Thrombotic microangiopathy and acute kidney injury in hump-nosed viper (Hypnale species) envenoming: a descriptive study in Sri Lanka

The Need for Next-Generation Antivenom for Snakebite Envenomation in India

The limitations posed by currently available antivenoms have emphasized the need for alternative treatments to counteract snakebite envenomation. Even though exact epidemiological data are lacking, reports have indicated that most global snakebite deaths are reported in India. Among the many problems associated with snakebite envenomation, issues related to the availability of safer and more efficient antivenoms are of primary concern. Since India has the highest number of global snakebite deaths, efforts should be made to reduce the burden associated with snakebite envenoming. Alternative methods, including aptamers, camel antivenoms, phage display techniques for generating high-affinity antibodies and antibody fragments, small-molecule inhibitors, and natural products, are currently being investigated for their effectiveness. These alternative methods have shown promise in vitro, but their in vivo effectiveness should also be evaluated. In this review, the issues associated with Indian polyvalent antivenoms in neutralizing venom components from geographically distant species are discussed in detail. In a nutshell, this review gives an overview of the current drawbacks of using animal-derived antivenoms and several alternative strategies that are currently being widely explored.

Cortical Blindness and Thrombotic Microangiopathy Following a Hemotoxic Snake Envenomation: An Unusual Presentation

Snake envenomation leads to significant morbidity and mortality with local, hematological, renal, and neurological complications. Hemotoxic envenomation activates a hemorrhagic cascade, leading to many manifestations ranging from skin bleeds to major organ bleeds and fatal intracranial hemorrhage. Although rare, ischemic manifestations are possible following a hemotoxic envenomation, and they may present as cortical blindness, an unusual ocular symptom. Snake envenomation is also known to cause multifactorial acute kidney injury (AKI), precipitated by hemodynamic disturbances secondary to rhabdomyolysis, hemoglobinuria, direct tubular toxicity, and thrombotic microangiopathy. Thrombotic microangiopathy (TMA) is often overlooked in snake bites, as the hematological manifestations are often conveniently attributed to venom-induced consumptive coagulopathy (VICC). The distinct clinical entity of thrombotic microangiopathy should factor into one's differential diagnosis in patients presenting with microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury following a snake bite. We report a patient who developed cortical blindness and thrombotic microangiopathy following snake envenomation, which are uncommon sequelae.

A case report of Ovophis monitcola (Mountain pit-viper) envenoming in northeastern India resulting in prolonged coagulopathy

India is home to a diverse spectrum of medically-significant snakes accounting for the world's largest burden of envenoming, morbidity and mortality. Indian polyspecific antivenom is derived from the venom of four snake species (Daboia russelii, Echis carinatus, Naja naja and Bungarus caeruleus), considered to be responsible for the majority of snakebite morbidity and mortality. The treatment of venomous bites from other less-commonly encountered venomous snake species can be challenging. In this report, we describe the case of a 32-year-old male who presented with features of local cytotoxicity and coagulopathy following a bite from Ovophis monitcola (mountain pit-viper) in Nagaland, northeast India. Local and systemic envenoming, confirmed by bedside and laboratory based clotting assays, failed to respond to polyspecific antivenom and venom-induced consumption coagulopathy persisted for 28 days. Remote consultation with a national Poison Control Centre helped establish the responsible snake species and guide appropriate medical management.

Therapeutic Plasma Exchange for Venom-Induced Thrombotic Microangiopathy Following Hump-Nosed Pit Viper (Genus: Hypnale) Bites: A Prospective Observational Study

INTRODUCTION

-Thrombotic microangiopathy (TMA), which is the triad of acute kidney injury (AKI), microangiopathic hemolytic anemia (MAHA), and thrombocytopenia, is a rare complication of snakebites, and in Sri Lanka, it is commonly seen with hump-nosed pit viper (HNPV) bites.

METHODS

-We conducted a prospective observational study of patients with AKI caused by HNPV bites in Teaching Hospital, Ratnapura, Sri Lanka for 6 y, commencing in June 2015. Some patients with TMA underwent therapeutic plasma exchange (TPE) and some did not. These 2 groups were compared. Statistical analysis was carried out using Minitab 18.1. Data were presented as median (IQR).

RESULTS

-There were 52 (8%) patients with TMA, of whom 21 (45%) were in the TPE group and 26 (55%) were in the non-TPE group. TPE improved time to platelet correction (4 d [IQR, 4-5 d] vs 7 d [IQR, 5-9 d]; P=0.009), time to MAHA correction (5 d [IQR, 3-4 d] vs 7 d [IQR, 6-9 d]; P=0.004), time to prothrombin time (PT)/international normalized ratio (INR) correction (1 d [IQR, 1-2 d] vs 3 d [IQR, 3-4 d]; P=0.003), and time to 20 min whole blood clotting test (WBCT20) correction (2 d [IQR, 1-2 d] vs 3 d [1QR 2-3 d]; P=0.020). Renal recovery was predicted by TPE (P=0.048) and highest creatinine level (P=0.001). There was no association between TPE and dialysis dependency at discharge (P=0.597), length of hospital stay (P=0.220), and the number of dialysis cycles prior to discharge (P=0.540). TPE did not improve the number of blood transfusions (5 packs [IQR, 3-8.5 packs] vs 4 packs [IQR, 0-9 packs]; P=0.290).

CONCLUSIONS

-TPE is effective for TMA in the early correction of platelet counts, MAHA, PT/INR, and WBCT20 in HNPV bites.

Clinico-epidemiology and management of hump-nosed pit viper (Hypnale spp.) bites in dogs

