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A fatal bite from the burrowing asp Atractaspis corpulenta (Hallowell 1854)
Toxicon 118 (2016) 21e26
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Case report
A fatal bite from the burrowing asp Atractaspis corpulenta (Hallowell 1854) Colin R. Tilbury a, *, Janette Verster b a b
Evolutionary Genomics Group, Department of Botany & Zoology, University of Stellenbosch, Private Bag X1, Stellenbosch 7602, South Africa Department of Forensic Medicine, Faculty of Health Sciences, University of Pretoria, South Africa
a r t i c l e i n f o
a b s t r a c t
Article history: Received 6 January 2016 Received in revised form 27 March 2016 Accepted 14 April 2016 Available online 16 April 2016
Bites from the various species of Atractaspis are a common occurrence in Africa but deaths are very unusual. Of the 19 described species, the clinical effects of the bite of only seven have been described, and in only three (Atractaspis irregularis, Atractaspis microlepidota and Atractaspis engaddensis) have fatalities been documented. A case of envenomation is described following a bite to a finger by Atractaspis corpulenta, which resulted in sudden death approximately two and a half hours later. The victim received antivenom and although anaphylaxis to this cannot be ruled out, we consider it to be unlikely to be the cause of death. A late autopsy was performed and the findings and their interpretation are discussed. The previous case fatalities, toxic fractions and clinical effects of Atractaspis venom are briefly reviewed. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Snakebite Africa Atractaspis Fatality Autopsy Sarafotoxins
1. Introduction Burrowing asps (Atractaspis, Atractaspidinae, Lamprophiidae) comprise a genus of fossorial snakes which although secretive, may be encountered on the surface after rains. Other common names for these mainly uniformly black, thin snakes include burrowing adders, stiletto snakes and mole vipers, and they are responsible for many bites every year. In some parts of Africa they may be among the commonest causes of snake envenomation in the lay public (Coetzer and Tilbury, 1982; McNally and Reitz, 1987; Tilbury and Branch, 1989; Chifundera, 1990). Along with the cobras and mambas (Elapidae) and vipers (Viperidae), the genus Atractaspis has independently evolved a sophisticated front-fanged venom delivery system that is probably designed to envenomate prey items within the confines of subterranean tunnels. They have a unique mechanism of fang erection in which a limited degree of rotation of the fang-bearing maxilla on the pre-frontal bone allows a partial ventrolateral ‘erection’ of their canaliculated fangs. This obviates the need to gape open the mouth when striking (Pasqual, 1962). A single fang is simply protruded over the lower jaw at an angle of 47e51 to the braincase (Dueffel and Cundall, 2003), and
* Corresponding author. E-mail address: [email protected] (C.R. Tilbury). http://dx.doi.org/10.1016/j.toxicon.2016.04.035 0041-0101/© 2016 Elsevier Ltd. All rights reserved.
instead of a forward strike, a backward and downward thrust of the neck is employed to embed the fang into the prey or victim. Characteristically, only one fang is employed at a time. This method of ‘biting’ makes them impossible to hold safely behind the head in the usual manner employed by snake handlers e as many would testify. Four deaths from Atractaspis microlepidota (Corkhill, 1949; Warrell et al., 1976) have been reported and one from Atractaspis engaddensis (Al-Sadoon and Abdo, 1991). Ismail et al. (2007) and Abd-Elsalam (2011) note an additional two fatalities from A. engaddensis (both of whom died within 30 min of their bites but for which no case reports were published), and two fatal bites have been recorded from Atractaspis irregularis e one in a small child (Britt, 1978) and the other e an anecdotal report e of a man who sustained 8 bites from a snake trapped inside his bedding (Loveridge, 1938). One thing in common with all the described severe or fatal bites, is that the onset of systemic symptoms occurred within minutes of the bite and death occurred within hours.
1.1. Case report A fit and healthy 46 year old male was working as a mechanical foreman in Mayoko, Republic of Congo (2170 S; 12 480 E). He attempted to remove a small black snake from an empty swimming
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pool. He donned a pair of “industrial” rubber gloves prior to picking up the snake behind its head, but while holding the snake he was punctured through the rubber glove with a single fang over the dorsal aspect of the middle phalanx of the left index finger. The snake was killed and kept for identification purposes. Approximately 30 min after the bite, he presented to the local clinic complaining of severe pain in the hand and arm, associated with some swelling of the hand. He complained of shortness of breath, had vomited and experienced diarrhoea. The patient was examined and managed by the nurse/medic at the site clinic. The medical record is unfortunately brief and suffers from a lack of important clinical detail. Nonetheless, in spite of its shortcomings, the case is considered to be of such significance to warrant publication. The following details were extracted from the medical record. Times in minutes (T¼) are calculated as minutes after the bite. On arrival, the victim was noted to be highly anxious, initial BP 120/80 mmHg, pulse 65/min, oxygen saturation 98% and he was afebrile. The bite site was cleaned, and an intravenous infusion of lactated Ringers solution commenced. 4 mg Celestene (betamethasone) was given intravenously and Enoxaparin (a low molecular weight heparin analogue) 0.8 ml (80 mg) was administered subcutaneously as per the local snake bite protocol. Five to 10 min later (T ¼ 35e40 min), he vomited again, had diarrhoea and complained of some discomfort over the lumbar region. He appeared highly agitated and BP was noted to rise to 180/ 100 mmHg, pulse 68/min, O2 saturation 98%. He then began to complain of abdominal pain which later became severe. He was given 1 g of Paracetamol intravenously and 1 ampoule (10mls) of SAVP (SAIMR) polyvalent antivenom intramuscularly. 30 min later (T ¼ 70 min), the vomiting and diarrhoea had ceased, but he continued to experience lower back pain. Vital signs were normal with BP 120/80 mmHg and O2 saturation 98%. After a further 30 min (T ¼ 100 min), the back pain and discomfort had regressed, vital signs were unchanged but a non-specified rash was noted on the victim's left hand and on the inside of the elbow. At approximately 2hr and 20 min (T ¼ 140 min) after the bite, the patient complained of a feeling of chest tightness which was shortly followed by the onset of apparently sudden cardio respiratory arrest. In spite of prolonged CPR, defibrillation, assisted ventilation and adrenalin, resuscitation was unsuccessful and called off after more than two hours from commencement. Unfortunately no ECG was obtained prior to or after the cardiac arrest and no clinical details of the time of the arrest are available. On review of the victim's previous medical history, it was established that he had no history of ischaemic heart disease or previous snake bites, and had no known allergies, diabetes, asthma or hypertension. His family history was unremarkable. The victim was known to suffer from moderate hypercholesterolaemia (total cholesterol of 6.7 mmol/l; LDL 4.5 mmol/l) and had been started on Atorvastatin 10 mg daily three years previously. This had had the effect of lowering total cholesterol to within normal limits for the previous two years. Resting 12-lead ECGs done in 2012 and November 2014, showed that apart from a sinus bradycardia (56e43 bpm), the ECG was otherwise essentially within normal limits. 1.2. Identification of the snake The dead snake was preserved in a fridge in a bottle. Unfortunately it later decomposed and was thrown away. However prior to its disposal, it was photographed by one of the authors (JV). Examination of the images of the snake (Figs. 1e3) showed the following features: the snake is a large, entirely black, most likely female specimen of Atractaspis with a total length of approximately 575 mm. Ventral scale count 195, anal scale entire, subcaudals 27,
Fig. 1. Head view of the dead snake with the left fang exposed in the erect position. Approximate length of the fang is 4 mm.
