Neurophysiological findings in patients 1 year after snake bite induced neurotoxicity in Sri Lanka

Oral and IV Varespladib Rescue Experiments in Juvenile Pigs with Weakness Induced by Australian and Papuan Oxyuranus scutellatus Venoms

Antivenom is currently the standard-of-care treatment for snakebite envenoming, but its efficacy is limited by treatment delays, availability, and in many cases, species specificity. Many of the rapidly lethal effects of envenoming are caused by venom-derived toxins, such as phospholipase A2 (sPLA2); therefore, small molecule direct toxin inhibitors targeting these toxins may have utility as initial and adjunct therapies after envenoming. Varespladib (intravenous, IV) and varespladib-methyl (oral) have been shown to potently inhibit sPLA2s from snake venoms in murine and porcine models, thus supporting their further study as potential treatments for snakebite envenoming. In this pilot study, we tested the ability of these compounds to reverse neurotoxic effects of venom from the Australian and Papuan taipan (Oxyuranus scutellatus) subspecies in juvenile pigs (Sus domesticus). The mean survival time for control animals receiving Australian taipan venom (0.03 mg/kg, n = 3) was 331 min ± 15 min; for those receiving Papuan taipan venom (0.15 mg/kg, n = 3) it was 178 ± 31 min. Thirteen pigs received Australian taipan venom and treatment with either IV or oral varespladib (or with IV to oral transition) and all 13 survived the duration of the study (≥96 h). Eight pigs received Papuan taipan venom followed by treatment: Briefly: Two animals received antivenom immediately and survived to the end of the study. Two animals received antivenom treatment delayed 45 min from envenoming and died within 4 h. Two animals received similarly delayed antivenom treatment and were rescued by varespladib. Two animals were treated with varespladib alone after a 45-min delay. Treatment with varespladib only was effective but required repeat dosing over the course of the study. Findings highlight both the importance of early treatment and, as well, a half-life for the investigational inhibitors now in Phase II clinical trials for snakebite. Varespladib rapidly reversed weakness even when administered many hours post-envenoming and, overall, our results suggest that varespladib and varespladib-methyl could be efficacious tools in the treatment of sPLA2-induced weakness from Oxyuranus envenoming. Further clinical study as initial therapy and as potential method of rescue from some types of antivenom-resistant envenomings are supported by these data.

Acute peripheral neuropathy following animal envenomation: A case report and systematic review

Animal envenomation in humans is usually accidental or for defensive purposes. Depending on the venom composition and administration, different reactions can be observed. After reporting the first case of acute polyradiculitis in a 57-year-old healthy male after red lionfish envenomation, we propose to analyze rare similar cases of acute neuritis after animal envenomation published in the medical literature. Including our case, we found 54 patients who developed acute peripheral neuropathy after having been stung or bitten by various animals, mainly hymenoptera (in half of the cases) but also jellyfishes, snakes, corals or nonhooked arthropods. We observed two distinct patterns of peripheral neuropathy: more than half of them were polyneuropathy while the others were focal neuropathy. The prognosis was favorable in most cases. The pathophysiological mechanism associated with these rare complications remain unknown, although some hypotheses may be proposed. A direct action of certain components of the venom, such as phospholipase-A2, could explain the focal forms of peripheral neuropathy trough toxic reactions and/or vasculitis processes. The more diffuse clinical situations could be due to an allergy-triggered immune-mediated reaction (possibly linked to a molecular mimicry mechanism between venom proteins and some myelin proteins of the peripheral nervous system), or to the action of some venom components on membrane ionic channels particularly at the node of Ranvier. Even if acute peripheral neuropathies are rare after envenomation, they may occur after envenomation from various animals, and their usually favorable prognoses should be known by neurologists.

Fight or Flee: An Interesting Case of Snakebite With Delayed Recovery

Snakebite is a neglected tropical disease, which is very common in the Indian subcontinent. The severity of respiratory muscle paralysis and the delay in recovery depend upon the dose of the venom injected, the severity of the venom, the species of the snake, the duration of presentation to the hospital, and the time and dose of administration of anti-snake venom (ASV). The reasons for this delayed neuromuscular recovery still remain an enigma. We highlight such a case of a young adult who had delayed neuromuscular recovery and prolonged ventilatory support following a neurotoxic snakebite.

Chronic health effects and cost of snakebite

The burden of disability among survivors and the socio-economic impact of snakebite have not been adequately researched. We reviewed original research articles, case reports and small case series relating to chronic physical, mental and psycho-social disability and economic burden of snakebite. Both physical and psychological health problems seem common in snakebite survivors and can lead to disability and loss of productivity. Chronic physical health effects, musculoskeletal disability being the commonest, can be largely attributed to limited and delayed access to optimal treatment of acute envenoming. The economic burden is considerable, and includes health system costs, out-of-pocket expenditure and opportunity costs, with regional variations. Health systems should be more responsive to needs and circumstances of bite victims, and a more holistic approach should be developed in the treatment of snakebite which incorporates the management of chronic health effects.

