Snakebites in Cameroon: Tolerance of a Snake Antivenom (Inoserp™ PAN-AFRICA) in Africa in Real-Life Conditions

Snakebite envenomation (SBE) is a public health issue in sub-Saharan countries. Antivenom is the only etiological treatment. Excellent tolerance is essential in managing SBE successfully. This study aimed to evaluate tolerance of InoserpTM PAN-AFRICA (IPA). It was conducted on fourteen sites across Cameroon. IPA was administered intravenously and repeated at the same dose every two hours if needed. Early and late tolerance was assessed by the onset of clinical signs within two hours and at a visit two weeks or more after the first IPA administration, respectively. Over 20 months, 447 patients presenting with a snakebite were included. One dose of IPA was administered to 361 patients and repeated at least once in 106 patients. No significant difference was shown between the proportion of adverse events in patients who received IPA (266/361, 73.7%) and those who did not (69/85, 81.2%) (p = 0.95). Adverse reactions, probably attributable to IPA, were identified in four (1.1%) patients, including one severe (angioedema) and three mild. All these reactions resolved favorably. None of the serious adverse events observed in twelve patients were attributed to IPA. No signs of late intolerance were observed in 302 patients. Tolerance appears to be satisfactory. The availability of effective and well-tolerated antivenoms would reduce the duration of treatment and prevent most disabilities and/or deaths.

Toxinological profile and histopathological alterations induced by Bothrocophias campbelli venom from Colombia

Snakebite envenomings most frequently reported in Colombia are caused by snakes of the genera Bothrops, Bothriechis, Bothrocophias, and Porthidium. Their venoms induce local and systemic pathophysiological effects, sometimes leading to permanent sequelae such as reduced mobility of the limbs, amputations, besides the risk of death. The genus Bothrocophias includes nine species, among which B. campbelli has a distribution restricted to the department of Nariño in Colombia. In this work we determined the toxinological profile its venom, by performing assays for the lethal, hemorrhagic, edematogenic, and myotoxic activities in mouse models, as well as for in vitro coagulant activity on human plasma. The lethal toxicity of the venom was 142.7 µg venom/mouse (111.4-179.8 µg/mouse; 6.6-10.6 µg/g body weight) by intraperitoneal route. Its hemorrhagic activity (minimum hemorrhagic dose: 12.7 ± 2.3 µg) is generally weaker compared to other South American vipers, but edematogenic (minimum edematogenic dose 1.0 ± 0.3 µg), and myotoxic (minimum myotoxic dose 3.9 ± 2.5 µg) activities are very potent. Histopathological examination of the injected mouse gastrocnemius muscle showed prominent disorganization of the myofibrils, myonecrosis, and an intense inflammatory leukocyte infiltrate. In vitro, the minimal coagulant dose was 12.3 ± 0.5 µg. Overall, this toxinological profile would predict that the clinical picture of envenomings by B. campbelli might be characterized by moderate disturbances in the coagulation cascade, mild local hemorrhage, and, conversely, severe myonecrosis and edema, which could potentially lead to compartment syndrome and gangrene.

Real life condition evaluation of Inoserp PAN-AFRICA antivenom effectiveness in Cameroon

BACKGROUND

Snakebites is a serious public health issue but remains a neglected tropical disease. Data on antivenom effectiveness are urgently needed in Africa. We assessed effectiveness of Inoserp PAN-AFRICA (IPA), the recommended antivenom available in Cameroon.

METHODOLOGY/PRINCIPAL FINDINGS

We enrolled 447 patients presenting with snakebite in 14 health facilities across Cameroon. At presentation, cytotoxicity, coagulation troubles and neurotoxicity were graded. We administered two to four vials of antivenom to patients based on hemotoxic or neurotoxic signs. We renewed antivenom administration to patients with persistence of bleedings or neurotoxicity 2 hours after each injection. We defined early improvement as a reduction of the grade of envenomation symptoms 2 hours after first injection. Medium-term effectiveness was investigated looking at disappearance of symptoms during hospitalization. After hospital discharge, a home visit was planned to assess long-term outcomes. Between October 2019 and May 2021, we enrolled 447 (93.7%), including 72% from the savannah regions. The median [IQR] age was 25 [14-40]. Envenomation was diagnosed in 369 (82.6%) participants. The antivenom was administered to 356 patients (96.5%) of whom 256 (71.9%) received one administration. Among these patients, cytotoxic symptoms were observed in 336 (94.4%) participants, coagulation disorders in 234 (65.7%) participants and neurotoxicity in 23 (6.5%) participants. Two hours after the first administration of antivenom, we observed a decrease in coagulation disorders or neurotoxicity in 75.2% and 39.1% of patients, respectively. Complete cessation of bleedings and neurotoxicity occurred in 96% and 93% of patients within 24 hours, respectively. Sequelae have been observed in 9 (3%) patients at the home visit 15 days after hospital admission and 11 (3%) died including one before antivenom injection.

CONCLUSIONS/SIGNIFICANCE

We confirmed good effectiveness of the IPA and highlighted the rapid improvement in bleeding or neurotoxicity after the first administration. Sequential administrations of low doses of antivenom, rigorously assessed at short intervals for an eventual renewal, can preserve patient safety and save antivenom.

TRIAL REGISTRATION

NCT03326492.

Pediatric Rattlesnake Envenomations Treated With Crotalidae Equine Immune F(Ab') 2 Antivenom : A 3-Year Retrospective Observational Analysis

OBJECTIVES

Rattlesnake envenomations are uncommon, and the majority occur in adults. Although Crotalidae equine immune F(ab') 2 antivenom (F(ab') 2 AV; trade name ANAVIP) was introduced in 2018, no pediatric specific studies of F(ab') 2 AV have been reported to date. The objective of this study was to evaluate the clinical performance and adverse effects of F(ab') 2 AV in children.

METHODS

A single-center, retrospective chart review was performed on patients with rattlesnake envenomation presenting to a children's hospital between October 2018 and August 2022. Inclusion criteria were age younger than 18 years and F(ab') 2 AV use. Exclusion criteria were other antivenom use at any time and presentation beyond 24 hours postenvenomation.Demographic characteristics, hemoglobin, platelet count, fibrinogen, international normalized ratio, number of F(ab') 2 AV vials used, infusion-related complications, and clinical outcomes were collected.

RESULTS

Twenty-six patients, 19 males and 7 females, with a mean age of 7.7 years (0.67 to 16 years) met inclusion criteria. Fourteen (54%) were treated with only the initial 10 vial F(ab') 2 AV doses. Twelve patients were given additional doses with a median additional vials of 10 (4-34 vials; interquartile range, 8.75-12 vials). The median total vials given for all patients was 10 (10-44 vials; interquartile range, 10-20 vials).Two patients developed acute infusion reactions. Both were treated by slowing the infusion rate and with medications (diphenhydramine, corticosteroids). No delayed reactions were noted. No patients required blood products or surgical interventions.After discharge, no complications, recurrent symptoms, return visits, or readmissions were reported. Follow-up by chart review or phone was obtained for 18 patients, and no postdischarge complications were noted. Seven patients had postdischarge hematologic laboratory evaluations and all were normal.

CONCLUSIONS

Although limited by small sample size and postdischarge follow-up, F(ab') 2 AV was well tolerated in our series of pediatric patients, consistent with prior studies of all age groups.

Safe administration of Crotalidae equine immune F(ab')2 antivenom in a patient who suffered anaphylaxis from Crotalidae polyvalent immune Fab antivenom

Allergic reactions to Crotalidae polyvalent immune Fab and Crotalidae immune F(ab')2 are uncommon but potentially life-threatening. It is unknown whether cross-reactivity reactions exist between these two antivenoms. We report a case of a patient who suffered anaphylaxis from Crotalidae polyvalent immune Fab but subsequently was safely administered Crotalidae immune F(ab')2 after a presumed Agkistrodon contortix (copperhead) envenomation. This single case supports the safety of Crotalidae immune F(ab')2 administration in patients with a history of anaphylaxis to Crotalidae polyvalent immune Fab treatment.

Impact of antivenom administration on the evolution of cutaneous lesions in loxoscelism: A prospective observational study

BACKGROUND

Spiders of the genus Loxosceles are distributed throughout tropical and temperate regions worldwide. Loxosceles spp. bites may evolve to necrosis, with or without intravascular hemolysis. There is no consensus regarding the best treatment to prevent necrosis. The objective of this study was to evaluate the factors associated with the development of necrosis and the impact that antivenom administration has on the evolution of cutaneous loxoscelism.