Fig. 2. Ventral surface of the snake showing 195 ventral scales, an entire anal scale with 27 undivided subcaudals.
all undivided, with a terminal caudal spike. It was not possible to accurately count the dorsal scale rows. The snout is cuneiform and projects strongly. Rostral scale is large, upper portion as long as its distance from the frontal. Five supralabials and five infralabials are present. Five gular scales are in contact with the first pair of sublinguals, and the sublinguals are fused with the second pair of infralabials. When compared with the four species of Atractaspis that are known to occur in the region (viz Atractaspis boulengeri, Atractaspis corpulenta, A. irregularis and Atractaspis reticulata), these characteristics are in keeping with the snake being positively identifiable as Atractaspis corpulenta (Moyer and Jackson, 2011; Branch pers. comm.). The snake involved in this case was a relatively large specimen (maximum size for the species 650 mm) and would have been capable of injecting a relatively large dose of venom. Atractaspis corpulenta's distribution is confined to West Africa, extending from DRC to Sierra Leone. Three sub-species are described, A. c. corpulenta, A.c. kivuensis, A.c. leucura, though the taxonomic status of these requires modern assessment. All are characteristically small black snakes with a ‘corpulent’ appearance e hence their scientific name.
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Fig. 3. Detail of the underside of the head of the dead snake showing diagnostic arrangement of the sublinguals fused with the second pair of sublabials. Five gular scales are in contact with the sublinguals.
1.3. Post mortem findings A post mortem examination was conducted by a local anatomical pathologist in Pointe Noire, Republic of Congo, which was attended in a watching brief capacity by a forensic pathologist from the Department of Forensic Medicine, University of Pretoria (JV). Due to factors beyond our control, the autopsy was unfortunately only able to be conducted 13 days after the demise of the victim by which time potentially vital histological clues were obscured by autolysis. The principal findings were as follows: An exclamation mark (!) shaped punctate wound was clearly visible distally and laterally on the dorsal aspect of the middle phalanx of the left index finger (Fig. 4). This small wound measured 2.5 mm in length and was surrounded by an area of apparent contusion, which measured 8 mm 9 mm in size. This area of blue-
Fig. 4. Puncture wound on the dorsal surface of the middle phalanx of the left index finger. Note the small incision extending from the lateral edge of the puncture.
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black discolouration showed indistinct proximal extension in a linear fashion across the dorsal aspect of the left index finger to the level of the proximal inter-phalangeal joint. Upon incision of the skin in the affected area, soft tissue haemorrhage was clearly noted surrounding a central area of necrosis and softening of the tissue. No rash was evident at autopsy. The organs had a congested appearance in general and showed autolytic changes. Inspection of the larynx showed slight hyperaemia of the laryngeal mucosa, but no findings representative of overt angio-oedema. Pink, frothy fluid was present in the trachea and the lungs were markedly oedematous and congested. A prominent branching microvascular pattern was noted on the epicardial surface of the heart; however the heart was flabby and extremely autolytic. No renal abnormalities, retroperitoneal soft tissue haemorrhage or haematoma formation were observed. Unfortunately, at the time of the autopsy the coronary arteries were not specifically inspected for the presence or absence of plaque formation. On histological examination, besides disruption of the epidermal and dermal tissue layers, with associated fresh haemorrhage, no acute inflammatory response or foreign material was observed in the section of skin surrounding the snakebite on the left index finger. Acute ischaemic changes, including foci of contraction band necrosis with no accompanying inflammatory response, were observed throughout the sections of the heart. No signs of pre-existing myocardial ischemia or fibrosis were observed in the sections of the myocardium. Histological examination of the lungs confirmed prominent pulmonary oedema and severe pulmonary congestion. No acute inflammatory reaction, including eosinophil infiltration or oedema, was present in the larynx. Sections of the liver showed Grade I, mainly microvesicular, centrilobular steatosis consistent with pre-existing fatty change. 2. Discussion Only four cases of envenomation from Atractaspis corpulenta are previously documented (Boulenger, 1913; Aylmer, 1922; Gunders et al., 1960; Pauwels et al., 2008). Boulenger (1913) and Aylmer (1922) document bites from the same specimen but at different times and places. All the bites were relatively mild and variously document local pain, parasthesia, swelling, lymphadenitis of the draining glands, local discolouration, muscular pain and in one case a transient haematuria with a transiently prolonged Prothrombin Time (32% of normal) (Gunders et al., 1960). On the basis of the known distribution of the species, Pauwels et al. (2008) ascribe the cases described by Boulenger 1913, Aylmer 1922 and Gunders et al., 1960 to the subspecies Atractaspis corpulenta leucura. One case of envenomation by the nominate subspecies A. c. corpulenta is described (Pauwels et al., 2008). The current case is also ascribed to the nominate form A. corpulenta corpulenta. No studies on the venom of A. corpulenta have been published and so the effects of its venom e until otherwise proved e are generally considered to be similar to the known venoms of other species in the genus. This report documents the first fatality from the bite of Atractaspis c. corpulenta. No clear pathophysiological mechanism for the death could be identified from either the clinical record or the results of the autopsy. The most likely causes of death are considered to be due to either the direct effects of the venom on the myocardium and its vasculature, or anaphylaxis induced by either the venom or medications administered to the victim. Early Acute Reactions (EAR) to antivenom administration may result in anaphylaxis and death, but although it cannot confidently be excluded, anaphylaxis resulting from antivenom or enoxaparin is considered to be the least likely of the potential causes due to the relatively long intervals between administration and death. In the current
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case, a localized rash noted shortly before the onset of cardiac arrest may well have been related to the antivenom injection. Urticarial rash is one of the commonest manifestations of EARs to SAVP (SAIMR) polyvalent antivenom (Moran et al., 1998) but severe reactions are relatively uncommon. In addition, during the resuscitation attempt, treatments that are usually effective for the management of anaphylaxis were administered (adrenalin and ventilation) but were unsuccessful in preventing death. Anaphylaxis typically presents with cardiovascular collapse, mucosal oedema, gastro-intestinal cramps, vomiting, pruritus and urticarial rash. Respiratory signs in severe EARs are generally associated with mucosal oedema and bronchospasm (Fisher and Boldo, 1985; Simons et al., 2012) and not pulmonary oedema. Findings at autopsy which may be consistent with anaphylaxis such as pharyngeal and or laryngeal oedema, upper respiratory tract oedema, visceral congestion, pulmonary congestion and oedema, and sometimes lung hyperinflation in association with mucous plugging of the airways (Da Broi and Moreschi, 2011; Edston et al., 2007) may only be present in 59% of deaths from anaphylaxis (Da Broi and Moreschi, 2011). Where the history is inconclusive, the post mortem diagnosis of anaphylaxis can be difficult e especially where macroscopic signs may be absent at autopsy and where blood or other biological fluids are unavailable or unsuitable for study (Simons et al., 2012). Elevated mast cell tryptase levels have been used as an indicator of anaphylaxis, but since mast cell degradation post-mortem also results in raised levels, levels should be tested within a post mortem interval of three days (Payne and Kam, 2004). In the current case no reliable post mortem analysis was deemed possible. It is however apparent from the autopsy that there was no macroscopic or histological evidence of angioedema present. Histological examination following anaphylaxis often reveals an eosinophilic infiltration in the lungs, heart (Da Broi and Moreschi, 2011) and other affected organ structures, for example the larynx or site of envenomation. In our case, eosinophilia was absent in all the tissue sections. Reactions mimicking anaphylaxis are described in victims with no known prior exposure to Atractaspis venoms, and include a well documented case of an ‘anaphylactoid reaction’ following a bite from A. engaddensis (Chajek et al., 1974). The above case was associated with acute Type II respiratory failure e presumably due to acute and severe bronchospasm. Apart from a non-specific history of chest tightness, we have no clinical evidence of coronary artery vasospasm in this victim, but it is possible that coronary vasospasm might have contributed to some of the histopathological findings (e.g. focal myocardial ischaemia) in this case. The appearance of contraction band necrosis and other histological changes of ischaemia in the myocardium, also cannot be interpreted to be solely due to the direct effects of venom or myocardial ischaemia as these findings could also be consistent with the prolonged cardiopulmonary resuscitation efforts and adrenalin administration (Karch, 1987; Baroldi et al., 2001). Pulmonary oedema per se has little diagnostic significance post mortem, as this finding is observed in many conditions at autopsy (Lee et al., 1986; Saukko and Knight, 2004) including myocardial ischaemia with acute left ventricular dysfunction, envenomation, anaphylaxis and agonal changes associated with prolonged resuscitation. The appearance of the bite wound (Fig. 4) deserves some comment. The cut through the skin inferior to the puncture, was most likely caused by the posterior surface of the fang. Visser (1975) and Kochva and Meier (1986) demonstrated that the fang of A. engaddensis had a serrated flange on the posterior edge near the tip. The presence of such a serrated flange in A. corpulenta could not be confirmed, however in the original description of the
