Epidemiological characteristics of scorpion sting in León, Guanajuato, México

Factors involved in the resilience of incidence and decrease of mortality from scorpion stings in Mexico

In Mexico, scorpion sting envenomation (SSE) is a significant public health issue that has engaged the attention of health authorities for more than a century. Rigorously characterized today, scorpion sting incidence is stable around 230 stings per 100,000 population, i.e. 300,000 annual stings treated in Mexican health centers and hospitals. Higher incidence is observed mainly in central and Pacific Mexico. Scorpion populations thrive in populated places, particularly in impoverished areas. Scorpion stings occur in houses. This could explain similar incidence according to gender and age. The number of scorpion stings has remained stable since the mid-2000s. In contrast, mortality, which was over 1500 deaths per year before the 1960s, underwent a dramatic drop after the 1970s, from 500 deaths per year to fewer than 50 annual deaths today. Case fatality rates have shown similar trend. We noted a significantly higher specific mortality in males than in females (0.199 and 0.168 per 100,000 respectively; P < 1.9·10^-6). Three causes explained the drop in mortality and case fatality rate, a) ongoing improvement in hospital care, particularly in terms of supportive standardized treatments, b) the use of highly purified immunoglobulin F(ab')₂ fragments after 1995 and, c) increasing access to health services for most of the Mexican population. The authors retrace the history of the management of SSE, including the development of antivenoms, in Mexico between 1905 and today.

North American scorpion species of public health importance with a reappraisal of historical epidemiology

Scorpionism is a severe threat to public health in North America. Historically, few species of Centruroides have been considered to be the offending taxa, but we know now that their diversity is greater and our knowledge incomplete. Current distribution maps are inadequate for some species. Epidemiologic studies are sporadic and local, and a complete synthesis for North America is missing. We analyze historical and recent knowledge about the identity, distribution and epidemiology of species of medical importance in North America. PubMed, Google Scholar, the National Collection of Arachnids, and results of recent field work were consulted in the preparation of our analysis. We recognized 21 species and one subspecies of medically important scorpions in need of precise geographical delimitation. All these species are found in Mexico, which is clearly a hotspot for scorpionism. Although mortality has been steadily decreasing, deaths still occur, and morbidity remains high. Mortality is most common at age classes of 0-10 years and >50. Morbidity is highest in age class 15-50 years, including the most economically active segment of the population. The season of the highest incidence of scorpion sting peaks between spring and summer but there appears to be a second, lower peak at the end of the summer. Although the systematics of the genus Centruroides has advanced considerably, our knowledge of its diversity remains fragmentary. There is a disconnection between the actual distribution of the scorpions and the incidence maps constructed from scorpion sting records. Despite a historically robust knowledge of the distribution of well-known species, most recently described species are known from only a few localities. Some of the epidemiological parameters are consistent among studies reported herein.

Clinical and Epidemiological Aspects of Scorpionism in the World: A Systematic Review

OBJECTIVE

Scorpion stings are registered worldwide, but the incidence and the features of the envenomations vary depending on the region. The aim of this review was to summarize the epidemiological, clinical, diagnostic, and therapeutic data worldwide regarding humans stung by scorpions.

METHODS

A systematic review of the literature was conducted through the online databases of the Virtual Health Library (VHL), which hosts Medline and the Latin American and Caribbean Center on Health Sciences Informational (LILACS) database. We selected articles published between January 1, 2002 and July 31, 2014.

RESULTS

Scorpion envenomation reports were found throughout the world, mainly in subtropical and tropical regions. The clinical manifestations were sympathetically and parasympathetically mediated, depending on the species of scorpion. Some of the most common severe complications of scorpionism included respiratory distress syndrome, pulmonary edema, cardiac dysfunction, impaired hemostasis, pancreatitis, and multiple organ failure. Scorpion envenomation could be classified as mild, moderate, and severe, and the therapeutic approach was based on the case severity. The treatment comprised 3 components: symptomatic measures, vital functions support, and injection of antivenom. Moreover, the time that elapsed between the sting and administration of the appropriate medical care was extremely important to the patient's prognosis.

