Serotherapy of the scorpion envenoming syndrome is irrationally convicted without trial

Toxicity and protein composition of venoms of Hottentotta saulcyi, Hottentotta schach and Androctonus crassicauda, three scorpion species collected in Iran

BACKGROUND

Scorpion stings comprise a serious problem throughout the globe, especially in regions where they are more frequent. Despite a recent upsurge of interest in scorpion venoms by various research groups, there remain many challenges.

OBJECTIVE

Therefore, in this study, we aimed to study the toxicity and protein composition of venoms of Hottentotta saulcyi, Hottentotta schach and Androctonus crassicauda, three scorpion species collected in Iran.

MATERIALS AND METHODS

Scorpion species were collected from Esfahan farm scorpion company and maintained in the laboratory in containers that mimic their natural habitat. Venom was extracted from A. crassicauda, H. schach and H. saulcyi by electrical stimulation of 8 and 10 V. The toxicity of each venom was established by using four groups of male Swiss albino mice aged 2 months (weighting 18-20 g) for testing each dose of venom. One group was used as a control. Venom was injected into mice by subcutaneous route. Then, animals were monitored for 24 h and LD₅₀ was estimated by the graphic method of Miller and Tainter. Thus, high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was used to determine amino acids in the venom, and protein concentrations were determined by the Biuret method.

RESULTS

LD₅₀ of scorpion venoms by subcutaneous route was found to be 1.70 mg/kg b.w (A. crassicauda), 1.47 mg/kg b.w (H. saulcyi) and 0.85 mg/kg b.w (H. schach). A. crassicauda, H. saulcyi and H. schach contain 26, 30, and 31 amino acids, respectively. A. crassicauda contains low concentrations of alpha-aminoadipic acid, beta-aminoisobutyric acid, beta-alanine and citrulline. H. saulcyi contains a concentration of hydroxylysine, whereas H. schach has no such concentration. A. crassicauda also had the highest levels of tyrosine and threonine. Only A. crassicauda venom contains a low proportion of proteins (14.80%) compared with those of H. schach (16.26%) and H. saulcyi (16.20%). Albumin content in the venoms was 11.7% (H. saulcyi), 5.4% (H. schach) and 4.4% (A. crassicauda).

CONCLUSION

Scorpions venoms have a variable toxicity and an interesting composition in amino acids and proteins. Work on the development of anti-venom is fundamental.

Role of some vasoactive mediators in scorpion envenomed children: Possible relation to envenoming outcome

Scorpion envenomation causes an autonomic storm resulting in changes in the vasoactive mediators' levels which lead to myocardial damage, cardiovascular disturbances, peripheral circulatory failure, pulmonary edema, multi-system-organ-failure and death. The study aimed to determine the circulating levels of adrenaline, noradrenaline, angiotensin converting enzyme (ACE), Angiotensin II (Ang II), kallikrein enzyme, nitric oxide (NO), aldosterone, and electrolytes Na⁺, K⁺ and Ca⁺² in scorpion envenomed children and to evaluate the potential relation between these vasoactive mediators, the severity of scorpion envenoming and the clinical outcome of envenomed children. Forty envenomed children (22 mild and 18 severe cases) along with 10 healthy control children were enrolled in the study. The circulating levels of adrenaline, noradrenaline, Ang II, ACE, kallikrein enzyme, and NO were determined by ELISA, and spectrophotometric assays on admission and 24 h later. On admission, serum aldosterone, and electrolytes; Na⁺, K⁺ and Ca⁺² were determined by RIA, Flame photometer and Flame atomic absorption respectively. All envenomed children showed significant surge of adrenaline, noradrenaline, ACE, Ang II, aldosterone, NO and Na⁺, that concomitantly faced by significant reduction in kallikrein, K⁺ and Ca⁺² on admission. Twenty four hours later, all envenomed children continued to show significant elevation of ACE, Ang II and NO. The severely envenomed children showed considerable reduction in circulating levels of adrenaline, noradrenaline, ACE and Ang II, while dramatic increase in kallikrein activity was reported in comparison to mildly envenomed children after 24 h of medical care. Also, NO exhibited considerable accumulation in non survivors, on admission, that was persistent for the subsequent 24 h and was accompanied by high kallikrein, low catecholamines and Ang II levels compared to survivors. Finally, the hypertensive cases showed substantial higher levels of catecholamine, ACE and Ang II, 24 h after admission. These findings indicated that, disturbances of the studied vasoactive mediators were common in scorpion envenomed children and may account for several inflammatory manifestations and clinical outcome. ACE inhibitors could be considered as possible therapeutic agent in victims with prominent increase in ACE and Ang II while kallikrein inhibitor and antioxidants may be effective in the treatment of late hypotensive ones.

