Management Strategies for Common Animal Bites in Pediatrics: A Narrative Review on the Latest Progress

Animal bites are a common reason for children to visit primary care and emergency departments. Dog bites are the most prevalent, followed by cat bites at 20-30%. Other animals such as bats, monkeys, snakes, and rats collectively contribute less than 1% of cases. Hospitalization is necessary in only 4% of animal bite incidents. The main aim of this narrative review is to summarize the main protocols currently followed in pediatrics in cases involving the most common bites from different animal species. Analysis of the literature showed that the management of common animal bites in children presents a multifaceted challenge requiring a comprehensive understanding of the epidemiology, clinical presentation, and treatment modalities associated with each specific species. Effective wound management is paramount in reducing the risk of infection and promoting optimal healing outcomes. Additionally, tetanus vaccination status should be assessed and updated as necessary, and prophylactic antibiotics may be indicated in certain cases to prevent secondary infections. Furthermore, the role of rabies prophylaxis cannot be overstated, particularly in regions where rabies is endemic or following bites from high-risk animals. In addition to medical management, psychosocial support for both the child and their caregivers is integral to the overall care continuum. Future studies exploring the efficacy of novel treatment modalities, such as topical antimicrobial agents or advanced wound dressings, may offer new insights into optimizing wound healing and reducing the risk of complications.

Mechanical ventilation in snake envenomation of dogs and cats

Envenomation by snakes in Elapidae and Viperidae families have been associated with respiratory failure in dogs and cats. Mechanical ventilation may be required for hypoventilation due to neuromuscular paralysis or hypoxemia due to pulmonary hemorrhage or aspiration pneumonia. Median incidence of dogs and cats with snake envenomation that require mechanical ventilation is 13% (0.06-40%). Standard treatment of snake envenomation in dogs and cats includes prompt administration of appropriate antivenom and management of envenomation complications such as coagulopathy, rhabdomyolysis and acute kidney injury. When mechanical ventilation is required, overall prognosis is good with appropriate treatment. Standard anesthetic protocols and mechanical ventilator settings are generally appropriate, with lung protective ventilation strategies typically reserved for patients with pulmonary disease. Median survival to discharge for cats and dogs with elapid envenomation is 72% (76-84%) with 33 h (19.5-58 h) median duration of mechanical ventilation and 140 h (84-196 h) median hospitalization. This article reviews indications for mechanical ventilation in cats and dogs with snake envenomation, and discusses ventilator settings, anesthetic and nursing considerations, complications and outcomes specific to this disease.

A prospective study of snakebite in a tertiary care hospital in south-western Nepal

BACKGROUND

Snakebite is a neglected public health issue in Nepal. We aimed to characterize patients with snake envenoming admitted to hospital in south-western Nepal.

METHODS

This was a prospective cohort study of 476 snakebite patients admitted to Bheri Hospital from May to December 2017. Data were collected on patient demographics, bite circumstances, snake type, treatment-seeking behavior, clinical effects, complications and treatment.

RESULTS

There were 139/476 (29%) patients with clinical features of envenomation and 10 deaths (8%), of which six were prehospital deaths; 325/476 (68%) patients used non-recommended prehospital first aid, including 278 (58%) who applied a tourniquet and 43 (9%) consulting traditional healers. Median time to hospital arrival was 1.5 (IQR: 0.8-4) h. Also, 127 envenomated patients (91%) developed neurotoxicity and 12 (9%) hemotoxicity, while 124 patients (89%) received antivenom, with a median dose of 10 (4-30) vials. Three patients developed anaphylaxis following antivenom administration; 111 of 139 (80%) cases were admitted to the ICU and 48 (35%) were intubated. Median length of hospital stay for all cases was 0.5 (IQR: 0.5-1.2) d, but it was 2.2 (IQR: 1.5-3.8) d for envenomated cases.

CONCLUSIONS

The majority of snakebite patients used non-recommended first aid or attended traditional healers. Almost one-third of patients developed systemic envenomation and required antivenom. The case fatality rate was high, but many died prior to arriving in hospital.

A retrospective study of antivenom-associated adverse reaction and anaphylaxis at Ngwelezana Hospital, South Africa

BACKGROUND

Snakebite victims are commonly seen in KwaZulu-Natal Hospitals, with only a minority of patients requiring antivenom. This study reviewed antivenom-associated adverse events at our institution, after administration of the South African Vaccine Producers (SAVP) polyvalent antivenom.

METHODS

A retrospective review, over 52 months (January 2016-April 2020), of patients who received antivenom. Demographics, clinical details and clinical course following antivenom administration were analysed.

RESULTS

Emergency department doctors treated 758 snakebites; 156 patients were admitted of which 51 (33%) received antivenom. Indications for antivenom included: neurotoxicity (24%), haemotoxicity (18%) and significant cytotoxicity (58%). Antivenom-associated adverse events occurred in 61% of patients; with 47% developing anaphylaxis requiring adrenaline infusion. There was a higher incidence of anaphylaxis in children (57%) than in adults (40%), p = 0.55. There was no association between antivenom dose and anaphylaxis. No benefit was noted with adrenaline premedication (p = 0.64), nor with the addition of antihistamine or steroid pre-medicants to adrenaline (p = 0.61). Multivariable logistic regression identified age as a predictor for anaphylaxis, but not dose or duration of antivenom and not any particular form of premedication. Intubation was required in 29% of patients developing anaphylaxis. There were no deaths and all patients made full recovery.

CONCLUSION

Almost half of the patients at Ngwelezana hospital in Kwazulu-Natal receiving the SAVP polyvalent antivenom developed anaphylaxis requiring adrenaline infusion, with children at higher risk. The administration of this antivenom must only be given for valid indications, in a high-care environment by medical personnel ready to manage anaphylactic shock. The addition of antihistamine and corticosteroids to adrenaline for premedication has no added benefit.

Hydrocortisone for Preventing Adverse Drug Reactions to Snake Antivenom: A Meta-Analysis

Objective

Pretreatment with hydrocortisone (prehydrocortisone) has been used to protect against adverse drug reactions (ADRs) following antivenom administration after snakebite. However, controversial results have been reported in studies evaluating its efficacy. Herein, we conducted a meta-analysis to evaluate the effect of prehydrocortisone on the risk of ADRs.

Methods

We conducted a systematic search of PubMed, Embase, and Cochrane for relevant studies on the literature published up to December 6, 2020, with no language restrictions. Premedications, including hydrocortisone with or without other drugs, were compared with placebo or no premedication. Our primary end point was the risk of ADRs, which was reported as the number of patients who developed ADRs divided by the total number of snakebite patients administered with antivenom separately for the prehydrocortisone and control groups for each study. We evaluated pooled data using of a random-effects model.

Results

Among 831 identified studies, 4 were eligible and included in our analysis (N = 1348 participants). Upon combining all eight comparisons from the four selected studies, the overall pooled odds ratio (OR) for ADRs was 0.47 (95% CI 0.19, 1.17; p=0.11; I² = 68%). When the analysis was restricted to only articles using hydrocortisone with other drugs, the pooled OR was 0.19 (95% CI 0.05, 0.75; p=0.02; I² = 55%). The result was not statistically significant when the analysis was restricted to studies using prehydrocortisone alone, or randomized controlled designs, or cohorts. Our study was limited by heterogeneity, quality, and a paucity of data.