•

Limited attention has been paid to chronic disability and the socio-economic impact of snakebite.

•

Physical and psychological health problems occur in snakebite survivors leading to disability and loss of productivity.

•

Chronic health effects can be largely attributed to limited and delayed access to optimal treatment of acute envenoming.

•

Economic burden includes health system costs, out-of-pocket expenditure and opportunity costs.

•

Health systems should be responsive to needs and circumstances of bite victims including care of chronic health effects.

Paediatric cases of Ceylon krait (Bungarus ceylonicus) bites and some similar looking non-venomous snakebites in Sri Lanka: Misidentification and antivenom administration

Ceylon krait (Bungarus ceylonicus) of the family Elapidae is a highly venomous endemic species inhabiting in the wet zone and some parts of the intermediate climatic zones of Sri Lanka. Clinical records of its bites are rare and limited to five case reports in the literature. It is of interest to note that there are several non-venomous snakes in Sri Lanka having similar morphological appearance to kraits causing identification difficulties which lead to unnecessary and unindicated administration of antivenom. We report two paediatric cases of proven Ceylon krait bites and three adult patients with similar looking non-venomous snakebites. These children were 1½ and 13 years old and developed neuroparalysis without progressing to respiratory failure and recovered. Both the children were administered Indian polyvalent antivenom which has not developed against endemic Ceylon krait venom. The two adult patients also received antivenom due to the misidentification without clinical and laboratory evidence of envenoming.

Unusually prolonged neuromuscular weakness caused by krait (Bungarus caeruleus) bite: Two case reports

Snakebites are common in India and the most common neurotoxic snakebites in India are due to Common krait (Bungarus caeruleus) and cobra (Naja naja). Severe envenomation may mimic brain death or a locked-in state with flaccid paralysis in a descending manner and total ophthalmoplegia. Usually, patients who receive timely antivenom and ventilator support recover completely without any sequalae. We are reporting two cases of krait bite with an unusually long period of flaccid paralysis, which required prolong ventilation. While case 1 required 10 days of mechanical ventilation followed by 5 days of non-invasive ventilation, case 2 required 11 days of mechanical ventilation followed by 5 days of non-invasive ventilation. Both the cases had delayed recovery and residual weakness at 3-month follow up. These case reports suggest that krait bite may cause prolong neuromuscular weakness in children, which has implications for both acute and chronic management.

Effect of Traditional Chinese Medicine on Long-Term Outcomes of Snakebite in Taiwan

Herein, we review the characteristics of the six predominant venomous snakes in Taiwan and the effects of traditional Chinese medicine on the long-term outcomes of snakebite venom. We electronically searched databases, including PubMed, ClinicalKey, China National Knowledge Infrastructure, National Digital Library of Theses and Dissertations in Taiwan, and Airiti Library, from their inception to November 2019 by using the following Medical Subject Headings' keywords: snakebite, long-term, chronic, Chinese medicine, CAM, herb, and Taiwan. The most common long-term effects of snakebite envenomation include "migraine-like syndrome", brain injuries caused by hypoxia or intracranial hemorrhage, and chronic kidney disease. In addition, hypopituitarism is also worth mentioning. Traditional Chinese medicine can potentially be used in a complementary or alternative treatment for these effects, but additional studies are needed.

Long-term Effects of Snake Envenoming

Long-term effects of envenoming compromise the quality of life of the survivors of snakebite. We searched MEDLINE (from 1946) and EMBASE (from 1947) until October 2018 for clinical literature on the long-term effects of snake envenoming using different combinations of search terms. We classified conditions that last or appear more than six weeks following envenoming as long term or delayed effects of envenoming. Of 257 records identified, 51 articles describe the long-term effects of snake envenoming and were reviewed. Disability due to amputations, deformities, contracture formation, and chronic ulceration, rarely with malignant change, have resulted from local necrosis due to bites mainly from African and Asian cobras, and Central and South American Pit-vipers. Progression of acute kidney injury into chronic renal failure in Russell's viper bites has been reported in several studies from India and Sri Lanka. Neuromuscular toxicity does not appear to result in long-term effects. Endocrine anomalies such as delayed manifestation of hypopituitarism following Russell's viper bites have been reported. Delayed psychological effects such as depressive symptoms, post-traumatic stress disorder and somatisation have been reported. Blindness due to primary and secondary effects of venom is a serious, debilitating effect. In general, the available studies have linked a clinical effect to a snakebite in retrospect, hence lacked accurate snake authentication, details of acute management and baseline data and are unable to provide a detailed picture of clinical epidemiology of the long-term effects of envenoming. In the future, it will be important to follow cohorts of snakebite patients for a longer period of time to understand the true prevalence, severity, clinical progression and risk factors of long-term effects of snake envenoming.

