Review of Eastern coral snake (Micrurus fulvius fulvius) exposures managed by the Florida Poison Information Center Network: 1998-2010

African polyvalent antivenom can maintain pharmacological stability and ability to neutralise murine venom lethality for decades post-expiry: evidence for increasing antivenom shelf life to aid in alleviating chronic shortages

INTRODUCTION

Antivenom is a lifesaving medicine for treating snakebite envenoming, yet there has been a crisis in antivenom supply for many decades. Despite this, substantial quantities of antivenom stocks expire before use. This study has investigated whether expired antivenoms retain preclinical quality and efficacy, with the rationale that they could be used in emergency situations when in-date antivenom is unavailable.

METHODS

Using WHO guidelines and industry test requirements, we examined the in vitro stability and murine in vivo efficacy of eight batches of the sub-Saharan African antivenom, South African Institute for Medical Research polyvalent, that had expired at various times over a period of 30 years.

RESULTS

We demonstrate modest declines in immunochemical stability, with antivenoms older than 25 years having high levels of turbidity. In vitro preclinical analysis demonstrated all expired antivenoms retained immunological recognition of venom antigens and the ability to inhibit key toxin families. All expired antivenoms retained comparable in vivo preclinical efficacy in preventing the lethal effects of envenoming in mice versus three regionally and medically important venoms.

CONCLUSIONS

This study provides strong rationale for stakeholders, including manufacturers, regulators and health authorities, to explore the use of expired antivenom more broadly, to aid in alleviating critical shortages in antivenom supply in the short term and the extension of antivenom shelf life in the longer term.

Myalgia as a Symptom of Envenomation by the Eastern Coral Snake, Micrurus Fulvius: A Case Report

We present the case of a patient who developed myalgia as the primary symptom of envenomation by the eastern coral snake, Micrurus fulvius. The patient was evaluated and treated in the emergency department. Physical examination did not demonstrate any neuromuscular abnormalities. On consultation with the poison control center, the patient's myalgia was determined to be an effect of envenomation, and 5 vials of North American coral snake antivenin were administered. The patient was admitted to the intensive care unit where his symptoms resolved. He was discharged the following day after remaining asymptomatic for 24 h.

Anticoagulant Micrurus venoms: Targets and neutralization

Snakebite is a neglected tropical disease with a massive global burden of injury and death. The best current treatments, antivenoms, are plagued by a number of logistical issues that limit supply and access in remote or poor regions. We explore the anticoagulant properties of venoms from the genus Micrurus (coral snakes), which have been largely unstudied, as well as the effectiveness of antivenom and a small-molecule phospholipase inhibitor-varespladib-at counteracting these effects. Our in vitro results suggest that these venoms likely interfere with the formation or function of the prothrombinase complex. We find that the anticoagulant potency varies widely across the genus and is especially pronounced in M. laticollaris. This variation does not appear to correspond to previously described patterns regarding the relative expression of the three-finger toxin and phospholipase A₂ (PLA₂) toxin families within the venoms of this genus. The coral snake antivenom Coralmyn, is largely unable to ameliorate these effects except for M. ibiboboca. Varespladib on the other hand completely abolished the anticoagulant activity of every venom. This is consistent with the growing body of results showing that varespladib may be an effective treatment for a wide range of toxicity caused by PLA₂ toxins from many different snake species. Varespladib is a particularly attractive candidate to help alleviate the burden of snakebite because it is an approved drug that possesses several logistical advantages over antivenom including temperature stability and oral availability.

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.

Epidemiology of fatal snakebites in the United States 1989-2018

BACKGROUND

There are 5000-10,000 snake envenomations annually in the United States. Fortunately, few are fatal. In this study we review the epidemiology of fatal snakebites.

METHODS

Native snakebite cases from the American Association of Poison Control Centers (AAPCC) National Poison Data System from 1989 to 2018 were reviewed. Additional cases that were not reported to the AAPCC were identified by reviewing Wikipedia and by searching PubMed and online news outlets using various combinations of relevant keywords.

RESULTS

We identified 101 fatal bites from native snakes. Rattlesnakes accounted for 74 (90.2%) of the 82 deaths for which the species was known or which occurred where rattlesnakes are the only native crotalids. There were five fatalities attributed to copperheads, two due to cottonmouths, and one caused by an eastern coral snake. Males were disproportionately affected. The median age for victims was 40 years old. In cases for which data were available, many of the snake interactions were intentional, e.g. religious services, animal husbandry, and attempting to kill the snake.