METHODOLOGY/PRINCIPAL FINDINGS

This was a prospective observational study carried out at a referral center for envenoming. Over a 6-year period, we included 146 patients with a presumptive or definitive diagnosis of loxoscelism. Depending on the symptom severity, a polyvalent anti-arachnid antivenom was administered or not-in 74 cases (50.7%) and 72 cases (49.3%), respectively. Cutaneous and systemic manifestations were assessed at admission and weekly thereafter. Adverse reactions to the antivenom were also evaluated. Cutaneous loxoscelism was observed in 141 cases (96.6%), and the spider was identified in 29 (19.9%). The mean time from bite to antivenom administration was 41.6 ± 27.4 h. After discharge, 130 patients (90.9%) were treated with corticosteroids, antihistamines and analgesics being prescribed as needed. The probability of developing necrosis was significantly lower among the patients who were admitted earlier, as well as among those who received antivenom (p = 0.0245). Among the 74 patients receiving antivenom, early and delayed adverse reactions occurred in seven (9.5%) and four (5.4%), respectively. Local infection was observed only in three (2.3%) of the 128 patients for whom that information was available.

CONCLUSIONS/SIGNIFICANCE

Necrosis after a Loxosceles sp. bite appears to more common when hospital admission is delayed or when antivenom is not administered. In addition, the administration of a polyvalent anti-arachnid antivenom appears to be safe, with a relatively low rate of adverse reactions.

Risk of stroke with antivenom usage after venomous snakebite in Taiwan: a population-based cohort study

BACKGROUND AND PURPOSE

Stroke is a rare complication of snakebites, but may lead to serious sequelae. We aimed to explore the relationship between venomous snakebite and the risk for acute stroke, in a nationwide population-based cohort study.

METHODS

This retrospective cohort study used claims data between 1 January 2000 and 31 December 2012, from the Taiwan National Health Insurance Research Database. The study included data of patients aged 18 years or older with venomous snakebite (n = 535), matched for propensity score with controls without venomous snakebite (n = 2140). The follow-up period was the duration from the initial diagnosis of venomous snakebite and administration of antivenom to the date of an acute stroke, or until 31 December 2013. The competing risk model was used to estimate the hazard ratio (HR) and 95% confidence intervals (CIs) of stroke, ischemic stroke and hemorrhagic stroke, after adjusting for demographic and other possible stroke risk factors.

RESULTS

The adjusted HR for the venomous snakebite group compared with the control group was 2.68 for hemorrhagic stroke (95% CI = 1.35-5.33). Stratified analysis showed that the older age group (>65 years old) had a higher risk of hemorrhagic stroke. A 2.72-fold significant increase in the risk for hemorrhagic stroke was observed following venomous snakebite with antivenom usage (95% CI = 1.41-5.26).

CONCLUSION

Venomous snakebite is associated with an increased risk of hemorrhagic stroke after the use of antivenom. Further study of the underlying mechanism is warranted.

Long-term health effects perceived by snakebite patients in rural Sri Lanka: A cohort study

The acute effects of snakebite are often emphasized, with less information on long-term effects. We aimed to describe the long-term health effects perceived by patients followed up after confirmed snakebites. Two groups of snakebite patients (>18y) from the Anuradhapura snakebite cohort were reviewed: Group I had a snakebite during August 2013-October 2014 and was reviewed after 4 years, and group II had a snakebite during May 2017-August 2018, and was reviewed after one year. Patients were invited by telephone, by sending letters, or doing home visits, including 199 of 736 patients (27%) discharged alive from group I and 168 of 438 patients (38%) from group II, a total of 367 followed up. Health effects were categorised as musculoskeletal, impact on daily life, and medically unexplained. Health issues were attributed to snakebite in 107/199 patients (54%) from group I and 55/168 patients (33%) from group II, suggesting the proportion with health issues increases with time. Sixteen patients (all viperine bites) had permanent musculoskeletal problems, none with a significant functional disability affecting daily routine. 217/367 reported being more vigilant about snakes while working outdoors, but only 21/367 were using protective footwear at review. Of 275 farmers reviewed, only six (2%) had restricted farming activities due to fear of snakebite, and only one stopped farming. 104/199 (52%) of group I and 42/168 (25%) of group II attributed non-specific symptoms (fatigue, body aches, pain, visual impairment) and/or oral cavity-related symptoms (avulsed teeth, loose teeth, receding gums) to the snakebite, which cannot be explained medically. In multivariate logistic regression, farming, type of snake, antivenom administration, and time since snakebite were associated with medically unexplained symptoms. The latter suggests medically unexplained effects increased with time. Based on two groups of snakebite patients reviewed one and four years post-bite, we show that long-term musculoskeletal disabilities are uncommon and not severe in snakebite survivors in rural Sri Lanka. However, a large portion of patients complain of various non-specific general and oral symptoms, not explainable based on the known pathophysiology of snakebite. These perceived effects of snakebite were more common in patients with systemic envenoming, and were more frequent the longer the time post-bite.

Treatment outcomes among snakebite patients in north-west Ethiopia-A retrospective analysis

BACKGROUND

Millions of people are bitten by venomous snakes annually, causing high mortality and disability, but the true burden of this neglected health issue remains unknown. Since 2015, Médecins Sans Frontières has been treating snakebite patients in a field hospital in north-west Ethiopia. Due to the poor market situation for effective and safe antivenoms for Sub-Saharan Africa, preferred antivenom was not always available, forcing changes in choice of antivenom used. This study describes treatment outcomes and the effectiveness and safety of different antivenoms used.

METHODOLOGY / PRINCIPAL FINDINGS

This retrospective observational study included 781 snakebite patients presenting at the field hospital between 2015 and 2019. Adjusted odds ratios, 95%-CI and p-values were used to compare the treatment outcome of patients treated with Fav-Afrique (n = 149), VacSera (n = 164), and EchiTAb-PLUS-ICP (n = 156) antivenom, and to identify the risk of adverse reactions for each antivenom. Whereas only incidental snakebite cases presented before 2015, after treatment was made available, cases rapidly increased to 1,431 in 2019. Envenomation was mainly attributed to North East African saw-scaled viper (Echis pyramidum) and puff adder (Bitis arietans). Patients treated with VacSera antivenom showed lower chance of uncomplicated treatment outcome (74.4%) compared to Fav-Afrique (93.2%) and EchiTAb-PLUS-ICP (90.4%). VacSera and EchiTAb-PLUS-ICP were associated with 16- and 6-fold adjusted odds of treatment reaction compared to Fav-Afrique, respectively, and VacSera was weakly associated with higher odds of death.

CONCLUSIONS / SIGNIFICANCE

Snakebite frequency is grossly underreported unless treatment options are available. Although EchiTAb-PLUS-ICP showed favorable outcomes in this retrospective analysis, prospective randomized trials are needed to evaluate the effectiveness and safety of the most promising antivenoms for Sub-Saharan Africa. Structural investment in sustained production and supply of antivenom is urgently needed.

Assessment of quality and pre-clinical efficacy of a newly developed polyvalent antivenom against the medically important snakes of Sri Lanka

Snake envenomation is a severe problem in Sri Lanka (SL) and Indian polyvalent antivenom (PAV) is mostly used for treating snakebite albeit due to geographical variation in venom composition, Indian PAV shows poor efficacy in neutralizing the lethality and toxicity of venom from the same species of snakes in SL. Therefore, the quality and in vivo venom neutralization potency of a country-specific PAV produced against the venom of the five most medically important snakes of SL (Daboia russelii, Echis carinatus, Hypnale hypnale, Naja naja, Bungarus caeruleus) was assessed. LC-MS/MS analysis of two batches of PAV showed the presence of 88.7-97.2% IgG and traces of other plasma proteins. The tested PAVs contained minor amounts of undigested IgG and F(ab')2 aggregates, showed complement activation, were devoid of IgE, endotoxin, and content of preservative was below the threshold level. Immunological cross-reactivity and in vitro neutralization of enzymatic activities, pharmacological properties demonstrated superior efficacy of SL PAV compared to Indian PAV against SL snake venoms. The in vivo neutralization study showed that the tested PAVs are potent to neutralize the lethality and venom-induced toxicity of SL snake venoms. Therefore, our study suggests that introduction of SL-specific PAV will improve snakebite management in SL.