Conclusions

The findings in this study revealed that prehydrocortisone alone was ineffective. However, the substantial beneficial effect of prehydrocortisone combinations with premedications (injectable antihistamines or adrenaline) used against ADRs cannot be excluded. Therefore, the use of prehydrocortisone combinations with premedications (injectable antihistamines or adrenaline) as a prophylaxis may reduce the ADRs to antivenom.

Antivenom: An immunotherapy for the treatment of snakebite envenoming in sub-Saharan Africa

Snakebite envenoming (SBE) leads to significant morbidity and mortality, resulting in over 90,000 deaths and approximately 400,000 amputations annually. In sub-Saharan Africa (SSA) alone, SBE accounts for over 30,000 deaths per annum. Since 2017, SBE has been classified as a priority Neglected Tropical Disease (NTD) by the World Health Organisation (WHO). The major species responsible for mortality from SBE within SSA are from the Bitis, Dendroaspis, Echis and Naja genera. Pharmacologically active toxins such as metalloproteinases, serine proteinases, 3-finger toxins, kunitz-type toxins, and phospholipase A₂s are the primary snake venom components. These toxins induce cytotoxicity, coagulopathy, hemorrhage, and neurotoxicity in envenomed victims. Antivenom is currently the only available venom-specific treatment for SBE and contains purified equine or ovine polyclonal antibodies, collected from donor animals repeatedly immunized with low doses of adjuvanted venom. The resulting plasma or serum contains a high titre of specific antibodies, which can then be collected and stored until required. The purified antibodies are either whole IgG, monovalent fragment antibody (Fab) or divalent fragment antibody F(ab')₂. Despite pharmacokinetic and pharmacodynamic differences, all three are effective in the treatment of SBE. No antivenom is without adverse reactions but, the level of their impact and severity varies from benign early adverse reactions to the rarely occurring fatal anaphylactic shock. However, the major side effects are largely reversible with immediate administration of adrenaline and corticosteroids. There are 16 different antivenoms marketed within SSA, but the efficacy and safety profiles are only published for less than 50% of these products.

Cytotoxin antibody-based colourimetric sensor for field-level differential detection of elapid among big four snake venom

Development of a rapid, on-site detection tool for snakebite is highly sought after, owing to its clinically and forensically relevant medicolegal significance. Polyvalent antivenom therapy in the management of such envenomation cases is finite due to its poor venom neutralization capabilities as well as diagnostic ramifications manifested as untoward immunological reactions. For precise molecular diagnosis of elapid venoms of the big four snakes, we have developed a lateral flow kit using a monoclonal antibody (AB1; IgG1 - κ chain; Kd: 31 nM) generated against recombinant cytotoxin-7 (rCTX-7; 7.7 kDa) protein of the elapid venom. The monoclonal antibody specifically detected the venoms of Naja naja (p < 0.0001) and Bungarus caeruleus (p<0.0001), without showing any immunoreactivity against the viperidae snakes in big four venomous snakes. The kit developed attained the limit of quantitation of 170 pg/μL and 2.1 ng/μL in spiked buffer samples and 28.7 ng/μL and 110 ng/μL in spiked serum samples for detection of N. naja and B. caeruleus venoms, respectively. This kit holds enormous potential in identification of elapid venom of the big four snakes for effective prognosis of an envenomation; as per the existing medical guidelines.

Examination of the Efficacy and Cross-Reactivity of a Novel Polyclonal Antibody Targeting the Disintegrin Domain in SVMPs to Neutralize Snake Venom

Snake envenomation can result in hemorrhage, local necrosis, swelling, and if not treated properly can lead to adverse systemic effects such as coagulopathy, nephrotoxicity, neurotoxicity, and cardiotoxicity, which can result in death. As such, snake venom metalloproteinases (SVMPs) and disintegrins are two toxic components that contribute to hemorrhage and interfere with the hemostatic system. Administration of a commercial antivenom is the common antidote to treat snake envenomation, but the high-cost, lack of efficacy, side effects, and limited availability, necessitates the development of new strategies and approaches for therapeutic treatments. Herein, we describe the neutralization ability of anti-disintegrin polyclonal antibody on the activities of isolated disintegrins, P-II/P-III SVMPs, and crude venoms. Our results show disintegrin activity on platelet aggregation in whole blood and the migration of the SK-Mel-28 cells that can be neutralized with anti-disintegrin polyclonal antibody. We characterized a SVMP and found that anti-disintegrin was also able to inhibit its activity in an in vitro proteolytic assay. Moreover, we found that anti-disintegrin could neutralize the proteolytic and hemorrhagic activities from crude Crotalus atrox venom. Our results suggest that anti-disintegrin polyclonal antibodies have the potential for a targeted approach to neutralize SVMPs in the treatment of snakebite envenomations.

Evaluation of Allergic Reactions Following Intravenous Infusion of Polyvalent Antivenom in Snakebite Patients

BACKGROUND

Antivenom is a gold-standard treatment for snakebite envenoming. However, adverse reactions to snake antivenom are common in many parts.

OBJECTIVE

The aim of this study was to evaluate the allergic reactions following intravenous administration of antivenom sera.

METHODS

This was retrospective study, conducted snakebites patients referred to the Rahimi Hospital in Khorramabad. The files of these patients were accessed for demographic data, snakebite-related data, treatment provided, clinical presentation and allergic reaction status as a result of antivenom treatment.

RESULTS

141 cases were investigated including 73.8% male and 26.2% female patients. The mean age of the patients was 38.1±17.1years. Age group 30-39 years accounted for highest number of snakebite cases (24.1%). A majority of victims (89.4%) were from the rural areas. Most of the patients (51.8%) were bitten in the spring and highest number of snakebite were reported in May (39.1%). The most common site of snakebite was lower extremities (50.4%) and upper extremities (44.7%). Among clinical feature of snakebite, pain was the most prevalent in 135 cases (95.7%) followed by swelling (83.7%). The mean antivenom vials used were 6.5±3.7 vials. Allergic reactions occurred in 6 patients (4.26%); reactions were mild in 5 patients and sever in 1patient. The commonest presentation was maculopapular rash (1.4%) and the least common were headache (0.71%), nausea (0.71%), fever (0.71) and hypotension (0.71%).

CONCLUSION

Snakebite is one of the significantlife-threatening environmental events.Immediate antivenom treatment can reduce mortality however, patients should be carefully monitored for adverse allergic reactions.

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.

Protein decomplexation and proteomics: A complementary assessment method of the physicochemical purity of antivenom

The quality of antivenom is governed by its safety and efficacy profiles. These quality characteristics are much influenced by the purity of antivenom content. Rigorous assessment and meticulous monitoring of antivenom purity at the preclinical setting is hence crucial. This study aimed to explore an integrative proteomic method to assess the physicochemical purity of four commercially available antivenoms in the region. The antivenoms were subjected to Superdex 200 HR 10/30 size-exclusion fast-protein liquid chromatography (SE-FPLC). The proteins in each fraction were trypsin-digested and analyzed by nano-ESI-liquid chromatography-tandem mass spectrometry (LC-MS/MS). SE-FPLC resolved the antivenom proteins into three major protein components of very high (>200 kDa), high (100-120 kDa) and medium (<60 kDa) molecular weights. The major components (80-95% of total proteins) in the antivenoms were proteins of 100-120 kDa consisting of mainly the light and partially digested heavy immunoglobulin chains, consistent with F(ab')₂ as the active principle of the antivenoms. However, LC-MS/MS also detected substantial quantity of large proteins (e.g. alpha-2-macroglobulins), immunoglobulin aggregates and impurities e.g. albumins in some products. The method is practical and able to unveil the quantitative and qualitative aspects of antivenom protein compositions. It is therefore a potentially useful preclinical assessment tool of antivenom purity.