CONCLUSIONS

The large number of scorpion stings worldwide is concerning and reaffirms the need for new prevention measures and policies to reduce the incidence, prevalence, morbidity, and mortality rates from these poisonous arachnids.

The role of dexamethasone in scorpion venom-induced deregulation of sodium and water transport in rat lungs

BACKGROUND

Severe scorpion envenomation can evolve to lung injury and, in some cases, death. The lung injury could be attributed to acute left ventricular failure and increased pulmonary vascular permeability secondary to the release of inflammatory mediators. In clinical practice, corticosteroids have been administered to reduce the early side effects of the anti-venom. We propose to study the effects of Tityus serrulatus venom and dexamethasone on pulmonary expression of sodium and water transporters, as well as on the inflammatory response.

METHODS

Wistar rats were injected intraperitoneally with saline (control group), dexamethasone, and saline (2.0 mg/kg body weight-60 min before saline injection; dexamethasone + saline group), venom (T. serrulatus venom-3.8 mg/kg body weight), or dexamethasone and venom (2.0 mg/kg body weight-60 min before venom injection; dexamethasone + venom group). At 60 min after venom/saline injection, experiments were performed in ventilated and non-ventilated animals. We analyzed sodium transporters, water transporters, and Toll-like receptor 4 (TLR4) by Western blotting, macrophage infiltration by immunohistochemistry, and serum interleukin (IL) by cytokine assay.

RESULTS

In the lung tissue of non-ventilated envenomed animals, protein expression of the epithelial sodium channel alpha subunit (α-ENaC) and aquaporin 5 (AQP5) were markedly downregulated whereas that of the Na-K-2Cl cotransporter (NKCC1) and TLR4 was elevated although expression of the Na,K-ATPase alpha 1 subunit was unaffected. Dexamethasone protected protein expression of α-ENaC, NKCC1, and TLR4 but not that of AQP5. We found that IL-6, IL-10, and tumor necrosis factor alpha were elevated in the venom and dexamethasone + venom groups although CD68 expression in lung tissue was elevated only in the venom group. Among the ventilated animals, both envenomed groups presented hypotension at 50 min after injection, and the arterial oxygen tension/fraction of inspired oxygen ratio was lower at 60 min than at baseline.

CONCLUSIONS

Our results suggest that T. serrulatus venom and dexamethasone both regulate sodium transport in the lung and that T serrulatus venom regulates sodium transport via the TLR4 pathway.

Neurological effects of venomous bites and stings: snakes, spiders, and scorpions

Snake and spider bites, as well as scorpion sting envenoming, are neglected diseases affecting millions of people all over the world. Neurological complications vary according to the offending animal, and are often directly related to toxic effects of the venom, affecting the central nervous system, the neuromuscular transmission, the cardiovascular system, or the coagulation cascade. Snake bite envenoming may result in stroke or muscle paralysis. Metalloproteinases and other substances (common in vipers and colubrids) have anticoagulant or procoagulant activity, and may induce ischemic or hemorrhagic strokes. The venom of elapids is rich in neurotoxins affecting the neuromuscular transmission at either presynaptic or postsynaptic levels. The clinical picture of scorpion sting envenoming is dominated by muscle weakness associated with arterial hypertension, cardiac arrythmias, myocarditis, or pulmonary edema. These manifestations occur as the result of release of catecholamines into the bloodstream or due to direct cardiac toxicity of the venom. Cerebrovascular complications have been reported after the sting of the Indian red scorpion. Intracranial hemorrhages occur in the setting of acute increases in arterial blood pressure related to sympathetic overstimulation, and cerebral infarctions are related to either cerebral hypoperfusion, consumption coagulopathy, vasculitis, or cardiogenic brain embolism. Three main syndromes result from spider bite envenoming: latrodectism, loxoscelism, and funnel-web spider envenoming. Latrodectism is related to neurotoxins present in the venom of widow spiders. Most cases present with headache, lethargy, irritability, myalgia, tremor, fasciculation, or ataxia. Loxoscelism is caused by envenoming by spiders of the family Sicariidae. It may present with a stroke due to a severe coagulopathy. The venom of funnel-web spiders also has neurotoxins that stimulate neurotransmitter release, resulting in sensory disturbances and muscle paralysis. Proper management of the envenomed patient, including prompt transport to the hospital, correction of the hemostatic disorder, ventilatory support, and administration of antivenom, significantly reduce the risk of neurological complications which, in turn, reduce the mortality and improve the functional outcome of survivors.