Medically important venomous animals: biology, prevention, first aid, and clinical management

Venomous animals are a significant health problem for rural populations in many parts of the world. Given the current level of the international mobility of individuals and the inquisitiveness of travelers, clinicians and travel clinics need to be able to give advice on the prevention, first aid, and clinical management of envenoming. Health professionals often feel overwhelmed by the taxonomy of venomous animals; however, venomous animals can be grouped, using a simple set of criteria, into cnidarians, venomous fish, sea snakes, scorpions, spiders, hymenoterans, and venomous terrestrial snakes. Geographic distribution, habitats, and circumstances of accidents further reduce the range of culprits that need to be considered in any single event. Clinical management of envenomed patients relies on supportive therapy and, if available, specific antivenoms. Supplies of life-saving antivenoms are scarce, and this scarcity particularly affects rural populations in resource-poor settings. Travel clinics and hospitals in highly industrialized areas predominantly see patients with injuries caused by accidents involving marine animals: in particular, stings by venomous fish and skin damage caused by jellyfish. However, globally, terrestrial venomous snakes are the most important group of venomous animals.

Treatment of the scorpion envenoming syndrome: 12-years experience with serotherapy

The pathophysiology of the scorpion envenoming syndrome is described with emphasis on the body systems commonly affected. Concepts of the mechanisms underlying venom action, as can be explained by the recently discovered effects on ionic channels, are discussed. A protocol for the treatment of scorpion stings based mainly on antivenom therapy was applied nationwide in Saudi Arabia. A list of drugs with alternatives was specified to be used in adjunctive therapy, when required. Analysis of the outcome from 1,033 cases at Al-Baha region, 791 cases at Al-Qassim region and more than 2,000 cases from 12 central and specialist hospitals in the Central Province, Saudi Arabia gave impressive results. The incidence of severe venom toxicity following antivenom administration was almost negligible. The period of stay in the hospital was reduced. The early reaction to antivenom administration was lower than expected the severity of the reaction consisting mainly of skin rashes, urticaria, wheezing and bronchial hypersensitivity, but no anaphylaxis. About 13.8% of the victims had been previously treated with antivenom but only 1.7% of the patients showed positive skin tests. This might be due to the low protein content of the antivenom and the action of the venom in releasing massive amounts of catecholamines.

Evaluation of antivenom therapy in children severely envenomed by Androctonus australis garzonii (Aag) and Buthus occitanus tunetanus (Bot) scorpions

One hundred and forty-seven cases of envenomed children under 15 years old presenting local and general symptoms without failure in vital functions (clinical grade II) or presenting serious general symptoms with failure in vital functions (clinical grade III) were collected during the summer seasons of 1993-1997. They were classified in six groups according to the use or not of antivenom, the route and the frequency of antivenom administration. The determination, by a sensitive ELISA, of blood venom concentration before and until 6 h after antivenom therapy, allowed the establishment of the venom toxicokinetic curve for each group. The intramuscular administration of antivenom did not show significant effects on venom toxicokinetic curves and on patients recovery time. However, the same amount of antivenom administered by intravenous route clear rapidly the blood free venom toxins. Also, the patient recovery time was significantly shortened. These data are in favor of intravenous application of an adequate dose of an efficient antivenom in order to treat successfully severe scorpion envenoming cases.

Serotherapy in scorpion envenomation: a randomised controlled trial

BACKGROUND

Evidence for the benefit of scorpion antivenom, the only specific treatment for scorpion envenomation, is scarce, despite its common use. We did a prospective, randomised, controlled trial to assess the efficacy of routine administration of scorpion antivenom to scorpion-stung patients, irrespective of clinical severity.

METHODS

We included 825 consecutive patients older than 10 years, who presented to the accident and emergency department of the hospital in Tozeur, Tunisia. We graded severity by absence (grade I) or presence (grade II) of systemic manifestations of scorpion envenomation. Patients were randomly assigned placebo (n=413) or 20 mL bivalent intraveneous scorpion antivenom (n=412). All patients were observed for 4 h. Patients who developed life-threatening symptoms were admitted to the intensive-care unit. At the end of 4 h observation we reassessed grade and discharged grade II patients and admitted grade II patients. We assessed the preventive and curative effects of scorpion antivenom by prevention of worsening grade or by improvement from grade II to grade I.