species, Hallowell (1857) noted that the fang of A. corpulenta had “ …. a superior and inferior ridge, compressed laterally with an elevation in the middle e resembling a squalus tooth”. Dueffel and Cundall (2003) noted that the fang stabs of A. microlepidota and Atractaspis bibronii produce slit-like incisions as the fang is thrust into and then withdrawn from the skin of prey items. Given the prolonged post-mortem storage of the corpse, one cannot exclude the effects of tissue plane deterioration on the appearance of the bite wound. 2.1. Atractaspis bites and venoms The symptomatology and clinical evolution of recorded Atractaspis bites from all species have remarkable similarities. Early severe local pain and draining lymphadenitis are accompanied by swelling and local discolouration, and when on a digit the bite is often associated with local blistering and necrosis. Muscle pains, painful tongue and eye movements, and autonomic symptoms such as nausea and vomiting, sweating, abdominal pain as well as watery diarrhoea, may occur. A variety of neurological symptoms and signs have also been described and transient haematuria (Gunders et al., 1960; Corkhill and Kirk, 1954) of questionable significance has been described (Corkhill et al., 1959). Abnormalities in liver enzymes have been noted in two cases of A. engaddensis bites, one with documented histological changes (Chajek et al., 1974); in other cases, early fluctuations in the level of consciousness, collapse, respiratory distress, peripheral and central cyanosis are described (Chajek et al., 1974; Al-Sadoon and Abdo, 1991; Kurnik et al., 1999). Transient hypertension and acute Type II respiratory failure is also described (Chajek et al., 1974; Kurnik et al., 1999). Apart from a small group of species (including A. microlepidota and A. engaddensis) with elongated venom glands (Kochva et al., 1967; Underwood and Kochva 1993), the venom glands of the other species of Atractaspis (including those of A. corpulenta) are usually small and produce only small amounts of venom, the toxicity of which varies significantly between the various species (Ducancel and Goyffon, 2008). Venom yields from large specimens are not unexpectedly higher than those from smaller specimens (Corkhill and Kirk, 1954; Branch, 1981). Atractaspis venoms are typically very viscous containing between at least 50e100 different molecular compounds (Ducancel and Goyffon, 2008; Quinton et al., 2005), including among others a number of known venom ‘families’ such as three-finger toxins, CRISPs, Kunitz-type/TFPI, C-type lectins, kallikrein/serine protease, metalloproteinase, disintegrin, venom nerve growth factor and PLA2 (Terrat et al., 2013). Haemorrhagic fractions have been isolated (Kochva et al., 1982; Ovadia, 1987) and transient abnormalities in human blood coagulation have been reported from various species (Tilbury and Branch, 1989; Chajek et al., 1974; Gunders et al., 1960). No pre e or post-synaptic effect on the neuromuscular synapse could be identified in A. engaddensis venom, although peripheral/autonomic effects were not excluded (Weiser et al., 1984). Atractaspis has evolved a class of toxins unique to the genus that have several specific effects. Considered to be among the most potent snake toxins yet described (Ducancel, 2002), Atractaspis venoms contain multiple isoforms of polypeptide chains consisting of between 15 and 30 amino acids (Quinton et al., 2005; Ducancel, 2005). Known as sarafotoxins (SRTX), these toxins are highly selective Endothelin ʙ (ETʙ) and Endothelin A (ETA) receptor agonists (Marshall and Johns, 1999; Fink et al., 2007; Rocha-Sousa et al., 2009) with a sequence homology of about 60% with mammalian vasoactive 21 amino acid endothelin peptides (Graur et al., 1988; Ducancel, 2002). Endothelin receptors are found throughout the cardiopulmonary (Hemsen et al., 1990; Maggi et al., 1990), renal (Marshall and Johns, 1999) and mesenteric vasculature (Han et al.,
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1990) and induce vasospasm at all these sites via activation of the ETʙ receptors. Both endothelins and SRTX induce contraction of smooth muscle in intestines (Weiser et al., 1984; Wollberg et al., 1991) and bronchi (Maggi et al., 1990; Hemsen et al., 1990). SRTX induce a dose-dependent positive inotropic response in myocardial muscle, a progressive atrio-ventricular blockade, ventricular tachycardia, atrial flutter and ventricular fibrillation in mouse and rat heart preparations (Weiser et al., 1984; Lee et al., 1986; Wollberg et al., 1988). These effects appear to be due to both a direct toxic effect on the myocardium as well as secondary to the onset of myocardial ischaemia caused by coronary artery spasm (Wollberg et al., 1988). The degree of vasospasm also appears to be dose dependent (Marshall and Johns, 1999). In vivo experiments in dogs using SRTX S6c caused a dose related reduction in the perfusion of all layers of the myocardium e with a maximum 71% decrease in blood flow in the epicardial layer (Teerlink et al., 1994). In the human cardiopulmonary system, the highest level of endothelin-like immunoreactivity was found in the left anterior descending coronary artery (Hemsen et al., 1990). In mice, A. engaddensis venom induces a transient hypertension postulated to be secondary to vasoconstriction of peripheral vascular beds (Lee et al., 1986). The onset of transient hypertension in humans has also been noted in several cases (Chajek et al., 1974; Kurnik et al., 1999) e also postulated to be secondary to SRTX induced systemic vasoconstriction. ECG abnormalities seen in humans envenomated by A. engaddensis are indicative of myocardial ischaemia with prolongation of the PR interval, ST segment depression, and flattening and-or inversion of the T waves (Chajek et al., 1974; Alkan and Sukenik, 1975; Kurnik et al., 1999). It is apparent that activation of human endothelin receptors by SRTX may give rise to the systemic symptoms and signs of intestinal colic, bronchospasm, hypertension, myocardial ischaemia and related ECG changes and effects. 2.2. Comments on treatment and other possible causes of death Given that a fatality from the bite of A. corpulenta is an unexpected outcome, it is important to consider other possible causes of death in this particular case. The case was managed according to a local snakebite protocol. The administration of low molecular weight heparin (Enoxaparin) and betamethasone are not usual components of modern snake bite protocols and in view of the symptoms and signs at the time when it was administered, the decision to inject polyvalent anti-venom is questionable e even given that the identity of the snake was unknown at the time. Both antivenom and Enoxaparin could potentially cause anaphylaxis. Lastly it could be speculated that circulating SRTX in a low concentration which might not induce significant coronary blood flow restriction in a person with patent coronary vessels, may be sufficient to provoke myocardial ischaemia and its consequences in someone with lipidemia and asymptomatic underlying coronary artery disease. Although the mechanism of action of SRTX is associated with the mobilisation and increase of intracellular Ca⁺⁺ and the hydrolysis of phosphoinositol (Kloog et al., 1988; Gairon et al., 1989), in animal models the binding of SRTX to specific endothelin receptors is unaffected by the action of calcium channel blockers such as verapamil and nitrodipine (Ducancel, 2002; Kloog et al., 1988; Kloog and Sokolovsky, 1989; Gairon et al., 1989) and nitroglycerine (Abd-Elsalam, 2011). No effective antivenoms against Atractaspis species are produced on a commercial scale and no burrowing asp venom is employed in the production of SAVP (SAIMR) polyvalent antivenom. The small molecular weight and simple tertiary structure of the SRTX molecules combine to produce low immunogenicity in typical antivenom production systems.