Pharmacokinetics of a F(ab')2 scorpion antivenom administered intramuscularly in healthy human volunteers

This paper presents the first study of F(ab')(2) scorpion antivenom pharmacokinetics in humans after intramuscular (im) administration. The specific anti-Centruroides scorpion antivenom was used in 6 human healthy volunteers. The fabotherapeutic was administered as a 47.5mg im bolus. Blood samples were drawn at 0, 5, 15, 30, 45, 60 , 90, 120, and 180 min, 6h and at 1, 2, 3, 4, 10 and 21 days after antivenom administration. We measured antivenom concentrations in serum using a specific high sensitivity ELISA method for F(ab')(2). Antivenom concentration in serum was fit to a 3 compartment model (inoculation site, plasma and extra vascular extracellular space), it was assumed that the venom may also be irreversibly removed from plasma. Calculated time course of antivenom content shows that at any time no more that 16.6 (5.3, 31.9)% (median and 95% confidence interval) of the antivenom bolus is present in plasma. The time to peak plasma [F(ab')(2)] was 45 (33, 74) h. The most significant antivenom pharmacokinetic parameters determined were: AUC(im,∞)=803 (605, 1463) mg·h·L(-1); V(c)=8.8 (2.8, 23.6) L; V(ss,im)=55 (47, 64) L; MRT(im)=776(326, 1335) h; CL(t)=3.7 (0.6, 1.9) mL·min(-1); f(im,)V(ss)=0.300 (0.153, 0.466). Comparing these parameters with the ones obtained intravenously by Vázquez et al., the parameters were more disperse between subjects, determined with more uncertainty in each individual subject, and the peak F(ab')(2) in plasma occurred with considerable delay; all indicating that the IM route should not be used to administer the antivenom, with the possible exception of cases occurring very far from hospitals, as an extreme means to provide some protection before the IV route becomes available.

Scorpion stings in Turkey: epidemiological and clinical aspects between the years 1995 and 2004

The most important health-threatening scorpions found in Turkey are; Androctonus crassicauda, Leiurus quinquestriatus, Mesobuthus gibbosus and M. eupeus species, all of which belong to the Buthidae family. The epidemiological and clinical findings of scorpion stings in Turkey were evaluated between the years 1995 and 2004 based on data recorded in the National Poison Information Center (NPIC). A total of 930 cases were recorded. The cases mostly occurred in the month of July. The gender distribution was 50.22% female and 45.48% male. It was shown that the 20-29 age group presented more scorpion stings. Most of the stings occurred in Central Anatolia and Marmara regions of Turkey. Patients at the hospital showed signs of localized (pain, hyperemia, edema and numbness) and systemic effects (hyperthermia, nausea and vomiting, tachycardia, shivering and lethargy) but no lethality was notified. According to records, 33% of the poisoned patients were treated with antivenin in healthcare facilities.

Epidemiology of scorpionism: a global appraisal

The scorpionism is an actual public health problem in several parts of the world because, either incidence, or severity of envenomations is high and managed with difficulty by health services, or for these two reasons at the same time. The treatment of scorpion envenomation is complex and controversial, in particular regarding the utility of the antivenoms and symptomatic treatments that must be associated. The authors reviewed the literature of last 30 years to discuss the epidemiologic importance of scorpionism and to point out the principal therapeutic or preventive measures. According to the most recent studies, seven areas were identified as at risk: north-Saharan Africa, Sahelian Africa, South Africa, Near and Middle-East, South India, Mexico and South Latin America, east of the Andes. These involve 2.3 billion at risk population. The annual number of scorpion stings exceeds 1.2 million leading to more than 3250 deaths (0.27%). Although adults are more often concerned, children experience more severe envenomations and among them, mortality is higher. Improvement of therapeutic management would reduce the lethality very significantly.