A Quest for a Universal Plasma-Derived Antivenom Against All Elapid Neurotoxic Snake Venoms

This review describes the research aimed at the development of universal antivenom against elapid neurotoxic snake venoms. The antivenoms produced in Thailand in the 1980s were of low potency, especially against the elapid venoms. This was thought to be due to the low immunogenicity of the α-neurotoxins, which are the most lethal toxins in these venoms. Comparisons of various α-neurotoxin conjugates and polymers, and also different immunological adjuvants, showed that the adjuvant used is the major determinant in the antibody response in horses. The potent Freund's adjuvant was not used due to its severe local side-effect in horses. Therefore, a novel immunization protocol termed 'low dose, low volume multi-site' was developed for use in horses. This immunization protocol has led to the production of highly potent monospecific antivenoms against several elapid and viperid venoms, and two potent polyspecific antivenoms, one against 4 neurotoxic and another against 3 hematotoxic venoms. The immunization protocol has also led to other improvements in antivenom production including: several fold increases in antiserum potency, a reduction in the time required to reach therapeutically useful antibody titers, a 90% reduction in the amount of venom used, and 100% of the horses responding to the immunization program. This development is partly responsible for significant decrease in the Thailand's annual snakebite death toll from a few dozens to mostly nil in recent years. Finally, a simple and novel immunization strategy, using a 'diverse toxin repertoire' composed of numerous elapid toxin fractions as immunogen, was proposed and tested. This immunization procedure has resulted in the successful production of a widely paraspecific antiserum against at least 36 neurotoxic venoms of 28 species encompassing 10 genera and from 20 countries on four continents, and possibly against all elapid venoms with α-neurotoxins as the lethal toxins. These results indicate that, with optimizations of the composition of the 'diverse toxin repertoire', the immunization scheme and antibody fractionation to increase the antivenom neutralizing potency, an effective universal antivenom against the neurotoxic elapid snakes of the world can be produced.

Health professionals' overestimation of knowledge on snakebite management, a threat to the survival of snakebite victims-A cross-sectional study in Ghana

Background

According to the World Health Organization, snakebites, a common occupational hazard in developing countries accounts for an annual loss of between 81,000 and 138, 000 lives following 5 million bites of which 2.7 million results in envenomation. Since snakebite-associated morbidity and mortality are more prevalent in agricultural economies such as Ghana, health professionals should be optimally knowledgeable on how to manage the incidence of snakebites. Lack of knowledge or overestimation of a professional's knowledge can affect heath delivery especially for emergencies such as snakebites. The three rurally situated Tongu districts in South-Eastern Ghana with agriculture as the major source of livelihood for their inhabitants, are prone to snakebites. This study, therefore, brings up the need to assess whether the health professionals in these districts are well-equipped knowledge-wise to handle such emergencies and whether they can rightly estimate their knowledge with regards to snakebite management.

Methodology/Principal findings

Data was collected using a de novo semi-structured questionnaire administered through google form whose link was sent via WhatsApp to 186 health workers made up of nurses, midwives, physician assistants, medical doctors, pharmacists, and pharmacy technicians. This data was analyzed using Statistical Package for the Social Sciences (SPSS) Version 25. Association between variables was determined using the appropriate tools where necessary, using a confidence interval of 95% and significance assumed when p ≤ 0.05. This study found male health workers significantly more knowledgeable about snakebite management (11.53±5.67 vs 9.64±5.46; p = 0.022) but it was the females who overestimated their knowledge level (27.9% vs 24.1%). The medical doctors exhibited the best knowledge on snakebite management with the registered general nurses least knowledgeable. Although most professionals overestimated their knowledge, the registered general nurses were the worst at that (53.7%). Overall knowledge of health care professionals on snakebite management was below average [10.60±5.62/22 (48.2%)] but previous in-service training and involvement in the management of snakebite were associated with better knowledge. Respondents who had no previous training overestimated their knowledge level compared to those who had some post-qualification training on snakebite management (38.1% vs 7.5%). The greatest knowledge deficit of respondents was on the management of ASV associated adverse reactions.

Conclusion

Health workers in rural Ghana overestimated their knowledge about snakebite management although their knowledge was low. Training schools, therefore, need to incorporate snakebite management in their curriculum and health authorities should also expose health workers to more in-service training on this neglected tropical disease.

World Health Organization estimates that every year between 81,000 and 138,000 die due to snake bites across the world. Mismanagement of snakebites can result in increased disabilities and death if not handled by knowledgeable health workers. This study assessed if various categories of health workers made up of professionals from the medical, pharmaceutical, and nursing categories in the three neighbouring Tongu districts in Ghana have the appropriate level of knowledge on snakebite management. Using a newly developed questionnaire, data were collected from the respondents using google forms sent to their WhatsApp platforms. Data were then analyzed using Statistical Package for the Social Sciences (SPSS) Version 25. Results were presented in the form of tables and association between the variables also determined. The level of knowledge of sampled health workers on snakebite was below average, especially among nursing professionals. However, those who had some previous post-qualification training on snakebite management exhibited a significant superior knowledge and least overestimated their knowledge hence policymakers should through workshops equip health workers especially the nurses on snakebites so that rural dwellers whose health care needs are mainly attended to by nurses can be better managed when they suffer snakebites.

A Bayesian phase 2 model based adaptive design to optimise antivenom dosing: Application to a dose-finding trial for a novel Russell's viper antivenom in Myanmar

For most antivenoms there is little information from clinical studies to infer the relationship between dose and efficacy or dose and toxicity. Antivenom dose-finding studies usually recruit too few patients (e.g. fewer than 20) relative to clinically significant event rates (e.g. 5%). Model based adaptive dose-finding studies make efficient use of accrued patient data by using information across dosing levels, and converge rapidly to the contextually defined 'optimal dose'. Adequate sample sizes for adaptive dose-finding trials can be determined by simulation. We propose a model based, Bayesian phase 2 type, adaptive clinical trial design for the characterisation of optimal initial antivenom doses in contexts where both efficacy and toxicity are measured as binary endpoints. This design is illustrated in the context of dose-finding for Daboia siamensis (Eastern Russell's viper) envenoming in Myanmar. The design formalises the optimal initial dose of antivenom as the dose closest to that giving a pre-specified desired efficacy, but resulting in less than a pre-specified maximum toxicity. For Daboia siamensis envenoming, efficacy is defined as the restoration of blood coagulability within six hours, and toxicity is defined as anaphylaxis. Comprehensive simulation studies compared the expected behaviour of the model based design to a simpler rule based design (a modified '3+3' design). The model based design can identify an optimal dose after fewer patients relative to the rule based design. Open source code for the simulations is made available in order to determine adequate sample sizes for future adaptive snakebite trials. Antivenom dose-finding trials would benefit from using standard model based adaptive designs. Dose-finding trials where rare events (e.g. 5% occurrence) are of clinical importance necessitate larger sample sizes than current practice. We will apply the model based design to determine a safe and efficacious dose for a novel lyophilised antivenom to treat Daboia siamensis envenoming in Myanmar.

Interventions for the management of snakebite envenoming: An overview of systematic reviews

INTRODUCTION

Snakebite is a neglected tropical disease that leads to more than 120,000 deaths every year. In 2019, World Health Organization (WHO) launched a strategy to decrease its global burden by 2030. There is a range of issues around different interventions for the management of snakebite. Decisions around these interventions should be informed by evidence from systematic reviews (SR).

METHODS

An overview of SRs was conducted by searching 12 electronic databases, PROSPERO, contacting experts and screening the bibliography of included reviews. Screening, data extraction, and quality assessment (through AMSTAR-2) was done by at least two overview authors independently with discrepancies sorted by consensus. A narrative synthesis was conducted.

PRINCIPLE FINDINGS

The overview found 13 completed SRs that has looked at various aspects of management of snakebite envenomation. There was one SR on first aid, nine on effectiveness and safety of snake anti-venom (SAV), two on drugs to prevent adverse reactions due to SAV therapy, and one on surgical interventions for management of snakebite envenomation. All, except one, SR was appraised to have critically low confidence as per AMSTAR-2 Criteria. Evidence base was restricted to few studies for most interventions.

DISCUSSION

High quality evidence from SRs is required to inform guidelines and health system decisions which can bring down the burden of snakebite. The review indicates the need to fund high-quality SRs, evidence gaps and core outcome sets which can inform guideline recommendations, funding priorities for conduct of future trials. Variation in species distribution as well as intra-species variation in venom composition implies the need for conduct of region or, nation or state (sub-national) specific randomised controlled trials and SRs on different SAVs and their dosing regimens.