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Small amounts of effective antivenom may be produced using adjuvants (Ismail et al., 2007). While specific antivenoms may not be available, a recent in vitro study suggested that Bosentan e a potent blocker of endothelin receptors A and B e was able to completely reverse the coronary vasospasm induced by A. engaddensis venom in isolated rabbit hearts more effectively than specific antivenom (Abd-Elsalam, 2011). 3. Conclusion/recommendations Although the vast majority of victims of Atractaspis envenomation survive their bites, the occasional bite from any of the various species of Atractaspis has the potential to cause serious envenomation and even fatality. In some cases the early onset of systemic symptoms and signs (such as shortness of breath/bronchospasm, peripheral or central cyanosis, chest pain, abdominal cramps, vomiting, diarrhoea and hypertension) if not due to anxiety, may be indicators of endothelin activation and signal the potential for a negative outcome. Venom to mass ratios are important and in the case of bites in children, or when multiple bites have been inflicted, the increased risk of severe envenomation and systemic effects must be recognised and actively managed. In all cases of proven or suspected Atractaspis bites, an ECG should be recorded and monitored if possible, particularly for the first 12e24 h after the bite. The use of endothelin receptor blockers to reverse the effects of SRTX on the myocardium might be usefully explored further, with a view to proposing a dosage schedule for severe human Atractaspis envenomation. Conflict of interest The authors declare that there are no conflicts of interest. Ethical statement Ethical approval for the publication of this case report was obtained from and endorsed by the University of Pretoria Faculty of Health Sciences Research Ethics Committee (Ref No.471/2015). Consent for publication of the case report was also provided by the widow of the deceased. Acknowledgements The authors would like to acknowledge the help of Professor William Branch and Johan Marais for assistance with the identification of the snake involved, and the support of the Department of Forensic Medicine, University of Pretoria. The two reviewers of the manuscript are thanked for their useful comments and advice. Transparency document Transparency document related to this article can be found online at http://dx.doi.org/10.1016/j.toxicon.2016.04.035. References Abd-Elsalam, M.A., 2011. Bosentan, a selective and more potent antagonist for Atractaspis envenomation than the specific antivenom. Toxicon 57, 861e870. Al-Sadoon, M.K., Abdo, N.M., 1991. Fatal envenoming by the snake Atractaspis newly recorded in the central region of Saudi Arabia. J. King Saud Univ. 3 Science (2), 123e131. Alkan, M.L., Sukenik, S., 1975. Atrioventricular block in a case of snakebite inflicted by Atractaspis engaddensis. Trans. R. Soc. Trop. Med. Hyg. 69, 166. Aylmer, G., 1922. The snakes of Sierra Leone. Sierra Leone Stud. 5, 7e37. Baroldi, G., Mittleman, R.E., Parolini, M., Silver, M.D., Vineschi, V., 2001. Myocardial Contraction Bands. Definition, quantification and significance in forensic pathology. Int. J. Leg. Med. 115, 142e151.
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Boulenger, E.G., 1913. Reptiles and Batrachians. J.M. Dent & Sons, London, p. 180. Branch, W.R., 1981. Venom yields from three species of side-biting snakes (Genus Atractaspis, Colubridae). Toxicon 19 (2), 271e277. Britt, D.P., 1978. Death following the bite of a burrowing Viper. Niger. Field 43, 41e42. Chajek, T., Rubinger, D., Alkan, M., Melmed, R.M., Gunders, A.E., 1974. Anaphylactoid reaction and tissue damage following bite by Atractaspis engaddensis. Trans. R. Soc. Trop. Med. Hyg. 68 (4), 333e337. Chifundera, K., 1990. Snakes of Zaire and their bites. Afr. Study Monogr. 10 (3), 137e157. Coetzer, P.W.W., Tilbury, C.R., 1982. The epidemiology of snakebite in northern Natal. South Afr. Med. J. 62, 206e212. Corkhill, N.L., 1949. Sudan thanatophidia. Sudan Notes Rec. 30, 101e106. Corkhill, N.L., Kirk, R., 1954. Poisoning by the Sudan mole viper, Atractaspis microlepidota Gunther. Trans. R. Soc. Trop. Med. Hyg. 48, 376. Corkhill, N.L., Ionides, C.J.P., Pitman, G.R.S., 1959. Biting and poisoning by the mole vipers of the genus Atractaspis. Trans. R. Soc. Trop. Med. Hyg. 53, 95e101. Da Broi, U., Moreschi, C., 2011. Post mortem diagnosis of anaphylaxis: a difficult task in forensic medicine. Forensic Sci. Int. 204, 1e5. Ducancel, F., 2002. The sarafotoxins. Toxicon 40, 1541e1545. Ducancel, F., 2005. Endothelin-like peptides. Cell. Mol. Life Sci. 62, 2828e2839. Ducancel, F., Goyffon, M., 2008. Les venins des Atractaspis. Med. Trop. 68 (4), 340e347. Dueffel, A., Cundall, D., 2003. Feeding in Atractaspis (Serpentes: Atractaspididae): a study in conflicting functional constraints. Zoology 106, 43e61. Edston, E., Eriksson, O., van Hage, M., 2007. Mast cell tryptase in postmortem serum e reference values and confounders. Int. J. Leg. Med. 121, 275e280. Fink, G., Li, M., Lau, Y., Osborn, J., Watts, S., 2007. Chronic activation of endothelin B receptors. Hypertension 50 (3), 512e518. Fisher, M.M., Boldo, B., 1985. Acute anaphylactic reactions. Med. J. Aust. 149, 34e38. Gairon, R., Kloog, Y., Bdolah, A., Sokolovsky, M., 1989. Functional endothelin/sarafotoxin receptors in rat heart myocytes: structure-activity relationships and receptor subtypes. Biochem. Biophy. Res. Commun. 163 (2), 936e943. Graur, D., Bdolah, A., Wollberg, Z., Kochva, E., 1988. Homology between snake venom sarafotoxins and mammalian endothelins. Israel J. Zool. 35, 171e175. Gunders, A.E., Walter, H.J., Etzel, E., 1960. Case of snakebite by Atractaspis corpulenta. Trans. R. Soc. Trop. Med. Hyg. 54, 279. Hallowell, E., 1857. Notes on a collection of reptiles from the Gaboon country, West Africa, recently presented to the Academy of Natural Sciences of Philadelphia, by Dr. Henry A. Ford. Proc. Acad. Nat. Sci. Phila. 9, 48e72. Han, S.-P., Knuepfer, M.M., Trapani, A.J., Fok, K.F., Westfall, T.C., 1990. Cardiac and vascular actions of sarafotoxin S6b and endothelin-1. Life Sci. 46 (11), 767e775. Hemsen, A., Franco-Cereceda, A., Matran, R., Rudehill, A., Lundberg, J.M., 1990. Occurrence, specific binding sites and functional effects of endothelin in human cardiopulmonary tissue. Eur. J. Pharmacol. 191 (3), 319e328. Ismail, M., Al-Ahaidib, M.S., Abdoon, N., Abd-Elsalam, M.A., 2007. Preparation of a novel antivenom against Atractaspis and Walterinnesia venoms. Toxicon 49, 8e18. Karch, S.B., 1987. Resuscitation-induced myocardial necrosis. Catecholamines and defibrillation. Am. J. Forensic Med. Pathol. Mar 8 (1), 3e8. Kloog, Y., Sokolovsky, M., 1989. Similarities in mode and sites of action of sarafotoxins and endothelins. Trends Pharmacol. Sci. 10, 212e214. Kloog, Y., Ambar, I., Sokolovsky, M., Kochva, E., Wollberg, Z., Bdolah, A., 1988. Sarafotoxin, a novel vasoconstrictor peptide: phosphoinositide hydrolysis in rat heart and brain. Science 242, 230e268. Kochva, E., Meier, J., 1986. The fangs of Atractaspis engaddensis Haas (Serpentes: Atractaspididae). Rev. Suisse Zool. 93, 749e754. Kochva, E., Shayer-Wollberg, M., Sobol, R., 1967. The special pattern of the venom gland in Atractaspis and its bearing on the taxonomic status of the genus. Copeia 4, 763e772. Kochva, E., Viljoen, C.C., Botes, D.P., 1982. A new type of toxin in the venom of snakes of the genus Atractaspis (Atractaspidinae). Toxicon 20, 581e592. Kurnik, D., Haviv, Y., Kochva, E., 1999. A snakebite by the burrowing asp Atractaspis engaddensis. Toxicon 37, 223e227.