A clinical score predicting the need for hospitalization in scorpion envenomation

OBJECTIVE

Predicting complications is a clinical challenge in the assessment of victims of scorpion envenomation (SE). We sought to develop a clinical score to predict need for hospitalization after scorpion sting.

METHODS

We prospectively collected data in patients attending the emergency department after SE in derivation (n = 868) and validation groups (n = 435). A score was derived from a multiple regression analyses using clinical variables as dependent variables and hospitalization as independent variable.

RESULTS

Discrimination power of the constructed score was good (area under the receiver operating characteristic curve, 0.85 and 0.83 in derivation and validation group, respectively). Goodness-of-fit tests indicated that the score performed well in the derivation and the validation groups (P = .88 and P = .67 respectively). The score has a good sensitivity and negative predictive value at cutoff value of 2.

CONCLUSION

Our clinical score could be used for efficient hospital admission decision in patient's victims of SE.

Toxicokinetic and toxicodynamic analyses of Androctonus australis hector venom in rats: optimization of antivenom therapy

This paper reports the simultaneous determination of toxicokinetic and toxicodynamic properties of Androctonus australis hector venom, in the absence and presence of antivenom (F(ab')(2) and Fab), in envenomed rats. After subcutaneous injection of the venom, toxins showed a complete absorption phase from the site of injection associated with a distribution into a large extravascular compartment. The injection of Fab and F(ab')(2) induced the neutralization of venom antigens in the blood compartment, as well as the redistribution of venom components from the extravascular compartment to the blood compartment. Interestingly, F(ab')(2) and Fab showed distinct efficiencies depending on their route of injection. F(ab')(2) induced a faster venom neutralization and redistribution than Fab when injected intravenously. Fab was more effective than F(ab')(2) by the intramuscular route. The hemodynamic effects of Aah venom were further investigated. Changes in mean arterial pressure and heart rate were observed in parallel with an upper airway obstruction. Fab was more effective than F(ab')(2) for preventing early symptoms of envenomation, whatever their route of administration. Intraperitoneal injection of F(ab')(2) and Fab was similar for the prevention of the delayed symptoms, even after a late administration. Fab was more effective than F(ab')(2) in the inhibition of airway resistance, independent of the route and time of administration. These results show that the treatment for scorpion stings might be improved by the intravascular injection of a mixture of Fab and F(ab')(2). If antivenom cannot be administered intravenously, Fab might be an alternative as they are more effective than F(ab')(2) when injected intramuscularly.

Epidemiological and clinical characteristics of scorpionism in Colima, Mexico (2000-2001)

We analyzed 13,223 clinical records of patients treated for scorpion sting in hospitals of the Mexican Institute of Public Health and the Ministry of Health in the state of Colima, Mexico, during the years 2000-2001. A database containing demographic, epidemiological and clinical information was constructed and analyzed retrospectively. Patients were classified in the categories as mild (49.2%), moderate (33.8%) and severe (17.0%) according to commonly accepted standards. Most common symptoms recorded were local pain (94.7%), local paresthesia (67.2%), pruritus/itching (54.3%), sensation of a lump or hair in the throat (47.3%), and sialorrhoea (27.7%). The median time from sting to admission to the emergency room (patient delay) was 33min (interquartile range: 12-60). We found that older and clinically severe patients were significantly associated with longer times of admission to the emergency room. Age was significantly associated with clinical severity: the age group 0-10 years included a higher proportion of severe cases than the group 11 years and older. In four cases, patients died. An educational campaign to inform the population about the importance of receiving prompt attention following a scorpion sting has potential value in reducing complications in the emergency room.

Predicting scorpion sting incidence in an endemic region using climatological variables

Scorpionism is a public health problem in several regions of the world. The highest mortality, with over 1000 deaths per year, has been reported in Mexico. We analysed the significance of climatological variables to predict the incidence of scorpion stings in humans in the state of Colima (Mexico) for the years 2000-2001. The pluvial precipitation (mm), the evaporation (mm), and the mean, maximum, and minimum temperatures (degrees C) were obtained from local meteorological offices. There are approximately 3 stings/year per 1000 people in municipalities of Colima and Villa de Alvarez and about 18-30 stings/year per 1000 people in the rest of the municipalities. There is very little rain and there are few stings in the winter when the minimum temperature is below about 16 degrees C. The number of scorpion stings is independent of the actual rainfall when this is above 30 mm/month. Using multiple linear regression, we used a backward model selection procedure to estimate that the minimum temperature is correlated with scorpion sting incidence with a statistically significance of 95%. We briefly discuss the application of predictive models of scorpion sting incidence in the appropriate allocation of antivenom serum in hospital clinics.