One Bite, Two Patients: Disparate Clinical Courses Following Simultaneous Crotalus oreganus abyssus Envenomation

A number of crotaline species have been associated with neurotoxic envenomation in North America. One clinical sign that can occur is myokymia: fine, involuntary, wave-like muscle movements occurring at regular intervals. We report an unusual scenario in which a single snakebite resulted in simultaneous envenomation of 2 patients. Both developed myokymia, with 1 having respiratory compromise. One patient also developed a hypersensitivity reaction to antivenom. Envenomation by the Grand Canyon rattlesnake, Crotalus oreganus abyssus, can produce significant neurotoxicity and resultant respiratory compromise. Antivenom may be helpful but can produce hypersensitivity reactions.

Adverse Reactions after Administration of Antivenom in Korea

Kovax® antivenom is the main treatment for toxins produced by the Gloydius species. However, research on adverse reactions after Kovax® antivenom administration is scarce. We aimed to identify the incidence and characteristics of adverse reactions after Kovax® antivenom administration. We conducted a retrospective review of the medical records of snakebite patients in Korea between January 2008 and September 2019. We identified the frequency, characteristics, and treatments of adverse reactions to Kovax® antivenom. There were 150 patients with snakebites, of whom 121 (80.7%) patients received Kovax® antivenom. Adverse reactions occurred in five patients (4.1%). Acute adverse reactions within 24 h of antivenom administration occurred in two patients (1.7%). The symptoms of patients with acute adverse reactions were nausea, diaphoresis, dizziness, and hypotension. Delayed adverse reactions that occurred 24 h after antivenom administration were reported in three patients (2.5%). One patient had a skin rash after 10 days, and two patients had fever 37 and 48 h after antivenom use. In conclusion, most patients were managed safely after Kovax® antivenom, and the incidence of adverse reactions was low. Severe adverse reactions occurred in a small percentage of patients, and there were no deaths.

What's eating you? bark scorpions (Centruroides exilicauda and Centruroides sculpturatus)

Centruroides is a common genus of bark scorpions in the United States with at least 21 species considered to be medically important, including the closely related Centruroides exilicauda and Centruroides sculpturatus. Stings from C exilicauda and C sculpturatus have been shown to cause fatality in children more often than in adults. More severe complications are caused by the neurotoxin released by Centruroides stings. Most stings can be managed at home, but for those patients who require treatment, antivenin has been shown to decrease time to symptom abatement.

Reviewing evidence of the clinical effectiveness of commercially available antivenoms in sub-Saharan Africa identifies the need for a multi-centre, multi-antivenom clinical trial

Background

Snakebite envenoming kills more than more than 20,000 people in Sub-Saharan Africa every year. Poorly regulated markets have been inundated with low-price, low-quality antivenoms. This review aimed to systematically collect and analyse the clinical data on all antivenom products now available in markets of sub-Saharan Africa.

Methodology/Principal findings

Our market analysis identified 12 polyspecific and 4 monospecific antivenom products in African markets. Our search strategy was first based on a systematic search of publication databases, followed by manual searches and discussions with experts. All types of data, including programmatic data, were eligible. All types of publications were eligible, including grey literature. Cohorts of less than 10 patients were excluded. 26 publications met the inclusion criteria. Many publications had to be excluded because clinical outcomes were not clearly linked to a specific product. Our narrative summaries present product-specific clinical data in terms of safety and effectiveness against the different species and envenoming syndromes. Three products (EchiTabPlus, EchiTabG, SAIMR-Echis-monovalent) were found to have been tested in robust clinical studies and found effective against envenoming caused by the West African carpet viper (Echis ocellatus). Four products (Inoserp-Panafricain, Fav-Afrique, SAIMR-Polyvalent, Antivipmyn-Africa) were found to have been evaluated only in observational single-arm studies, with varying results. For nine other products, there are either no data in the public domain, or only negative data suggesting a lack of effectiveness.

Conclusions/Significance

Clinical data vary among the different antivenom products currently in African markets. Some products are available commercially although they have been found to lack effectiveness. The World Health Organization should strengthen its capacity to assess antivenom products, support antivenom manufacturers, and assist African countries and international aid organizations in selecting appropriate quality antivenoms.

Snakebite envenomation represents one of the most neglected tropical medical conditions worldwide. Despite high levels of morbidity and mortality associated with snakebite, its neglected nature has compromised the availability and evaluation of antivenom treatment. This review was initiated by Médecins Sans Frontières’ / Doctors Without Borders (MSF) Access Campaign, as the existing antivenom access crisis in sub-Saharan Africa was deepening. This study sought to review the clinical data pertaining to each antivenom product currently available for use in sub-Saharan Africa. 16 different antivenoms were identified. A total of 26 studies met the inclusion criteria. Given the heterogeneity of study methodology and quality, data for individual antivenoms are presented in the form of a narrative analysis. Only two studies reported clinical data collected from randomized controlled trials. Consistent monitoring of the side effects of antivenom treatment was lacking. The absence of good quality data for the majority of antivenoms in sub-Saharan Africa is a major concern. Further robust data collection is required, while urgent investments are needed at the global level to ensure a sustained production of safe and effective antivenom treatment, and its affordable access across sub-Saharan Africa.

Safety and efficacy of a freeze-dried trivalent antivenom for snakebites in the Brazilian Amazon: An open randomized controlled phase IIb clinical trial

BACKGROUND

In tropical areas, a major concern regarding snakebites treatment effectiveness relates to the failure in liquid antivenom (AV) distribution due to the lack of an adequate cold chain in remote areas. To minimize this problem, freeze-drying has been suggested to improve AV stability.

METHODS AND FINDINGS

This study compares the safety and efficacy of a freeze-dried trivalent antivenom (FDTAV) and the standard liquid AV provided by the Brazilian Ministry of Health (SLAV) to treat Bothrops, Lachesis and Crotalus snakebites. This was a prospective, randomized, open, phase IIb trial, carried out from June 2005 to May 2008 in the Brazilian Amazon. Primary efficacy endpoints were the suppression of clinical manifestations and return of hemostasis and renal function markers to normal ranges within the first 24 hours of follow-up. Primary safety endpoint was the presence of early adverse reactions (EAR) in the first 24 hours after treatment. FDTAV thermal stability was determined by estimating AV potency over one year at 56°C. Of the patients recruited, 65 and 51 were assigned to FDTAV and SLAV groups, respectively. Only mild EARs were reported, and they were not different between groups. There were no differences in fibrinogen (p = 0.911) and clotting time (p = 0.982) recovery between FDTAV and SLAV treated groups for Bothrops snakebites. For Lachesis and Crotalus snakebites, coagulation parameters and creatine phosphokinase presented normal values 24 hours after AV therapy for both antivenoms.

CONCLUSIONS/SIGNIFICANCE

Since promising results were observed for efficacy, safety and thermal stability, our results indicate that FDTAV is suitable for a larger phase III trial.

TRIAL REGISTRATION

ISRCTNregistry: ISRCTN12845255; DOI: 10.1186/ISRCTN12845255 (http://www.isrctn.com/ISRCTN12845255).

A prospective cohort study of the effectiveness of the primary hospital management of all snakebites in Kurunegala district of Sri Lanka

INTRODUCTION

Sri Lanka records substantial numbers of snakebite annually. Primary rural hospitals are important contributors to health care. Health care planning requires a more detailed understanding of snakebite within this part of the health system. This study reports the management and epidemiology of all hospitalised snakebite in the Kurunegala district in Sri Lanka.

METHODOLOGY

The district has 44 peripheral/primary hospitals and a tertiary care hospital-Teaching Hospital, Kurunegala (THK). This prospective study was conducted over one year. All hospitals received copies of the current national guidelines on snakebite management. Clinical and demographic details of all snakebite admissions to primary hospitals were recorded by field researchers and validated by comparing with scanned copies of the medical record. Management including hospital transfers was independently assessed against the national guidelines recommendation. Population rates were calculated and compared with estimates derived from recent community based surveys.

RESULTS

There were 2186 admissions of snakebites and no deaths in primary hospitals. An additional 401 patients from the district were admitted directly to the teaching hospital, 2 deaths were recorded in this group. The population incidence of hospitalized snakebite was 158/100,000 which was significantly lower than community survey estimates of 499/100,000. However there was no significant difference between the incidence of envenomation of 126/100,000 in hospitalised patients and 184/100,000 in the community survey. The utilisation of antivenom was appropriate and consistent with guidelines. Seventy patients received antivenom. Anaphylactic reactions to antivenom occurred in 22 patients, treatment reactions was considered to be outside the guidelines in 5 patients. Transfers from the primary hospital occurred in 399(18%) patients but the majority (341) did not meet the guideline criteria. A snake was identified in 978 cases; venomous snakebites included 823 hump-nosed viper (Hypnalespp), 61 Russell's viper, 14 cobra, 13 common krait, 03 saw scaled viper.