Lee, Shu-Yue, Lee, C.Y., Chen, Y.M., Kochva, E., 1986. Coronary vasospasm as the primary cause of death due to the venom of the burrowing asp Atractaspis engaddensis. Toxicon 24 (3), 285e291. Loveridge, A., 1938. On a collection of reptiles and amphibians from Liberia. Proc. N. Engl. Zool. Club, Camb. Mass. 17, 49e74. Maggi, C.A., Giuliani, S., Patacchini, R., Santicioli, P., Giachetti, A., Meli, A., 1990. Further studies on the response of the guinea-pig isolated bronchus to endothelins and sarafotoxin S6b. Eur. J. Pharmacol. 176 (1), 1e9. Marshall, J.L., Johns, E.J., 1999. Influence of endothelins and sarafotoxin 6c and LNAME on renal vasoconstriction in the anaesthetised rat. Br. J. Pharmacol. 128 (3), 809e815. McNally, S.L., Reitz, C.J., 1987. Victims of snakebite. A five-year study at Shongwe Hospital, Kangwane, 1978-1982. South Afr. Med. J. 72, 855e860. Moran, N.F., Newman, W.J., Theakston, R.D.G., Warrell, D.A., Wilkenson, D., 1998. High incidence of early anaphylactoid reactions to SAIMR polyvalent snake antivenom. Trans. R. Soc. Trop. Med. Hyg. 92 (1), 60e70. Moyer, K., Jackson, K., 2011. Phylogenetic relationships among the Stiletto Snakes (genus Atractaspis) based on external morphology. Afr. J. Herpetol. 60 (1), 30e46. Ovadia, M., 1987. Isolation and characterisation of a haemorrhagic factor from the venom of the snake Atractaspis engaddensis (Atractaspididae). Toxicon 25 (6), 621e630. Pasqual, J.R.H., 1962. The biting mechanism of Atractaspis. Niger. Field 27 (3), 137e142. Pauwels, O.S.G., Mbini, J.-C., Peaud, P., Tobi, E., 2008. Human envenoming by Atractaspis corpulenta in Gabon: a first case report. Hamadryad 22 (2), 112e115. Payne, V., Kam, P.C.A., 2004. Mast cell tryptase: a review of its physiology and clinical significance. Anaesthesia 59 (7), 695e703. Quinton, L., Le Caer, J.-P., Phan, G., Ligny-Lemaire, C., Bourdais-Jomaron, J., Ducancel, F., Chamot-Rooke, J., 2005. Characterization of toxins within crude venoms by combined use of Fourier Transform Mass Spectrometry and cloning. Anal. Chem. 77, 6630e6639. Rocha-Sousa, A., Saraiva, J., Amaral, M., Alves-Faria, P., Falcao-Reis, F., LeiteMoreira, A.F., 2009. ETB2 Receptor subtype stimulation relaxes the iris sphincter muscle. Physiol. Res. 58 (6), 835e842. Saukko, P., Knight, B., 2004. Suffocation and asphyxia. Knight’s Forensic Pathology (Chapter 14), p. 356. Simons, F.E.R., Ardusso, L.R.F., Bilo, M.B., et al., 2012. 2012 Update: world Allergy Organization guidelines for the assessment and management of anaphylaxis. J. Allergy Clin. Immunol. 127, 593e22. Teerlink, J.R., Breu, V., Sprecher, U., Clozel, M., Clozel, J.P., 1994. Potent vasoconstriction mediated by endothelin ETB receptors in canine coronary arteries. Circ. Res. 74 (1), 105e114. Terrat, Y., Verdenaud, M., Ducancel, F., 2013. High-throughput venom-gland transcriptome of an Atractaspididae burrowing asp Snake: Atractaspis aterrima. Toxicon 75, 205e223. Underwood, G., Kochva, E., 1993. On the affinities of the burrowing asps Atractaspis (Serpentes: Atractaspididae). Zool. J. Linn. Soc. 107 (1), 3e64. Tilbury, C.R., Branch, W.R., 1989. Observations on the bite of the southern burrowing asp (Atractaspis bibronii) in Natal. South Afr. Med. J. 75, 327e331. Visser, J., 1975. Atractaspis e how does it bite? J. Herpetol. Assoc. Afr. 14, 18e20. Warrell, D.A., Ormerod, L.D., Davidson, N.McD., 1976. Bites by the night adder (Causus maculatus) and burrowing vipers (Genus Atractaspis) in Nigeria. Am. J. Trop. Med. Hyg. 25, 517e524. Weiser, E., Wollberg, Z., Kochva, E., Lee, S.Y., 1984. Cardiotoxic effects of the venom of the burrowing asp, Atractaspis engaddensis (Atractaspidae, Ophidia). Toxicon 22, 767. Wollberg, Z., Shabo-Shina, R., Intrator, N., Bdolah, A., Kochva, E., Shavit, G., Oron, Y., Vidne, B.A., Gitter, S., 1988. A novel cardiotoxic polypeptide from the venom of Atractaspis engaddensis (Burrowing Asp): cardiac effects in mice and isolated rat and human heart preparations. Toxicon 26 (6), 525e534. Wollberg, Z., Bdolah, A., Gairon, R., Sokolovsky, M., Kochva, E., 1991. Contractile effects and binding properties of endothelins/sarafotoxins in the guinea pig ileum. Eur. J. Pharmacol. 198 (1), 31e36.
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Case report
A fatal bite from the burrowing asp Atractaspis corpulenta (Hallowell 1854) Colin R. Tilbury a, *, Janette Verster b a b
Evolutionary Genomics Group, Department of Botany & Zoology, University of Stellenbosch, Private Bag X1, Stellenbosch 7602, South Africa Department of Forensic Medicine, Faculty of Health Sciences, University of Pretoria, South Africa
a r t i c l e i n f o
a b s t r a c t
Article history: Received 6 January 2016 Received in revised form 27 March 2016 Accepted 14 April 2016 Available online 16 April 2016
Bites from the various species of Atractaspis are a common occurrence in Africa but deaths are very unusual. Of the 19 described species, the clinical effects of the bite of only seven have been described, and in only three (Atractaspis irregularis, Atractaspis microlepidota and Atractaspis engaddensis) have fatalities been documented. A case of envenomation is described following a bite to a finger by Atractaspis corpulenta, which resulted in sudden death approximately two and a half hours later. The victim received antivenom and although anaphylaxis to this cannot be ruled out, we consider it to be unlikely to be the cause of death. A late autopsy was performed and the findings and their interpretation are discussed. The previous case fatalities, toxic fractions and clinical effects of Atractaspis venom are briefly reviewed. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Snakebite Africa Atractaspis Fatality Autopsy Sarafotoxins
1. Introduction Burrowing asps (Atractaspis, Atractaspidinae, Lamprophiidae) comprise a genus of fossorial snakes which although secretive, may be encountered on the surface after rains. Other common names for these mainly uniformly black, thin snakes include burrowing adders, stiletto snakes and mole vipers, and they are responsible for many bites every year. In some parts of Africa they may be among the commonest causes of snake envenomation in the lay public (Coetzer and Tilbury, 1982; McNally and Reitz, 1987; Tilbury and Branch, 1989; Chifundera, 1990). Along with the cobras and mambas (Elapidae) and vipers (Viperidae), the genus Atractaspis has independently evolved a sophisticated front-fanged venom delivery system that is probably designed to envenomate prey items within the confines of subterranean tunnels. They have a unique mechanism of fang erection in which a limited degree of rotation of the fang-bearing maxilla on the pre-frontal bone allows a partial ventrolateral ‘erection’ of their canaliculated fangs. This obviates the need to gape open the mouth when striking (Pasqual, 1962). A single fang is simply protruded over the lower jaw at an angle of 47e51 to the braincase (Dueffel and Cundall, 2003), and
* Corresponding author. E-mail address: [email protected] (C.R. Tilbury). http://dx.doi.org/10.1016/j.toxicon.2016.04.035 0041-0101/© 2016 Elsevier Ltd. All rights reserved.
instead of a forward strike, a backward and downward thrust of the neck is employed to embed the fang into the prey or victim. Characteristically, only one fang is employed at a time. This method of ‘biting’ makes them impossible to hold safely behind the head in the usual manner employed by snake handlers e as many would testify. Four deaths from Atractaspis microlepidota (Corkhill, 1949; Warrell et al., 1976) have been reported and one from Atractaspis engaddensis (Al-Sadoon and Abdo, 1991). Ismail et al. (2007) and Abd-Elsalam (2011) note an additional two fatalities from A. engaddensis (both of whom died within 30 min of their bites but for which no case reports were published), and two fatal bites have been recorded from Atractaspis irregularis e one in a small child (Britt, 1978) and the other e an anecdotal report e of a man who sustained 8 bites from a snake trapped inside his bedding (Loveridge, 1938). One thing in common with all the described severe or fatal bites, is that the onset of systemic symptoms occurred within minutes of the bite and death occurred within hours.