CONCLUSIONS

Death following envenomation from a native U.S. snake is unlikely, particularly if medical attention is sought promptly. Rattlesnake envenomations are more likely to be fatal than bites from other species. Intentionally engaging with a venomous snake raises the risk of incurring a fatal bite, as does concurrent alcohol or drug use. Age less than 12 years old does not appear to be a risk factor for a fatal outcome, while elderly patients may have a slightly increased risk of death.

Epidemiology, Clinical Features, and Management of Texas Coral Snake (Micrurus tener) Envenomations Reported to the North American Snakebite Registry

INTRODUCTION

Few of the 5000-8000 snakebites reported to poison control centers annually in the USA are attributed to coral snakes. This study describes Texas coral snake envenomations reported to the North American Snakebite Registry.

METHODS

All Texas coral snake envenomation cases reported to the registry were identified for the period from January 1, 2015, through December 31, 2019. Data reviewed for this study included details regarding the snake encounter, patient demographics, signs and symptoms, treatment, and outcomes. Descriptive statistics were used to report results.

RESULTS

Ten men and four nonpregnant women reported coral snake bites. The median patient age was 15.5 (range 5-72 years). There were 12 upper extremity bites and two bites to the lower extremity. The most common symptoms reported were paresthesias and pain. All subjects had paresthesias, often described as an "electric" sensation. Seven patients described them as painful. The most common clinical findings were erythema and swelling. No patient developed tissue damage, hematotoxicity, rhabdomyolysis, hypotension, weakness, or respiratory symptoms. Thirteen subjects were treated with opioids. Six patients were treated with antiemetics: three prophylactically and two for opioid-induced nausea. One patient developed nausea and non-bloody, nonbilious emesis within 1 hour of the bite, prior to receiving opioids. No patients were treated with antivenom. Antibiotics were not administered to any patient, and no infections were reported.

CONCLUSIONS

Envenomations from M. tener in Southeast Texas are characterized by painful paresthesias. Mild swelling and erythema are common. Neurotoxicity necessitating antivenom or mechanical ventilation did not occur.

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.

Retrospective evaluation of Micrurus fulvius (Eastern coral snake) envenomation and the use of mechanical ventilation in dogs and a cat (2011-2016): 8 cases

OBJECTIVE

To describe the use of mechanical ventilation (MV) in the management of Eastern coral snake envenomation in 7 dogs and a cat.

DESIGN

Retrospective study (2011-2016).

SETTING

University teaching hospital.

ANIMALS

Seven dogs and 1 cat receiving MV for ventilatory failure secondary to Eastern coral snake envenomation.

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

The medical records of 8 animals that received MV following Eastern coral snake envenomation were reviewed. Data collected included signalment, time to veterinary assessment, physical and laboratory characteristics at arrival, clinical course during hospitalization, management including antivenom administration, MV settings, duration of ventilation, length of hospitalization, cost of care, and survival to discharge. The mean ± SD age was 4 ± 3.2 years. Median (range) time to onset of clinical signs was 30 (5-240) minutes. Coral snake antivenom was administered to 7 of the 8 animals following arrival at a median (range) of 30 (5-90) minutes. All animals had progressive hypoventilation and received MV, specifically volume controlled, synchronized intermittent mandatory ventilation with pressure support. The median (range) duration of MV was 58 (25-84) hours and the median (range) duration of hospitalization was 8.2 (6-11) days. Ventilator associated complications occurred in all animals, but overall outcome was excellent with 7 of 8 surviving to discharge. No dog, but the 1 cat, had an adverse reaction to antivenom.

CONCLUSIONS

Ventilatory failure secondary to Eastern coral snake envenomation necessitating MV carries an excellent prognosis and is better than reported for other causes of lower motor neuron disease. Successful response to ventilation was achieved even with associated complications being common in this cohort of animals.

