Snakebite by Micrurus averyi (Schmidt, 1939) in the Brazilian Amazon basin: Case report

Evaluation of Saxifraga stolonifera phenolic extracts as a potential antivenom against Deinagkistrodon acutus venom: In vitro and in vivo studies

ETHNOPHARMACOLOGICAL RELEVANCE

In the snake-infested mountainous regions of China, Saxifraga stolonifera [L.] Meeb is widely utilized as an immediate remedy for venomous snake bites. However, the scientific understanding of S. stolonifera's efficacy in snakebite treatment remains limited and requires further investigation.

AIM OF THE STUDY

The aim of this study was to assess the inhibitory effects of Saxifraga stolonifera phenolic extracts (SSPE) on Deinagkistrodon acutus venom (DAV) and explore the potential of S. stolonifera as a valuable candidate for antivenom development.

MATERIALS AND METHODS

We employed our previously optimized extraction conditions to obtain SSPE. In vitro experiments utilizing diverse models were conducted to assess the inhibitory effects of the extracted phenolic compounds on DAV, specifically targeting phospholipase A2 (PLA2), proteolytic, fibrinolytic, and hyaluronidase enzymes. Furthermore, in vivo investigations were conducted to evaluate the inhibitory potential of the extracted compounds against DAV-induced hemorrhagic and edematogenic activity. To elucidate the chemical composition of the phenolic extracts, Ultra Performance Liquid Chromatography-mass spectrometry (UPLC-MS) analysis was performed.

RESULTS

Our in vitro inhibition study showed that S. stolonifera was able to inhibit the activities of PLA2 enzyme, proteolytic enzyme, hyaluronidase and fibrinogenolytic. The median effective dose (ED50) values of SSPE for inhibiting PLA2 enzyme, proteolytic enzyme and hyaluronidase activities were 0.115 mg/mL, 0.026 mg/mL and 0.238 mg/mL, respectively. The DAV-induced hemorrhagic and edematogenic effects of the SSPE were also successfully inhibited in vivo, and the high SSPE concentration was able to completely inhibit the hemorrhage and edema. It is noteworthy that the mice suffered no harm from the high SSPE concentration. The composition analysis showed that the phenolic substances contained in SSPE are gallic acid, protocatechuic acid, chlorogenic acid, rutin, kaempferol-3-O-ɑ-L-rhamnoside, kaempferol-3-O-β-D-glucopyranoside, quercetin and kaempferol.

CONCLUSIONS

This study provides scientific validation of the inhibitory efficacy of S. stolonifera as an emergency treatment for venomous snake bites, offering a theoretical foundation for future drug development strategies targeting snakebite.

Snakebite envenoming in Brazilian children: clinical aspects, management and outcomes

Snakebite envenoming is currently considered a neglected tropical disease, which affects over 5 million people worldwide, and causes almost 150 000 deaths every year, as well as severe injuries, amputations and other sequelae. Snakebite envenoming in children, although proportionally less frequent, is generally more severe, and represents an important challenge for pediatric medicine, since they often result in worse outcomes. In Brazil, given its ecological, geographic and socioeconomic characteristics, snakebites are considered an important health problem, presenting approximately 30 000 victims per year, approximately 15% of them in children. Even with low snakebite incidence, children tend to have higher snakebite severity and complications due to the small body mass and same venom volume inoculated in comparison to adults, even though, due to the lack of epidemiological information about pediatric snakebites and induced injuries, it is difficult to measure the treatment effectiveness, outcomes and quality of emergency medical services for snakebites in children. In this review, we report how Brazilian children are affected by snakebites, describing the characteristics of this affected population, clinical aspects, management, outcomes and main challenges.

Envenomations by coral snakes in an Amazonian metropolis: Ecological, epidemiological and clinical aspects

Envenomation by coral snakes represents a little known burden in Brazilian Amazonia. So far, details on clinical and epidemiological aspects remain obscure in the region. We gathered data from medical charts and from the scientific collection of snakes from Fundação de Medicina Tropical Doutor Heitor Vieira Dourado, finding 26 cases of envenomation by five species of Micrurus in Manaus region, between 1987 and 2018. They represent 0.7% of the snakebites treated in the hospital since the records began, in 1979. Micrurus lemniscatus was responsible for most of the bites (10), followed by M. hemprichii (five), M. spixii (three), M. surinamensis (three) and M. averyi (one). There was no difference between the sexes of the snakes that caused bites. Patients were mostly males, and most of the cases were reported in urban areas. Bites predominated in dry season, and there was a clear geographical segregation among species. We describe seven cases of envenomation, three mild and four severe, all of which evolved to cure. Paresthesia (six), pain (five) and edema (four) were the most common local symptoms. Systemic features such as dyspnea/shallow breath (four), palpebral ptosis (four), blurred vision (three), dysarthria (three) and difficulty to walk (three) were also detected. Two patients bitten by Micrurus sp. and M. hemprichii, showed slight increased serum levels of creatine kinase (reference level <190 U/L), 1184 U/L and 1229 U/L, respectively, indicative of mild systemic myotoxicity. This is the first report of myotoxic manifestation in the envenomation by M. hemprichii. No patient developed respiratory failure, though one bitten by an adult M. spixii required intubation and mechanical ventilation due to decreased level of consciousness during evolution, probably related to induced sedation caused by concurrent alcohol intoxication. All patients were treated with Brazilian Micrurus antivenom (soro antielapídico, median = 10 vials). Six patients were pretreated intravenously with H1 and H2 antagonists and steroids, with two patients developing early adverse reactions. The median length of hospital stay was four days. Envenomations by coral snakes in Manaus region are clinically severe, but rare and sparsely distributed over time, making the detection of epidemiological and clinical patterns a challenge for public health.