FINDINGS

Distribution of severity grades was similar in the two groups at baseline, as were the cure rates (55% scorpion antivenom, 66% placebo, absolute difference, 11% [95% CI -4.8 to 26.8]; p=0.234). Preventive effects were seen in 94% and 96% of patients in the scorpion antivenom and placebo groups, respectively, who were initially grade I and who remained symptom-free (absolute difference, 2% [-1.27 to 5.27]; p=0.377). Time from scorpion sting to administration of scorpion antivenom did not affect curative and preventive effects.

INTERPRETATION

We found no benefit in routine administration of scorpion antivenom after scorpion sting, irrespective of clinical severity. Future studies should focus on patients with the most severe symptoms and signs.

Efficacy of serotherapy in scorpion sting: a matched-pair study

BACKGROUND/OBJECTIVE

Although evidence of scorpion antivenin effectiveness in the clinical setting is lacking, scorpion antivenin is generally considered the only specific treatment for scorpion sting irrespective of its clinical severity. We conducted a matched-pair study to assess the efficacy of systematic administration of scorpion antivenin.

METHODS

Among 600 stung patients who participated in a study on the efficacy of high-dose hydrocortisone after scorpion sting, 135 (cases) had been treated with 10 to 20 mL intravenous scorpion antivenin (neutralizing 10 LD50 venom/mL). Controls were matched on disease severity on arrival to the emergency department. The severity of envenomation was graded I or II according to the absence (grade I) or the presence (grade II) of systemic manifestations of scorpion envenomation. Assessment of scorpion antivenin efficacy was based on the rate of changing severity grade in both groups (clinical improvement or worsening during an observation period of at least 4 hours).

RESULTS

Both groups were similar with respect to clinical severity (36 patients were graded II in each group), age, sex, time-lapse between scorpion sting and ED arrival, and the administration of adjunctive therapy such as hydrocortisone. By the 4-hour evaluation, 50% and 64% of patients initially graded II exhibited a substantial clinical improvement in cases and controls, respectively, suggesting similar effects in cases and controls. There was no difference in preventive effects: 13% and 10% of cases and controls developed systemic manifestations of scorpion envenomation during the 4-hour observation period; 23% of cases and 17% controls were hospitalized by this time. There was no difference in the duration of hospitalization. Three cases developed anaphylactic shock as a consequence of scorpion antivenin administration, while 1 scorpion antivenin-untreated patient died from refractory shock.

CONCLUSION

Systematic administration of scorpion antivenin irrespective of clinical severity did not alter the clinical course of scorpion sting. A prospective study is needed concerning the response of the more severe scorpion envenomations.

Development of an ELISA for the detection of scorpion venoms in sera of humans envenomed by Androctonus australis garzonii (Aag) and Buthus occitanus tunetanus (Bot): correlation with clinical severity of envenoming in Tunisia

A sandwich ELISA was set up for measuring scorpion venom levels in sera of accidentally envenomed humans with the aim to establish a quantitative relationship between these levels, envenoming severity and clinical symptoms. This assay used equine polyclonal F(ab')2, specific to two North African scorpion (Androctonus australis garzonii: Aag and Buthus occitanus tunetanus: Bot) venoms. The test proved to be simple, reproducible, very sensitive (detection limit = 0.9 ng/ml) and linear between 0.5 and 15 ng/ml of venom concentrations. A large survey on scorpion sting envenomings was conducted from 1993 to 1996 in Tunisia to gather accurate epidemiological, clinical and biological data from victims as well as informations on the treatment that they had received. Victims were classified into three grades (GI, GII and GIII) of increasing severity according to clinical signs of envenoming. Blood samples were collected from victims and tested by ELISA for their content of Aag and Bot venoms. A strong correlation was found between clinical symptoms of envenoming and the level of scorpion venom antigens in serum (r = 0.980). Mean serum venom concentrations were: 2.65 +/- 0.81 ng/ml in GI envenoming, 9.79 +/- 4.08 ng/ml in GII and 21.7 +/- 6.51 ng/ml in GIII. The difference between each group was statistically significant (p < 0.01). This ELISA may prove to be helpful to establish a rationale approach of specific antivenom therapy.