Human envenoming from the bite of the abundant hump-nosed pit viper (Hypnale spp.) (HNPV) is a frequent occurrence with victims experiencing unpleasant and sometimes life-threatening consequences. Further, clinico-pathology, treatment and management measures in HNPV envenomed dogs are under recognized. Prospective investigations were performed to assess the clinico-pathology and management options for HNPV envenomed dogs brought to the University of Peradeniya's Veterinary Teaching Hospital from January, 2012 to March 2018. We recorded the local and systemic manifestations, hematological and urinary abnormalities of 78 dogs in which HNPV bite had been witnessed by the owner. Mild swelling, extensive swelling, hemorrhagic blistering and hemorrhagic bullae at the site of bite were observed in 59%, 31%, 6% and 4% of the dogs, respectively. Some dogs were subjected to surgical excision of necrotized tissue including limb amputation. We observed the following systemic clinical effects in envenomed dogs: neurotoxicity (13%), acute kidney injury (AKI) (14%) and coagulopathy (16%). All dogs showed leukocytosis with mean white blood cell count of 25.25 × 103/µL. Mild anemia and thrombocytopenia were detected in 29% of the dogs. There was a significant correlation between extent of local tissue injuries with length of hospitalization (LH). The mean time of coagulopathy observed was 21.3 h (IQR: 8-48 h). In coagulopathic dogs, there was a strong correlation between LH and extent of local tissue injury (rs = 0.7751, P < 0.0001); LH and whole blood clotting time(CT) (rs = 1.0, P < 0.0001); PT and aPTT (rs = 0.4712, P < 0.001). LH was significantly correlated with the development of AKI (p = 0.0013). Lack of specific antivenom (AVS) for HNPV envenoming provided an opportunity to study the remaining treatment options. Therefore, the study allowed the identification of local and systemic effects, hematological abnormalities, possible supportive treatments and drawbacks of management measures for envenomed dogs.

Indian Polyvalent Antivenom Accelerates Recovery From Venom-Induced Consumption Coagulopathy (VICC) in Sri Lankan Russell’s Viper (Daboia russelii) Envenoming

Background

Venom-induced consumption coagulopathy (VICC) is an important clinical consequence of Russell’s viper (Daboia russelii) envenoming. There is limited evidence for antivenom effectiveness in resolving VICC. We aimed to compare the recovery of VICC in patients who received and did not receive antivenom following Russell’s viper envenoming.

Patients and Methods

This was a non-randomized observational study comparing patients with VICC from Russell’s viper envenoming given antivenom for systemic envenoming and those not given antivenom. Antivenom administration was decided by the treating physicians. We included 44 patients with confirmed Russell’s viper bites with one or more International Normalized Ratio (INR) value ≥ 1.5 (VICC). We compared five patients who did not receive antivenom with 39 patients who did receive antivenom. The primary outcome was the proportion of patients with an INR < 1.5 by 48 h post-bite.

Results

The antivenom group had higher peak serum venom concentrations [median (IQR) = 272 (96–1,076) ng/mL versus 21 (8–58) ng/mL] and more severe VICC compared to the no antivenom group. Twenty seven of 39 patients (69%) in the antivenom group had an INR < 1.5 at 48 h post-bite compared to none of the five patients (0%) in the no antivenom group (absolute difference: 69%; 95%CI: 13 to 83%; p = 0.006; Fisher’s exact test). The fibrinogen recovered in 32 of 39 patients (82%) in the antivenom group compared to one of five patients (20%) in the no antivenom group (absolute difference 62%; 95% CI: 28 to 95%; p = 0.001; Fisher’s exact test). Both INR and fibrinogen were significantly improved between 24 and 48 h post-bite in the antivenom group compared to the no antivenom group.

Conclusion

Antivenom accelerated the recovery of VICC in patients with Russell’s viper envenoming, compared to no recovery in a smaller group of patients with milder VICC not receiving antivenom. This supports the efficacy of antivenom in patients with VICC.

Snakebite Associated Thrombotic Microangiopathy and Recommendations for Clinical Practice

Snakebite is a significant and under-resourced global public health issue. Snake venoms cause a variety of potentially fatal clinical toxin syndromes, including venom-induced consumption coagulopathy (VICC) which is associated with major haemorrhage. A subset of patients with VICC develop a thrombotic microangiopathy (TMA). This article reviews recent evidence regarding snakebite-associated TMA and its epidemiology, diagnosis, outcomes, and effectiveness of interventions including antivenom and therapeutic plasma-exchange. Snakebite-associated TMA presents with microangiopathic haemolytic anaemia (evidenced by schistocytes on the blood film), thrombocytopenia in almost all cases, and a spectrum of acute kidney injury (AKI). A proportion of patients require dialysis, most survive and achieve dialysis free survival. There is no evidence that antivenom prevents TMA specifically, but early antivenom remains the mainstay of treatment for snake envenoming. There is no evidence for therapeutic plasma-exchange being effective. We propose diagnostic criteria for snakebite-associated TMA as anaemia with >1.0% schistocytes on blood film examination, together with absolute thrombocytopenia (<150 × 10⁹/L) or a relative decrease in platelet count of >25% from baseline. Patients are at risk of long-term chronic kidney disease and long term follow up is recommended.

Serum and urinary biomarkers for early detection of acute kidney injury following Hypnale spp. envenoming

Background

Hump-nosed pit viper (HNV; Hypnale spp.) bites account for most venomous snakebites in Sri Lanka. Acute kidney injury (AKI) is the most serious systemic manifestation (1–10%) following HNV envenoming. We aimed to identify the value of functional and injury biomarkers in predicting the development of AKI early following HNV bites.

Methods

We conducted a prospective cohort study of patients with confirmed HNV envenoming presenting to two large tertiary care hospitals in Sri Lanka. Demographics, bite details, clinical effects, complications and treatment data were collected prospectively. Blood and urine samples were collected from patients for coagulation and renal biomarker assays on admission, at 0-4h, 4-8h, 8-16h and 16-24h post-bite and daily until discharge. Follow-up samples were obtained 1 and 3 months post-discharge. Creatinine (sCr) and Cystatin C (sCysC) were measured in serum and kidney injury molecule-1 (uKIM-1), clusterin (uClu), albumin (uAlb), β2-microglobulin (uβ2M), cystatin C (uCysC), neutrophil gelatinase associated lipocalin (uNGAL), osteopontin (uOPN) and trefoil factor-3 (uTFF-3) were measured in urine. Definite HNV bites were based on serum venom specific enzyme immunoassay. Kidney Disease: Improving Global Outcomes (KDIGO) criteria were used to stage AKI. Two patients had chronic kidney disease at 3 month follow-up, both with pre-existing abnormal sCr, and one developed AKI following HNV envenoming.

Results

There were 52 patients with confirmed HNV envenoming; median age 48y (Interquartile range [IQR]:40-59y) and 29 (56%) were male. Median time to admission was 1.87h (IQR:1–2.75h). Twelve patients (23%) developed AKI (AKI stage 1 = 7, AKI stage 2 = 1, AKI stage 3 = 4). Levels of five novel biomarkers, the functional marker serum Cystatin C and the damage markers urinary NGAL, cystatin C, β2-microglobulin and clusterin, were elevated in patients who developed moderate/severe acute kidney injury. sCysC performed the best at 0–4 h post-bite in predicting moderate to severe AKI (AUC-ROC 0.95;95%CI:0.85–1.0) and no biomarker performed better than sCr at later time points.