The neutralization efficacy of expired polyvalent antivenoms: An alternative option

The expense of production and distribution of snakebite antivenom, as well as its relatively infrequent use, has caused antivenom to be increasingly difficult to obtain and ultimately producing an alarming global shortage. Unused, expired antivenom may represent a significant, untapped resource to ameliorate this crisis. This study examines the efficacy of expired antivenom over time using in vitro, whole blood clotting, and platelet function statistics. Representatives from three years for four different global brands of polyvalent antivenom were chosen and tested against their corresponding venoms as well as other venoms that could display cross-reactivity. These antivenoms include Wyeth Polyvalent (U.S.; exp. 1997, 2001, 2003), Antivipmyn^® (Mexico; exp. 2005, 2013, 2017), Biotecfars Polyvalent (Venezuela; exp. 2010, 2014, 2016), and SAIMR (South Africa; exp. 1997, 2005, 2017). Venoms of species tested were Crotalus atrox against Wyeth; C. atrox and Crotalus vegrandis against Antivipmyn^®; C. atrox, C. vegrandis and Bothrops colombiensis against Biotecfar; and Bitis gabonica and Echis carinatus against South African Institute for Medical Research (SAIMR). Parameters recorded were activated clotting time (ACT), clotting rate (CR), and platelet function (PF). Preliminary results are encouraging as the antivenoms maintained significant efficacy even 20 y after their expiration date. We anticipate these results will motivate further studies and provide hope in the cases of snakebite emergencies when preferable treatments are unavailable.

Use of infrared thermography in a case of systemic envenomation by the coral snake Micrurus frontalis (Duméril et al., 1854) in Sao Paulo, Brazil

Infrared thermography is a technique that quantifies the thermal (infrared) radiation emitted by an object and produces a high-resolution, digital thermal image of it. Medically, this technique is used to visualize the body's surface temperature distribution in a non-invasive, safe, and convenient fashion. However, to the best of our knowledge, the use of infrared thermography for assessing the systemic effects of envenomation by coral snakes has not been reported. In this case report, we describe the use of this technique in the management of a case of snakebite in Sao Paulo, Brazil. A 51-year-old woman was bitten on the back of the right hand by Micrurus frontalis, a species of coral snake, 10 min prior to her arrival at the hospital. Infrared imaging performed at admission revealed elevated temperatures at the bite site and in the elbow, as well as the preservation of a normal distal thermal gradient in both hands. A few minutes later, the patient developed muscle weakness in the upper limbs and in the eyelids, and infrared imaging showed an alteration of the thermal gradient in both hands, reflecting the systemic action of the venom. Following these observations, the patient was treated with the specific antivenom and was discharged 48 h post admission. At the two-week follow-up, the thermal image obtained showed no anomalies, indicating the recovery of the patient. Hence, infrared thermography can be very useful in the early identification of systemic neurotoxicity in cases of Micrurus snake bites, facilitating the decision to prescribe the antivenom.

Snake Eyes: Coral Snake Neurotoxicity Associated With Ocular Absorption of Venom and Successful Treatment With Exotic Antivenom

BACKGROUND

Coral snake bites from Micrurus fulvius and Micrurus tener account for < 1% of all snake bites in North America. Coral snake envenomation may cause significant neurotoxicity, including respiratory insufficiency, and its onset may be delayed up to 13 h.

CASE REPORT

We present a unique patient encounter of M. tener venom exposure through the ocular mucous membranes and a small cutaneous bite, resulting in neurotoxicity. To our knowledge, this is the first reported case of systemic neurotoxicity associated with ocular contact with coral snake venom. Our patient developed rapid-onset skeletal muscle weakness, which is very uncommon for M. tener, along with cranial nerve deficits. Acquisition of antivenom was challenging, but our patient provides a rare report of resolution of suspected M. tener neurotoxicity after receiving Central American coral snake (Micrurus nigrocinctus) antivenom. Our patient subsequently developed serum sickness, a known delayed complication of antivenom. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: The emergency physician should be aware that coral snake venom may be absorbed through different routes. Neurotoxicity and respiratory insufficiency may be fatal and onset may be delayed up to 13 h. North American Coral Snake Antivenom is in very limited supply, so non-Food and Drug Administration-approved alternative coral snake antivenoms may be used for patients demonstrating neurotoxicity. Emergency physicians should be proactive in contacting a toxicologist to procure antivenom, as well as consideration of adjunctive treatments, such as neostigmine. Furthermore, whole immunoglobulin G products, such as antivenom, may result in immediate and delayed reactions.