CONCLUSIONS

Primary hospitals received a significant number of snakebites that would be missed in surveys conducted in tertiary hospitals. Adherence to guidelines was good for the use of antivenom but not for hospital transfer or treatment of anaphylaxis. The large difference in snakebite incidence between community and hospital studies could possibly be due to non-envenomed patients not presenting. As the majority of snakebite management occurs in primary hospitals education and clinical support should be focused on that part of the health system.

Dose of antivenom for the treatment of snakebite with neurotoxic envenoming: Evidence from a randomised controlled trial in Nepal

BACKGROUND

Currently, there is inadequate evidence on which to base clinical management of neurotoxic snakebite envenoming, especially in the choice of initial antivenom dosage. This randomised controlled trial compared the effectiveness and safety of high versus low initial antivenom dosage in victims of neurotoxic envenoming.

METHODOLOGY/ PRINCIPAL FINDINGS

This was a balanced, randomised, double-blind trial that was conducted in three health care centers located in the Terai plains of Nepal. Participants received either low (two vials) or high (10 vials) initial dosage of Indian polyvalent antivenom. The primary composite outcome consisted of death, the need for assisted ventilation and worsening/recurrence of neurotoxicity. Hourly evaluations followed antivenom treatment. Between April 2011 and October 2012, 157 snakebite victims were enrolled, of which 154 were analysed (76 in the low and 78 in the high initial dose group). Sixty-seven (43·5%) participants met the primary outcome definition. The proportions were similar in the low (37 or 48.7%) vs. high (30 or 38.5%) initial dose group (difference = 10·2%, 95%CI [-6·7 to 27·1], p = 0·264). The mean number of vials used was similar between treatment groups. Overall, patients bitten by kraits did worse than those bitten by cobras. The occurrence of treatment-related adverse events did not differ among treatment groups. A total of 19 serious adverse events occurred, including seven attributed to antivenom.

CONCLUSIONS

This first robust trial investigating antivenom dosage for neurotoxic snakebite envenoming shows that the antivenom currently used in Nepal performs poorly. Although the high initial dose regimen is not more effective than the low initial dose, it offers the practical advantage of being a single dose, while not incurring higher consumption or enhanced risk of adverse reaction. The development of new and more effective antivenoms that better target the species responsible for bites in the region will help improve future patients' outcomes.

TRIAL REGISTRATION

The study was registered on clinicaltrials.gov (NCT01284855) (GJ 5/1).

Adverse reactions to snake antivenom, and their prevention and treatment

Antivenom is the mainstay of treatment of snakebite envenoming. However, adverse reactions to snake antivenom that is available are common in many parts of the world where snakebite is prevalent. Both acute (anaphylactic or pyrogenic) and delayed (serum sickness type) reactions occur. Acute reactions are usually mild but severe systemic anaphylaxis may develop, often within an hour or so of exposure to antivenom. Serum sickness after antivenom has a delayed onset between 5 and 14 days after its administration. Ultimately, the prevention reactions will depend mainly on improving the quality of antivenom. Until these overdue improvements take place, doctors will have to depend on pharmacological prophylaxis, where the search for the best prophylactic agent is still on-going, as well as careful observation of patients receiving antivenom in preparation for prompt management of acute as well as delayed reactions when they occur.

Venomous snakebites in children in southern Croatia

This retrospective study represents observation of 160 children and adolescents aged up to 18 years that experienced venomous snakebites in southern Croatia and were treated in the Clinical Department of Infectious Diseases in the University Hospital Centre Split from 1979 to 2013. The main purpose of this research was to determine the epidemiological characteristics, clinical presentation, local and general complications, and received treatment. Most bites occurred during warm months, from early May to late August (80%), mostly in May and June. Upper limb bites were more frequent (59%) than lower limb bites (40%). Out of the total number of poisoned children, 24% developed local, and 25% general complications. The most common local complications were haemorrhagic blisters that occurred in 20% children, followed by compartment syndrome presented in 7.5% patients. The most dominated general complication was cranial nerve paresis or paralysis, which was identified in 11.2% patients, whereas shock symptoms were registrated in 7% children. According to severity of poisoning, 9.4% children had minor, 35% mild, 30.6% moderate, and 24.4% had severe clinical manifestation of envenomation. Only one (0.6%) child passed away because of snakebite directly on the neck. All patients received antivenom produced by the Institute of Immunology in Zagreb, tetanus prophylaxis as well, and almost all of them received antibiotics, and a great majority of them also received corticosteroids and antihistamines. Neighter anaphylactic reaction nor serum disease were noticed in our patients after administrating antivenom. A total of 26% children underwent surgical interventions, and incision of haemorrhagic blister was the most common applied surgical treatment, which was preformed in 15.6% patients, while fasciotomy was done in 7.5% subjects. All of our surgically treated patients recovered successfully.

Cost-effectiveness of antivenoms for snakebite envenoming in Nigeria

Background

Snakebite envenoming is a major public health problem throughout the rural tropics. Antivenom is effective in reducing mortality and remains the mainstay of therapy. This study aimed to determine the cost-effectiveness of using effective antivenoms for Snakebite envenoming in Nigeria.

Methodology

Economic analysis was conducted from a public healthcare system perspective. Estimates of model inputs were obtained from the literature. Incremental Cost Effectiveness Ratios (ICERs) were quantified as deaths and Disability-Adjusted-Life-Years (DALY) averted from antivenom therapy. A decision analytic model was developed and analyzed with the following model base-case parameter estimates: type of snakes causing bites, antivenom effectiveness to prevent death, untreated mortality, risk of Early Adverse Reactions (EAR), mortality risk from EAR, mean age at bite and remaining life expectancy, and disability risk (amputation). End-user costs applied included: costs of diagnosing and monitoring envenoming, antivenom drug cost, supportive care, shipping/freezing antivenom, transportation to-and-from hospital and feeding costs while on admission, management of antivenom EAR and free alternative snakebite care for ineffective antivenom.

Principal Findings

We calculated a cost/death averted of ($2330.16) and cost/DALY averted of $99.61 discounted and $56.88 undiscounted. Varying antivenom effectiveness through the 95% confidence interval from 55% to 86% yield a cost/DALY averted of $137.02 to $86.61 respectively. Similarly, varying the prevalence of envenoming caused by carpet viper from 0% to 96% yield a cost/DALY averted of $254.18 to $78.25 respectively. More effective antivenoms and carpet viper envenoming rather than non-carpet viper envenoming were associated with lower cost/DALY averted.

Conclusions/Significance

Treatment of snakebite envenoming in Nigeria is cost-effective with a cost/death averted of $2330.16 and cost/DALY averted of $99.61 discounted, lower than the country's gross domestic product per capita of $1555 (2013). Expanding access to effective antivenoms to larger segments of the Nigerian population should be a considered a priority.

Snake bite is a major public health problem throughout rural communities in West Africa and leads to a significant number of deaths and disabilities per year. Even though effective antivenoms exist against the locally prevalent carpet viper and other poisonous snakes, they are generally not available in community settings, possibly because of their high acquisition cost. We evaluated the cost-effectiveness of making antivenom more broadly available in Nigeria by comparing the treatment costs associated with antivenom therapy against their medical benefit in reducing the risk of mortality. We find that the incremental cost effectiveness ratio (ICER) associated with making antivenom available in Nigeria was $2,330 per death averted and $100 per disability adjusted life year (DALY) averted. Both of these suggest that snakebite antivenom is highly cost-effective in Nigeria and they also compare very favorably against other commonly funded health interventions for which similar estimates exist. Since a substantial reduction in mortality and DALYs could be achieved at a relatively modest upfront cost, expanding access to antivenom to broader parts of the population should be a priority consideration for future investments in healthcare.

Immune response to snake envenoming and treatment with antivenom; complement activation, cytokine production and mast cell degranulation

Background

Snake bite is one of the most neglected public health issues in poor rural communities worldwide. In addition to the clinical effects of envenoming, treatment with antivenom frequently causes serious adverse reactions, including hypersensitivity reactions (including anaphylaxis) and pyrogenic reactions. We aimed to investigate the immune responses to Sri Lankan snake envenoming (predominantly by Russell's viper) and antivenom treatment.