Conclusions

sCysC appears to be a better marker than sCr for early prediction of moderate to severe AKI following HNV envenoming.

Snakebite is a major public health problem associated with considerable morbidity and mortality worldwide. Acute kidney injury is one of the major systemic complications of snakebites. Its pathophysiology is poorly understood and the diagnosis is often delayed due to lack of sensitive biomarkers. We aimed to investigate the value of selected biomarkers in the early diagnosis of acute kidney injury following hump-nosed pit viper (Hypnale spp.) envenoming. In a group of 52 patients with confirmed hump-nosed pit viper envenoming acute kidney injury was found to be common and was associated with severe disease in some. Levels of five novel biomarkers, the functional marker serum Cystatin C and the damage markers urinary NGAL, cystatin C, β2-microglobulin and clusterin, were elevated in patients who developed moderate/ severe acute kidney injury. Serum Cystatin C performed better than serum creatinine in early prediction of moderate/severe acute kidney injury. Serum Cystatin C appears to be a promising novel biomarker in diagnosing acute kidney injury in the setting of hump-nosed pit viper envenoming.

Atypical Hemolytic Uremic Syndrome in a Patient With Bothrops asper Envenomation

Bothrops asper envenomation is common in Colombia and is characterized by local tissue injury and venom-induced consumption coagulopathy (VICC). Rarely, thrombotic microangiopathy is associated with envenomation by this species. The case of a 57-y-old man with B asper bite and envenomation on the left foot is presented. The patient was admitted 8 h after the event and progressively developed edema, hemorrhage at the site of the bite, and hemorrhagic blisters. His coagulation test results (prothrombin and partial thromboplastin times) were prolonged, and his fibrinogen levels were severely reduced. The diagnosis of VICC was made. Administration of Colombian polyvalent viper antivenom controlled the VICC within a few hours. Subsequently, the patient developed severe microangiopathic anemia, thrombocytopenia, and acute kidney injury. A diagnosis of thrombotic microangiopathy was made, and the patient met the criteria for hemolytic uremic syndrome. Management with hemodialysis in addition to therapeutic plasma exchange and replacement with fresh frozen plasma was indicated. The patient's condition resolved 14 d later. To the best of our knowledge, this is the first case of B asper envenomation in which the patient presented with hemolytic uremic syndrome after VICC. A proposal is made regarding the pathogenesis of this chain of events.

Hypnale coagulopathy: snake envenomation of a different kind

Hypnale hypnale is a small pit viper that is known as the hump-nosed pit viper (HNV) or 'Merrem's hump-nosed pit viper' and is endemic to Sri Lanka and the Western Ghats of South India. Previously, it was thought that this viper bite would result in mild systemic or local envenomation, however, we now know that HNV bites could cause severe systemic toxicity and mortality. The most common systemic toxicity of this viper envenomation is coagulopathy, which is known as 'Hypnale coagulopathy'. Hypnale coagulopathy is quite different from the haemotoxicity caused by other vipers. In this paper, an effort has been made to discuss the unique and unpredictable nature of this coagulopathy due to Hypnale envenomation.

Chronic health effects and cost of snakebite

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

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

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

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

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

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

Schistocyte quantitation, thrombotic microangiopathy and acute kidney injury in Australian snakebite coagulopathy [ASP28]

INTRODUCTION

The major systemic manifestation of hemotoxicity in human snakebite envenoming is venom-induced consumption coagulopathy (VICC). A subset of patients with VICC develop thrombotic microangiopathy (TMA), in which acute kidney injury (AKI) occurs. We aimed to investigate the association between schistocytosis in snakebite patients with VICC and AKI, compared to non-envenomed patients.

METHODS

Serial blood films collected from a prospective cohort of snakebite patients (Australian Snakebite Project) were examined. Cases were classified a priori as non-envenomed snakebites (normal controls), envenomed without VICC, partial VICC without AKI, complete VICC without AKI, and VICC with AKI based on defined clinical and laboratory criteria. The percentage of schistocytes between groups was compared and correlated by Kendall's tau b test.

RESULTS

Seven hundred and eighty blood films from 234 snakebite cases were analyzed. There was a statistically significant correlation (τ = .69, SE .03, P < .001) for schistocytosis between the ordered groups of non-envenomed snakebites, envenomed without VICC, partial VICC without AKI, complete VICC without AKI, and VICC with AKI groups. Patients with VICC and AKI had a platelet nadir median of 42 × 10⁹ /L (interquartile range [IQR] :25-130 × 10⁹ /L), hemoglobin nadir of median 107 g/L (IQR 66-122 g/L), and maximum LDH median of 1128 U/L (IQR 474-3255 U/L). A 1.0% threshold for schistocytosis yielded 90% sensitivity (95% CI: 67%-98%) and 71% specificity (95% CI: 62%-79%) for predicting AKI in patients with VICC.

CONCLUSION

Schistocyte quantitation has good diagnostic utility in snakebite patients with VICC. A definition of snakebite TMA as MAHA with ≥1.0% schistocytes and thrombocytopenia, would appear to be appropriate.

Snakebite associated thrombotic microangiopathy: a systematic review of clinical features, outcomes, and evidence for interventions including plasmapheresis

Snakebite is a neglected tropical disease with significant morbidity and mortality. Thrombotic microangiopathy (TMA) is an important but poorly understood complication of snakebite associated with acute kidney injury (AKI). Numerous treatments have been attempted based on limited evidence. We conducted a systematic review of TMA following snakebite using a pre-determined case definition of blood film red cell schistocytes or histologically diagnosed TMA. The search strategy included major electronic databases and grey literature. We present a descriptive synthesis for the outcomes of AKI, dialysis free survival (DFS), other end-organ damage, overall survival, and interventions with antivenom and therapeutic plasmapheresis (TPE). This study was prospectively registered with PROSPERO (CRD42019121436). Seventy-two studies reporting 351 cases were included, predominantly small observational studies. Heterogeneity for study selection, design, reporting and outcomes were observed. The commonest envenoming species were hump-nosed vipers (Hypnale spp.), Russell's viper (Daboia russelii) and Australian brown snakes (Pseudechis spp.). The prevalence of TMA was at least 5.4% in proven and probable Hypnale bites, and 10-15% of Australian elapid envenomings, AKI occurred in 94% (293/312) of TMA cases, excluding case reports. The majority of cases with AKI required dialysis. Included prospective and retrospective cohort studies reporting interventions and renal outcomes showed no evidence for benefit from antivenom or TPE with respect to DFS in dialysis dependant AKI. The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) assessment for quality of accumulated evidence for interventions was low. The major complication of TMA following snakebite is AKI. AKI improves in most cases. We found no evidence to support benefit from antivenom in snakebite associated TMA, but antivenom remains the standard of care for snake envenoming. There was no evidence for benefit of TPE in snakebite associated TMA, so TPE cannot be recommended. The quality of accumulated evidence was low, highlighting a need for high quality larger studies.