1.1. Case report A fit and healthy 46 year old male was working as a mechanical foreman in Mayoko, Republic of Congo (2170 S; 12 480 E). He attempted to remove a small black snake from an empty swimming
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pool. He donned a pair of “industrial” rubber gloves prior to picking up the snake behind its head, but while holding the snake he was punctured through the rubber glove with a single fang over the dorsal aspect of the middle phalanx of the left index finger. The snake was killed and kept for identification purposes. Approximately 30 min after the bite, he presented to the local clinic complaining of severe pain in the hand and arm, associated with some swelling of the hand. He complained of shortness of breath, had vomited and experienced diarrhoea. The patient was examined and managed by the nurse/medic at the site clinic. The medical record is unfortunately brief and suffers from a lack of important clinical detail. Nonetheless, in spite of its shortcomings, the case is considered to be of such significance to warrant publication. The following details were extracted from the medical record. Times in minutes (T¼) are calculated as minutes after the bite. On arrival, the victim was noted to be highly anxious, initial BP 120/80 mmHg, pulse 65/min, oxygen saturation 98% and he was afebrile. The bite site was cleaned, and an intravenous infusion of lactated Ringers solution commenced. 4 mg Celestene (betamethasone) was given intravenously and Enoxaparin (a low molecular weight heparin analogue) 0.8 ml (80 mg) was administered subcutaneously as per the local snake bite protocol. Five to 10 min later (T ¼ 35e40 min), he vomited again, had diarrhoea and complained of some discomfort over the lumbar region. He appeared highly agitated and BP was noted to rise to 180/ 100 mmHg, pulse 68/min, O2 saturation 98%. He then began to complain of abdominal pain which later became severe. He was given 1 g of Paracetamol intravenously and 1 ampoule (10mls) of SAVP (SAIMR) polyvalent antivenom intramuscularly. 30 min later (T ¼ 70 min), the vomiting and diarrhoea had ceased, but he continued to experience lower back pain. Vital signs were normal with BP 120/80 mmHg and O2 saturation 98%. After a further 30 min (T ¼ 100 min), the back pain and discomfort had regressed, vital signs were unchanged but a non-specified rash was noted on the victim's left hand and on the inside of the elbow. At approximately 2hr and 20 min (T ¼ 140 min) after the bite, the patient complained of a feeling of chest tightness which was shortly followed by the onset of apparently sudden cardio respiratory arrest. In spite of prolonged CPR, defibrillation, assisted ventilation and adrenalin, resuscitation was unsuccessful and called off after more than two hours from commencement. Unfortunately no ECG was obtained prior to or after the cardiac arrest and no clinical details of the time of the arrest are available. On review of the victim's previous medical history, it was established that he had no history of ischaemic heart disease or previous snake bites, and had no known allergies, diabetes, asthma or hypertension. His family history was unremarkable. The victim was known to suffer from moderate hypercholesterolaemia (total cholesterol of 6.7 mmol/l; LDL 4.5 mmol/l) and had been started on Atorvastatin 10 mg daily three years previously. This had had the effect of lowering total cholesterol to within normal limits for the previous two years. Resting 12-lead ECGs done in 2012 and November 2014, showed that apart from a sinus bradycardia (56e43 bpm), the ECG was otherwise essentially within normal limits. 1.2. Identification of the snake The dead snake was preserved in a fridge in a bottle. Unfortunately it later decomposed and was thrown away. However prior to its disposal, it was photographed by one of the authors (JV). Examination of the images of the snake (Figs. 1e3) showed the following features: the snake is a large, entirely black, most likely female specimen of Atractaspis with a total length of approximately 575 mm. Ventral scale count 195, anal scale entire, subcaudals 27,
Fig. 1. Head view of the dead snake with the left fang exposed in the erect position. Approximate length of the fang is 4 mm.
Fig. 2. Ventral surface of the snake showing 195 ventral scales, an entire anal scale with 27 undivided subcaudals.
all undivided, with a terminal caudal spike. It was not possible to accurately count the dorsal scale rows. The snout is cuneiform and projects strongly. Rostral scale is large, upper portion as long as its distance from the frontal. Five supralabials and five infralabials are present. Five gular scales are in contact with the first pair of sublinguals, and the sublinguals are fused with the second pair of infralabials. When compared with the four species of Atractaspis that are known to occur in the region (viz Atractaspis boulengeri, Atractaspis corpulenta, A. irregularis and Atractaspis reticulata), these characteristics are in keeping with the snake being positively identifiable as Atractaspis corpulenta (Moyer and Jackson, 2011; Branch pers. comm.). The snake involved in this case was a relatively large specimen (maximum size for the species 650 mm) and would have been capable of injecting a relatively large dose of venom. Atractaspis corpulenta's distribution is confined to West Africa, extending from DRC to Sierra Leone. Three sub-species are described, A. c. corpulenta, A.c. kivuensis, A.c. leucura, though the taxonomic status of these requires modern assessment. All are characteristically small black snakes with a ‘corpulent’ appearance e hence their scientific name.
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Fig. 3. Detail of the underside of the head of the dead snake showing diagnostic arrangement of the sublinguals fused with the second pair of sublabials. Five gular scales are in contact with the sublinguals.
1.3. Post mortem findings A post mortem examination was conducted by a local anatomical pathologist in Pointe Noire, Republic of Congo, which was attended in a watching brief capacity by a forensic pathologist from the Department of Forensic Medicine, University of Pretoria (JV). Due to factors beyond our control, the autopsy was unfortunately only able to be conducted 13 days after the demise of the victim by which time potentially vital histological clues were obscured by autolysis. The principal findings were as follows: An exclamation mark (!) shaped punctate wound was clearly visible distally and laterally on the dorsal aspect of the middle phalanx of the left index finger (Fig. 4). This small wound measured 2.5 mm in length and was surrounded by an area of apparent contusion, which measured 8 mm 9 mm in size. This area of blue-
Fig. 4. Puncture wound on the dorsal surface of the middle phalanx of the left index finger. Note the small incision extending from the lateral edge of the puncture.