Methodology/Principal Findings

Plasma concentrations of Interleukin (IL)-6, IL-10, tumor necrosis factor α (TNFα), soluble TNF receptor I (sTNFRI), anaphylatoxins (C3a, C4a, C5a; markers of complement activation), mast cell tryptase (MCT), and histamine were measured in 120 Sri Lankan snakebite victims, both before and after treatment with antivenom. Immune mediator concentrations were correlated with envenoming features and the severity of antivenom-induced reactions including anaphylaxis. Envenoming was associated with complement activation and increased cytokine concentrations prior to antivenom administration, which correlated with non-specific systemic symptoms of envenoming but not with coagulopathy or neurotoxicity. Typical hypersensitivity reactions to antivenom occurred in 77/120 patients (64%), satisfying criteria for a diagnosis of anaphylaxis in 57/120 (48%). Pyrogenic reactions were observed in 32/120 patients (27%). All patients had further elevations in cytokine concentrations, but not complement activation, after the administration of antivenom, whether a reaction was noted to occur or not. Patients with anaphylaxis had significantly elevated concentrations of MCT and histamine.

Conclusions/Significance

We have demonstrated that Sri Lankan snake envenoming is characterized by significant complement activation and release of inflammatory mediators. Antivenom treatment further enhances the release of inflammatory mediators in all patients, with anaphylactic reactions characterised by high levels of mast cell degranulation but not further complement activation. Anaphylaxis is probably triggered by non allergen-specific activation of mast cells and may be related to the quality of available antivenom preparations, as well as a priming effect from the immune response to the venom itself.

Snakebites cause life-threatening symptoms including uncontrolled bleeding and paralysis. The body's immune responses to snake venom may contribute to the severity of these symptoms but have not been well characterized in humans. Treatment with antivenom is potentially lifesaving, but also carries risk, as severe allergic reactions (anaphylaxis) are common. Anaphylaxis occurs when mast cells, triggered by either allergen-specific antibodies, other immunological mechanisms, or non-immune mechanisms, release mediators that cause skin rashes, shortness of breath and, in severe cases, life-threatening hypotension and/or hypoxia. We have studied 120 snakebite victims in Sri Lanka, both before and after treatment with antivenom. Our results have shown snakebite triggers activation of the complement cascade (an important part of the body's innate immune defence) and production of proinflammatory mediators. In addition, we have demonstrated a quite astonishing level of immune activation after antivenom treatment in virtually every person treated, regardless of whether they had a reaction to the antivenom. Half of the patients treated experienced anaphylaxis, with clear evidence of mast cell activation. Anaphylaxis to antivenom is unlikely to be triggered by allergen-specific antibodies, as patients had not been previously exposed to antivenom, but may be related to the quality of available antivenom preparations, as well as a priming effect from the immune response to the venom itself.

A randomized controlled trial of fresh frozen plasma for treating venom-induced consumption coagulopathy in cases of Australian snakebite (ASP-18)

BACKGROUND

Venom-induced consumption coagulopathy (VICC) is a major effect of snake envenoming.

OBJECTIVES

To investigate whether fresh frozen plasma (FFP) given after antivenom resulted in more rapid correction of coagulation.

PATIENTS/METHODS

This was a multicenter open-label randomized controlled trial in patients with VICC of FFP vs. no FFP within 4 h of antivenom administration. Patients (> 2 years) recruited to the Australian snakebite project with VICC (International Normalized Ratio [INR] > 3) were eligible. Patients were randomized 2 : 1 to receive FFP or no FFP. The primary outcome was the proportion with an INR of < 2 at 6 h after antivenom administration. Secondary outcomes included time from antivenom administration to discharge, adverse effects, major hemorrhage, and death.

RESULTS

Of 70 eligible patients, 65 consented to be randomized: 41 to FFP, and 24 to no FFP. Six hours after antivenom administration, more patients randomized to FFP had an INR of < 2 (30/41 [73%] vs. 6/24 [25%]; absolute difference, 48%; 95% confidence interval 23-73%; P = 0.0002). The median time from antivenom administration to discharge was similar (34 h, range 14-230 h vs. 39 h, range 14-321 h; P = 0.44). Seven patients developed systemic hypersensitivity reactions after antivenom administration - two mild and one severe (FFP arm), and three mild and one severe (no FFP). One serious adverse event (intracranial hemorrhage and death) occurred in an FFP patient with pre-existing hypertension, who was hypertensive on admission, and developed a headache 6 h after FFP administration. Post hoc analysis showed that the median time from bite to FFP administration was significantly shorter for non-responders to FFP than for responders (4.7 h, interquartile range [IQR] 4.2-6.7 h vs. 7.3 h, IQR 6.1-8 h; P = 0.002).

CONCLUSIONS

FFP administration after antivenom administration results in more rapid restoration of clotting function in most patients, but no decrease in discharge time. Early FFP administration (< 6-8 h) post-bite is less likely to be effective.

[Role of antivenoms in the treatment of snake envenomation]

The production of antivenoms, which were long deemed ineffective, dangerous and difficult to use, has improved dramatically. These antibodies (immunoglobulin G) are now fragmented, purified and controlled for their quality, leading to significantly better safety and facilitating their emergency use. Envenomation can result in various syndromes depending on the snake species: Viperidae venoms are highly inflammatory, hemorrhagic and necrotising, while Elapidae venoms can cause fatal respiratory paralysis. However, some Viperidae venoms can lead to asphyxiation similar to that observed in Elapidae envenomation while, conversely, Elapidae bites may be complicated by hemorrhage or necrosis, thus complicating etiologic diagnosis. Symptomatic treatment is complex, often insufficient, and frequently associated with adverse events. In contrast, antivenoms neutralize the venom and accelerate its clearance, thus providing an etiological treatment for envenomation, particularly in remote healthcare facilities in developing countries. Current formulations consist of polyvalent antivenoms covering most of the venomous species present in a specific region. The main limitation is their high cost, and the priority should be to develop new treatment strategies, including more affordable antivenoms, especially in developing countries where they are most needed.

Characterization of the aqueous extract of the root of Aristolochia indica: evaluation of its traditional use as an antidote for snake bites

ETHNOPHARMACOLOGICAL RELEVANCE

The aqueous extract of the roots of Aristolochia indica is used as a decoction for the ailment of a number of diseases including snake bite treatment. Though the alcoholic extract of the different parts of the plant are well studied, information on the aqueous extract is limited. We have estimated aristolochic acid, different enzymes, enzyme inhibitors and anti-snake venom potency of its root extract.

MATERIALS AND METHODS

Reverse phase-HPLC was used to quantify aristolochic acid. Zymography, DQ-gelatin assay and atomic force microscopy were done to demonstrate gelatinase and collagenase activities of the extract. SDS-PAGE followed by MS/MS analysis revealed the identity of major protein components. Toxicity of the extract was estimated on animal model. Interaction of the extract with Russell's viper venom components was followed by Rayleigh scattering and enzyme assay.

RESULTS

The aristolochic acid content of the root extract is 3.08 ± 1.88 × 10(-3)mg/ml. The extract possesses strong gelatinolytic, collagenase, peroxidase and nuclease activities together with l-amino acid oxidase and protease inhibitory potencies. Partial proteomic studies indicated presence of starch branching enzymes as major protein constituent of the extract. The extract did not show any acute and sub-chronic toxicity in animals at lower doses, but high dose causes liver and kidney damage. The extract elongated duration of survival of animals after application of Russell's viper venom.

CONCLUSIONS

Considering the low aristolochic acid content of the extract, its consumption for a short time at moderate dose does not appear to cause serious toxicity. Strong inhibition of l-amino acid oxidase may give partial relief from snake bite after topical application of the extract.

Emerging options for the management of scorpion stings

Scorpion stings are common in many tropical countries. Although most scorpion stings cause only localized pain without life-threatening envenoming, about one third of stings cause systemic envenoming which can result in death. Children are particularly sensitive to scorpion envenoming. The severity of scorpion stings is related to the presence of neurotoxins in the venom that cause a sudden release of neurotransmitters from the autonomic nervous system, predominantly sympathetic. There is also a strong inflammatory response that worsens symptoms, including those of a respiratory nature. Several vital functions may be directly affected, including the cardiovascular, respiratory, and neuromuscular systems. Hypertension is constant at the beginning of systemic envenoming and sometimes has a severe cardiac and respiratory impact. Although controversial, immunotherapy is the only etiological treatment. Administered early, it prevents many complications and improves the outcome. New antivenoms are highly purified immunoglobulin fragments, the efficacy and safety of which are excellent. As a consequence, adverse reactions to antivenoms are now very rare and usually mild, which should limit any reluctance regarding their routine use. Symptomatic treatment is still necessary to support immunotherapy, especially in cases of delayed arrival at hospital. A combination of both approaches should be considered, based on local resources and constraints.