Hump-nosed pit viper (Hypnale hypnale and Hypnale zara) envenoming in Deniyaya, Sri Lanka: Epidemiological and clinical features from a prospective observational study

Hypnale hypnale, Hypnale zara and Hypnale nepa are the three species of Hump nosed pit vipers that are implicated in human bites in Sri Lanka. H. zara and H. nepa are two endemic species to the country. The objective of the study was to characterize epidemiology and clinical features after different Hump nosed pit viper species bites. A prospective observational study was conducted in Base Hospital Deniyaya from 2013 to 2015. Hump nosed pit viper as the offending snake was identified when the victims brought live or dead specimens. Species identification of dead specimen was done by a herpetologist. Clinical details were recorded during the hospital stay. 83 Hump nosed pit viper bite patients (19-81 years) were studied. Fifty two dead specimens were identified as 39 of H. zara and 13 of H. hypnale by the herpetologist. No H. nepa was identified. Thirty one live snakes were identified as Hump nosed pit vipers and released in to the wild. Envenoming was reported throughout the year. Eighty (96.4%) were daytime bites. Hands (43.4%), feet (55.4%) and arms (1.2%) were affected sites. Sixty two (74.7%) were bitten in tea plantations. All had pain over bite site. Overall, sixty nine (83.1%) had local swelling, seven (8.4%) extensive limb swelling, nineteen (22.9%) haemorrhagic blisters, and seven (8.4%) regional lymphadenopathy. Four (4.8%) patients had incoagulable blood by 20WBCT. H. zara bites had 28.2% haemorrhagic blisters, 7.7% extensive limb swelling and 2.6% coagulopathy. H. hypnale bites had 7.7% each extensive limb swelling and coagulopathy and 23.1% haemorrhagic blisters. None developed elevated serum creatinine. Neurotoxicity was not noted. Hump nosed pit viper bites caused substantial morbidity. Risk factors included day time outdoor activities and occupation. Pain, extensive limb swelling, bite site swelling, haemorrhagic blisters, regional lymphadenopathy and coagulopathy were prominent clinical features. Nephrotoxicity and neurotoxicity were notably absent. Clinical features varied depending on the species implicated.

Thrombotic microangiopathy and acute kidney injury following Sri Lankan Daboia russelii and Hypnale species envenoming

Context: Thrombotic microangiopathy (TMA) resulting in acute kidney injury (AKI) is an important complication of venomous snakebites. We aimed to describe TMA secondary to Russell's viper (Daboia russelli) and hump-nosed viper (Hypnale spp.) bites and assess the effect of different treatments.Materials and methods: We undertook a prospective observational study of patients with AKI secondary to snakebite over a two-year period. Data recorded included: demographic details, clinical and laboratory features, treatment, complications and outcomes, until hospital discharge and at three months post-discharge. TMA was defined as the development of microangiopathic hemolytic anemia and thrombocytopenia along with AKI. Treatment with therapeutic plasma exchange (TPE; also known as plasmapheresis) and/or fresh frozen plasma (FFP) was determined by the treating clinician. Antivenom was given to all patients with evidence of systemic envenoming following Russell's viper bites.Results: Fifty-nine patients were included in the analysis. Thirty-three (56%) were males and median age was 56 years. Forty-five (76%) developed TMA while a further 11 and two developed isolated thrombocytopenia and microangiopathic hemolytic anemia, respectively. Presence of TMA was associated with increased dialysis requirements (5 vs. 3) and longer hospital stay (18 vs. 12 days). Of the patients with TMA, nine received TPE with or without FFP infusions. The use of TPE was not associated with improved outcomes in patients with TMA based on requirement for blood transfusion, recovery of thrombocytopenia, requirement of dialysis and duration of hospital stay. Patients who did not receive TPE had better renal function at three months compared to patients who received this treatment.Conclusion: Presence of TMA in patients with Daboia and Hypnale bites was associated with a more prolonged course of AKI. Patients with TMA who were treated with TPE did not have improved early or late outcomes compared to patients who were not treated with TPE.

Severe acute kidney injury following Sri Lankan Hypnale spp. envenoming is associated with thrombotic microangiopathy

CONTEXT

Acute kidney injury (AKI) is the most serious clinical manifestation of the Sri Lankan hump-nosed pit viper (Hypnale spp.) bites. Thrombotic microangiopathy (TMA) is increasingly recognized in association with AKI in cases of Hypnale spp envenomation. We investigated AKI in a cohort of cases of Hypnale envenomation, its association with TMA and the early diagnostic value of common biomarkers for AKI occurring.

MATERIALS AND METHODS

We conducted a prospective observational study of suspected viper bites and included 103 confirmed cases of Hypnale envenomation, based on venom specific enzyme immunoassay of blood. AKI was defined using the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Thrombotic microangiopathy was diagnosed based on thrombocytopenia (platelet count < 150,000 × 10³/μL) and microangiopathic haemolytic anaemia (MAHA). We investigated the diagnostic performance of creatinine, platelet count and INR for AKI within 4 h and 8 h post-bite by area under the receiver operator characteristic curve (AUC-ROC).

RESULTS

Ten patients developed AKI: seven AKI stage 1 and three AKI stage 3. Ten patients (10%) developed thrombocytopaenia while 11 (11%) had MAHA. All three AKI stage 3 had thrombocytopaenia and MAHA fulfilling the criteria for TMA. Two of them presented with oliguria/anuria and all three required haemodialysis. Serum creatinine within 4 h post-bite was the best predictor of AKI with AUC-ROC of 0.83 (95% CI: 0.67-0.99) and was no better within 8 h of the bite.

CONCLUSIONS

We found that AKI is uncommon in Hypnale spp. envenomation, but an important serious complication. Severe AKI was associated with TMA. A creatinine within 4 h post-bite was the best predictor of AKI.