Delayed antivenom for life-threatening tiger snake bite: Lessons learnt

An adolescent victim of an urban snakebite developed respiratory failure, rhabdomyolysis and consumption procoagulopathy but recovered with two vials of tiger snake antivenom administered after a delay of 48 hours. The clinical significance of a post-bite collapse was not initially appreciated. Tiger snake (Notechis spp.) venom antigen was measurable in blood before antivenom but not after whereas antivenom was measurable in blood for nine ensuing days. This case adds to growing evidence that further pharmacokinetic research of venom-antivenom interaction is required to establish the correct dose and timing of tiger snake antivenom. Antivenom therapy, even when delayed, facilitates recovery from snake envenomation.

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.

SnakeMap: four years of experience with a national small animal snake envenomation registry

SnakeMap is a national cloud-based, veterinary snakebite registry. It was designed to prospectively collect data of the clinical circumstances and temporospatial information on cases of snake envenomation in dogs and cats. We herein introduce the project and summarise the data from the first 4 years of SnakeMap. The registry is a veterinary community-based online database allowing case entry from veterinary hospitals across Australia. Registry data comprise hospital characteristics, patient characteristics, envenoming snake type, treatment and outcome variables, including time and geolocation of the snake bite. We present summative information on select key variables from the SnakeMap registry (1 July 2015 to 30 June 2019). Twenty-eight hospitals from 6 states/territories entered 624 cases into the registry, including 419 dogs (67%) and 205 cats (33%). Bite time was available in 216 animals of which 90 (42%) were reported to be bitten in the 3 hours between 03:00 pm and 05:59 pm; median bite to presentation interval was 60 (interquartile range [IQR] 30, 211) minutes in dogs and 95 (IQR 41, 238) minutes in cats. Bites occurred in the owner's yard in 356 dogs (85%) and 53 cats (26%). A snake venom detection kit was used in 172 cases (28%) and antivenom was administered in 523 cases (85%). Most animals (n = 534, 88%) survived to discharge (median hospitalisation of 25 [IQR 16, 62] hours). SnakeMap effectively collects relevant clinical data from dogs and cats with presumed snake bite and provides locally specific information on the epidemiology of snake envenomation in small animals.

Sensitivity and specificity of 20-minute whole blood clotting test, prothrombin time, activated partial thromboplastin time tests in diagnosis of defibrination following Malayan pit viper envenoming

Malayan pit vipers (Calloselasma rhodostoma) are major health hazard in Southern Thailand causing systemic bleeding by defibrination and thrombocytopenia. Twenty minute whole blood clotting test (20WBCT) is a useful and informative bedside test recommended by WHO for diagnosis of significant coagulopathy following snakebite envenoming since it to some extent predicts the need for anti-venom therapy. Prothrombin time (PT), international normalized ratio (INR) and activated partial thromboplastin time (APTT) are standard clotting assays that are widely used for diagnosis of coagulopathy. The purpose of this study is to compare 20WBCT with the standard clotting assays (PT, INR, APTT, fibrinogen) in management of Malayan pit viper bitten-patients. We studied 296 victims prospectively during a 3-year period. In total, 115 (38.9%) cases showed a positive 20WBCT (un-clot) suggesting systemic envenomation. Thrombocytopenia (platelet count less than 100,000/μL), prolonged PT, prolonged APTT, INR ≥ 1.2, and fibrinogen level <100 mg/dl were found in 12.2%, 47.6%, 18.9%, 34.8% and 40.9%, respectively. Significant predictors for thrombocytopenia by multivariate analysis included systemic bleeding (p < 0.001), higher INR (p < 0.001), 20WBCT showing unclotted blood (p = 0.049), and longer bite-to-hospital time (p = 0.031). When a fibrinogen level below 100 mg/dl was determined as hypofibrinogenemic condition, INR had the highest area under ROC curve followed by 20WBCT and APTT, respectively, to identify such as hypofibrinogenemic condition. The diagnostic accuracy of 20WBCT and INR at or more than 1.155 were better than APTT at any cut-off points. INR >1.155 had a sensitivity of 78.5% and specificity of 90.3% while 20WBCT had sensitivity of 81.0% and specificity of 90.3%. CONCLUSIONS: Both 20WBCT and INR are useful to assess coagulation abnormality in Malayan pit viper-bitten patients.

An in vivo examination of the differences between rapid cardiovascular collapse and prolonged hypotension induced by snake venom

We investigated the cardiovascular effects of venoms from seven medically important species of snakes: Australian Eastern Brown snake (Pseudonaja textilis), Sri Lankan Russell’s viper (Daboia russelii), Javanese Russell’s viper (D. siamensis), Gaboon viper (Bitis gabonica), Uracoan rattlesnake (Crotalus vegrandis), Carpet viper (Echis ocellatus) and Puff adder (Bitis arietans), and identified two distinct patterns of effects: i.e. rapid cardiovascular collapse and prolonged hypotension. P. textilis (5 µg/kg, i.v.) and E. ocellatus (50 µg/kg, i.v.) venoms induced rapid (i.e. within 2 min) cardiovascular collapse in anaesthetised rats. P. textilis (20 mg/kg, i.m.) caused collapse within 10 min. D. russelii (100 µg/kg, i.v.) and D. siamensis (100 µg/kg, i.v.) venoms caused ‘prolonged hypotension’, characterised by a persistent decrease in blood pressure with recovery. D. russelii venom (50 mg/kg and 100 mg/kg, i.m.) also caused prolonged hypotension. A priming dose of P. textilis venom (2 µg/kg, i.v.) prevented collapse by E. ocellatus venom (50 µg/kg, i.v.), but had no significant effect on subsequent addition of D. russelii venom (1 mg/kg, i.v). Two priming doses (1 µg/kg, i.v.) of E. ocellatus venom prevented collapse by E. ocellatus venom (50 µg/kg, i.v.). B. gabonica, C. vegrandis and B. arietans (all at 200 µg/kg, i.v.) induced mild transient hypotension. Artificial respiration prevented D. russelii venom induced prolonged hypotension but not rapid cardiovascular collapse from E. ocellatus venom. D. russelii venom (0.001–1 μg/ml) caused concentration-dependent relaxation (EC₅₀ = 82.2 ± 15.3 ng/ml, R_max = 91 ± 1%) in pre-contracted mesenteric arteries. In contrast, E. ocellatus venom (1 µg/ml) only produced a maximum relaxant effect of 27 ± 14%, suggesting that rapid cardiovascular collapse is unlikely to be due to peripheral vasodilation. The prevention of rapid cardiovascular collapse, by ‘priming’ doses of venom, supports a role for depletable endogenous mediators in this phenomenon.

Australian snake antivenom dosing: What is scientific and safe?