The mitochondrial genome sequence of the scorpion Centruroides limpidus (Karsch 1879) (Chelicerata; Arachnida)

The mitochondrial genome of the scorpion Centruroides limpidus (Chelicerata; Arachnida) has been completely sequenced and is 14519 bp long. The genome contains 13 protein-encoding genes, two ribosomal RNA genes, 21 transfer RNA genes and a large non-coding region related to the control region. The overall A+T composition is the lowest among the complete mitochondrial sequences published within the Chelicerata subphylum. Gene order and gene content differ slightly from that of Limulus polyphemus (Chelicerata: Xiphosura): i.e., the lack of the trnD gene, and the translocation-inversion of the trnI gene. Preliminary phylogenetic analysis of some Chelicerata shows that scorpions (C. limpidus and Mesobuthus gibbosus) make a tight cluster with the spiders (Arachnida; Araneae). Our analysis does not support that Scorpiones order is the sister group to all Arachnida Class, since it is closer to Araneae than to Acari orders.

Mortality and antibody responses of mice to three successive episodes of experimental scorpion (Centruroides limpidus limpidus) envenomation and immunological rescue

Mortality rates of mice and their levels of anti-venom and anti-F(ab')2 antibodies were assessed after three episodes of subcutaneous envenomations with or without treatment with horse F(ab')2. Soluble venom from the Mexican scorpion Centruroides limpidus limpidus was used for these experiments. Repetition of episodes did not induce different mortality rates in untreated mice. F(ab')2 rescued about 85% of the mice in the first two episodes and 66% in the third, without distinction of gender or ostensible side-effects: a suggestion of selection of the most resistant mice. Surviving mice produced in vitro neutralizing antibodies to the scorpion venom and also antibodies to F(ab')2, when injected alone but more so if combined: a possible immunological adjuvant or alarm effect of the venom or of the cascading physiopathology of envenomation. In the few surviving mice, both anti-venom and anti-F(ab')2 antibodies increased significantly after the first envenomation but not thereafter, showing no correlation with mortality rates: a suggestion of their clinical irrelevance, the few hard-to kill mice appeared to resist envenomation by mechanisms other than antibody response. Injection of F(ab')2 alone induced production of detectable anti-venom antibodies in a few mice and injection of venom alone induced that of anti-F(ab')2 antibodies, perhaps due to trace amounts of venom in the high affinity fraction of F(ab')2 and to anti-idiotypic antibodies or polyclonal activity in the envenomation episode, respectively.

Pediatric electrocardiograph abnormalities following Centruroides limpidus tecomanus scorpion envenomation

Scorpionism is an endemic public health problem in Mexico [Hoffmann, C.C., 1936. La distribucion geografica de los alacranes peligrosos en la Republica Mexicana. Bol. Inst. Hygiene Mex. 2, 321; Hoffmann, C.C., Nieto, D.R., 1939. Segunda contribucion al conocimiento de los alacranes mexicanos. Anal. Inst. Biol. 10, 83-92; Mazzoti, L., Bravo-Becherelle, M.A., 1963. Scorpionism in the Mexican Republic. In: Keegan, H.L., McFarlane, W.V. (Eds.), Venomous and Poissonous Animals and Noxious Plants of the Pacific Area. Pergamon Press, London, pp. 119-131; Monroy-Velasco, J., 1961. Alacranes venenosos de Mexico. Rev. Mex. Cien. Med. Biol., Mex. 1, 1-23; Diaz-Najera, A., 1975. Listas y datos de distribucion geografica de los alacranes de Mexico. Rev. Inv. Salud. Publica. (Mex.) 35, 1; Velasco-Castrejon, O., Lara-Aguilera, R., Alatorre, H., 1976. Aspectos epidemiologicos y clinicos de la picadura de alacran en una area hiperendemica. Rev. Inv. Salud Publica. (Mex.) 36, 93-103; Dehesa-Davila, M., Possani, L.D., 1994. Scorpionism and serotherapy in Mexico. Toxicon 32 (9), 1015-1018]. In this prospective study, we assess cardiovascular disorders in children via electrocardiographic (ECG) recordings following envenomation by scorpion species Centruroides limpidus tecomanus found in the state of Colima, Mexico. We analyzed 113 cases between the ages of 5 and 14 years. Among the most frequent symptoms presented included local pain (99.1%) and paresthesia (75.2%), pruritus (36.3%), sialorrhoea (35.4%), and nystagmus (24.8%). Cardiovascular disorders were observed in 39.8% of cases, 71% of which were rhythm abnormalities. We find a significant association between the frequency of ECG alterations and age, whereby 8-9-year-old children are more likely to experience ECG alterations when compared with other tested age groups.