Snakebite envenomation in the Brazilian Amazon: a descriptive study

Snakebite envenomation in the Brazilian Amazon is a recognized public health problem that does not receive the appropriate attention from key stakeholders. The morbidity rate is relevant, but still underestimated. Thus, the present study updates the current state of knowledge on snakebite envenomation in the Brazilian Amazon. It follows a descriptive method and contributes new knowledge about the dynamics of snakebites and the associated morbidity and mortality reported in the Brazilian Amazon. The study is based on information from cases registered and retrieved from the Brazilian Information System for Notifiable Diseases (Sistema de Informação de Agravos de Notificação-SINAN). The registers we studied covers a period of six years, 2010-2015. Most snakebites occurred in the states of Pará (30 693 cases, 43.34%) and Amazonas (9386 cases, 13.25%), with a higher prevalence in males of an economically active age. The main genus involved in bites was Bothrops sp. The mortality rate was 0.24 per hundred thousand and the case fatality rate was 0.51%. Although low case fatality and mortality rates were observed, much can still be done to prevent snakebites as they continue to be a serious public health problem considering the severity and potentially high economic impact for the individual and to society.

A Combined Strategy to Improve the Development of a Coral Antivenom Against Micrurus spp

Accidents involving Micrurus snakes are not the most common ones but are noteworthy due to their severity. Victims envenomed by Micrurus snakes are at high risk of death and therefore must be treated with coral antivenom. In Brazil, the immunization mixture used to fabricate coral antivenom contains Micrurus frontalis and Micrurus corallinus venoms, which are difficult to be obtained in adequate amounts. Different approaches to solve the venom limitation problem have been attempted, including the use of synthetic and recombinant antigens as substitutes. The present work proposes a combined immunization protocol, using priming doses of M. frontalis venom and booster doses of synthetic B-cell epitopes derived from M. corallinus toxins (four three-finger toxins-3FTX; and one phospholipase A₂-PLA₂) to obtain coral antivenom in a rabbit model. Immunized animals elicited a humoral response against both M. frontalis and M. corallinus venoms, as detected by sera reactivity in ELISA and Western Blot. Relevant cross-reactivity of the obtained sera with other Micrurus species (Micrurus altirostris, Micrurus lemniscatus, Micrurus spixii, Micrurus surinamensis) venoms was also observed. The elicited antibodies were able to neutralize PLA₂ activity of both M. frontalis and M. corallinus venoms. In vivo, immunized rabbit sera completely protected mice from a challenge with 1.5 median lethal dose (LD₅₀) of M. corallinus venom and 50% of mice challenged with 1.5 LD₅₀ of M. frontalis venom. These results show that this combined protocol may be a suitable alternative to reduce the amount of venom used in coral antivenom production in Brazil.

Neurotoxicity of Micrurus lemniscatus lemniscatus (South American coralsnake) venom in vertebrate neuromuscular preparations in vitro and neutralization by antivenom

We investigated the effect of South American coralsnake (Micrurus lemniscatus lemniscatus) venom on neurotransmission in vertebrate nerve-muscle preparations in vitro. The venom (0.1-30 µg/ml) showed calcium-dependent PLA₂ activity and caused irreversible neuromuscular blockade in chick biventer cervicis (BC) and mouse phrenic nerve-diaphragm (PND) preparations. In BC preparations, contractures to exogenous acetylcholine and carbachol (CCh), but not KCl, were abolished by venom concentrations ≥ 0.3 µg/ml; in PND preparations, the amplitude of the tetanic response was progressively attenuated, but with little tetanic fade. In low Ca²⁺ physiological solution, venom (10 µg/ml) caused neuromuscular blockade in PND preparations within ~ 10 min that was reversible by washing; the addition of Ca²⁺ immediately after the blockade temporarily restored the twitch responses, but did not prevent the progression to irreversible blockade. Venom (10 µg/ml) did not depolarize diaphragm muscle, prevent depolarization by CCh, or cause muscle contracture or histological damage. Venom (3 µg/ml) had a biphasic effect on the frequency of miniature end-plate potentials, but did not affect their amplitude; there was a progressive decrease in the amplitude of evoked end-plate potentials. The amplitude of compound action potentials in mouse sciatic nerve was unaffected by venom (10 µg/ml). Pre-incubation of venom with coralsnake antivenom (Instituto Butantan) at the recommended antivenom:venom ratio did not neutralize the neuromuscular blockade in PND preparations, but total neutralization was achieved with a tenfold greater volume of antivenom. The addition of antivenom after 50% and 80% blockade restored the twitch responses. These results show that M. lemniscatus lemniscatus venom causes potent, irreversible neuromuscular blockade, without myonecrosis. This blockade is apparently mediated by pre- and postsynaptic neurotoxins and can be reversed by coralsnake antivenom.