Because the median dose of one vial 'clears the blood of circulating venom', the authors of the Australian Snakebite Project recommend restriction of antivenom to one vial for all envenomated victims. This is neither scientific nor safe. Methodological flaws in the case series include limited detection of venom toxins and misinterpretation of data. The recommendation fails to consider larger doses of venom than that neutralised by one vial of antivenom. Although one vial may be adequate for minor envenomation, the initial dose should be two vials with more on a clinical basis.

Adverse Events in the Efficacy of Crotalidae Polyvalent Immune Fab Antivenom vs Placebo in Recovery from Copperhead Snakebite Trial

OBJECTIVE

To compare the incidence of hypersensitivity reactions following copperhead envenomation treated with Fab antivenom (FabAV) or placebo.

METHODS

Patients with copperhead snakebites received treatment and follow-up in a prospective, randomized, double-blind, placebo-controlled trial of FabAV or placebo. The treatment allocation ratio was 2:1 (FabAV:placebo). All of the included patients received at least one dose of study treatment. We reviewed all treatment-emergent adverse events (AEs) using a previously published scale to classify likely hypersensitivity reactions as mild, moderate, or severe.

RESULTS

We enrolled 74 patients at 13 sites. Forty-five patients received FabAV, and 29 patients received placebo. Five FabAV patients and 4 placebo patients had moderate envenomations; the rest were mild. Twenty-five FabAV patients and 8 placebo patients had at least 1 AE. Mild skin reactions occurred in 11 (24%) FabAV patients (pruritis, urticaria, rash, ecchymosis, erythema) and 1 (3%) placebo patient (pruritis). Moderate gastrointestinal AEs occurred in 7 (16%) FabAV patients (nausea, vomiting, constipation, diarrhea, oral paresthesia) and in 2 (7%) placebo patients (nausea). Respiratory AEs occurred in 3 (7%) FabAV patients (dyspnea, pulmonary embolism, nasal congestion, sneezing) and no placebo patients. Hypotension occurred in 1 patient in each group.

CONCLUSIONS

In a randomized controlled trial of FabAV for copperhead bites, the incidence of hypersensitivity reactions was low. Most reactions were mild skin reactions.

Acute Severe Anaphylaxis in Nepali Patients with Neurotoxic Snakebite Envenoming Treated with the VINS Polyvalent Antivenom

Diagnosing and treating acute severe and recurrent antivenom-related anaphylaxis (ARA) is challenging and reported experience is limited. Herein, we describe our experience of severe ARA in patients with neurotoxic snakebite envenoming in Nepal. Patients were enrolled in a randomised, double-blind trial of high vs. low dose antivenom, given by intravenous (IV) push, followed by infusion. Training in ARA management emphasised stopping antivenom and giving intramuscular (IM) adrenaline, IV hydrocortisone, and IV chlorphenamine at the first sign/s of ARA. Later, IV adrenaline infusion (IVAI) was introduced for patients with antecedent ARA requiring additional antivenom infusions. Preantivenom subcutaneous adrenaline (SCAd) was introduced in the second study year (2012). Of 155 envenomed patients who received ≥ 1 antivenom dose, 13 (8.4%), three children (aged 5−11 years) and 10 adults (18−52 years), developed clinical features consistent with severe ARA, including six with overlapping signs of severe envenoming. Four and nine patients received low and high dose antivenom, respectively, and six had received SCAd. Principal signs of severe ARA were dyspnoea alone (n=5 patients), dyspnoea with wheezing (n=3), hypotension (n=3), shock (n=3), restlessness (n=3), respiratory/cardiorespiratory arrest (n=7), and early (n=1) and late laryngeal oedema (n=1); rash was associated with severe ARA in 10 patients. Four patients were given IVAI. Of the 8 (5.1%) deaths, three occurred in transit to hospital. Severe ARA was common and recurrent and had overlapping signs with severe neurotoxic envenoming. Optimising the management of ARA at different healthy system levels needs more research. This trial is registered with NCT01284855.

D. russelii Venom Mediates Vasodilatation of Resistance Like Arteries via Activation of Kv and KCa Channels

Russell's viper (Daboia russelii) venom causes a range of clinical effects in humans. Hypotension is an uncommon but severe complication of Russell's viper envenoming. The mechanism(s) responsible for this effect are unclear. In this study, we examined the cardiovascular effects of Sri Lankan D. russelii venom in anaesthetised rats and in isolated mesenteric arteries. D. russelii venom (100 μg/kg, i.v.) caused a 45 ± 8% decrease in blood pressure within 10 min of administration in anaesthetised (100 μg/kg ketamine/xylazine 10:1 ratio, i.p.) rats. Venom (1 ng/mL⁻1 μg/mL) caused concentration-dependent relaxation (EC50 = 145.4 ± 63.6 ng/mL, Rmax = 92 ± 2%) in U46619 pre-contracted rat small mesenteric arteries mounted in a myograph. Vasorelaxant potency of venom was unchanged in the presence of the nitric oxide synthase inhibitor, L-NAME (100 µM), or removal of the endothelium. In the presence of high K⁺ (30 mM), the vasorelaxant response to venom was abolished. Similarly, blocking voltage-dependent (Kv: 4-aminopryidine; 1000 µM) and Ca2+-activated (KCa: tetraethylammonium (TEA; 1000 µM); SKCa: apamin (0.1 µM); IKCa: TRAM-34 (1 µM); BKCa; iberiotoxin (0.1 µM)) K⁺ channels markedly attenuated venom-induced relaxation. Responses were unchanged in the presence of the ATP-sensitive K⁺ channel blocker glibenclamide (10 µM), or H1 receptor antagonist, mepyramine (0.1 µM). Venom-induced vasorelaxtion was also markedly decreased in the presence of the transient receptor potential cation channel subfamily V member 4 (TRPV4) antagonist, RN-1734 (10 µM). In conclusion, D. russelii-venom-induced hypotension in rodents may be due to activation of Kv and KCa channels, leading to vasorelaxation predominantly via an endothelium-independent mechanism. Further investigation is required to identify the toxin(s) responsible for this effect.

Snakebite: When the Human Touch Becomes a Bad Touch

Many issues and complications in treating snakebite are a result of poor human social, economic and clinical intervention and management. As such, there is scope for significant improvements for reducing incidence and increasing patient outcomes. Snakes do not target humans as prey, but as our dwellings and farms expand ever farther and climate change increases snake activity periods, accidental encounters with snakes seeking water and prey increase drastically. Despite its long history, the snakebite crisis is neglected, ignored, underestimated and fundamentally misunderstood. Tens of thousands of lives are lost to snakebites each year and hundreds of thousands of people will survive with some form of permanent damage and reduced work capacity. These numbers are well recognized as being gross underestimations due to poor to non-existent record keeping in some of the most affected areas. These underestimations complicate achieving the proper recognition of snakebite’s socioeconomic impact and thus securing foreign aid to help alleviate this global crisis. Antivenoms are expensive and hospitals are few and far between, leaving people to seek help from traditional healers or use other forms of ineffective treatment. In some cases, cheaper, inappropriately manufactured antivenom from other regions is used despite no evidence for their efficacy, with often robust data demonstrating they are woefully ineffective in neutralizing many venoms for which they are marketed for. Inappropriate first-aid and treatments include cutting the wound, tourniquets, electrical shock, immersion in ice water, and use of ineffective herbal remedies by traditional healers. Even in the developed world, there are fundamental controversies including fasciotomy, pressure bandages, antivenom dosage, premedication such as adrenalin, and lack of antivenom for exotic snakebites in the pet trade. This review explores the myriad of human-origin factors that influence the trajectory of global snakebite causes and treatment failures and illustrate that snakebite is as much a sociological and economic problem as it is a medical one. Reducing the incidence and frequency of such controllable factors are therefore realistic targets to help alleviate the global snakebite burden as incremental improvements across several areas will have a strong cumulative effect.

