Epidemiology of fatal snakebites in the United States 1989-2018

Regional Differences in Systemic Toxicity Following Texas Coral Snake (Micrurus tener) Envenomations

BackgroundThe Texas coral snake, Micrurus tener, is one of three elapid species native to the continental United States. The purpose of the study was to describe the clinical features of their envenomation.MethodsWe reviewed all human coral snake bites reported to the Texas Poison Center Network between January 2000 and December 2023. We excluded informational calls and cases in which the snake responsible for the bite was not confirmed as M. tener. Finally, we excluded bite victims who did not seek medical attention and those for whom no clinical information was available. The data collected included patient demographics, the county in which the patient was treated, clinical features, and treatment.ResultsThere were 501 human bites. In 472 (94.2%) cases, symptoms were limited to pain and paresthesias. Systemic toxicity, for example, weakness, dysphagia, and ptosis, was observed in 18 (3.6%) patients. Eleven (2.2%) patients had no clinical findings. Antivenom was administered in 126 (25.1%) cases. Antivenom use decreased over time; in the 5-year period from 2000-2007, antivenom was administered to 74 (55.6%) patients. Conversely, only 8 (4.1%) of patients from 2016-2023 received antivenom. Systemic findings were observed in 13 (6.5%) cases in Northeast and Central Texas compared to 5 (1.6%) in Southeast and South Texas.ConclusionMicrurus tener envenomations were characterized primarily by pain and paresthesias. Additional systemic findings may be observed, particularly in Northeast and Central Texas. Antivenom was administered to a minority of Texas coral snake envenomation victims.

Leandro A, Leandro M, Peralta J, Williams-Blangero S, Sanchez EE, Galan JA, Blangero J, Curran JE. Neurocellular Stress Response to Mojave Type A Rattlesnake Venom: Study of Molecular Mechanisms Using Human iPSC-Derived Neural Stem Cell Model

The Mojave rattlesnake venom shows significant geographical variability. The venom of Type A animals primarily contains β-neurotoxin referred to as Mojave Toxin (MTX), which makes bites from this snake particularly feared. We performed a genome-wide transcriptomic analysis of the neurocellular response to Mojave Type A rattlesnake venom using induced pluripotent stem cell-derived neural stem cells to unveil the molecular mechanisms underlying the damage caused by this snake's envenomation. Our results suggest that snake venom metalloproteases, although having a limited repertoire in Type A venom, facilitate venom spread by digesting the tissue's extracellular matrix. The MTX, which is composed of heterodimers of basic and acidic phospholipase-A2, co-opts the host arachidonic acid and Ca2+ second messenger mechanisms and triggers multiple signaling cascades, such as the activation of MAPKs and NF-κB-regulated proinflammatory genes; the neurotransmitter overload in excitatory synapses leading to a presynaptic blockade of nerve signals; and the upregulation of unfolded protein response (UPR) due to the depletion of Ca2+ from the endoplasmic reticulum. The upregulated UPR and the oxidative stress caused by reactive oxygen species generated in cytochromeP4501A1-mediated hydroxylation of arachidonic acid contribute to mitochondrial toxicity. The activation of UPR, mitochondrial toxicity, and oxidative stress synergistically contributed to apoptotic and ferroptotic cell death.

Myocardial infarction during treatment of Crotalinae envenomation: A case report

While myocardial infarction is a rare, but known, potential side effect of snakebite envenomation, snake antivenom has thus far not been associated with any cardiovascular adverse events. We report the case of a 71-year-old man who developed an anterolateral MI during administration of Crotalidae immune F(ab')2 (equine) (ANAVIP), given as treatment for Crotalidae envenomation. The patient required cardiac catheterization with stenting of the left anterior descending artery and was discharged two days later on long-term clopidogrel and aspirin. Treatment of MI in the setting of envenomation should mirror typical management, with consideration of additional antivenom if the ischemia is determined to be venom-induced. Clinicians should have a high index of suspicion for patients with chest pain after snake envenomation or administration of antivenom.

Epidemiologic and clinical features of cyanobacteria harmful algal bloom exposures reported to the National Poison Data System, United States, 2010-2022: a descriptive analysis

BACKGROUND

Harmful algal bloom occurrences have been increasingly reported globally and over time. Exposure to the variety of toxins and co-contaminants that may be present in harmful algal blooms can cause illness and even death. Poison control data is a valuable public health information source that has been used to characterize many types of toxin exposures, including harmful algal blooms. Prior studies have been limited by location and time, and knowledge gaps remain regarding cyanobacteria harmful algal bloom (cyanoHAB) exposure circumstances, and the breadth and severity of associated clinical effect.