Thrombotic Microangiopathy Following Arabian Saw-Scaled Viper (Echis coloratus) Bite: Case Report

BACKGROUND Consumption coagulopathy post envenomation is one the most common complications after a snakebite. It occurs secondary to activation of a coagulation cascade by snake venom and could be followed by a syndrome consistent with thrombotic microangiopathy. The efficacy of plasma exchange for the treatment of thrombotic microangiopathy post envenomation is a matter of debate. CASE REPORT We reported the case of a 50-year-old male who had Arabian saw-scaled viper envenomation. He developed venom induced coagulopathy that improved within 24 hours of antivenom therapy. He subsequently developed micro-angiopathic hemolytic anemia, thrombocytopenia, and renal failure that was consistent with thrombotic microangiopathy. The patient was treated by plasma exchange and hemodialysis. He made a full recovery and was discharged after 4 weeks. CONCLUSIONS This case report supports plasmapheresis as an option for management of a patient who develops thrombotic microangiopathy secondary to snake bite, especially those who do not improve with antivenom and supportive therapy.

Kidney injury following envenoming by hump-nosed pit viper (Genus: Hypnale) in Sri Lanka: proven and probable cases

BACKGROUND

Hump-nosed pit vipers (Hypnale hypnale) are highly venomous snakes found in Sri Lanka and the Western Ghats region of India. They are the most common cause of venomous snakebites in Sri Lanka, mainly causing local envenoming leading to pain, swelling and necrosis. Systemic envenoming causing acute kidney injury and coagulopathy are more commonly recognized following their bites.

METHOD

A series of 465 patients with hump-nosed viper bites was prospectively studied over four years from January 2014. All patients were assessed and the data were collected by the principal investigator (primary data).

RESULTS

Forty-four (9.5%) patients developed acute kidney injury, of which 23 (5%) were proven cases and 21 (4.5%) were probable cases. Of the proven cases, 4 (17%) progressed to chronic kidney disease and 12 (52%) had thrombotic microangiopathy, from which 11 (48%) developed haemolytic uremic syndrome and 1 (4%) had thrombotic thrombocytopenic purpura. Twelve (52%) showed microangiopathic haemolysis and 15 (65%) had thrombocytopenia. Oliguria was observed in 10 (43%) whereas 7 (30%) each had anuria and normal urine output. Ten patients (43%) developed haematuria, from which 6 had microscopic haematuria and 4 had macroscopic haematuria. Proteinuria was observed in 8 (35%). Coagulopathy developed in 3 (13%) patients. In probable cases, 3 (14%) died due to complications of kidney injury.

CONCLUSION

A significant proportion of patients develop acute kidney injury following hump-nosed pit viper bite. Who will develop acute kidney injury or succumb to the venom is unpredictable. Reliable and accessible treatments are a critical unmet need.

Thrombotic Microangiopathy Following Hypnale zara (Hump-Nosed Pit Viper) Envenoming: The First Known Case Report from Sri Lanka

A 65-y-old previously healthy farmer developed thrombotic microangiopathy (TMA) comprising the triad of acute kidney injury, microangiopathic haemolysis, and thrombocytopenia after a proven Hypnale zara (hump-nosed pit viper) bite. He developed coagulopathy, which was treated with fresh frozen plasma, and underwent 8 cycles of hemodialysis. He is being followed up in the nephrology clinic for acute kidney injury. TMA caused by Hypnale hypnale, the commonest species of genus Hypnale, has previously been reported, but this is the first known case of TMA following a bite by H zara, the endemic species in Sri Lanka.

Nephrotoxicity induced by the venom of Hypnale hypnale from Sri Lanka: Studies on isolated perfused rat kidney and renal tubular cell lines

The hump-nosed pit viper Hypnale hypnale is responsible for a high number of snakebite cases in southwestern India and Sri Lanka. Although most patients only develop local signs and symptoms of envenoming, there is a growing body of evidence indicating that these envenomings may be associated with systemic alterations, including acute kidney injury. In this study we evaluated the renal toxicity of H. hypnale venom by using a perfused isolated rat kidney system and by assessing cytotoxicity in two different renal tubular cell lines in culture. The venom caused alterations in several renal functional parameters, such as reduction on perfusion pressure, renal vascular resistance, and sodium and chloride tubular transport, whereas glomerular filtration rate and urinary flow initially decreased and then increased after venom perfusion. In addition, this venom was cytotoxic to proximal and distal renal tubular cells in culture, with predominance of necrosis over apoptosis. Moreover, the venom affected the mitochondrial membrane potential and induced an increment in reactive oxygen species in these cells. Taken together, our results demonstrate a nephrotoxic activity of H. hypnale venom in these experimental models, in agreement with clinical observations.

An Atypical Clinical Manifestation of a Hump-Nosed Pit Viper Envenomation

Envenomations by hump-nosed pit vipers (HNVs) are frequent in Sri Lanka and in South India. Until recently, HNV was considered a moderately venomous snake. Here, we report a case of a previously healthy female developing all the known serious complications, plus some previously unreported complications following a HNV envenomation. She had muscarinic symptoms like profuse sweating and salivation within a couple of minutes and a seizure several minutes after envenomation. Her acute kidney injury (AKI) was swift onset and progressed to end-stage renal failure at three months. She had mild parotid swelling, crepitations in her lungs, and edema of the bitten leg. She had evidence of microangiopathic hemolytic anemia and hemolytic uremic syndrome as well. She developed local tissue necrosis, a non-ST-elevation myocardial infarction (non-STEMI), and anterior ischemic optic neuropathy (AION) following the envenomation. We believe the best explanation for her swift onset complication is intravascular injection of venom. We believe ischemia due to thrombotic microangiopathy has contributed to local tissue necrosis. Those ischemia and kidney failure have contributed to non-STEMI and AION. We illustrate the issue of the sluggish progress made by medicine in understanding the complications of envenomation by using HNV as an example.

Basal but divergent: Clinical implications of differential coagulotoxicity in a clade of Asian vipers

Envenomations by Asian pitvipers can induce multiple clinical complications resulting from coagulopathic and neuropathic effects. While intense research has been undertaken for some species, functional coagulopathic effects have been neglected. As these species' venoms affect the blood coagulation cascade we investigated their effects upon the human clotting cascade using venoms of species from the Azemiops, Calloselasma, Deinagkistrodon and Hypnale genera. Calloselasma rhodostoma, Deinagkistrodon acutus, and Hypnale hypnale produced net anticoagulant effects through pseudo-procoagulant clotting of fibrinogen, resulting in weak, unstable, transient fibrin clots. Tropidolaemus wagleri was only weakly pseudo-procoagulant, clotting fibrinogen with only a negligible net anticoagulant effect. Azemiops feae and Tropidolaemus subannulatus did not affect clotting. This is the first study to examine in a phylogenetic context the coagulotoxic effects of related genera of basal Asiatic pit-vipers. The results reveal substantial variation between sister genera, providing crucial information about clinical effects and implications for antivenom cross-reactivity.

