc Trop Med Hyg 100 :693–695.

    • Search Google Scholar
    • Export Citation
  • 4

    de Silva A, 1990. Colour Guide to the Snakes of Sri Lanka. Portishead, United Kingdom: R & A Publishing Ltd.

  • 5

    Ranasinghe L, Uragoda CG, 1983. Symposium: medically important snakes and snake-bite in Sri Lanka. Ceylon Med J 28 :107–201.

  • 6

    Theakston RD, Reid HA, 1977. Micro-ELISA for detecting and assaying snake venom and venom antibody. Lancet ii :639–641.

  • 7

    Virivan C, Veeravat U, Warrell MJ, Theakston RD, Warrell DA, 1986. ELISA confirmation of acute and past envenoming by the monocellate Thai cobra (Naja kaouthia). Am J Trop Med Hyg 35 :173–181.

    • Search Google Scholar
    • Export Citation
  • 8

    Ho M, Warrell MJ, Warrell DA, Bidwell D, Voller A, 1986. A critical reappraisal of the use of enzyme-linked immunosorbent assays in the study of snake bite. Toxicon 24 :211–221.

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  • 9

    Phillips RE, Theakston RD, Warrell DA, Galagedera Y, Abeysekera DT, Dissanayake P, Hutton RA, Aloysius DJ, 1988. Paralysis, rhabdomyolysis and haemolysis caused by bites of Russell’s viper (Vipera russelli pulchella) in Sri Lanka: failure of Haffkine antivenom. Q J Med 68 :691–716.

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  • 10

    Dong le V, Selvanayagam ZE, Gopalakrishnakone P, Eng KH, 2002. A new avidin-biotin optical immunoassay for the detection of beta-bungarotoxin and application in diagnosis of experimental snake envenomation. J Immunol Methods 260 :125–136.

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  • 11

    Chandler HM, Hurrell JG, 1982. A new enzyme immunoassay system suitable for field use and its application in a snake venom detection kit. Clin Chim Acta 21 :225–230.

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  • 12

    Viravan C, Looareesuwan S, Kosakarn W, Wuthiekanun V, McCarthy CJ, Stimson AF, Bunnag D, Harinasuta T, Warrell DA, 1992. A national hospital-based survey of snakes responsible for bites in Thailand. Trans R Soc Trop Med Hyg 86 :100–106.

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  • 13

    Warrell DA, Davidson NMcD, Greenwood BM, Ormerod LD, Pope HM, Watkins BJ, Prentice CR, 1977. Poisoning by bites of the saw-scaled viper (Echis carinatus) in Nigeria. Q J Med 46 :33–62.

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  • 14

    Sano-Martins IS, Fan HW, Castro SC, Tomy SC, Franca FO, Jorge MT, Kamiguti AS, Warrell DA, Theakston RD, 1994. Reliability of the 20 minute whole blood clotting test (WBCT20) as an indicator of low plasma fibrinogen concentration in patients envenomed by Bothrops snakes, Butantan Institute Antivenom Study Group. Toxicon 32 :1045–1050.

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  • 15

    Ariaratnam CA, Thuraisingam V, Kularatne SA, Sheriff MH, Theakston RD, de Silva A, Warrell DA, 2008. Frequent and potentially fatal envenoming by hump-nosed pit vipers (Hypnale hypnale and H. nepa) in Sri Lanka: lack of effective antivenom. Trans R Soc Trop Med Hyg 102 :1120–1126.

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  • 16

    Ariaratnam CA, Sheriff MH, Theakston RD, Warrell DA, 2008. Distinctive epidemiologic and clinical features of common krait (Bungarus caeruleus) bites in Sri Lanka. Am J Trop Med Hyg 79 :458–462.

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  • 17

    Amarasekera N, Jayawardena A, Ariyaratnam A, Hewage UC, De Silva A, 1994. Bites of a sea snake (Hydrophis spiralis): a case report from Sri Lanka. Am J Trop Med Hyg 97 :195–198.

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  • 18

    Senanayake MP, Ariaratnam CA, Abeywickrema S, Belligaswatte A, 2005. Two Sri Lankan cases of identified sea snake bites without envenoming. Toxicon 45 :861–863.

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  • 19

    Warrell DA, 1994. Sea snake bites in the Asia-Pacific Region. Gopalakrishnakone P, ed. Sea Snake Toxinology. Singapore: Singapore University Press, 1–36.

  • 20

    Gnanathasan CA, Rodrigo PC, Peranantharajah S, Anitha Coonghe, Pieris P, 2008. A Case Series of Envenoming by Saw-Scaled Viper (Echis carinatus) in Sri Lanka. Global Issues in Clinical Toxinology, Melbourne. Available at: http://www.snakebiteinitiative.org/files/GICT%20Conference%202008/Session%204/Dr%20Ariaranee%20Gnanathasan.ppt. Accessed July 12, 2009.

  • 21

    Pathmeswaran A, Kasturiratne A, Fonseka M, Nandasena S, Lalloo DG, de Silva HJ, 2006. Identifying the biting species in snakebite by clinical features: an epidemiological tool for community surveys. Trans R Soc Trop Med Hyg 100 :874–878.

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  • 22

    Sellahewa KH, Gunawardena G, Kumararatne MP, 1995. Efficacy of antivenom in the treatment of severe local envenomation by the hump-nosed viper (Hypnale hypnale). Am J Trop Med Hyg 53 :260–262.

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  • 23

    Seneviratne SL, Opanayake CJ, Ratnayake NS, Sarath Kumara KE, Sugathadasa AM, Weerasooriya N, Wickrema WA, Gunatilake SB, de Silva HJ, 2000. Use of antivenom serum in snake bite: a prospective study of hospital practice in the Gampaha district. Ceylon Med J 45 :65–68.

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  • 24

    Premawardhena AP, de Silva CE, Fonseka MM, Gunatilake SB, de Silva HJ, 1999. Low dose subcutaneous adrenaline to prevent acute adverse reactions to antivenom serum in people bitten by snakes: randomised placebo controlled trial. BMJ 318 :730–733.

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