METHODS

The objective of this study was to characterize epidemiologic and clinical features of cyanoHAB exposure cases reported to 55 US poison control centers and available in the National Poison Data System (NPDS). We identified 4260 NPDS cyanoHAB exposure cases reported from 2010 to 2022, including symptomatic exposure cases with and without clinical effects related to the exposure and asymptomatic exposure cases. We assessed demographics; exposure routes, locations, chronicity; clinical effects; and medical outcomes. We calculated case rates annually and 13-year case rates by US geographic division.

RESULTS

Over half of cyanoHAB exposure cases were children < 20 years old (n = 2175). Most cyanoHABs exposures occurred in a "public area" (n = 2902, 68.1%); most were acute (≤ 8 h) (n = 3824, 89.8%). Dermal and ingestion routes and gastrointestinal effects predominated. 2% (n = 102) of cases experienced a moderate or major medical outcome; no deaths were reported. National rates increased from 0.4 cases/1 million (1 M) person-years in 2010 to 1.4 cases/1 M person-years in 2022. The Mountain division had the highest 13-year rate (7.8 cases/1 M person-years).

CONCLUSIONS

CyanoHAB exposure case rates increased 2010-2022, despite a decrease in all-cause exposure cases during the same period. NPDS data provide valuable public health information for characterization of cyanoHAB exposures, an emerging public health challenge.

Snake Envenomation

Snakebite envenomation (SBE) in horses can have devastating outcomes. Tissue damage, cardiotoxicity, coagulopathy, and neurotoxicity can be concerns with SBE. Understanding the actions of venom components is important in developing a successful treatment plan. Antivenom is the mainstay of treatment. Long-term deleterious effects can occur including cardiac dysfunction and lameness.

Geographic variation in the clinical features of Mohave rattlesnake (Crotalus scutulatus) envenomations reported to the North American Snakebite Registry

The geographic variation of Mohave rattlesnake (Crotalus scutulatus) venom is well established. We reviewed all the Mohave rattlesnake bites reported to the Toxicology Investigators Consortium's North American Snakebite Registry between January 1, 2015 and 12/31/2021. Data reviewed for this study included details regarding the snake encounter, patient demographics, signs and symptoms, treatment, and outcomes. Our objective was to describe the epidemiology, clinical manifestations, and management of Mohave rattlesnake envenomations using prospective data from two geographically distinct sites. There were 20 subjects, including eight nonpregnant females. Ages ranged from seven to 75 years, median age 48. Nine of the bites were managed in Arizona and 11 in California. In Arizona, all envenomated patients had local swelling. None had neurological toxicity. In California, swelling was present in nine patients. Neurological effects were observed in five subjects. Four Arizona patients and one California patient had hypotension requiring treatment. Each site had one patient with thrombocytopenia. An Arizona patient who sustained a bite to the face was intubated. Rhabdomyolysis occurred in two California patients. All envenomated patients received antivenom. Mohave rattlesnakes have the potential to cause significant local and/or systemic toxicity. Neurotoxicity was not observed in envenomations from Mohave rattlesnakes that presumably lack Mohave toxin, but hypotension and gastrointestinal signs were more common than in bites from snakes believed to possess Mohave toxin. Neurological toxicity was limited to paresthesias and fasciculations. Significant skeletal or respiratory muscle weakness was not observed in our study population.

The Association Between Ambient Temperature and Snakebite in Georgia, USA: A Case-Crossover Study

The World Health Organization has identified snakebite envenoming as a highest priority neglected tropical disease, yet there is a dearth of epidemiologic research on environmental risk factors, including outdoor temperature. Temperature may affect snakebites through human behavior or snake behavior; snakes are ectotherms, meaning outdoor temperatures influence their internal body temperature and thus their behavior. Here we investigate the relationship between short-term temperature and snakebites in Georgia, one of the most biodiverse US states in terms of herpetofauna. We acquired emergency department (ED) visit data for Georgia between 1 January 2014 and 31 December 2020. Visits for venomous and non-venomous snakebites were identified using diagnosis codes. For comparison, we also considered visits for non-snake (e.g., insects, spiders, scorpions) envenomation. Daily meteorology from the Daymet 1 km product was linked to patient residential ZIP codes. We applied a case-crossover design to estimate associations of daily maximum temperature and snakebite ED visits. During the 7-year study period, there were 3,908 visits for venomous snakebites, 1,124 visits for non-venomous bites and 65,187 visits for non-snake envenomation. Across the entire period, a 1°C increase in same-day maximum temperature was associated with a 5.6% (95%CI: 4.0-7.3) increase in the odds of venomous snakebite and a 5.8% (95%CI: 3.0-8.8) increase in non-venomous snakebite. Associations were strongest in the spring. We also observed a positive and significant (p < 0.05) association for non-snake envenomation, albeit slightly smaller and more consistent across seasons compared to those for snakebites.