Neuromuscular Effects of Common Krait (Bungarus caeruleus) Envenoming in Sri Lanka

Objective

We aimed to investigate neurophysiological and clinical effects of common krait envenoming, including the time course and treatment response.

Methodology

Patients with definite common krait (Bungarus caeruleus) bites were recruited from a Sri Lankan hospital. All patients had serial neurological examinations and stimulated concentric needle single-fibre electromyography (sfEMG) of orbicularis oculi in hospital at 6wk and 6–9mth post-bite.

Principal Findings

There were 33 patients enrolled (median age 35y; 24 males). Eight did not develop neurotoxicity and had normal sfEMG. Eight had mild neurotoxicity with ptosis, normal sfEMG; six received antivenom and all recovered within 20–32h. Seventeen patients developed severe neurotoxicity with rapidly descending paralysis, from ptosis to complete ophthalmoplegia, facial, bulbar and neck weakness. All 17 received Indian polyvalent antivenom a median 3.5h post-bite (2.8–7.2h), which cleared unbound venom from blood. Despite this, the paralysis worsened requiring intubation and ventilation within 7h post-bite. sfEMG showed markedly increased jitter and neuromuscular blocks within 12h. sfEMG abnormalities gradually improved over 24h, corresponding with clinical recovery. Muscle recovery occurred in ascending order. Myotoxicity was not evident, clinically or biochemically, in any of the patients. Patients were extubated a median 96h post-bite (54–216h). On discharge, median 8 days (4–12days) post-bite, patients were clinically normal but had mild sfEMG abnormalities which persisted at 6wk post-bite. There were no clinical or neurophysiological abnormalities at 6–9mth.

Conclusions

Common krait envenoming causes rapid onset severe neuromuscular paralysis which takes days to recover clinically consistent with sfEMG. Subclinical neuromuscular dysfunction lasts weeks but was not permanent. Antivenom effectively cleared venom but did not prevent worsening or reverse neuromuscular paralysis.

Common krait bites cause muscular paralysis due to the venom disrupting communication between the nerves and muscles. This becomes life-threatening for the patient if there is paralysis of the muscles used for breathing. We studied the severity of paralysis, long term effects and the value of antivenom treatment in authenticated Indian krait bite patients from Sri Lanka. In addition to standard treatment with antivenom, the patients had single-fibre electromyography done, a sensitive neurophysiological test that detects the abnormalities of communication between the nerves and muscles. Half of the patients had severe paralysis and required mechanical ventilation, and the remainder had mild or no effects. Antivenom was given to all patients with severe paralysis and most with mild effects. However, despite antivenom binding all free venom after it was administered, it did not prevent or reverse already developed paralysis. Clinically evident paralysis resolved after a few days, but the neurophysiological abnormalities lasted for weeks. No permanent neurological damages were noted at 6 to 9 months after the snake bite.

Neurotoxicity in snakebite--the limits of our knowledge

Snakebite is classified by the WHO as a neglected tropical disease. Envenoming is a significant public health problem in tropical and subtropical regions. Neurotoxicity is a key feature of some envenomings, and there are many unanswered questions regarding this manifestation. Acute neuromuscular weakness with respiratory involvement is the most clinically important neurotoxic effect. Data is limited on the many other acute neurotoxic manifestations, and especially delayed neurotoxicity. Symptom evolution and recovery, patterns of weakness, respiratory involvement, and response to antivenom and acetyl cholinesterase inhibitors are variable, and seem to depend on the snake species, type of neurotoxicity, and geographical variations. Recent data have challenged the traditional concepts of neurotoxicity in snake envenoming, and highlight the rich diversity of snake neurotoxins. A uniform system of classification of the pattern of neuromuscular weakness and models for predicting type of toxicity and development of respiratory weakness are still lacking, and would greatly aid clinical decision making and future research. This review attempts to update the reader on the current state of knowledge regarding this important issue.

Clinical toxinology

Clinical toxinology is a specialized area of clinical medicine focused on the pathophysiology, diagnosis, treatment, and prevention of diseases caused by animal, plant, and fungal toxins. This review focuses on recent developments in snakebite. Snakebite is newly recognized as a Neglected Tropical Disease by the World Health Organization (WHO), reflecting the large human and economic cost of this disease. New WHO guidelines on antivenom production are available. The methods of producing antivenom and dosing are changing as understanding of envenoming improves. Lower antivenom doses in some regions are delivering equal outcomes, but antivenom cannot fully treat all envenoming types. Early antivenom treatment may reduce local tissue damage in some types of snakebite.