Antivenom effect on lymphatic absorption and pharmacokinetics of coral snake venom using a large animal model

Context: Historically, administration and dosing of antivenom (AV) have been guided primarily by physician judgment because of incomplete understanding of the envenomation process. As demonstrated previously, lymphatic absorption plays a major role in the availability and pharmacokinetics (PK) of coral snake venom injected subcutaneously, which suggests that absorption from subcutaneous tissue is the limiting step for venom bioavailability, supporting the notion that the bite site is an ongoing venom depot. This feature may underlie the recurrence phenomena reported in viperid envenomation that appear to result from a mismatch between venom and AV PK. The role of lymphatic absorption in neutralization of venom by AV administered intravenously remains unclear. Methods: The effect of AV on systemic bioavailability and neutralization of Micrurus fulvius venom was assessed using a central lymph-cannulated sheep model. Venom was administered by subcutaneous injection in eight sheep, four with and four without thoracic duct cannulation and drainage. Two hours after venom injection, AV was administered intravenously. Venom and AV concentrations in serum and lymph were determined by ELISA assay from samples collected over a 6-h period and in tissues harvested post-mortem. Results: After AV injection, venom levels in serum fell immediately to undetectable with a subsequent increase in concentration attributable to non-toxic venom proteins. In lymph, AV became detectable 6 min after treatment; venom levels dropped concurrently but remained detectable 4 h later. Post-mortem samples from the venom injection site confirmed the presence of venom near the point of injection. Neither venom nor AV was detected at significant concentrations in major organs or contralateral skin. Conclusions: Intravenous AV immediately neutralizes venom in the bloodstream and can extravasate to neutralize venom absorbed by lymph but this neutralization seems to be slow and incomplete. Residual venom in the inoculation site demonstrates that this site functions as a depot where it is not neutralized by AV, which allows the venom to remain active with slow delivery to the bloodstream for ongoing systemic distribution.

Incidence and mortality due to snakebite in the Americas

BACKGROUND

Better knowledge of the epidemiological characteristics of snakebites could help to take measures to improve their management. The incidence and mortality of snakebites in the Americas are most often estimated from medical and scientific literature, which generally lack precision and representativeness.

METHODOLOGY/PRINCIPAL FINDINGS

Authors used the notifications of snakebites treated in health centers collected by the Ministries of Health of the American countries to estimate their incidence and mortality. Data were obtained from official reports available on-line at government sites, including those of the Ministry of Health in each country and was sustained by recent literature obtained from PubMed. The average annual incidence is about 57,500 snake bites (6.2 per 100,000 population) and mortality is close to 370 deaths (0.04 per 100,000 population), that is, between one third and half of the previous estimates. The incidence of snakebites is influenced by the abundance of snakes, which is related to (i) climate and altitude, (ii) specific preferences of the snake for environments suitable for their development, and (iii) human population density. Recent literature allowed to notice that the severity of the bites depends mainly on (i) the snake responsible for the bite (species and size) and (ii) accessibility of health care, including availability of antivenoms.

CONCLUSIONS/SIGNIFICANCES

The main limitation of this study could be the reliability and accuracy of the notifications by national health services. However, the data seemed consistent considering the similarity of the incidences on each side of national boundaries while the sources are distinct. However, snakebite incidence could be underestimated due to the use of traditional medicine by the patients who escaped the reporting of cases. However, gathered data corresponded to the actual use of the health facilities, and therefore to the actual demand for antivenoms, which should make it possible to improve their management.

North American Snake Envenomation

Native US snakes that produce clinically significant envenomation can be divided into 2 groups, crotalids and elapids. The crotalids include rattlesnakes, cottonmouths, and copperheads. Crotalid envenomation can result in significant local tissue damage as well as thrombocytopenia and coagulopathy. Rarely are bites fatal. Native US elapids are all coral snakes that possess neurotoxic venom that can cause weakness, respiratory paralysis, and rarely death. Treatment of both types of envenomation revolves around general supportive care and antivenom administration when indicated. Previously advocated treatments, such as tourniquets, venom extraction, and bite site excision are not recommended.

Efficacy of Trypsin in Treating Coral Snake Envenomation in the Porcine Model

Antivenom is the definitive treatment for venomous snakebites. Alternative treatments warrant investigation because antivenom is sometimes unavailable, expensive, and can have deleterious side effects. This study assesses the efficacy of trypsin to treat coral snake envenomation in an in vivo porcine model. A randomized, blinded study was conducted. Subjects were 13 pigs injected subcutaneously with 1 mL of eastern coral snake venom (10 mg/mL) in the right distal hind limb. After 1 min, subjects were randomized to have the envenomation site injected with either 1 mL of saline or 1 mL of trypsin (100 mg/mL) by a blinded investigator. Clinical endpoint was survival for 72 h or respiratory depression defined as respiratory rate <15 breaths per minute, falling pulse oximetry, or agonal respirations. Fisher's exact t test was used for between group comparisons. Average time to toxicity for the saline control was 263 min (191-305 min). The development of respiratory depression occurred more frequently in control pigs than treated pigs (p = 0.009). Four of the six pigs that received trypsin survived to the end of the 3-day study. No control pigs survived. Two of the trypsin treatment pigs died with times to toxicity of 718 and 971 min. Survival to 12 and 24 h was significantly greater in the trypsin treatment group (p = 0.002, p = 0.009, respectively). Local injection of trypsin, a proteolytic enzyme, at the site of envenomation decreased the toxicity of eastern coral snake venom and increased survival significantly. Further investigation is required before these results can be extended to human snakebites.