Acidentes por escorpião em uma área do Nordeste de Amaralina, Salvador, Bahia, Brasil

Um estudo epidemiológico mediu a prevalência de pessoas que referiram acidentes por escorpião em uma amostra populacional do Areal, bairro Nordeste de Amaralina, Salvador, Bahia. Examinou-se uma amostra aleatória sistemática de 1367 indivíduos, correspondendo a 44,4% da população da área. Oitenta e dois indivíduos referiram haver sido picados por escorpião desde que residiam no Areal, resultando numa prevalência de 6% (IC 95% 4,7 - 7,3). A prevalência de pessoas picadas por escorpião aumentou nos grupos com maior tempo de residência no domicílio e com maior idade atual. Chamou atenção que 92,7% dos acidentes aconteceram dentro do domicílio. A incidência estimada para o período mais recente (janeiro a julho de 2000) foi de 1,15 casos/1.000 habitantes por mês. Este coeficiente compara-se ao mais elevado já referido na literatura especializada para uma área epidêmica para acidentes escorpiônicos.

Clinical symptoms observed in children envenomated by scorpion stings, at the children's hospital from the State of Morelos, Mexico

Scorpion sting is a public health problem in Mexico (Toxicon, 32 (1994) 1015). Since the most severe cases occur in children, cases treated at the Hospital del Niño Morelense, Cuernavaca, during the entire year of 1997 were registered and studied. During this 12-month period, 163 cases required medical attention, with the following results: 45% were mild, 25% moderate and 30% were severe cases of envenoming. Thanks to anti-venom therapy none of the children died. The most frequently observed clinical symptoms were: local pain and redness, salivation, dysphagia, tachycardia, irritability, odynophagia, paresthesia, nasal pruritus and emesis. The mild cases had one or two symptoms, moderate envenoming was characterized by several of the symptoms, whereas severe cases had most of the clinical symptoms listed. The moderate and severe cases were all treated with horse F(ab)2-anti-venom, while the mild cases were kept only for observation. Male children constituted 63% of the cases. The mean time that elapsed between sting and first medical attention was 54min.

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.

Scorpion poisoning in the Acosta and Caripe Counties of Monagas State, Venezuela. part 1: characterization of some epidemiological aspects

Scorpion poisoning was surveyed in Acosta and Caripe counties, located in the Turimiquire subregion of Monagas State, Venezuela, aiming to expand information on stings by characterizing some epidemiological aspects. From 1987 to 1993, 298 cases of scorpion stings were recorded in Acosta and Caripe counties. Acosta had 212 cases, with an annual incidence rate of 18.3 (cases per 10,000 inhabitants) and a period median incidence rate of 128 . The scorpion poisoning index is 4.18 times greater in Acosta than in Caripe, confirming the former as a hyperendemic zone for this type of injury, with a phenomenon of cyclical temporal fluctuations and an upward trend. This area is infested with scorpions of the genus Tityus. Our results show that the region surveyed in Monagas State is endemic for scorpion stings, posing a major public health problem.