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black discolouration showed indistinct proximal extension in a linear fashion across the dorsal aspect of the left index finger to the level of the proximal inter-phalangeal joint. Upon incision of the skin in the affected area, soft tissue haemorrhage was clearly noted surrounding a central area of necrosis and softening of the tissue. No rash was evident at autopsy. The organs had a congested appearance in general and showed autolytic changes. Inspection of the larynx showed slight hyperaemia of the laryngeal mucosa, but no findings representative of overt angio-oedema. Pink, frothy fluid was present in the trachea and the lungs were markedly oedematous and congested. A prominent branching microvascular pattern was noted on the epicardial surface of the heart; however the heart was flabby and extremely autolytic. No renal abnormalities, retroperitoneal soft tissue haemorrhage or haematoma formation were observed. Unfortunately, at the time of the autopsy the coronary arteries were not specifically inspected for the presence or absence of plaque formation. On histological examination, besides disruption of the epidermal and dermal tissue layers, with associated fresh haemorrhage, no acute inflammatory response or foreign material was observed in the section of skin surrounding the snakebite on the left index finger. Acute ischaemic changes, including foci of contraction band necrosis with no accompanying inflammatory response, were observed throughout the sections of the heart. No signs of pre-existing myocardial ischemia or fibrosis were observed in the sections of the myocardium. Histological examination of the lungs confirmed prominent pulmonary oedema and severe pulmonary congestion. No acute inflammatory reaction, including eosinophil infiltration or oedema, was present in the larynx. Sections of the liver showed Grade I, mainly microvesicular, centrilobular steatosis consistent with pre-existing fatty change. 2. Discussion Only four cases of envenomation from Atractaspis corpulenta are previously documented (Boulenger, 1913; Aylmer, 1922; Gunders et al., 1960; Pauwels et al., 2008). Boulenger (1913) and Aylmer (1922) document bites from the same specimen but at different times and places. All the bites were relatively mild and variously document local pain, parasthesia, swelling, lymphadenitis of the draining glands, local discolouration, muscular pain and in one case a transient haematuria with a transiently prolonged Prothrombin Time (32% of normal) (Gunders et al., 1960). On the basis of the known distribution of the species, Pauwels et al. (2008) ascribe the cases described by Boulenger 1913, Aylmer 1922 and Gunders et al., 1960 to the subspecies Atractaspis corpulenta leucura. One case of envenomation by the nominate subspecies A. c. corpulenta is described (Pauwels et al., 2008). The current case is also ascribed to the nominate form A. corpulenta corpulenta. No studies on the venom of A. corpulenta have been published and so the effects of its venom e until otherwise proved e are generally considered to be similar to the known venoms of other species in the genus. This report documents the first fatality from the bite of Atractaspis c. corpulenta. No clear pathophysiological mechanism for the death could be identified from either the clinical record or the results of the autopsy. The most likely causes of death are considered to be due to either the direct effects of the venom on the myocardium and its vasculature, or anaphylaxis induced by either the venom or medications administered to the victim. Early Acute Reactions (EAR) to antivenom administration may result in anaphylaxis and death, but although it cannot confidently be excluded, anaphylaxis resulting from antivenom or enoxaparin is considered to be the least likely of the potential causes due to the relatively long intervals between administration and death. In the current
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case, a localized rash noted shortly before the onset of cardiac arrest may well have been related to the antivenom injection. Urticarial rash is one of the commonest manifestations of EARs to SAVP (SAIMR) polyvalent antivenom (Moran et al., 1998) but severe reactions are relatively uncommon. In addition, during the resuscitation attempt, treatments that are usually effective for the management of anaphylaxis were administered (adrenalin and ventilation) but were unsuccessful in preventing death. Anaphylaxis typically presents with cardiovascular collapse, mucosal oedema, gastro-intestinal cramps, vomiting, pruritus and urticarial rash. Respiratory signs in severe EARs are generally associated with mucosal oedema and bronchospasm (Fisher and Boldo, 1985; Simons et al., 2012) and not pulmonary oedema. Findings at autopsy which may be consistent with anaphylaxis such as pharyngeal and or laryngeal oedema, upper respiratory tract oedema, visceral congestion, pulmonary congestion and oedema, and sometimes lung hyperinflation in association with mucous plugging of the airways (Da Broi and Moreschi, 2011; Edston et al., 2007) may only be present in 59% of deaths from anaphylaxis (Da Broi and Moreschi, 2011). Where the history is inconclusive, the post mortem diagnosis of anaphylaxis can be difficult e especially where macroscopic signs may be absent at autopsy and where blood or other biological fluids are unavailable or unsuitable for study (Simons et al., 2012). Elevated mast cell tryptase levels have been used as an indicator of anaphylaxis, but since mast cell degradation post-mortem also results in raised levels, levels should be tested within a post mortem interval of three days (Payne and Kam, 2004). In the current case no reliable post mortem analysis was deemed possible. It is however apparent from the autopsy that there was no macroscopic or histological evidence of angioedema present. Histological examination following anaphylaxis often reveals an eosinophilic infiltration in the lungs, heart (Da Broi and Moreschi, 2011) and other affected organ structures, for example the larynx or site of envenomation. In our case, eosinophilia was absent in all the tissue sections. Reactions mimicking anaphylaxis are described in victims with no known prior exposure to Atractaspis venoms, and include a well documented case of an ‘anaphylactoid reaction’ following a bite from A. engaddensis (Chajek et al., 1974). The above case was associated with acute Type II respiratory failure e presumably due to acute and severe bronchospasm. Apart from a non-specific history of chest tightness, we have no clinical evidence of coronary artery vasospasm in this victim, but it is possible that coronary vasospasm might have contributed to some of the histopathological findings (e.g. focal myocardial ischaemia) in this case. The appearance of contraction band necrosis and other histological changes of ischaemia in the myocardium, also cannot be interpreted to be solely due to the direct effects of venom or myocardial ischaemia as these findings could also be consistent with the prolonged cardiopulmonary resuscitation efforts and adrenalin administration (Karch, 1987; Baroldi et al., 2001). Pulmonary oedema per se has little diagnostic significance post mortem, as this finding is observed in many conditions at autopsy (Lee et al., 1986; Saukko and Knight, 2004) including myocardial ischaemia with acute left ventricular dysfunction, envenomation, anaphylaxis and agonal changes associated with prolonged resuscitation. The appearance of the bite wound (Fig. 4) deserves some comment. The cut through the skin inferior to the puncture, was most likely caused by the posterior surface of the fang. Visser (1975) and Kochva and Meier (1986) demonstrated that the fang of A. engaddensis had a serrated flange on the posterior edge near the tip. The presence of such a serrated flange in A. corpulenta could not be confirmed, however in the original description of the
species, Hallowell (1857) noted that the fang of A. corpulenta had “ …. a superior and inferior ridge, compressed laterally with an elevation in the middle e resembling a squalus tooth”. Dueffel and Cundall (2003) noted that the fang stabs of A. microlepidota and Atractaspis bibronii produce slit-like incisions as the fang is thrust into and then withdrawn from the skin of prey items. Given the prolonged post-mortem storage of the corpse, one cannot exclude the effects of tissue plane deterioration on the appearance of the bite wound. 