Indian red scorpion envenoming

The clinical course and treatment outcome of scorpion envenoming in 293 children was studied in a hospital at Mahad in Raigad district of Maharastra. 111 (38%) children who reported 1-10 hours (mean 3.5 hours) after sting had hypertension, 87 (29.6%) with tachycardia reported within 1-24 hours (mean 6.7 hours) of being envenomed and 72 (24.5%) children developed acute pulmonary edema after 6-24 hours (mean 8 hours) of sting. Six victims were brought dead, while 17 (6%) died later owing to multiorgan failure with loss of consciousness and convulsions (who reported after 24 hours of sting). Early administration of prazosin (125-250 ug orally) improved the clinical symptoms. Morbidity and mortality due to scorpion envenoming depends upon time lapse between sting and administration of post synaptic alpha-1 blocker, prazosin hydrochloride.

High-dose hydrocortisone hemisuccinate in scorpion envenomation

STUDY OBJECTIVE

Scorpion envenomation is a common life-threatening hazard in tropical and subtropical countries. Standard treatment is not clearly defined. Many therapies, such as steroids, are prescribed without experimental justification. We sought to assess the efficacy of systematic administration of intravenous hydrocortisone hemisuccinate (50 mg/kg) in scorpion envenomation.

METHODS

Six hundred consecutive envenomated patients older than 10 years who presented to the ED of a nonteaching secondary hospital in an area of Tunisia endemic for scorpion envenomation were randomly assigned to receive hydrocortisone hemisuccinate 50 mg/kg (n = 305) or placebo (n = 295) in addition to standard medical care. Patients in the two groups had similar clinical characteristics on initial clinical evaluation. Each was categorized as grade 1 (absence of systemic symptoms) or grade 2 (systemic symptoms of scorpion envenomation). Patients were treated in the ED for up to 4 hours or in the ICU, depending on clinical severity. Steroid and placebo groups were compared according to mortality rate, change of severity grade 4 hours after presentation and treatment, and duration of hospital stay.

RESULTS

Distribution of patients with respect to severity grade was similar in the two groups at the 4-hour clinical evaluation. We detected no significant difference at the time of discharge between steroid-and placebo-treated patients with respect to mortality (one patient in each group) or duration of hospital stay. Extra costs incurred through steroid administration totaled US $989,000.

CONCLUSION

Our findings do not support the use of intravenous high-dose steroids in scorpion-envenomated patients. The discontinuation of this practice would reduce costs substantially.

The use of synthetic peptides can be a misleading approach to generate vaccines against scorpion toxins

Seven peptides corresponding to the amino acid sequence of toxin 2 from the scorpion Centruroides noxius were chemically synthesized, purified and assayed in mice for their putative neutralizing properties against scorpion toxins. All the peptides were immunogenic and some produced neutralizing antibodies, as verified by injecting the antisera with toxin into naive animals. However, direct challenge of pre-immunized mice (with the longest synthetic peptides of 27 and 57 amino acid residues) revealed an unexpected sensitization phenomena: the animals did not resist injection of one LD50 of purified toxin 2 (5% survival), but pre-immunization of mice with native toxin protected 100% of the animals. These findings suggest that vaccine preparations with synthetic peptides corresponding to the amino acid sequence of certain toxins should be analyzed cautiously.

[Scorpion stings in children. Saudi Arabian experience]

Scorpion stings are a major public health problem in Saudi Arabia. The main victims are children who accidentally tread on a scorpion, about 900 children being admitted to hospitals each summer for such stings. Many cases are fatal. The pathophysiology of scorpion stings is complex and its management is difficult. Almost all body systems are affected but circulatory shock and pulmonary oedema are the usual cause of death. The treatment is based on scorpion antivenom and symptomatic treatment of the envenoming manifestations in an intensive care unit. The currently used antivenom is a polyvalent horse serum preparation given intravenously.

A comparative study of severe scorpion envenomation in children caused by Tityus bahiensis and Tityus serrulatus

From January 1984 to May 1994, 17 of 239 children under 15 years old stung by Tityus serrulatus (15.1%) or Tityus bahiensis (84.9%) presented severe envenoming. Of these 17 patients (1-11 years old; median = 2 yr) 14 were stung by T. serrulatus and three by T. bahiensis. All of them received scorpion antivenom i.v. at times ranging from 45 min. to 5 h after the accident (median = 2 h). On admission, the main clinical manifestations and laboratory and electrocardiographic changes were: vomiting (17), diaphoresis (15), tachycardia (14), prostration (10), tachypnea (8), arterial hypertension (7), arterial hypotension (5), tremors (5), hypothermia (4), hyperglycemia (17), leukocytosis (16/16), hypokalemia (13/17), increased CK-MB enzyme activity (> 6% of the total CK, 11/12), hyperamylasemia (11/14), sinusal tachycardia (16/17) and a myocardial infarction-like pattern (11/17). Six patients stung by T. serrulatus had depressed left ventricular systolic function assessed by means of echocardiography. Of these, five presented pulmonary edema and four had shock. A child aged two-years old presented severe respiratory failure and died 65 h after being stung by T. serrulatus. Severe envenomations caused by T. serrulatus were 26.2 times more frequent than those caused by T. bahiensis (p < 0.001).