Scorpion sting epidemiology in Montes Municipality of the State of Sucre, Venezuela: geographic distribution

Scorpion stings were surveyed in the Montes Municipality of the State of Sucre, Venezuela, aiming to extend the information on these poisonous accidents by characterizing their geographic distribution. From 1980 to 1990, 184 cases of scorpion stings were recorded with an incidence rate of 38.6 cases per 10,000 inhabitants. The locality of San Fernando presented the highest incidence (68.3/1000) of poisonous accidents. The highest percentages of severe cases were recorded in the towns of Arenas (27%), San Lorenzo (21%), and Cocollar (19%), which are located at the foot of the Turimiquire Mountains. This region is a dispersion area of scorpions of the Tityus genus. Our results show that this region of the State of Sucre is endemic for scorpion stings which are an important public health problem.

Structural and functional comparison of toxins from the venom of the scorpions Centruroides infamatus infamatus, Centruroides limpidus limpidus and Centruroides noxius

Two novel toxins containing 66 amino acid residues each were isolated from the venom of the scorpions Centruroides infamatus infamatus and Centruroides limpidus limpidus, respectively. Their full amino acid sequences were determined. Comparison of primary structures showed that they share 97% similarity among themselves and 83% to that of toxin 2 from Centruroides noxius. The three toxins studied compete with each other for the same binding sites on membranes prepared from rat brain synaptosomes, suggesting that they are all beta-scorpion toxins. Toxin action was assayed into the microI-2 rat skeletal muscle Na+ channel heterologously expressed into Xenopus oocytes. All three toxins block this Na+ channel in a similar fashion, without affecting inactivation, and showed IC50 values in the micromolar concentration range.

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.

Isolation of a toxin from Centruroides infamatus infamatus Koch scorpion venom that modifies Na+ permeability on chick dorsal root ganglion cells

A novel toxin was isolated and characterized from the venom of the Mexican scorpion Centruroides infamatus infamatus. It has an apparent mol. wt of 7600, compatible with the presence of 66 amino acid residues per molecule. The N-terminal amino acid sequence was determined (up to residue 48) and showed approximately 95% similarity with toxins from other Mexican scorpions of the gnus Centruroides. Experiments conducted with chick dorsal root ganglion cells showed that toxin 1 is a Na+ channel effector, causing a decrease in the peak Na+ permeability, similar to decreases observed for typical beta-scorpion toxins.

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.

Isolation and characterization of a novel toxin from the venom of the scorpion Centruroides limpidus limpidus Karsch

A novel peptide, toxic to mice, was purified from the venom of the Mexican scorpion Centruroides limpidus limpidus, by means of gel filtration and ion exchange chromatography, followed by high performance liquid chromatography (HPLC). The complete amino acid sequence was determined by automatic Edman degradation of reduced and alkylated toxin, and by overlapping sequences of fragments of the toxin, generated by cleavage with proteinase V8 separated by HPLC. This toxin is composed of 66 amino acid residues, contains eight half-cystine residues, and is highly similar (91%) to the amino acid sequence deduced for toxin 1 of C. limpidus tecomanus and toxin 4 from C. noxius venom (89%). This peptide displaces the binding of radiolabeled toxin 2 of C. noxius from synaptosomal membranes of rat brain with superimposable kinetics, supporting the conclusion that it belongs to the beta-scorpion toxin class. Further characterization of C. l. limpidus toxin 1, as we have named it, was performed by means of competition experiments with monoclonal antibodies and various purified scorpion toxins, using an ELISA assay. A panel of six distinct monoclonal antibodies (mAB) against toxin 2 and 3 of C. noxius was used. From these, only three clones, originally named BCF1, BCF8 and BCF9, were able to recognize toxin 1 from C. l. limpidus.

Cloning and characterization of cDNAs that code for Na(+)-channel-blocking toxins of the scorpion Centruroides noxius Hoffmann

With the purpose of studying the organization and characteristics of the genes that code for toxins present in the venom of the Mexican scorpion, Centruroides noxius Hoffmann (CnH), we prepared a lambda gt11 cDNA library from the venom glands. Using specific oligodeoxyribonucleotides (oligos) designed according to known amino acid (aa) sequences of CnH toxins (STox), we detected several positive clones, determined their nucleotide (nt) sequences and deduced their aa sequences. A comparative analysis of these sequences with previously reported STox revealed that CnH cDNAs code for a family of very similar STox. The cDNA coding for a known STox, II-10, was cloned. Additionally, three other complete (new) nt sequences were obtained for cDNAs encoding peptides similar to STox 1 from CnH or variants 2 and 3 from Centruroides sculpturatus Ewing. Southern blot genomic DNA analysis showed a minimum size of approximately 600 bp as EcoRI fragments for elements of this family. PCR amplifications of CnH genomic DNA and hybridization of PCR products with specific probes indicated that the genomic structural regions that code for these genes do not contain introns, or at least not large introns.