Thrombotic Microangiopathy: An Under-Recognised Cause of Snake-bite-related Acute Kidney Injury

Introduction:

Thrombotic microangiopathy (TMA) as a cause of snake-bite-induced acute kidney injury (AKI) is rarely reported. Very little is known about the clinical course, optimal management, and prognosis of this entity. We describe a series of snake-bite-induced TMA and compare their outcomes with those without TMA.

Methods:

This was a single-center retrospective study of patients with AKI following snake envenomation admitted between January 2012 and December 2017. Demographic profile, clinical parameters, and outcomes were studied. TMA was diagnosed based on presence of triad of microangiopathic hemolytic anemia, thrombocytopenia, and AKI, and groups with and without TMA were compared.

Results:

Of 103 patients with AKI following snake bite, 19 (18.5%) had clinical evidence of TMA. All patients with TMA had advanced azotemia (mean peak serum creatinine 9.5 ± 3.0 mg/dL), with 18 (95%) requiring renal replacement therapy (RRT). Thirteen (68%) had either complete or partial recovery of renal functions, two (10%) progressed to end-stage renal disease, and one died (three patients were lost to follow-up). Age ≥50 years, presence of oliguria/anuria, anti-snake venom dose ≥10 vials, and urea ≥80 mg/dL at presentation were independently associated with TMA (P < 0.05). RRT requirement (95% vs. 57%), mean number of RRT sessions (18 vs. 4.5 sessions), and hospital stay ≥7 days (84% vs. 58%) were higher in patients with TMA (P < 0.05), but patient outcomes did not differ.

Conclusions:

In conclusion, TMA was seen in 18.5% of patients with snake-bite-related AKI in our study and was associated with almost universal need for RRT, longer duration on RRT, and hospital stay compared with patients without TMA.

Thrombotic microangiopathy following Bothrops jararaca snakebite: case report

CONTEXT

Thrombotic microangiopathy (TMA) is an uncommon and severe complication of snakebites, and is similar, in general, to hemolytic-uremic syndrome (HUS). We describe a case of TMA following envenomation by Bothrops jararaca.

CASE DETAILS

A 56-y-old-woman with controlled hypertension was transferred from a primary hospital to our ER ∼7 h after being bitten by B. jararaca in the distal left leg. She developed edema extending from the bite site to the proximal thigh, associated with intense radiating local pain, local paresthesia and ecchymosis at the bite site. Laboratory features upon admission revealed coagulopathy (20 min whole blood clotting time - WBCT20 > 20 min), thrombocytopenia (76,000 platelets/mm³) and slight increase in serum creatinine (1.58 mg/dL; RV < 1.2 mg/dL). Upon admission, the patient was treated with bothropic antivenom and fluids replacement. During evolution, her thrombocytopenia and anemia worsened, with blood films showing fragmented red cells, haptoglobin consumption, increase in serum lactate dehydrogenase, and progressive increase of serum creatinine (KDIGO stage = 3). No RBC transfusion, renal replacement therapy or plasmapheresis was done. The patient showed progressive improvement from day nine (D9) onwards and was discharged on D20; there was complete recovery of hemoglobin levels at follow-up (D50). ADAMTS-13 activity, assayed 10 months post-bite, was within reference values.

DISCUSSION

TMA following snakebite has been reported mainly in India, Sri Lanka and Australia, with several patients needing renal replacement therapy. Although controversial, plasmapheresis has also been used in some cases. Our patient developed microangiopathic hemolytic anemia, thrombocytopenia and acute kidney injury, a triad of features compatible with TMA similar to HUS. Despite the severity, the outcome following conservative treatment was good, with complete recovery.

Acute kidney injury induced by thrombotic microangiopathy in two cases of Bothrops envenomation

CONTEXT

Bothrops snakes are the most frequent agents of snakebites in South and Central America. Acute kidney injury (AKI) is one of its complications and has multifactorial origin. Thrombotic microangiopathy (TMA)-induced AKI in snakebites is uncommon and is not described in Bothrops envenomation.

CASE DETAILS

We report two cases of patients bitten by young Bothrops jararaca who developed AKI induced by TMA. Both patients evolved with mild envenomation and received the specific antivenom within 4 h after the snakebite. None of them had hypotension or shock, bleeding or secondary infection. Patient 1 (P1) was diabetic and using oral hypoglycemic drugs, and patient 2 (P2) was hypertensive without regular use of medication. On admission, both patients had levels of fibrinogen lower than 35 mg/dL, D-dimer higher than 10,000 ng/mL. They evolved with AKI, thrombocytopenia, normal coagulation assays, anemia, lactate dehydrogenase (LDH) elevation, low haptoglobin levels, negative direct antiglobulin test, and presence of schizocytes in peripheral blood. Only P1 required renal replacement therapy, and plasmapheresis was not required. Both patients were discharged and did not require outpatient dialysis, and subsequently had normal creatinine levels.

DISCUSSION

TMA may occur in Bothrops jararaca envenomation, even in mild cases that received early specific antivenom.

Determination of the sub-lethal nephrotoxic dose of Russell's viper (Daboia russelii) venom in Wistar rats

Wistar rats were administered increasing doses of Russell's viper venom (RVV; 0.025-0.4 mg/kg) intraperitoneally to investigate acute kidney injury (AKI) by measuring creatinine (1.5-fold increase in serum creatinine above baseline) and examining kidney histology. Approximately 50% of rats receiving 0.25-0.4 mg/kg venom died within 72 h. An increase in serum creatinine only occurred at a venom dose of 0.4 mg/kg, except in two rats. Acute tubular necrosis, glomerular necrosis, cortical necrosis and interstitial inflammation were observed at venom doses of ≥0.25 mg/kg in 12/36 rats. However, of those 12 rats only four survived to 48 h compared to the 24 rats not developing nephrotoxicity, in which 18 were alive at 48 h. There was poor correlation between histological nephrotoxicity and AKI based on creatinine measurement. The early death in rats with AKI makes this a poor model for studying RVV-induced AKI.