Total CroFab and Anavip Antivenom Vial Administration in US Rattlesnake Envenomations: 2019-2021

INTRODUCTION

In 2018, Anavip became available for the treatment of rattlesnake envenomations in the USA. No comparisons between the treatment characteristics of patients have been made since Anavip and CroFab have both been widely available. The objective of this study was to compare the number of antivenom vials administered of CroFab and Anavip during the treatment of rattlesnake envenomations in the USA.

METHODS

This was a secondary analysis of rattlesnake envenomations utilizing the North American Snakebite Registry (NASBR) from 2019 through 2021. Frequencies and proportions were used to summarize demographics and baseline clinical characteristics. The primary outcome was total antivenom vials administered during treatment. Secondary outcomes included the number antivenom administration events, total treatment time, and hospital length of stay.

RESULTS

Two hundred ninety-one rattlesnake envenomations were analyzed; most occurred in the Western USA (n = 279, 96 %). One hundred one patients (35%) received only CroFab, 110 (38%) received Anavip only, and 80 (27%) received both products. The median number of vials used was 10 for CroFab, 18 for Anavip, and 20 for both antivenoms. More than one antivenom administration was necessary in thirty-nine (39%) patients that received only CroFab and 76 (69%) patients that received Anavip only. The median total treatment time was 5.5 hours for CroFab, 6.5 for Anavip, and 15.5 hours when both antivenoms were administered. All antivenom groups had a median hospital length of stay of 2 days.

CONCLUSIONS

Rattlesnake envenomated patients in the Western USA treated with CroFab had fewer antivenom vials and fewer antivenom administrations compared to patients treated with Anavip.

Perspectives on snakebite envenoming care needs across different sociocultural contexts and health systems: A comparative qualitative analysis among US and Brazilian health providers

With the advancements in therapeutics and available treatment options, almost all deaths and permanent disabilities from snakebite envenoming (SBE) are preventable. The challenge lies in implementing these evidence-based treatments and practices across different settings and populations. This study aims to compare data on provider perceptions of SBE care across health systems and cultural contexts to inform potential implementation science approaches. We hypothesize different health systems and cultural contexts will influence specific perceived needs to provide adequate snakebite care within central tenets of care delivery (e.g., cost, access, human resources). We previously conducted exploratory descriptive studies in the US and Brazil in order to understand the experience, knowledge, and perceptions of health professionals treating SBE. In the US, in-depth interviews were performed with emergency physicians from January 2020 to March 2020. In BR, focus group discussions were conducted with health professionals from community health centers at the end of June 2021. The focus group discussions (BR) were originally analyzed through an inductive thematic analysis approach. We conducted a secondary qualitative analysis in which this codebook was then applied to the interviews (US) in a deductive content analysis. The analysis concluded in August 2022. Brazil participants were physicians (n=5) or nurses (n=20) from three municipalities in the State of Amazonas with an average of three years of professional experience. US participants were emergency physicians (n=16) with an average of 15 years of professional experience. Four main themes emerged: 1) barriers to adequate care on the patient and/or community side and 2) on the health system side, 3) perceived considerations for how to address SBE, and 4) identified needs for improving care. There were 25 subthemes within the four themes. These subthemes were largely the same across the Brazil and US data, but the rationale and content within each shared subtheme varied significantly. For example, the subtheme "role of health professionals in improving care" extended across Brazil and the US. Brazil emphasized the need for task-shifting and -sharing amongst health care disciplines, whereas the US suggested specialized approaches geared toward increasing access to toxicologists and other referral resources. Despite similar core barriers to adequate snakebite envenoming care and factors to consider when trying to improve care delivery, health professionals in different health systems and sociocultural contexts identified different needs. Accounting for, and understanding, these differences is crucial to the success of initiatives intended to strengthen snakebite envenoming care. Implementation science efforts, with explicit health professional input, should be applied to develop new and/or adapt existing evidence-based treatments and practices for SBE.

The BRAVO Clinical Study Protocol: Oral Varespladib for Inhibition of Secretory Phospholipase A2 in the Treatment of Snakebite Envenoming

INTRODUCTION

Snakebite is an urgent, unmet global medical need causing significant morbidity and mortality worldwide. Varespladib is a potent inhibitor of venom secretory phospholipase A2 (sPLA2) that can be administered orally via its prodrug, varespladib-methyl. Extensive preclinical data support clinical evaluation of varespladib as a treatment for snakebite envenoming (SBE). The protocol reported here was designed to evaluate varespladib-methyl for SBE from any snake species in multiple geographies.