Incidence of immediate hypersensitivity reaction and serum sickness following administration of Crotalidae polyvalent immune Fab antivenom: a meta-analysis

OBJECTIVES

  Crotalidae polyvalent immune Fab (ovine) (FabAV) is commonly used in the treatment of symptomatic North American crotaline snake envenomation. When approved by the U.S. Food and Drug Administration in 2000, the incidences of immediate hypersensitivity reactions and serum sickness were reported as 0.14 and 0.18, respectively. The objective of this meta-analysis was to evaluate the incidence of immediate hypersensitivity reactions and serum sickness reported in studies of patients treated with FabAV therapy after North American crotaline envenomation.

METHODS

  The authors searched PubMed, Ovid MEDLINE, and EMBASE from January 1, 1997, to September 20, 2010, for English-language medical literature and cross-referenced bibliographies of reviewed articles. The published abstracts of the major toxicology conferences were also searched. All prospective and retrospective cohort studies with patients receiving FabAV therapy for North American crotaline envenomations were eligible for data abstraction. Two content experts reviewed full-text articles and extracted relevant study design and outcome data. Proportions of immediate hypersensitivity and serum sickness for each study were analyzed in a random-effects model to produce an overall estimate of immediate hypersensitivity and serum sickness incidence associated with FabAV administration.

RESULTS

  The literature search revealed 11 unique studies of patients who received FabAV that contained information on immediate hypersensitivity reactions and serum sickness. The meta-analysis produced a combined estimate of the incidence of immediate hypersensitivity of 0.08 (95% confidence interval [CI] = 0.05 to 0.11) and a combined estimate of the incidence of serum sickness of 0.13 (95% CI = 0.07 to 0.21).

CONCLUSIONS

  In this systematic literature review and meta-analysis, the combined estimates of the incidence of immediate hypersensitivity reactions and serum sickness from FabAV in the treatment of symptomatic North American crotaline envenomations appear to be lower than previously reported, at 0.08 and 0.13, respectively.

[FAV-Africa: a polyvalent antivenom serum used in Africa and Europe]

FAV-Afrique is a polyvalent snake antivenom, elaborated by immunisation of horses with venom from 10 different snake species among the most dangerous in Africa and belonging to Elapidae and Viperidea families. Only F(ab')2 fragments are kept and purified. This serum is able to decrease the quantity of circulating venom and therefore its toxicity. Its use is indicated as soon as the first signs of poisoning are observed (local oedema). Twenty millimetres are administrated via intra-venous route whatever the weight of the patient. Re-administration may be performed if improvement is not sufficient. Treatment should be initiated as soon as possible but can be realized as long as the symptoms are present. Side effects (allergy) should be considered but balanced with the seriousness of poisoning. There is no absolute contraindication or drug interaction reported with FAV-Africa. It is authorized and distributed in several African countries and has a temporary regulatory approval in France. The major limits to its use are high cost and storage conditions (maximum 36 months between +2 degrees C and +8 degrees C). In the future, the new serum Antivipmyn Africa, available as a freeze-dried product, which can be preserved at room temperature, should improve storage conditions and availability of treatment, especially in rural Africa.

Epidemiology of snakebites in Europe: a systematic review of the literature

Snakebites are rare medical emergency cases in Europe but may sometimes be severe and lead to complications. A better knowledge of snakebite epidemiology may help health authorities to better understand therapeutic requirements, especially concerning antivenoms, and thus improve treatment of snakebite. An extensive literature search for studies and articles published between 1970 and 2010 was performed. Both indexed and non-indexed articles were examined, the analysis of which took into account the heterogeneity between the studies and weighted the studies according to size of the study population covered. Most of the articles involved hospitalized patients who represented more than 90% of snakebites. Incidence, mortality and population at risk were estimated after stratification into three regions (northern, central and southern Europe) based both on viper species distribution and climatic characteristics. There was no significant variation in incidence from the north to the south of Europe. In the whole of Europe, including European Russia and Turkey, the annual number of snakebite cases was estimated at 7992 [CI 95% = 6860-9178] bites, out of which approximately 15% were considered severe (grade 3). These bites usually occurred between May and September, with a more dispersed distribution in southern Europe. The average number of deaths per annum was 4 [0.7-7.7]. Children and male victims are more affected, contrary to what one would expect given their respective proportion in the entire population. Both upper and lower limb bites were recorded at an equal frequency while the bites in other parts of the body were very rare. Immunotherapy was prescribed in one out of three snakebites in Europe, with a very high geographical variability, in spite of excellent tolerance, at least considering highly-purified immunoglobulin fragments. Snakebites are uncommon in Europe but can cause life-threatening envenomation. Fragments of highly-purified immunoglobulins are now very well tolerated and dramatically reduce both severity and mortality of snakebites when used in treatment.

Low-dose adrenaline, promethazine, and hydrocortisone in the prevention of acute adverse reactions to antivenom following snakebite: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Envenoming from snakebites is most effectively treated by antivenom. However, the antivenom available in South Asian countries commonly causes acute allergic reactions, anaphylactic reactions being particularly serious. We investigated whether adrenaline, promethazine, and hydrocortisone prevent such reactions in secondary referral hospitals in Sri Lanka by conducting a randomised, double-blind placebo-controlled trial.

METHODS AND FINDINGS

In total, 1,007 patients were randomized, using a 2 × 2 × 2 factorial design, in a double-blind, placebo-controlled trial of adrenaline (0.25 ml of a 1∶1,000 solution subcutaneously), promethazine (25 mg intravenously), and hydrocortisone (200 mg intravenously), each alone and in all possible combinations. The interventions, or matching placebo, were given immediately before infusion of antivenom. Patients were monitored for mild, moderate, or severe adverse reactions for at least 96 h. The prespecified primary end point was the effect of the interventions on the incidence of severe reactions up to and including 48 h after antivenom administration. In total, 752 (75%) patients had acute reactions to antivenom: 9% mild, 48% moderate, and 43% severe; 89% of the reactions occurred within 1 h; and 40% of all patients were given rescue medication (adrenaline, promethazine, and hydrocortisone) during the first hour. Compared with placebo, adrenaline significantly reduced severe reactions to antivenom by 43% (95% CI 25-67) at 1 h and by 38% (95% CI 26-49) up to and including 48 h after antivenom administration; hydrocortisone and promethazine did not. Adding hydrocortisone negated the benefit of adrenaline.

CONCLUSIONS

Pretreatment with low-dose adrenaline was safe and reduced the risk of acute severe reactions to snake antivenom. This may be of particular importance in countries where adverse reactions to antivenom are common, although the need to improve the quality of available antivenom cannot be overemphasized.

Unified treatment algorithm for the management of crotaline snakebite in the United States: results of an evidence-informed consensus workshop

BACKGROUND

Envenomation by crotaline snakes (rattlesnake, cottonmouth, copperhead) is a complex, potentially lethal condition affecting thousands of people in the United States each year. Treatment of crotaline envenomation is not standardized, and significant variation in practice exists.

METHODS

A geographically diverse panel of experts was convened for the purpose of deriving an evidence-informed unified treatment algorithm. Research staff analyzed the extant medical literature and performed targeted analyses of existing databases to inform specific clinical decisions. A trained external facilitator used modified Delphi and structured consensus methodology to achieve consensus on the final treatment algorithm.

RESULTS

A unified treatment algorithm was produced and endorsed by all nine expert panel members. This algorithm provides guidance about clinical and laboratory observations, indications for and dosing of antivenom, adjunctive therapies, post-stabilization care, and management of complications from envenomation and therapy.

CONCLUSIONS

Clinical manifestations and ideal treatment of crotaline snakebite differ greatly, and can result in severe complications. Using a modified Delphi method, we provide evidence-informed treatment guidelines in an attempt to reduce variation in care and possibly improve clinical outcomes.

Efficacy and safety of scorpion antivenom plus prazosin compared with prazosin alone for venomous scorpion (Mesobuthus tamulus) sting: randomised open label clinical trial

OBJECTIVE

Envenomation by Mesobuthus tamulus scorpion sting can result in serious cardiovascular effects. Scorpion antivenom is a specific treatment for scorpion sting. Evidence for the benefit of scorpion antivenom and its efficacy compared with that of commonly used vasodilators, such as prazosin, is scarce. We assessed the efficacy of prazosin combined with scorpion antivenom, compared with prazosin alone, in individuals with autonomic storm caused by scorpion sting.

DESIGN

Prospective, open label randomised controlled trial.

SETTING

General hospital inpatients (Bawaskar Hospital and Research Centre Mahad Dist-Raigad Maharashtra, India).