Cardiac arrest and atrial fibrillation in a patient after hump-nosed pit viper (Hypnale hypnale) bite

A 42-year-old previously healthy male patient died 16 days after a proven hump-nosed pit viper (Hypnale hypnale) envenoming due to multi-organ failure. On admission he had cardiac arrest that recovered from cardiopulmonary resuscitation then developed atrial fibrillation which was reverted to normal rhythm by application of synchronized electrical cardioversion. He also had persistent coagulopathy and thrombotic microangiopathy comprising the triad of microangiopathic haemolysis, acute kidney injury and thrombocytopenia. This is the second reported case with cardiac complications following hump-nosed pit viper bites in Sri Lanka.

Therapeutic plasma exchange for pediatric nonrenal disease indications and outcomes: A single-center experience

INTRODUCTION

Outcome data in pediatric plasma exchange, especially in nonrenal indications are scarce. We aimed to evaluate its role and outcome in our patients.

SUBJECTS AND METHODS

A retrospective study of children admitted in the year 2016 to the Pediatric Intensive Care Unit requiring plasma exchange for nonrenal indications was undertaken. Plasma exchange was given as adjunctive therapy along with primary treatment for the disease concerned. Demographic and clinical data were studied, and descriptive statistical analysis was carried out.

RESULTS

Ten children underwent plasma exchange during this 1-year period with a male: female ratio of 3:2 and a mean age of 10 years (range 3-16 years). The indications were acute disseminated encephalomyelitis (n = 2), acute neuromyelitis optica (n = 1), catastrophic antiphospholipid antibody syndrome secondary to systemic lupus erythematosus (SLE) (n = 1), severe SLE with cerebritis/hemophagocytic lymphohistiocytosis (HLH) (n = 2), severe dengue sepsis with HLH/multi-organ dysfunction syndrome (n = 2), and thrombotic microangiopathy secondary to snake bite envenomation (n = 2). All received either 1.5 or 2 times plasma volume exchange (mean sessions - 4, range = 1-6). The mean duration of stay in hospital was 17.2 days (range = 3-40 days), and follow-up was 78 days (range = 3-180 days), with the majority of children (8/10, 80%) survived from the catastrophic illness at the time of discharge. Two children (2/10, 20%) succumbed due to the disease per se in severe dengue sepsis in one and enterobacteriaceae sepsis (hospital-acquired pneumonia) in another.

CONCLUSION

Plasma exchange was found to be beneficial as complementary therapy in a critical care setting, especially for nonrenal indications.

Snakebite Induced Thrombotic Microangiopathy Leading to Renal Cortical Necrosis

Renal complications from snakebite result in high mortality and morbidity. Acute kidney injury (AKI) occurs in 5–30% of cases. Renal manifestation could include acute tubular necrosis, cortical necrosis, interstitial nephritis, glomerulonephritis, and vasculitis. We present a case of thrombotic microangiopathy (TMA) resulting in renal cortical necrosis. Renal biopsy showed fibrin thrombi in glomeruli and arterioles with cortical necrosis. Our patient progressed to end-stage renal disease.

Disseminated intravascular coagulation caused by moojenactivase, a procoagulant snake venom metalloprotease

Snake venom toxins that activate coagulation factors are key players in the process of venom-induced coagulopathy, and account for severe clinical manifestations. The present study applies a variety of biochemical, hematological, and histopathological approaches to broadly investigate the intravascular and systemic effects of moojenactivase (MooA), the first described PIIId subclass metalloprotease isolated from Bothrops sp. venom that activates coagulation factors. MooA induced consumption coagulopathy with high toxic potency, characterized by prolongation of prothrombin and activated partial thromboplastin time, consumption of fibrinogen and the plasma coagulation factors X and II, and thrombocytopenia. MooA promoted leukocytosis and expression of the proinflammatory cytokines interleukin-6 and tumor necrosis factor-α, accompanied by tissue factor-dependent procoagulant activity in peripheral blood mononuclear cells. This metalloprotease also caused intravascular hemolysis, elevated plasma levels of creatine kinase-MB, aspartate transaminase, and urea/creatinine, and induced morphopathological alterations in erythrocytes, heart, kidney, and lungs associated with thrombosis and hemorrhage. Diagnosis of MooA-induced disseminated intravascular coagulation represents an important approach to better understand the pathophysiology of Bothrops envenomation and develop novel therapeutic strategies targeting hemostatic disturbances.

Melatonin inhibits snake venom and antivenom induced oxidative stress and augments treatment efficacy

Snakebite is a neglected health hazard. Its patho-physiology has largely been focused on systemic and local toxicities; whereas, venom and antivenom induced oxidative stress has long been ignored. Antivenom therapy although neutralizes venom lethality and saves many lives, remains ineffective against oxidative stress. This prompted us to complement antivenom with an antioxidant molecule melatonin that would protect against oxidative stress and increase the efficacy of the existing snakebite therapy. Here we show that D. russelli and E. carinatus venoms induce strong oxidative stress that persists even after antivenom administration in mice model. Additionally, antivenoms also induce oxidative stress. Polyvalent antivenom induce more oxidative stress than monovalent antivenom. Strikingly, antivenom and melatonin together not only inhibit venom and antivenom induced oxidative stress but also significantly reduce the neutralizing antivenom dose. This study provides a therapeutic potential for enhancing the existing snakebite therapy. The combined treatment of antivenom+melatonin would prevent the upsurge of oxidative stress as well as minimize the antivenom load. Thus the investigation offers immense scope for physicians and toxinologists to reinvestigate, design new strategies and think beyond the conventional mode of antivenom therapy.

Thrombotic microangiopathy due to Viperidae bite: Two case reports

Snake bite is mainly an occupational hazard and causes serious health problems in rural India. Acute kidney injury (AKI) occurs in 5-30% cases. Renal pathologic findings include acute tubular necrosis, cortical necrosis, interstitial nephritis, glomerulonephritis, and vasculitis. Thrombotic microangiopathy (TMA) occurrence after a snake bite is reported rarely. Here, we present two patients who developed TMA after viper bite treated with hemodialysis and plasmapheresis. Renal biopsy showed fibrin thrombi in glomeruli and arterioles with cortical necrosis. One patient progressed to end-stage renal disease and other was lost to follow-up. TMA should be considered as a possible pathogenesis of AKI after snake bite. The role of plasma exchanges in snake bite TMA is yet to be defined.

