Clinico-epidemiology of Hypnale zara (hump-nosed pit viper) envenoming in Sri Lanka

BACKGROUND

Hump-nosed vipers of the genus Hypnale are the most common cause of venomous snakebites in Sri Lanka. The genus includes three species: Hypnale hypnale, Hypnale zara and Hypnale nepa. Of them, H. hypnale bites are the most common and are the subject of many publications. The epidemiology and clinical features of bites by the other two species have been less investigated.

METHODS

We conducted a prospective observational study of H. zara bites from January 2015 to June 2020 at the Teaching Hospital, Ratnapura, Sri Lanka. Data were collected for 5.5 years in the wet zone of the island, where the principal investigator did assessment of all patients and the data collection.

RESULTS

H. zara envenoming was confirmed through identification of dead or live snake specimens brought with the patients. Of the 480 patients with proven hump-nosed viper bites, H. zara bites accounted for 105 (22%), including dry bites (n=5 [5%]) and envenoming (n=100 [95%]), with gender distribution of 65 (62%) males and a mean age of 43.1 y. Most bites occurred on the lower limbs (n=71 [68%]) in the daytime (n=69 [66%]) in home gardens (n=45 [43%]). A total of 100 (95%) patients had local manifestations, including pain (n=100 [95%]), swelling (n=100 [95%]), bleeding (n=20 [19%]), bruising (n=11 [10%]), lymphadenopathy (n=10 [9%]), necrosis at the bite site (n=9 [9%]) and blistering (n=8 [8%]). Seven (6.7%) patients showed systemic effects, including acute kidney injury (n=2 [2%]), microangiopathic haemolysis (n=2 [2%]), sinus bradycardia (2 [2%]) and one (1%) each had coagulopathy, thrombotic microangiopathy, Kounis syndrome and ischaemic changes on electrocardiography. Eosinophilia was a significant haematological finding (n=26 [25%]) and 16 (15%) had leucocytosis and 15 (14%) had neutrophilia. Ninety six percent of patients (n=101) recovered. Antivenom is not available for hump-nosed viper bites in Sri Lanka and therefore patients were managed conservatively.

CONCLUSIONS

This study shows that H. zara bites mainly cause local envenoming and rarely systemic effects.

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.

Clinical and epidemiologic profile and predictors of outcome of poisonous snake bites - an analysis of 1,500 cases from a tertiary care center in Malabar, North Kerala, India

Background

Snake bites are a neglected public health problem in all tropical countries, and particularly in Malabar region of Kerala, India. Demographic characteristics and clinical parameters vary in this part of the world, and studies based on them are scarce. Increased incidence of capillary leak syndrome (CLS) in hemotoxic snake bites and emergence of cases of hump-nosed pit viper (HNPV, Hypnale hypnale) envenomation are some notable features seen here.

Objectives

The study was conducted to assess the epidemiological profile and clinical features to identify factors contributing to outcome in patients with venomous snakebites.

Materials and methods

An observational cross-sectional study was done among patients with snakebite envenomation, admitted to Government Medical College, Kozhikode, Kerala, from January 2012 to October 2016.

Results

There were 1,500 cases of toxic snake bites, of which 65% of these cases were males. Forty eight percent of them were aged between 21 and 40 years. Hemotoxic snake bites predominated, accounting for 912 cases. Viperine bite was the most commonly observed snakebite, and 70% of this was due to Russell’s viper and 25% due to HNPV. Among the neurotoxic bites, common krait bites predominated. Overall mortality was 8.8%. CLS was the major cause of death (80%). The mean dose of antivenom given for neuroparalytic snakebite was 10.25 vials, and 18.5 vials for hemotoxic bites. Albuminuria, neutrophilic leucocytosis, thrombocytopenia, acute kidney injury (AKI), and early onset of symptoms were associated with poor outcome.

Conclusion

This study emphasizes the importance of snakebite as a significant threat to the community in the tropics. CLS in hemotoxic snake bites is the leading cause of mortality and is often refractory to any treatment measures. This study also brings to light the graveness of complications caused by HNPV envenomation. Anti-snake venom with activity against HNPV venom needs to be manufactured. Lack of awareness, delayed presentation to the hospital, and treatment by nonmedical personnel also add to the risk of mortality.