Use of dantrolene in experimental scorpion envenomation by Androctonus australis hector

Epidemiological, clinical, biological and evolutionary profile of scorpion envenomed children under one year to 15 years in the Souss Massa region of Morocco

Morocco is one of the main countries affected in North African with the scorpion envenomations. Faced with the threat, significant morbidity and a major risk of death especially in children, a detailed identification of scorpionic profile of stings remains important for health authorities at national or even regional level. The current study aims to establish the epidemiological, clinical, biological and evolutionary data of the scorpionism by analyzing 383 cases of scorpion stings in children from three age groups (<1 year, 1-5 years and >5 years), admitted at the Regional Hospital Hassan II-Agadir in the Souss Massa region during the period of 9 years and 10 months from January 2013 to October 2022. Our results showed that patients under 1 year of age presented the most severe cases and had the highest mortality rate. However, the clinical signs and symptoms observed illustrated severe damages to vital systems, particularly the cardiovascular, neurological and pulmonary systems, although the signs associated with the latter were present only in cases admitted in grades 2 and 3 for the three age categories studied. Fluctuations in vital constants (temperature and peripheral oxygen saturation, blood pressure, heart rate and respiratory rate), biochemical parameters (ASAT, ALAT, urea and blood creatine, as well as blood sugar) and CBC results revealed major functional disturbances in vital organs, especially in envenomated cases admitted in grade 3. A positive correlation was mentioned between the state of evolution and the various epidemiological parameters, digestive symptoms, as well as signs and symptoms linked to hemodynamic state, general and neurological state. The main interest is to illustrate the seriousness of scorpion envenomations, especially in the high-risk population, for whom an improved therapeutic approach in health centers will undoubtedly be reinforced, and the admission of immunotherapy, as a fundamental part of the treatment, remains important.

Scorpions and scorpion sting envenoming (scorpionism) in the Arab Countries of the Middle East

The twelve Arab countries of the Middle East are inhabited by 117 species of scorpions of varying medical importance within six families. Scorpion stings are a very common occurrence throughout the region. Twenty-two scorpion species are considered to be dangerously venomous, causing potentially life threatening stings. Accessible literature in English and Arabic on scorpions, scorpion stings and available antivenoms was reviewed to document the scorpion fauna and scorpion stings in each country. Saudi Arabia, Iraq and Jordan report the highest numbers of stings and envenomings. Clinically, the most important toxins in Old World scorpion venoms are α-toxins that target voltage-gated sodium (Na_v) channels at neurotoxin binding site 3, causing sympathetic excitation and the endogenous release of catecholamines that is responsible for transient, but life-threatening myocardial damage. Most victims of scorpion stings suffer severe local pain, but a few, especially children, develop systemic envenoming which, in the case of most Middle Eastern buthid species, such as Androctonus and Leiurus species, is dominated by the cardiovascular and respiratory consequences of hypercatecholinaemic myocarditis. Other syndromes include paralysis (Parabuthus leiosoma), coagulopathy (Nebo hierichonticus and Hemiscorpius species), and local tissue damage, haemolysis and acute kidney injury (H. lepturus). Early antivenom treatment is recommended but its value remains controversial. However, intensive care, with the ancillary use of vasoactive drugs such as prazosin and dobutamine, has proved effective.

Neurotoxicity of Tityus bahiensis (brown scorpion) venom in sympathetic vas deferens preparations and neuronal cells

Systemic scorpion envenomation is characterized by massive neurotransmitter release from peripheral nerves mediated primarily by scorpion venoms neurotoxins. Tityus bahiensis is one of the medically most important species in Brazil, but its venom pharmacology, especially regarding to peripheral nervous system, is poorly understood. Here, we evaluated the T. bahiensis venom activity on autonomic (sympathetic) neurotransmission by using a variety of approaches, including vas deferens twitch-tension recordings, electrophysiological measurements (resting membrane potentials, spontaneous excitatory junctional potentials and whole-cell patch-clamp), calcium imaging and histomorphological analysis. Low concentrations of venom (≤ 3 μg/mL) facilitated the electrically stimulated vas deferens contractions without affecting postsynaptic receptors or damaging the smooth muscle cells. Transient TTX-sensitive sustained contractions and resting membrane depolarization were mediated mainly by massive spontaneous ATP release. High venom concentrations (≥ 10 μg/mL) blocked the muscle contractions and induced membrane depolarization. In neuronal cells (ND7-23wt), the venom increased the peak sodium current, modified the current-voltage relationship by left-shifting the Nav-channel activation curve, thereby facilitating the opening of these channels. The venom also caused a time-dependent increase in neuronal calcium influx. These results indicate that the sympathetic hyperstimulation observed in systemic envenomation is presynaptically driven, probably through the interaction of α- and β-toxins with neuronal sodium channels.

In vivo neurotoxicity of Androctonus australis hector scorpion venom: evidence that the supra-thoracic nervous system is not implicated in the clinical manifestations

The severity of scorpion stings is related to the highly active neurotoxins in the venom. In this study, rats whose supra-spinal central nervous system was deprived of its peripheral connections were experimentally poisoned by the venom of Androctonus australis hector scorpion. Clinical signs of severity were not modified when the rats had previously undergone high medullar section. These results suggest that the supra-thoracic nervous system is not implicated in the neurotoxicity manifestations of scorpion envenomation.

Toxicity during early development of the mouse nervous system of a scorpion neurotoxin active on sodium channels

The lethal effects of scorpion envenomation is due to neurotoxins active on voltage-sensitive sodium channels. Dysfunctions of the peripheral and central nervous systems with neurological manifestations are commonly observed after scorpion stings, specially in young children. Since the neurotoxicity of venom fraction is greatly higher by intracerebroventricular than by subcutaneous injections, a direct effect of venom on CNS cannot be excluded specially in infants where the blood-brain barrier is not fully functional. We investigated the activity of a neurotoxin from the scorpion Androctonus australis hector (AahII) in newborn mice at 3, 7 and 14 days after birth and in adults. Young mice (P3, P7) were more sensitive to AahII injected subcutaneously than were adults, but were less sensitive to intracerebroventricular injection. The affinity of AahII for its receptor site on brain synaptosomes from P3 and P7 mice was slightly higher and the density of the binding sites was half that of adult mice. After subcutaneous injection of [125I]-AahII it was also observed that a small amount of radioactivity was found in brains of neonate mice but not in that of adults. This amount is however extremely lower than the value of the LD50 determined by intracerebroventricular injection. Results are consistent with a peripheral action of AahII and show that its toxic activity changes during the mouse nervous system development.