Antivenom therapy: efficacy of premedication for the prevention of adverse reactions

Antivenoms or antitoxins have been effectively used for more than a century. During this time, these products have always proven to be highly effective in the treatment of infections and envenomations. However, antivenoms did not exhibit good safety results in their initial applications. After many improvements, antivenoms have substantially better safety profiles but still have some side effects. Due to the occurrence of adverse reactions, the practice of using premedication with the intent to decrease side effects has become accepted or mandatory in many countries. The drugs used for premedication belong to the histamine H1 antagonist, glucocorticoid and catecholamine groups. Currently, this practice is being questioned due to low or controversial efficacies in clinical assays. In this article, we discuss the causes of adverse reactions, the mechanisms of drugs that block the undesired effects and the results obtained in clinical trials. Although these three families of drugs could have positive effects on reducing adverse reactions, only adrenaline has demonstrated positive results in clinical assays.

Snakebites in Hong Kong: How to Face the Possible Changes?

Introduction

Over the past years, the environmental and scientific changes have shaped the snakebite scenarios and will continue to do so. Their effects ahead are discussed.

Incidence

Because of declining plant agricultural industry and rising urbanization, a falling incidence is reasonably expected in future. In order to maintain the knowledge and skills, training for clinicians will become more crucial.

Venom detection kits

Kits for Naja atra and Cryptelytrops albolabris have been available overseas. Local data should be gathered regarding their clinical application.

Antivenoms

The common local species covered by the haemotoxic and neurotoxic polyvalent antivenoms from Thailand is only Cryptelytrops albolabris. Introduction into Hong Kong is not recommended.

Enzyme inhibitors

With an aim to improve the control of local injury that is unsatisfactorily accomplished by antivenoms, therapy with venom enzyme inhibitors is under research.

Conclusion

A decreasing number of snakebite is anticipated. Venom detection kits should be explored for the use in appropriate cases. (Hong Kong j.emerg.med. 2011;18:217-220)

Development of an elisa for the diagnosis of reactive IgE antibodies anti-therapeutic horse sera

Hypersensitive diseases that involve IgE reactivity are important concern of public, especially those encompassing the potential pathogenesis from the administration of horse serum-based therapeutics such as antivenoms. A method for the definitive diagnosis of reactive IgE is important for identifying allergic patients to control severe collateral effects during planned and emergency application of immunotherapies when the allergy source cannot be avoided for treatment. To date, no tests have been developed to accompany the wide range of antivenoms produced from horse sera. The aim of this was to develop a cost-effective ELISA of high sensitivity and specificity to detect circulating patient IgE that binds horse IgG₃, the most prevalent antibody class in passive antibody therapies. Horse IgG₃ was purified in a single step on jacalin-Sepharose and absorbed to standard ELISA plates as the capture molecule for reactive human IgE. The direct performance evaluation with allergenic and non-allergenic patient, together with competitive peptides assays, showed high sensitivity and specificity to detect human IgE that recognized horse IgG₃. The analytical sensitivity and ED₅₀ were calculated to be 0.01 μg mL^-1 and 0.052 μg mL^-1, respectively. The intra- and inter-assay coefficient of variation ranged from 3.3 to 11.1% and 4.0-8.0%, respectively. The horse IgG₃-based ELISA assay can detect reactive allergenic IgE at picomolar concentrations. The coefficient of variation suggests that it can be easily standardized between laboratories, provide rapid and can be applied to population surveillance. Patient management during treatment for envenomation would be greatly improved by a robust and reliable diagnostic test for preexisting allergies to mitigate life-threating consequences of hypersensitivity.

Clinical Serum Therapy: Benefits, Cautions, and Potential Applications

Blood serum from immunized humans or animals (e.g., horses) contains relevant antibodies and has been used as serum therapy to treat many diseases or envenomation events. The effectiveness of blood serum was initially discovered in 1890 when Kitasato and von Behring observed the effectiveness of this type of therapy against diphtheria and tetanus. Serum therapies played an important role in the advancement of modern medicine prior to the development of penicillin and steroids. At present, several types of serum therapy remain in clinical use. However, some physicians have a limited understanding of the nature and the benefits of serum therapy and the factors that require particular attention. In this review, we set out to clarify the benefits, cautions, and potential applications of serum therapy in the context of conditions such as gas gangrene, diphtheria, botulism, and tetanus and bites from three snake species (mamushi, habu, and yamakagashi) and the redback spider. It is hoped that this review will help clinicians to learn about clinical serum therapies and become familiar with their applications.

Australian taipan (Oxyuranus spp.) envenoming: clinical effects and potential benefits of early antivenom therapy - Australian Snakebite Project (ASP-25)

CONTEXT

Taipans (Oxyuranus spp.) are medically important venomous snakes from Australia and Papua New Guinea. The objective of this study was to describe taipan envenoming in Australian and its response to antivenom.

METHODS

Confirmed taipan bites were recruited from the Australian Snakebite Project. Data were collected prospectively on all snakebites, including patient demographics, bite circumstances, clinical effects, laboratory results, complications and treatment. Blood samples were taken and analysed by venom specific immunoassay to confirm snake species and measure venom concentration pre- and post-antivenom.

RESULTS

There were 40 confirmed taipan bites: median age 41 years (2-85 years), 34 were males and 21 were snake handlers. Systemic envenoming occurred in 33 patients with neurotoxicity (26), complete venom induced consumption coagulopathy (VICC) (16), partial VICC (15), acute kidney injury (13), myotoxicity (11) and thrombocytopenia (7). Venom allergy occurred in seven patients, three of which had no evidence of envenoming and one died. Antivenom was given to 34 patients with a median initial dose of one vial (range 1-4), and a median total dose of two vials (range 1-9). A greater total antivenom dose was associated with VICC, neurotoxicity and acute kidney injury. Early antivenom administration was associated with a decreased frequency of neurotoxicity, acute kidney injury, myotoxicity and intubation. There was a shorter median time to discharge of 51 h (19-432 h) in patients given antivenom <4 h post-bite, compared to 175 h (27-1104 h) in those given antivenom >4 h. Median peak venom concentration in 25 patients with systemic envenoming and a sample available was 8.4 ng/L (1-3212 ng/L). No venom was detected in post-antivenom samples, including 20 patients given one vial initially and five patients bitten by inland taipans.

DISCUSSION

Australian taipan envenoming is characterised by neurotoxicity, myotoxicity, coagulopathy, acute kidney injury and thrombocytopenia. One vial of antivenom binds all measurable venom and early antivenom was associated with a favourable outcome.