Role of biomarkers of nephrotoxic acute kidney injury in deliberate poisoning and envenomation in less developed countries

Acute kidney injury (AKI) has diverse causes and is associated with increased mortality and morbidity. In less developed countries (LDC), nephrotoxic AKI (ToxAKI) is common and mainly due to deliberate ingestion of nephrotoxic pesticides, toxic plants or to snake envenomation. ToxAKI shares some pathophysiological pathways with the much more intensively studied ischaemic AKI, but in contrast to ischaemic AKI, most victims are young, previously healthy adults. Diagnosis of AKI is currently based on a rise in serum creatinine. However this may delay diagnosis because of the kinetics of creatinine. Baseline creatinine values are also rarely available in LDC. Novel renal injury biomarkers offer a way forward because they usually increase more rapidly in AKI and are normally regarded as absent or very low in concentration, thereby reducing the need for a baseline estimate. This should increase sensitivity and speed of diagnosis. Specificity should also be increased for urine biomarkers since many originate from the renal tubular epithelium. Earlier diagnosis of ToxAKI should allow earlier initiation of appropriate therapy. However, translation of novel biomarkers of ToxAKI into clinical practice requires better understanding of non-renal factors in poisoning that alter biomarkers and the influence of dose of nephrotoxin on biomarker performance. Further issues are establishing LDC population-based normal ranges and assessing sampling and analytical parameters for low resource settings. The potential role of renal biomarkers in exploring ToxAKI aetiologies for chronic kidney disease of unknown origin (CKDu) is a high research priority in LDC. Therefore, developing more sensitive biomarkers for early diagnosis of nephrotoxicity is a critical step to making progress against AKI and CKDu in the developing world.

Pulmonary effects and complications of snakebites

This review is on the pulmonary complications of snakebites, which can have fatal consequences. We identified three common themes as reported in the literature regarding envenomation: generalized neuromuscular paralysis affecting airway and respiratory muscles, pulmonary edema, and pulmonary hemorrhages or thrombosis due to coagulopathy. Respiratory paralysis and pulmonary edema can be due to either elapid or viper bites, whereas pulmonary complications of coagulopathy are exclusively reported with viper bites. The evidence for each complication, timeline of appearance, response to treatment, and details of pathophysiology are discussed.

Presumptive thrombotic thrombocytopenic purpura following a hump-nosed viper (Hypnale hypnale) bite: a case report

Hump-nosed viper bites are frequent in southern India and Sri Lanka. However, the published literature on this snakebite is limited and its venom composition is not well characterized. In this case, we report a patient with thrombotic thrombocytopenic purpura-like syndrome following envenoming which, to the best of our knowledge, has not been reported in the literature before. A 55-year-old woman from southern Sri Lanka presented to the local hospital 12 hours after a hump-nosed viper (Hypnale hypnale) bite. Five days later, she developed a syndrome that was characteristic of thrombotic thrombocytopenic purpura with fever, thrombocytopenia, microangiopathic hemolysis, renal impairment and neurological dysfunction in the form of confusion and coma. Her clinical syndrome and relevant laboratory parameters improved after she was treated with therapeutic plasma exchange. We compared our observations on this patient with the current literature and concluded that thrombotic thrombocytopenic purpura is a theoretically plausible yet unreported manifestation of hump-nosed viper bite up to this moment. This study also provides an important message for clinicians to look out for this complication in hump-nosed viper bites since timely treatment can be lifesaving.

Hump-nosed viper bite: an important but under-recognized cause of systemic envenoming

Hump-nosed viper bites are common in the Indian subcontinent. In the past, hump-nosed vipers (Hypnale species) were considered moderately venomous snakes whose bites result mainly in local envenoming. However, a variety of severe local effects, hemostatic dysfunction, microangiopathic hemolysis, kidney injury and death have been reported following envenoming by Hypnale species. We systematically reviewed the medical literature on the epidemiology, toxin profile, diagnosis, and clinical, laboratory and postmortem features of hump-nosed viper envenoming, and highlight the need for development of an effective antivenom.

Fatal Envenomations - Snakes and Other Creatures

Envenomations by toxic creatures is a global health problem with an annual mortality from snake envenomation of over 125,000 cases. While various snake species bites are the most commonly encountered fatal envenomation, scorpions, spiders and marine creatures can all cause fatalities. Although venomous creatures have specific geographical habitats, the keeping of exotic pets and modern transportation, along with venomous collections in zoos, means that fatal envenomations may be encountered in non-endemic areas. There are a variety of toxins that may be encountered including neurotoxins, proteases, and myotoxins that will result in a variable amount of tissue damage depending upon the species involved and the toxin they carry. The autopsy findings may be relatively nonspecific and a careful search of the skin may be required to identify the envenomation site, along with a consideration of the history and the scene. External and internal damage will vary with the specific toxin. This paper reviews fatal envenomations, the toxinology and likely autopsy findings.

Comparative in-vivo toxicity of venoms from South Asian hump-nosed pit vipers (Viperidae: Crotalinae: Hypnale)

Background

Envenoming by south Asian hump-nosed pit vipers (Genus: Hypnale) is a significant health issue in Sri Lanka and in peninsular India. Bites by these snakes frequently lead to local envenoming, coagulopathy and acute renal failure even resulting in death. Recently the genus was revised and the existence of three species viz H. hypnale, H. nepa and H. zara were recognized. There is, however, a paucity of information on the toxicity of the venoms of these species. Hence, we compared the toxic effects of the three Hypnale venoms using BALB/c mice.

Findings

Intraperitoneal median lethal doses (LD₅₀) for H. hypnale, H. zara and H. nepa venoms were 1.6, 6.0 and 9.5 μg protein/g respectively. Minimum haemorrhagic doses for venoms of H. hypnale, H. zara and H. nepa were 3.4, 11.0 and 16.6 μg protein/mouse respectively. The minimum necrotic doses for the same venoms were 15.0, 55.1 and 68.2 μg protein/mouse respectively. Severe congestion and petecheal haemorrhages were observed in lungs, kidneys, liver and the alimentary tract. Histopathogical examination of kidneys revealed proximal tubular cell injury and acute tubular necrosis with intact basement membrane indicating possible direct nephrotoxicity. Hypnale venoms caused pulmonary oedema, hepatocellular degeneration and necrosis, focal neuronal degeneration in brain and extramedullary haemopoiesis in spleen. H. hypnale venom caused all above histopathological alterations at lower doses compared to the other two.

Conclusion

Hypnale venoms cause similar pathological changes with marked differences in the severity of the toxic effects in vivo. Therefore, differences in the severity of the clinical manifestations could possibly be seen among bite victims of the three Hypnale species.