Biodistribution and Lymphatic Tracking of the Main Neurotoxin of Micrurus fulvius Venom by Molecular Imaging

The venom of the Eastern coral snake Micrurus fulvius can cause respiratory paralysis in the bitten patient, which is attributable to β-neurotoxins (β-NTx). The aim of this work was to study the biodistribution and lymphatic tracking by molecular imaging of the main β-NTx of M. fulvius venom. β-NTx was bioconjugated with the chelator diethylenetriaminepenta-acetic acid (DTPA) and radiolabeled with the radionuclide Gallium-67. Radiolabeling efficiency was 60%–78%; radiochemical purity ≥92%; and stability at 48 h ≥ 85%. The median lethal dose (LD₅₀) and PLA₂ activity of bioconjugated β-NTx decreased 3 and 2.5 times, respectively, in comparison with native β-NTx. The immune recognition by polyclonal antibodies decreased 10 times. Biodistribution of β-NTx-DTPA-⁶⁷Ga in rats showed increased uptake in popliteal, lumbar nodes and kidneys that was not observed with ⁶⁷Ga-free. Accumulation in organs at 24 h was less than 1%, except for kidneys, where the average was 3.7%. The inoculation site works as a depot, since 10% of the initial dose of β-NTx-DTPA-⁶⁷Ga remains there for up to 48 h. This work clearly demonstrates the lymphatic system participation in the biodistribution of β-NTx-DTPA-⁶⁷Ga. Our approach could be applied to analyze the role of the lymphatic system in snakebite for a better understanding of envenoming.

Integrative characterization of the venom of the coral snake Micrurus dumerilii (Elapidae) from Colombia: Proteome, toxicity, and cross-neutralization by antivenom

In Colombia, nearly 2.8% of the 4200 snakebite accidents recorded annually are inflicted by coral snakes (genus Micrurus). Micrurus dumerilii has a broad distribution in this country, especially in densely populated areas. The proteomic profile of its venom was here studied by a bottom-up approach combining RP-HPLC, SDS-PAGE and MALDI-TOF/TOF. Venom proteins were assigned to eleven families, the most abundant being phospholipases A2 (PLA2; 52.0%) and three-finger toxins (3FTx; 28.1%). This compositional profile shows that M. dumerilii venom belongs to the 'PLA2-rich' phenotype, in the recently proposed dichotomy for Micrurus venoms. Enzymatic and toxic venom activities correlated with protein family abundances. Whole venom induced a conspicuous myotoxic, cytotoxic and anticoagulant effect, and was mildly edematogenic and proteolytic, whereas it lacked hemorrhagic activity. Some 3FTxs and PLA2s reproduced the lethal effect of venom. A coral snake antivenom to Micrurus nigrocinctus demonstrated significant cross-recognition of M. dumerilii venom proteins, and accordingly, ability to neutralize its lethal effect. The combined compositional, functional, and immunological data here reported for M. dumerilii venom may contribute to a better understanding of these envenomings, and support the possible use of anti-M. nigrocinctus coral snake antivenom in their treatment.

BIOLOGICAL SIGNIFICANCE

Coral snakes represent a highly diversified group of elapids in the New World, with nearly 70 species within the genus Micrurus. Owing to their scarce yields, the biochemical composition and toxic activities of coral snake venoms have been less well characterized than those of viperid species. In this work, an integrative view of the venom of M. dumerilii, a medically relevant coral snake from Colombia, was obtained by a combined proteomic, functional, and immunological approach. The venom contains proteins from at least eleven families, with a predominance of phospholipases A2 (PLA2), followed by three-finger toxins (3FTx). According to its compositional profile, M. dumerilii venom can be grouped with those of several Micrurus species from North and Central America that present a PLA2-predominant phenotype, to date it is the most southerly coral snake species to do so. Other coral snake species that a 'PLA2-rich' venom, M. dumerilii venom contains both components that form MitTx, a pain-inducing heterodimeric complex recently characterized from the venom of Micrurus tener, also present in Micrurus mosquitensis and M. nigrocinctus venoms. In addition to a lethal three-finger toxin, PLA2s participate in the toxicity of M. dumerilii venom, some of them displaying ability to induce cytolysis, muscle necrosis, and lethality to mice. An antivenom to M. nigrocinctus demonstrated significant cross-recognition of M. dumerilii venom proteins, and accordingly, ability to neutralize its lethal effect, being of potential therapeutic usefulness in these envenomings.