Snakebite Envenoming - A Combined Density Equalizing Mapping and Scientometric Analysis of the Publication History

Estimates suggest that more than 25,000 to 125,000 people die annually from snakebite envenomation worldwide. In contrast to this major disease burden, thorough bibliometric studies do not exist so far that illustrate the overall research activity over a long time span. Therefore, the NewQIS-platform conducted an analysis on snakebite envenoming using the Thomson Reuters database Web of Science. To determine and assess changes regarding the scientific activities and to specifically address the more recent situation we analyzed two time intervals (t). During the first time interval from 1900 to 2007 (t1) 13,015 publications (p) were identified. In the following period (2008-2016 = t2) 4,982 publications were identified by the same search strategy. They originate from 114 (t1) respectively 121 countries (t2), with the USA (p = 3518), Brazil (p = 1100) and Japan (p = 961) being most productive in the first period, and the USA (p = 1087), Brazil (p = 991) and China (p = 378) in the second period, respectively. Setting the publication numbers in relation to GDP/capita, Brazil leads with 92 publications per 10,000 Int$GDP/capita, followed by India with 79 publications per 10000 Int$GDP/capita (t1). Comparing the country's publication activity with the Human Development Index level indicates that the majority of the publications is published by highly developed countries. When calculating the average citation rates (citations per published item = CR) mainly European countries show the highest ranks: From 1900-2007 Sweden ranks first with a CR = 27, followed by the Netherlands (CR = 24.8), Switzerland (CR = 23), Spain, Austria and the USA (CR = 22). From 2008 to 2016 the highest rate achieves Switzerland with a value of 24.6, followed by Belgium (CR = 18.1), Spain (CR = 16.7), Costa Rica (CR = 14.9) and Netherlands (CR = 14). Compared with this, the USA was placed at rank 13 (CR = 9,5). In summary, the present study represents the first density-equalizing map projection and in-depth scientometric analysis of the global research output on snakebites and its venoms. So it draws a sketch of the worldwide publication architecture and indicates that countries with a high incidence of snakebites and a low economical level still need to be empowered in carrying out research in this area.

Severe rhabdomyolysis from red-bellied black snake (Pseudechis porphyriacus) envenoming despite antivenom

Envenoming by the Australian red-bellied black snake (Pseudechis porphyriacus) causes non-specific systemic symptoms, anticoagulant coagulopathy, myotoxicity and local effects. Current management for systemic envenoming includes administration of one vial of tiger snake antivenom within 6 h of the bite to prevent myotoxicity. We present a case of severe rhabdomyolysis in a 16 year old male which developed despite early administration of one vial of tiger snake antivenom. Free venom was detected after the administration of antivenom concurrent with rapidly decreasing antivenom concentrations. The case suggests that insufficient antivenom was administered and the use of larger doses of antivenom need to be explored for red-bellied black snake envenoming.

Benefits of using heterologous polyclonal antibodies and potential applications to new and undertreated infectious pathogens

BACKGROUND

Passive immunotherapy using polyclonal antibodies (immunoglobulins) has been used for over a century in the treatment and post-exposure prophylaxis of various infections and toxins. Heterologous polyclonal antibodies are obtained from animals hyperimmunised with a pathogen or toxin.

AIMS

The aims of this review are to examine the history of animal polyclonal antibody therapy use, their development into safe and effective products and the potential application to humans for emerging and neglected infectious diseases.

METHODS

A literature search of OVID Medline and OVID Embase databases was undertaken to identify articles on the safety, efficacy and ongoing development of polyclonal antibodies. The search contained database-specific MeSH and EMTREE terms in combination with pertinent text-words: polyclonal antibodies and rare/neglected diseases, antivenins, immunoglobulins, serum sickness, anaphylaxis, drug safety, post marketing surveillance, rabies, human influenza, Dengue, West Nile, Nipah, Hendra, Marburg, MERS, Hemorrhagic Fever Virus, and Crimean-Congo. No language limits were applied. The final search was completed on 20.06.2015. Of 1960 articles, title searches excluded many irrelevant articles, yielding 303 articles read in full. Of these, 179 are referenced in this study.

RESULTS

Serum therapy was first used in the 1890s against diphtheria. Early preparation techniques yielded products contaminated with reactogenic animal proteins. The introduction of enzymatic digestion, and purification techniques substantially improved their safety profile. The removal of the Fc fragment of antibodies further reduces hypersensitivity reactions. Clinical studies have demonstrated the efficacy of polyclonal antibodies against various infections, toxins and venoms. Products are being developed against infections for which prophylactic and therapeutic options are currently limited, such as avian influenza, Ebola and other zoonotic viruses.

CONCLUSIONS

Polyclonal antibodies have been successfully applied to rabies, envenomation and intoxication. Polyclonal production provides an exciting opportunity to revolutionise the prognosis of both longstanding neglected tropical diseases as well as emerging infectious threats to humans.

A definite bite by the Ornamental Snake (Denisonia maculata) causing mild envenoming

CONTEXT

Many bites from mildly venomous elapids occur but identification or presence of systemic envenoming is rarely confirmed.

OBJECTIVE

To confirm systemic envenoming and binding of venom components to a commercial antivenom in a definite bite by the Ornamental Snake (Denisonia maculata) using enzyme immunoassays.

CASE

A 9-year old boy was bitten by an identified Ornamental Snake. He developed nausea, vomiting, local pain, and swelling. He had a leucocytosis (white cell count, 20.8 × 10(9)/L), an elevated international normalised ratio (INR) of 1.6, but otherwise normal blood tests including D-Dimer and activated partial thromboplastin time. He was treated with Australian Black Snake antivenom because the commercial venom detection kit was positive for Black snake. He was admitted for 36 h with continuing local pain and swelling requiring parenteral analgesia.

MATERIALS AND METHODS

Blood samples were collected with informed consent for measurement of venom and antivenom concentrations. Venom-specific enzyme immunoassays were developed using the closely related D. devisi venom with Rabbit anti-Notechis (Tiger Snake) and anti-Tropidechis (Rough-scaled Snake) IgG antibodies to detect venom in serum. Standard curves for measured venom versus actual venom concentrations were made to interpolate Denisonia venom concentrations. In vitro procoagulant and anticoagulant activity of venom was assayed.

RESULTS

Denisonia venom was detected in the pre-antivenom sample as 9.6 ng/mL D. devisi venom. No antigenic venom components were detected in post-antivenom samples and there were high antivenom concentrations. D. devisi venom had mild in vitro procoagulant activity with a minimum concentration required to clot after 5 min of 2.5-5 μg/mL and even weaker anticoagulant activity.

CONCLUSIONS

Denisonia bites appear to cause local effects and possibly mild systemic envenoming (with only non-specific systemic symptoms and leucocytosis), confirmed by detection of antigenic venom components in blood. A significant coagulopathy does not appear to occur.

Incidence of serum sickness after the administration of Australian snake antivenom (ASP-22)

CONTEXT

Serum sickness is a delayed immune reaction resulting from the injection of foreign protein or serum. Antivenom is known to cause serum sickness but the incidence and characteristics are poorly defined.

OBJECTIVE

To investigate the incidence and clinical features of serum sickness following the administration of Australian snake antivenoms.

MATERIALS AND METHODS

This was a prospective cohort study of patients recruited to the Australian Snakebite Project who received snake antivenom from November 2012 to March 2014. Demographics, clinical information, laboratory tests and antivenom treatment were recorded prospectively. Patients administered antivenom were followed up at 7-10 days and 6 weeks' post-antivenom. The primary outcome was the proportion with serum sickness, pre-defined as three or more of: fever, erythematous rash/urticaria, myalgia/arthralgia, headache, malaise, nausea/vomiting 5-20 days post-antivenom.