The scorpion envenoming syndrome

The pathophysiology of the scorpion envenoming syndrome is reviewed with emphasis on the body systems commonly affected. Concepts of the mechanisms underlying venom action, as can be explained by the recently discovered effects on ionic channels, are discussed. The results of clinical analysis of cases of scorpion sting victims and animal experiments with scorpion envenomation supporting these concepts are presented. The pharmacokinetic characteristics of scorpion venoms and their correlation to the magnitude of toxic effects are presented in relation to the potentials of therapeutic intervention. The pharmacological basis of the therapeutic usefulness and toxicities of the drugs commonly used in the treatment of scorpion envenoming is also projected. Finally, the results of a successful nation-wide clinical study with serotherapy of scorpion envenoming are presented and evaluated.

Reversion by polyclonal antibodies of alpha effects of Tityus serrulatus venom on frog sciatic nerve

Fraction T2 from Tityus serrulatus venom produced a marked lengthening of action potentials recorded with the single sucrose-gap technique, a characteristic effect of alpha scorpion toxins. This effect was not reversed by thorough washing of the nerve. On the other hand, T2 fraction deactivated by complete iodination did not cause any alteration of the compound action potential, even if applied in concentration as high as 4000 times the half saturation dose of the unmodified T2 fraction. This high dose of deactivated T2 did not hinder the onset of the full effect of a single dose of T2 fraction applied subsequently. Polyclonal antibodies against native or against iodinated venom reverted the action of T2 fraction, restoring normal electrical response. We conclude that both types of antibodies may remove the effect of alpha toxins on sodium channel.

Androctonus crassicauda (Olivier), a dangerous and unduly neglected scorpion--I. Pharmacological and clinical studies

Androctonus crassicauda venom has an i.v. LD50 in mice of 0.32 +/- 0.02 mg/kg, which makes the scorpion among the most toxic species in the world. Fifty-one non-fatal and one fatal cases of scorpion sting were presented. Pain and tenderness were very common following the sting. Generalized erythema occurred in 20-25% of all infants and children below the age of 5 years. Severe CNS manifestations including seizures, unconsciousness and marked irritability occurred mainly in infants and young children, while hypertension occurred in the majority of victims below the age of 11 years. Two pregnant victims were treated with antivenom with no bad consequences on mothers or foetuses. The fatal case described was inadequately treated with antivenom and presented a rare situation of intracranial coagulation in the basal cisterns or low in the cranial subarachnoid space. The victim developed moderate hydrocephalus of the communicating type with clear ventricular CSF and strongly xanthocromic fluid from lumbar puncture. The effects of A. crassicauda venom on isolated hearts, atria and anaesthetized rat blood pressure appeared to be mediated largely through stimulation of the autonomic nervous system with predominance of sympathetic stimulation and release of tissue catecholamines. Electrocardiograms recorded simultaneously with blood pressure changes showed evidence of ectopic foci during the hypertensive phase and ischaemia, inferior wall infarction and different degrees of heart block during the late hypotensive phase. Androctonus crassicauda venom was unique in following a three-compartment open model comprising a central compartment 'blood', a rapidly equilibrating 'shallow' tissue compartment and a slowly equilibrating 'deep' tissue compartment. The overall elimination half-life, t1/2 beta, was 24 hr, indicating that the venom has the slowest elimination among all known scorpion venoms. The long stay of the venom in the body might explain the increased risk of toxicity and the good potential for treatment with serotherapy even hours after the sting.

Scorpionism and serotherapy in Mexico

In Mexico, scorpionism is an endemic public health problem. The exact number of human accidents is unknown, but partial statistics suggests numbers close to 200,000 per year. The documented number of fatality cases is in the order of 310 people per year. We currently use horse antiserum in patients who show a clear picture of intoxication. Our personal experience in treating 38,068 people, from which over 20,000 received serotherapy, shows that the antiserum is very effective, in that none of the patients died.