Neutralizing capacity of murine sera induced by different antigens of scorpion venom

Approximately 700 people die in Mexico each year from scorpion stings. The only useful therapy available is antiserum obtained from horses immunized with macerates of venomous gland from scorpions of the genus Centruroides. We report the results of experiments conducted with mice and rats in order to evaluate the relevant components of the venom from Centruroides noxius in the induction of a protective response against scorpion envenomation, either in vivo or in vitro. Gland macerates of whole telsons (stinger), soluble venom extracted by electrical stimulation, toxic fractions from gel filtration on Sephadex G-50 and highly purified toxin 2 from this scorpion venom were all used to produce hyperimmune mice and rats, which were challenged in vivo with the equivalent of the lethal dose 50% (LD50) of soluble venom, or their sera were prepared for in vitro neutralization experiments using non-immunized animals. The maximum neutralizing capacity (100%) was obtained when soluble venom was used as antigen, while purified toxin 2 produces 80% survival in vivo. The neutralizing capacity of murine antisera evaluated in vitro was: sera antifraction II > antitoxin 2 > antitotal venom > anti-gland macerates of whole telsons. Two additional aspects were further investigated in the present work. One is the demonstration by immunoblotting that proteins corresponding to the electrophoretic mobility of toxins known to block sodium channels are highly immunodominant in this venom. Second, there is a strong cross-reactivity of antisera produced with Centruroides noxius when assayed against venoms from other dangerous species of Centruroides scorpions from Mexico, but not against the Israeli scorpion Leiurus quinquestriatus. Finally, the immunodominance of toxic fractions in the immune response was observed either with immunization using Freund's adjuvant or by means of adsorption to nitrocellulose membranes. This latter vehicle was shown to be an excellent detoxifying agent, without changing the immunogenicity of the toxins, as might occur with chemical treatment of these neurotoxic peptides.

Reações de hipersensibilidade imediatas após uso intravenoso de soros antivenenos: valor prognóstico dos testes de sensibilidade intradérmicos

Foram admitidos no Hospital das Clínicas da FMRPUSP, durante os anos de 1983 a 1988, 494 pacientes vítimas de acidentes ofídicos e escorpiônicos que receberam soro antiveneno (SAV) e nos quais foi avaliada a freqüência e tipo das manifestações imediatas, bem como o valor prognóstico do teste de sensibilidade. Do total de pacientes vítimas de ofidismo, 82 (25,6%) apresentaram reações imediatas, das quais as mais comuns foram as cutâneas, isoladas (40%) ou associadas com sintomas respiratórios (19%), seguidas de manifestações gastrintestinais (17%). Choque anafilático foi detectado em 10 pacientes (12%). Em relação aos acidentes escorpiônicos, reações imediatas foram observadas em 13 pacientes (7,5%), também com predomínio de lesões cutâneas. Sintomatologia cardiocirculatória foi detectada em apenas 1 paciente. Devido ao baixo valor preditivo positivo (31,8%) e à baixa sensibilidade (54,6%), propomos que o teste de sensibilidade intradérmico seja abolido da rotina de atendimento de urgência aos pacientes vítimas de acidentes por animais peçonhentos. Anti-histamínicos (bloqueadores dos receptores H1 e H2) e corticosteróides devem ser administrados por via parenteral anteriormente à soroterapia, no sentido de prevenir ou minimizar as reações de hipersensibilidade imediatas que podem ocorrer. O soro antiveneno deve ser sempre administrado por via intravenosa, de preferência sem diluição, gota a gota, durante 15 a 30 minutos, sob contínua supervisão da equipe médica.