PARTICIPANTS

Seventy patients with grade 2 scorpion envenomation, older than six months, with no cardiorespiratory or central nervous system abnormalities.

INTERVENTION

Scorpion antivenom plus prazosin (n=35) or prazosin alone (n=35) assigned by block randomisation. Treatment was not masked. Analysis was by intention to treat.

MAIN OUTCOME MEASURES

The primary end point was the proportion of patients achieving resolution of the clinical syndrome (sweating, salivation, cool extremities, priapism, hypertension or hypotension, tachycardia) 10 hours after administration of study drugs. Secondary end points were time required for complete resolution of clinical syndrome, prevention of deterioration to higher grade, doses of prazosin required overall and within 10 hours, and adverse events. The study protocol was approved by the independent ethics committee of Mumbai.

RESULTS

Mean (SD) recovery times in hours for the prazosin plus scorpion antivenom group compared with the prazosin alone groups were: sweating 3 (1.1) v 6.6 (2.6); salivation 1.9 (0.9) v 3 (1.9); priapism 4.7 (1.5) v 9.4 (1.5). Mean (SD) doses of prazosin in the groups were 2 (2.3) and 4 (3.5), respectively. 32 patients (91.4%, 95% confidence interval 76.9% to 97.8%) in the prazosin plus antivenom group showed complete resolution of the clinical syndrome within 10 hours of administration of treatment compared with eight patients in the prazosin group (22.9%, 11.8% to 39.3%). Patients from the antivenom plus prazosin group recovered earlier (mean 8 hours, 95% CI 6.5 to 9.5) than those in the control group (17.7 hours, 15.4 to 19.9; mean difference -9.7 hours, -6.9 to -12.4). The number of patients whose condition deteriorated to a higher grade was similar in both groups (antivenom plus prazosin four of 35, prazosin alone five of 35). Hypotension was reported in fewer patients in the antivenom plus prazosin group (12 of 35, 34.3%) than in the prazosin group (19 of 35, 54.3%), but the difference was not statistically significant. No difference was noted in change in blood pressure and pulse rate over time between two groups.

CONCLUSION

Recovery from scorpion sting is hastened by simultaneous administration of scorpion antivenom plus prazosin compared with prazosin alone.

TRIAL REGISTRATION NUMBER

CTRI/2010/091/000584 (Clinical Trials Registry India).

Surveillance of the clinical use of mamushi (Gloydius blomhoffii) antivenom in tertiary care centers in Japan

We report the results of the first large-scale questionnaire surveillance on the clinical use of pit viper antivenom in tertiary care centers in Japan. The questionnaire surveillance was conducted over a period of 3 years (April 2006 to March 2009). Completed questionnaires were received from the tertiary care centers of 108 (49.3%) medical institutions. In that period, 574 cases of pit viper bites, including 2 severe cases, were reported. Antivenom was administered in 44% of the cases of pit viper bites, and of these cases, 2.4% had adverse reactions but no severe symptoms. Approximately half of the clinicians indicated that antivenom was effective. Antivenom was recognized to be safe; however, the remarkable finding was that although the severity of treated cases was unclear, some clinicians reported using cepharanthine as the first choice of treatment for pit viper bites.

Antivenin-related serum sickness

Serum sickness is a type III hypersensitivity reaction that occurs due to the deposition of excessive circulating immune complexes in patients treated with foreign proteins or haptens. Serum sickness induced by antivenin for snakebites has been frequently reported in the USA, but not in Taiwan. This difference may be due to the efficacy and dosage of antivenins administered to treat snakebites in Taiwan. We report a case presenting with serum sickness after receiving a total of 20 vials of polyvalent antivenin therapy for the treatment of snakebite. A 59-year-old male suffered from fever, headaches, polyarthritis, and diffused skin rash approximately 10 days after administration of the antivenin. The large dose of antivenin administered in this case might have been the cause of the development of serum sickness. Physicians should be aware of the potential for serum sickness in cases of large-dose antivenin use.

Acute demyelinating encephalomyelitis after anti-venom therapy in Russell's viper bite

INTRODUCTION

Russell's viper is a commonly encountered venomous snake in India. Morbidity and mortality following envenomation and the treatment thereof are frequent. We report a rarely seen complication after a treated Russell's viper bite.

CASE REPORT

A 36-year-old male farmer received 30 vials polyvalent anti-snake venom after a viper bite to his right leg. Improvement in initial hematemesis and circulatory shock was followed by acute renal failure managed with regular hemodialysis. He displayed no abnormalities on neurological examination at admission. Fourth day onwards his neurologic status started deteriorating with development of behavioral abnormalities, hemi-spatial neglect of left upper limb, paralysis of left facial nerve, left upper limb, and right lower limb. Acute disseminated encephalomyelitis was confirmed on magnetic resonance imaging (MRI) of brain with typical spectroscopic characteristics. High dose methyl prednisolone was administered and a rapid recovery followed.

CONCLUSION

Russell's viper bite followed by treatment with antivenom may be complicated by the development of immune complex mediated demyelination and development of acute disseminated encephalomyelitis. MRI spectroscopy helps in early identification of demyelination and in a definite diagnosis. Treatment with corticosteroids was associated with resolution of symptoms in this case.

Randomised controlled double-blind non-inferiority trial of two antivenoms for saw-scaled or carpet viper (Echis ocellatus) envenoming in Nigeria

BACKGROUND

In West Africa, envenoming by saw-scaled or carpet vipers (Echis ocellatus) causes great morbidity and mortality, but there is a crisis in supply of effective and affordable antivenom (ISRCTN01257358).

METHODS

In a randomised, double-blind, controlled, non-inferiority trial, "EchiTAb Plus-ICP" (ET-Plus) equine antivenom made by Instituto Clodomiro Picado was compared to "EchiTAb G" (ET-G) ovine antivenom made by MicroPharm, which is the standard of care in Nigeria and was developed from the original EchiTAb-Fab introduced in 1998. Both are caprylic acid purified whole IgG antivenoms. ET-G is monospecific for Echis ocellatus antivenom (initial dose 1 vial) and ET-Plus is polyspecific for E. ocellatus, Naja nigricollis and Bitis arietans (initial dose 3 vials). Both had been screened by pre-clinical and preliminary clinical dose-finding and safety studies. Patients who presented with incoagulable blood, indicative of systemic envenoming by E. ocellatus, were recruited in Kaltungo, north-eastern Nigeria. Those eligible and consenting were randomly allocated with equal probability to receive ET-Plus or ET-G. The primary outcome was permanent restoration of blood coagulability 6 hours after the start of treatment, assessed by a simple whole blood clotting test repeated 6, 12, 18, 24 and 48 hr after treatment. Secondary (safety) outcomes were the incidences of anaphylactic, pyrogenic and late serum sickness-type antivenom reactions.

FINDINGS

Initial doses permanently restored blood coagulability at 6 hours in 161/194 (83.0%) of ET-Plus and 156/206 (75.7%) of ET-G treated patients (Relative Risk [RR] 1.10 one-sided 95% CI lower limit 1.01; P = 0.05). ET-Plus caused early reactions on more occasions than did ET-G [50/194 (25.8%) and 39/206 (18.9%) respectively RR (1.36 one-sided 95% CI 1.86 upper limit; P = 0.06). These reactions were classified as severe in 21 (10.8%) and 11 (5.3%) of patients, respectively.

CONCLUSION

At these doses, ET-Plus was slightly more effective but ET-G was slightly safer. Both are recommended for treating E. ocellatus envenoming in Nigeria.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN01257358.

Snakebites in Mostar region, Bosnia and Herzegovina

The aim of this study was to provide an overview of the snakebites in patients hospitalized at the Mostar Clinical Hospital, admitted between 1983 and 2006. A total of 341 patients were recorded, with moderate men predominance (52.8%). Majority of patients were bitten for the first time (99.1%). In 98.8% of patients snakebite occurred to the bare skin, most commonly during June to September period (64.2%). Snakebites were the commonest in agricultural workers (48.1%). Until 2003 all admitted patients were treated according to Russel's scheme (3-anti). As of 2003 new treatment scheme was applied, resulting in the reduction of antidote and supportive treatment use, causing a reduction in the number of clinically apparent allergic reactions. Serum sickness was recorded in only 2 patients, while lethal outcome was recorded in one (0.3%). Overall results indicate that lethality of snakebite is low, and that patients were often administered treatment without medical indication. High number of tourists as well as the presence of the peace keeping troops and other visiting personnel in this region make the snakebites and awareness on snakes not only a local issue, but also more general concern.