RESULTS

During the 16-month period, 138 patients received antivenom. 23 were not followed up (unable to contact, tourist, child, bee sting) and 6 died in hospital. Of 109 patients followed up, the commonest reason for antivenom was venom induced consumption coagulopathy in 77 patients. An acute systemic hypersensitivity reaction occurred post-antivenom in 25 (23%) and 8 (7%) were severe with hypotension. Serum sickness occurred in 32/109 (29%) patients, including 15/37 (41%) given tiger snake, 6/15 (40%) given polyvalent and 4/23 (17%) given brown snake antivenom. There was no association between the volume of antivenom and serum sickness, p = 0.18. The commonest effects were lethargy, headache, muscle/joint aches and fever.

DISCUSSION

The incidence of serum sickness after snake antivenom in Australia was higher than earlier investigations which failed to define symptoms or follow-up patients, but similar to more recent studies of antivenoms in the United States.

CONCLUSION

Serum sickness is common with Australian snake antivenom but does not appear to be predictable based on the volume of antivenom administered.

Diagnosis of snake envenomation using a simple phospholipase A2 assay

Diagnosis of snake envenomation is challenging but critical for deciding on antivenom use. Phospholipase A2 enzymes occur commonly in snake venoms and we hypothesized that phospholipase activity detected in human blood post-bite may be indicative of envenomation. Using a simple assay, potentially a bedside test, we detected high phospholipase activity in sera of patients with viper and elapid envenomation compared to minimal activity in non-envenomed patients.

Snakebite in Australia: a practical approach to diagnosis and treatment

Snakebite is a potential medical emergency and must receive high-priority assessment and treatment, even in patients who initially appear well. Patients should be treated in hospitals with onsite laboratory facilities, appropriate antivenom stocks and a clinician capable of treating complications such as anaphylaxis. All patients with suspected snakebite should be admitted to a suitable clinical unit, such as an emergency short-stay unit, for at least 12 hours after the bite. Serial blood testing (activated partial thromboplastin time, international normalised ratio and creatine kinase level) and neurological examinations should be done for all patients. Most snakebites will not result in significant envenoming and do not require antivenom. Antivenom should be administered as soon as there is evidence of envenoming. Evidence of systemic envenoming includes venom-induced consumption coagulopathy, sudden collapse, myotoxicity, neurotoxicity, thrombotic microangiopathy and renal impairment. Venomous snake groups each cause a characteristic clinical syndrome, which can be used in combination with local geographical distribution information to determine the probable snake involved and appropriate antivenom to use. The Snake Venom Detection Kit may assist in regions where the range of possible snakes is too broad to allow the use of monovalent antivenoms. When the snake identification remains unclear, two monovalent antivenoms (eg, brown snake and tiger snake antivenom) that cover possible snakes, or a polyvalent antivenom, can be used. One vial of the relevant antivenom is sufficient to bind all circulating venom. However, recovery may be delayed as many clinical and laboratory effects of venom are not immediately reversible. For expert advice on envenoming, contact the National Poisons Information Centre on 13 11 26.

Scale reduction of a systems coagulation model with an application to modeling pharmacokinetic-pharmacodynamic data

Bridging systems biology and pharmacokinetics–pharmacodynamics has resulted in models that are highly complex and complicated. They usually contain large numbers of states and parameters and describe multiple input–output relationships. Based on any given data set relating to a specific input–output process, it is possible that some states of the system are either less important or have no influence at all. In this study, we explore a simplification of a systems pharmacology model of the coagulation network for use in describing the time course of fibrinogen recovery after a brown snake bite. The technique of proper lumping is used to simplify the 62-state systems model to a 5-state model that describes the brown snake venom–fibrinogen relationship while maintaining an appropriate mechanistic relationship. The simplified 5-state model explains the observed decline and recovery in fibrinogen concentrations well. The techniques used in this study can be applied to other multiscale models.

Hypotensive and vascular relaxant effects of phospholipase A2 toxins from Papuan taipan (Oxyuranus scutellatus) venom

Phospholipase A2 (PLA2) toxins are common and abundant components of Australasian elapid venoms. These toxins are associated with a range of activities including neurotoxicity, myotoxicity and coagulation disturbances. We have recently reported that sudden cardiovascular collapse induced by Papuan taipan (Oxyuranus scutellatus) venom involves a combination of the release of dilator autacoids and a direct effect on the smooth muscle. In this study, we aimed to isolate PLA2 components from Papuan taipan venom and investigate their contribution to the hypotensive action of this venom. O. scutellatus venom was fractionated using size-exclusion high performance liquid chromatography (HPLC), and fractions screened for activity in anaesthetized rats. Fraction three from O. scutellatus venom (i.e. OSC3, 14.2±1.0% of whole venom) produced a 64% decrease in mean arterial pressure. Reverse-phase HPLC indicated that OSC3 consisted of two major components (i.e. OSC3a and OSC3b). OSC3a and OSC3b produced a significant hypotensive response in anaesthetized rats which were attenuated by prior administration of indomethacin or the combination of mepyramine and heparin. N-terminal analysis indicated that OSC3a and b displayed sequence homology to PLA2 toxins isolated from coastal taipan (O. scutellatus scutellatus) venom. These findings indicate that PLA2 components may play an important role in the development of hypotension and vascular relaxation which may contribute to the effects observed after envenoming by these Australasian elapids.

Diagnostic 20-min whole blood clotting test in Russell's viper envenoming delays antivenom administration

BACKGROUND

The 20-min whole blood clotting test (WBCT20) is widely used for the identification of coagulopathy in snake envenoming, but its performance in practice has not been evaluated.

AIM

We aimed to investigate the diagnostic utility of the WBCT20 for coagulopathy in Russell's viper envenoming.

DESIGN

Prospective observational study.

METHODS

Adult patients with snake envenoming were recruited. Age, sex, bite information, clinical effects, serial WBCT20 and antivenom treatment were recorded. Definite Russell's viper envenoming was confirmed with venom specific enzyme immunoassay. We assessed sensitivity of admission WBCT20 to coagulopathy (international normalized ratio, INR > 1.5) in Russell's viper envenoming, the specificity of negative WBCT20 in non-envenomed patients and directly compared paired WBCT20 and INR.

RESULTS

Admission WBCT20 was done in 140 Russell's viper bites with coagulopathy and was positive in 56/140 [sensitivity 40% (95% confidence interval (CI): 32-49%)]. A negative WBCT20 led to delayed antivenom administration [WBCT20-ve tests: median delay, 1.78 h (interquartile range (IQR): 0.83-3.7 h) vs. WBCT20 + ve tests: median delay, 0.82 h (IQR: 0.58-1.48 h); P = 0.0007]. Delays to antivenom were largely a consequence of further WBCT20 being performed and more common if the first test was negative (41/84 vs. 12/56). Initial WBCT20 was negative in 9 non-envenomed patients and 48 non-venomous snakebites [specificity: 100% (95% CI: 94-100%)]. In 221 paired tests with INR > 1.5, the WBCT20 was positive in 91(41%). The proportion of positive WBCT20 only increased slightly with higher INR.

CONCLUSION

In clinical practice, the WBCT20 has low sensitivity for detecting coagulopathy in snake envenoming and should not over-ride clinical assessment-based decisions about antivenom administration. There is an urgent need to develop a simple bedside test for coagulopathy in snake envenoming.