Three months of methoxetamine administration is associated with significant bladder and renal toxicity in mice

CONTEXT.: Methoxetamine is a ketamine analogue that has recently emerged as a novel psychoactive substance. Chronic ketamine use is associated with significant bladder and renal toxicity. Methoxetamine has been marketed as "bladder friendly", but there is no data to be able to substantiate this claim.

OBJECTIVE

To characterise the patterns of bladder and renal toxicity associated with 3 months of methoxetamine administration in an animal model.

MATERIALS AND METHODS

Two-month-old Institute of Cancer Research mice were administered 30 mg/kg methoxetamine intraperitoneally (n = 5) or saline (n = 3 control) for 3 months. The animals were then sacrificed and histological examination, immuno-cytochemistry using polyclonal anti-CD4 antibodies and sirius-red staining for collagen were performed.

RESULTS

The kidneys of methoxetamine-treated animals showed inflammatory cell infiltration, tubular cell necrosis and glomerular damage (1.9 ± 0.3% shrunken glomeruli in control, 9.8 ± 0.8% in methoxetamine-treated mice (p < 0.0001); 2.9 ± 0.3% tubular cell degeneration in control, 20.4 ± 1.1% in methoxetamine-treated mice (p < 0.0001)). There was a greater density of mononuclear cells in the bladder lamina propria and submucosa in methoxetamine-treated mice (43.0 ± 2.1 per 250 × 250 μm) than controls (7.1 ± 1.2 per 250 × 250 μm), p < 0.001. CD4-positive staining was seen in the bladder submucosa and lamina propria of all methoxetamine-treated mice and muscle-layer of two methoxetamine-treated mice; these changes were not seen in the control mice. There was an increase in sirius-red collagen in the bladder sub-mucosa and muscle-layer in the methoxetamine-treated mice compared with control mice.

DISCUSSION

This study has shown that 3 months of daily 30 mg/kg intra-peritoneal methoxetamine results in significant bladder and renal toxicity in mice. Changes in the bladder included inflammatory changes with subsequent fibrosis and changes in the kidney were seen at both a tubular and glomerular level. These changes are similar to those seen in comparable animal models of chronic ketamine administration. Further work is required to determine the time course of the onset of these effects and whether the effects are reversible with methoxetamine cessation.

Eastern coral snake Micrurus fulvius venom toxicity in mice is mainly determined by neurotoxic phospholipases A2

Here we show for the first time that the venom from an elapid (Micrurus fulvius) contains three finger toxin (3FTxs) peptides with low toxicity but high content of lethal phospholipases A2 (PLA2). The intravenous venom LD50 in mice was 0.3μg/g. Fractionation on a C18 column yielded 22 fractions; in terms of abundance, 58.3% of them were components of 13-14kDa and 24.9% were molecules of 6-7kDa. Two fractions with PLA2 activity represented 33.4% of the whole venom and were the most lethal fractions. Fractions with low molecular mass (<7000Da) partially and reversibly blocked the nicotinic acetylcholine receptor (nAChR), with the exception of one that blocked it completely. The fraction that blocked 100% contained two protein species whose dose-response was determined; the IC50s were 13±1 and 9.5±0.3nM. Despite the apparent effect on nAChR none of the low molecular mass fractions were lethal in mice, at concentrations of 1μg/g. From 2D-PAGE and LC-MS/MS, we identified fourteen species of PLA2, four protein species of C-type lectin, three zinc metalloproteinases, one phosphodiesterase and one 3FTx. The N-terminal amino acid sequence of fractions with biological interest was obtained.

BIOLOGICAL SIGNIFICANCE

In contrast with coral snake venoms from South America, M. fulvius has minor amounts of low molecular mass components, but high content of PLA2, which is responsible for the venom lethality of this species. The results reported here contribute to better understanding of envenomation development and to improve antivenom design and production. These findings break from the paradigm that neurotoxicity caused by Micrurus venoms is mainly attributable to 3FTx neurotoxins and encourage future studies on Micrurus evolution and venom specialization. This article is part of a Special Issue entitled Non-model organisms.