2.1. Atractaspis bites and venoms The symptomatology and clinical evolution of recorded Atractaspis bites from all species have remarkable similarities. Early severe local pain and draining lymphadenitis are accompanied by swelling and local discolouration, and when on a digit the bite is often associated with local blistering and necrosis. Muscle pains, painful tongue and eye movements, and autonomic symptoms such as nausea and vomiting, sweating, abdominal pain as well as watery diarrhoea, may occur. A variety of neurological symptoms and signs have also been described and transient haematuria (Gunders et al., 1960; Corkhill and Kirk, 1954) of questionable significance has been described (Corkhill et al., 1959). Abnormalities in liver enzymes have been noted in two cases of A. engaddensis bites, one with documented histological changes (Chajek et al., 1974); in other cases, early fluctuations in the level of consciousness, collapse, respiratory distress, peripheral and central cyanosis are described (Chajek et al., 1974; Al-Sadoon and Abdo, 1991; Kurnik et al., 1999). Transient hypertension and acute Type II respiratory failure is also described (Chajek et al., 1974; Kurnik et al., 1999). Apart from a small group of species (including A. microlepidota and A. engaddensis) with elongated venom glands (Kochva et al., 1967; Underwood and Kochva 1993), the venom glands of the other species of Atractaspis (including those of A. corpulenta) are usually small and produce only small amounts of venom, the toxicity of which varies significantly between the various species (Ducancel and Goyffon, 2008). Venom yields from large specimens are not unexpectedly higher than those from smaller specimens (Corkhill and Kirk, 1954; Branch, 1981). Atractaspis venoms are typically very viscous containing between at least 50e100 different molecular compounds (Ducancel and Goyffon, 2008; Quinton et al., 2005), including among others a number of known venom ‘families’ such as three-finger toxins, CRISPs, Kunitz-type/TFPI, C-type lectins, kallikrein/serine protease, metalloproteinase, disintegrin, venom nerve growth factor and PLA2 (Terrat et al., 2013). Haemorrhagic fractions have been isolated (Kochva et al., 1982; Ovadia, 1987) and transient abnormalities in human blood coagulation have been reported from various species (Tilbury and Branch, 1989; Chajek et al., 1974; Gunders et al., 1960). No pre e or post-synaptic effect on the neuromuscular synapse could be identified in A. engaddensis venom, although peripheral/autonomic effects were not excluded (Weiser et al., 1984). Atractaspis has evolved a class of toxins unique to the genus that have several specific effects. Considered to be among the most potent snake toxins yet described (Ducancel, 2002), Atractaspis venoms contain multiple isoforms of polypeptide chains consisting of between 15 and 30 amino acids (Quinton et al., 2005; Ducancel, 2005). Known as sarafotoxins (SRTX), these toxins are highly selective Endothelin ʙ (ETʙ) and Endothelin A (ETA) receptor agonists (Marshall and Johns, 1999; Fink et al., 2007; Rocha-Sousa et al., 2009) with a sequence homology of about 60% with mammalian vasoactive 21 amino acid endothelin peptides (Graur et al., 1988; Ducancel, 2002). Endothelin receptors are found throughout the cardiopulmonary (Hemsen et al., 1990; Maggi et al., 1990), renal (Marshall and Johns, 1999) and mesenteric vasculature (Han et al.,
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1990) and induce vasospasm at all these sites via activation of the ETʙ receptors. Both endothelins and SRTX induce contraction of smooth muscle in intestines (Weiser et al., 1984; Wollberg et al., 1991) and bronchi (Maggi et al., 1990; Hemsen et al., 1990). SRTX induce a dose-dependent positive inotropic response in myocardial muscle, a progressive atrio-ventricular blockade, ventricular tachycardia, atrial flutter and ventricular fibrillation in mouse and rat heart preparations (Weiser et al., 1984; Lee et al., 1986; Wollberg et al., 1988). These effects appear to be due to both a direct toxic effect on the myocardium as well as secondary to the onset of myocardial ischaemia caused by coronary artery spasm (Wollberg et al., 1988). The degree of vasospasm also appears to be dose dependent (Marshall and Johns, 1999). In vivo experiments in dogs using SRTX S6c caused a dose related reduction in the perfusion of all layers of the myocardium e with a maximum 71% decrease in blood flow in the epicardial layer (Teerlink et al., 1994). In the human cardiopulmonary system, the highest level of endothelin-like immunoreactivity was found in the left anterior descending coronary artery (Hemsen et al., 1990). In mice, A. engaddensis venom induces a transient hypertension postulated to be secondary to vasoconstriction of peripheral vascular beds (Lee et al., 1986). The onset of transient hypertension in humans has also been noted in several cases (Chajek et al., 1974; Kurnik et al., 1999) e also postulated to be secondary to SRTX induced systemic vasoconstriction. ECG abnormalities seen in humans envenomated by A. engaddensis are indicative of myocardial ischaemia with prolongation of the PR interval, ST segment depression, and flattening and-or inversion of the T waves (Chajek et al., 1974; Alkan and Sukenik, 1975; Kurnik et al., 1999). It is apparent that activation of human endothelin receptors by SRTX may give rise to the systemic symptoms and signs of intestinal colic, bronchospasm, hypertension, myocardial ischaemia and related ECG changes and effects. 2.2. Comments on treatment and other possible causes of death Given that a fatality from the bite of A. corpulenta is an unexpected outcome, it is important to consider other possible causes of death in this particular case. The case was managed according to a local snakebite protocol. The administration of low molecular weight heparin (Enoxaparin) and betamethasone are not usual components of modern snake bite protocols and in view of the symptoms and signs at the time when it was administered, the decision to inject polyvalent anti-venom is questionable e even given that the identity of the snake was unknown at the time. Both antivenom and Enoxaparin could potentially cause anaphylaxis. Lastly it could be speculated that circulating SRTX in a low concentration which might not induce significant coronary blood flow restriction in a person with patent coronary vessels, may be sufficient to provoke myocardial ischaemia and its consequences in someone with lipidemia and asymptomatic underlying coronary artery disease. Although the mechanism of action of SRTX is associated with the mobilisation and increase of intracellular Ca⁺⁺ and the hydrolysis of phosphoinositol (Kloog et al., 1988; Gairon et al., 1989), in animal models the binding of SRTX to specific endothelin receptors is unaffected by the action of calcium channel blockers such as verapamil and nitrodipine (Ducancel, 2002; Kloog et al., 1988; Kloog and Sokolovsky, 1989; Gairon et al., 1989) and nitroglycerine (Abd-Elsalam, 2011). No effective antivenoms against Atractaspis species are produced on a commercial scale and no burrowing asp venom is employed in the production of SAVP (SAIMR) polyvalent antivenom. The small molecular weight and simple tertiary structure of the SRTX molecules combine to produce low immunogenicity in typical antivenom production systems.
25
Small amounts of effective antivenom may be produced using adjuvants (Ismail et al., 2007). While specific antivenoms may not be available, a recent in vitro study suggested that Bosentan e a potent blocker of endothelin receptors A and B e was able to completely reverse the coronary vasospasm induced by A. engaddensis venom in isolated rabbit hearts more effectively than specific antivenom (Abd-Elsalam, 2011). 3. Conclusion/recommendations Although the vast majority of victims of Atractaspis envenomation survive their bites, the occasional bite from any of the various species of Atractaspis has the potential to cause serious envenomation and even fatality. In some cases the early onset of systemic symptoms and signs (such as shortness of breath/bronchospasm, peripheral or central cyanosis, chest pain, abdominal cramps, vomiting, diarrhoea and hypertension) if not due to anxiety, may be indicators of endothelin activation and signal the potential for a negative outcome. Venom to mass ratios are important and in the case of bites in children, or when multiple bites have been inflicted, the increased risk of severe envenomation and systemic effects must be recognised and actively managed. In all cases of proven or suspected Atractaspis bites, an ECG should be recorded and monitored if possible, particularly for the first 12e24 h after the bite. The use of endothelin receptor blockers to reverse the effects of SRTX on the myocardium might be usefully explored further, with a view to proposing a dosage schedule for severe human Atractaspis envenomation. Conflict of interest The authors declare that there are no conflicts of interest. Ethical statement Ethical approval for the publication of this case report was obtained from and endorsed by the University of Pretoria Faculty of Health Sciences Research Ethics Committee (Ref No.471/2015). Consent for publication of the case report was also provided by the widow of the deceased. Acknowledgements The authors would like to acknowledge the help of Professor William Branch and Johan Marais for assistance with the identification of the snake involved, and the support of the Department of Forensic Medicine, University of Pretoria. The two reviewers of the manuscript are thanked for their useful comments and advice. Transparency document Transparency document related to this article can be found online at http://dx.doi.org/10.1016/j.toxicon.2016.04.035. References Abd-Elsalam, M.A., 2011. Bosentan, a selective and more potent antagonist for Atractaspis envenomation than the specific antivenom. Toxicon 57, 861e870. Al-Sadoon, M.K., Abdo, N.M., 1991. Fatal envenoming by the snake Atractaspis newly recorded in the central region of Saudi Arabia. J. King Saud Univ. 3 Science (2), 123e131. Alkan, M.L., Sukenik, S., 1975. Atrioventricular block in a case of snakebite inflicted by Atractaspis engaddensis. Trans. R. Soc. Trop. Med. Hyg. 69, 166. Aylmer, G., 1922. The snakes of Sierra Leone. Sierra Leone Stud. 5, 7e37. Baroldi, G., Mittleman, R.E., Parolini, M., Silver, M.D., Vineschi, V., 2001. Myocardial Contraction Bands. Definition, quantification and significance in forensic pathology. Int. J. Leg. Med. 115, 142e151.
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