Point-of-care derived INR does not reliably detect significant coagulopathy following Australian snakebite

INTRODUCTION

Point-of-care international normalised ratio (INR) has been suggested as a way to screen for venom-induced consumption coagulopathy following snakebite, but has not been validated for this. This study aimed to assess the diagnostic reliability of point-of-care INR for venom-induced consumption coagulopathy.

METHODS

This was a prospective study of snakebite patients recruited between January 2011 and May 2012 where a point-of-care INR was done and compared to an INR done on a laboratory coagulation analyser, as part of a quality assurance exercise. Data was obtained for each patient, including demographics, information on the snake bite, the point-of-care INR results and any laboratory derived coagulation studies. Snake identification was confirmed by expert identification or venom specific enzyme immunoassay.

RESULTS

There were 15 patients with a median age of 29 years (2 to 68 y) and 13 were male. Four of the 7 patients with venom-induced consumption coagulopathy had an abnormal point-of-care INR (3 false negatives) and 1 of the 7 non-envenomed patients had an abnormal point-of-care INR (1 false positive). The patient with a falsely elevated point-of-care INR was given antivenom prior to formal coagulation studies. The point-of-care INR was also negative in the patient with an anticoagulant coagulopathy.

CONCLUSIONS

The study shows that point-of-care INR testing devices should not be used in suspected snakebite cases in Australia to diagnose venom-induced consumption coagulopathy.

Safety of intravenous equine F(ab')2: insights following clinical trials involving 1534 recipients of scorpion antivenom

INTRODUCTION

The technology of antivenom production has gradually changed since the earliest production of antisera around the turn of the 20th century. Use of early antisera was associated with frequent acute adverse reactions and serum sickness. New F(ab')2 products, manufactured using pepsin degradation of immunoglobulin together with precipitation of unwanted protein and albumin serum fractions, should in concept cause fewer immune reactions in clinical use.

METHODS

A linked set of five prospective clinical trials of an equine F(ab')2 antivenom, together with one historical control study, were completed during development of the product for a Biological License Application through the US FDA. Adverse events were recorded and categorized, with particular attention to the frequency of immune reactions.

RESULTS

A total of 1534 patients ages 0.1-90.5 years received antivenom, in Arizona and in Mexico, for treatment of scorpion envenomation. Total dosing ranged from 1 to 5 vials except for one outlier who received 10 vials. Estimated protein exposure was 12-275 mg per patient (outlier, up to 550 mg). Three patients (0.2%) had acute reactions to antivenom infusion (one urticaria, one urticaria and dyspnea, and one panic attack). Eight (0.5%) had rashes suggestive of Type 3 immune reactions, although none had the full syndrome of serum sickness. Two women were treated for envenomation during the first trimester of pregnancy, one of whom subsequently experienced a spontaneous abortion.

CONCLUSIONS

Rates of immune reaction to this product were two orders of magnitude lower than the range (up to 75% for early and 81% for late reactions) historically reported with use of minimally refined whole immunoglobulin products against a variety of infections and envenomations. Lower protein dose, greater purity of the active component, lack of the immunogenic Fc portion of the immunoglobulin molecule, and slow intravenous infusion are likely to be the reason for this. Clinical implications of a safer product include that it can be employed in settings where antivenom was once considered too dangerous to use, such as primary care clinics and remote rural areas.

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.

Mulga snake (Pseudechis australis) envenoming: a spectrum of myotoxicity, anticoagulant coagulopathy, haemolysis and the role of early antivenom therapy - Australian Snakebite Project (ASP-19)

CONTEXT

Mulga snakes (Pseudechis australis) are venomous snakes with a wide distribution in Australia. Objective. The objective of this study was to describe mulga snake envenoming and the response of envenoming to antivenom therapy.

MATERIALS AND METHODS

Definite mulga bites, based on expert identification or venom-specific enzyme immunoassay, were recruited from the Australian Snakebite Project. Demographics, information about the bite, clinical effects, laboratory investigations and antivenom treatment are recorded for all patients. Blood samples are collected to measure the serum venom concentrations pre- and post-antivenom therapy using enzyme immunoassay.

RESULTS

There were 17 patients with definite mulga snake bites. The median age was 37 years (6-70 years); 16 were male and six were snake handlers. Thirteen patients had systemic envenoming with non-specific systemic symptoms (11), anticoagulant coagulopathy (10), myotoxicity (7) and haemolysis (6). Antivenom was given to ten patients; the median dose was one vial (range, one-three vials). Three patients had systemic hypersensitivity reactions post-antivenom. Antivenom reversed the coagulopathy in all cases. Antivenom appeared to prevent myotoxicity in three patients with high venom concentrations, given antivenom within 2 h of the bite. Median peak venom concentration in 12 envenomed patients with samples was 29 ng/mL (range, 0.6-624 ng/mL). There was a good correlation between venom concentrations and the area under the curve of the creatine kinase for patients receiving antivenom after 2 h. Higher venom concentrations were also associated with coagulopathy and haemolysis. Venom was not detected after antivenom administration except in one patient who had a venom concentration of 8.3 ng/ml after one vial of antivenom, but immediate reversal of the coagulopathy.

DISCUSSION

Mulga snake envenoming is characterised by myotoxicity, anticoagulant coagulopathy and haemolysis, and has a spectrum of toxicity that is venom dose dependant. This study supports a dose of one vial of antivenom, given as soon as a systemic envenoming is identified, rather than waiting for the development of myotoxicity.

Clinical effects and antivenom dosing in brown snake (Pseudonaja spp.) envenoming--Australian snakebite project (ASP-14)

Background

Snakebite is a global health issue and treatment with antivenom continues to be problematic. Brown snakes (genus Pseudonaja) are the most medically important group of Australian snakes and there is controversy over the dose of brown snake antivenom. We aimed to investigate the clinical and laboratory features of definite brown snake (Pseudonaja spp.) envenoming, and determine the dose of antivenom required.

Methods and Finding

This was a prospective observational study of definite brown snake envenoming from the Australian Snakebite Project (ASP) based on snake identification or specific enzyme immunoassay for Pseudonaja venom. From January 2004 to January 2012 there were 149 definite brown snake bites [median age 42y (2–81y); 100 males]. Systemic envenoming occurred in 136 (88%) cases. All envenomed patients developed venom induced consumption coagulopathy (VICC), with complete VICC in 109 (80%) and partial VICC in 27 (20%). Systemic symptoms occurred in 61 (45%) and mild neurotoxicity in 2 (1%). Myotoxicity did not occur. Severe envenoming occurred in 51 patients (38%) and was characterised by collapse or hypotension (37), thrombotic microangiopathy (15), major haemorrhage (5), cardiac arrest (7) and death (6). The median peak venom concentration in 118 envenomed patients was 1.6 ng/mL (Range: 0.15–210 ng/mL). The median initial antivenom dose was 2 vials (Range: 1–40) in 128 patients receiving antivenom. There was no difference in INR recovery or clinical outcome between patients receiving one or more than one vial of antivenom. Free venom was not detected in 112/115 patients post-antivenom with only low concentrations (0.4 to 0.9 ng/ml) in three patients.

Conclusions

Envenoming by brown snakes causes VICC and over a third of patients had serious complications including major haemorrhage, collapse and microangiopathy. The results of this study support accumulating evidence that giving more than one vial of antivenom is unnecessary in brown snake envenoming.