METHODS AND ANALYSIS

BRAVO (Broad-spectrum Rapid Antidote: Varespladib Oral for snakebite) is a multicenter, randomized, double-blind, placebo-controlled, phase 2 study to evaluate the safety, tolerability, and efficacy of oral varespladib-methyl plus standard of care (SoC) vs. SoC plus placebo in patients presenting with acute SBE by any venomous snake species. Male and female patients 5 years of age and older who meet eligibility criteria will be randomly assigned 1:1 to varespladib-methyl or placebo. The primary outcome is the Snakebite Severity Score (SSS) that has been modified for international use. This composite outcome is based on the sum of the pulmonary, cardiovascular, nervous, hematologic, and renal systems components of the updated SSS.

ETHICS AND DISSEMINATION

This protocol was submitted to regulatory authorities in India and the US. A Clinical Trial No Objection Certificate from the India Central Drugs Standard Control Organisation, Drug Controller General-India, and a Notice to Proceed from the US Food and Drug Administration have been obtained. The study protocol was approved by properly constituted, valid institutional review boards or ethics committees at each study site. This study is being conducted in compliance with the April 1996 ICH Guidance for Industry GCP E6, the Integrated Addendum to ICH E6 (R2) of November 2016, and the applicable regulations of the country in which the study is conducted. The trial is registered on Clinical trials.gov, NCT#04996264 and Clinical Trials Registry-India, 2021/07/045079 000062.

Delayed Recognition of Severe Systemic Envenomation after Copperhead Bite: A Case Report

Introduction

We report a case of severe systemic copperhead, Agkistrodon contortrix, envenomation that resulted in long-term sequelae.

Case Report

A 72-year-old man presented to the emergency department after suffering a copperhead snakebite. He developed severe systemic toxicity before local tissue injury developed. Clinicians did not initially recognize his envenomation syndrome and sought alternative explanations for his systemic symptoms before polyvalent immune fab (ovine) antivenom was administered. Although the patient improved, he was discharged with new stage three chronic kidney disease.

Conclusion

Although rare, copperhead envenomation can cause severe systemic toxicity. Envenomation should be promptly treated with antivenom.

Predictors of FabAV use in copperhead envenomation

CONTEXT

Crotaline snake envenomation is a serious medical condition affecting thousands of Americans each year. Variation in the treatment of Crotaline snakebites exists among physicians in the United States. Management of copperhead snakebites is controversial with some experts advocating minimal intervention, rarely necessitating antivenom use and, even more rarely, surgical intervention. This study assessed the use of Crotaline Polyvalent Immune Fab antivenom (Ovine) (FabAV) and explored factors influencing the decision to prescribe antivenom for copperhead envenomation in patients in Northeastern Oklahoma.

METHODS

A retrospective cohort study examining electronic medical records of patients with copperhead snakebites from July 1, 2014 to August 31, 2019. Data collected included: patient demographics, transfer information, snake species, bite site, progression of local tissue effects, additional clinical and lab results, patient comorbidities, and treatment strategy. Associations between patient variables and treatment were evaluated using the chi-square test of independence, median test, and logistic regression analysis. Associations were statistically significant if p < 0.05.

DISCUSSION

Of the 130 patients bitten by a copperhead, a majority (75%) received FabAV. Symptoms of copperhead envenomation were mostly limited to the progression of tissue damage. Predictors of treatment with FabAV included progression of venom effects across major joints, younger age, comorbidities, and upper extremity bites.

CONCLUSIONS

Patients who have multiple comorbidities, upper extremity bites and progression of venom effects across major joints are more likely to be treated with FabAV. The high usage of FabAV at the study site underscores the need for continued work to optimize the use of antivenom for copperhead envenomations.

Neutralization of crotamine by polyclonal antibodies generated against two whole rattlesnake venoms and a novel recombinant fusion protein

Crotamine is a paralyzing toxin (MW: ~5 kDa) found in different proportions in some rattlesnake venoms (up to 62%). Mexican pit viper antivenoms have shown low immunoreactivity against crotamine, which is an urgent quality to be improved. The objective of this work was to evaluate the ability of a novel recombinant fusion protein composed of sphingomyelinase D and crotamine, and two whole venoms from Crotalus molossus nigrescens and C. oreganus helleri to produce neutralizing antibodies against crotamine. These immunogens were separately used for immunization procedures in rabbits. Then, we generated three experimental antivenoms to test their cross-reactivity via western-blot against crotamine from 7 species (C. m. nigrescens, C. o. helleri, C. durissus terrificus, C. scutulatus salvini, C. basiliscus, C. culminatus and C. tzabcan). We also performed pre-incubation neutralization experiments in mice to measure the neutralizing potency of each antivenom against crotamine induced hind limb paralysis. Our antivenoms showed broad recognition across crotamine from most of the tested species. Also, neutralization against crotamine paralysis symptom was successfully achieved by our three antivenoms, albeit with different efficiencies. Our results highlight the use of crotamine enriched venoms and our novel recombinant fusion protein as promising immunogens to improve the neutralizing potency against crotamine for the improvement of Mexican antivenoms.