Snake Bites in North Kerala, Demographic Profile and Meaurses for Prevention

Snake Bites in North Kerala, Demographic Profile and Meaurses for Prevention

DOI: 10.14260/jemds/2014/1937



Krishnadas T1,Sasidharan P.K2


Krishnadas T, Sasidharan P.K. “Snake Bites in North Kerala, Demographic Profile and Measuresfor Prevention”. Journal of Evolution of Medical and Dental Sciences 2014; Vol. 3, Issue 04, January 27; Page: 990-998,

DOI: 10.14260/jemds/2014/1937

ABSTRACT: AIM: The study was done to verify the clinical and demographic profile, the predictors of outcome and to assess the degree of awareness about preventive measures against snakebite among the victims.METHODS AND OBSERVATIONS: It was a prospective observational study which included all patients above 12 years presenting to Calicut Medical College with history of snakebite from 1st March 2003 to 28th February 2004. There were 874 cases of which 213(24.4%) showed features of toxicity. 68.4% (598)were males. 52% belonged to 21-40 age group. 50%of nontoxic bites occurred during the months of March to June. Toxic bite did not have any seasonal variation. Viper was the commonest toxic snake and Eryx conicus the commonest nonpoisonous snake identified. Of the 213 toxic cases 111 cases showed hemotoxicity, 24 cases had local/regional toxicity; 40 cases with neurotoxicity and 38 cases showed mixed heamo and neurotoxicity.40 cases showed features of capillary leak and had high mortality rate. The median dose of polyvalent ASV used was 15.5 vials. Overall mortality among toxic cases was 14%(28cases). Capillary leak syndrome contributed to majority (23 of 28) of deaths. CONCLUSIONS: Overall mortality among toxic cases was 14%(28cases). Capillary leak syndrome contributed to majority (23 of 28) of deaths. Bite by Viper, presence of vomiting, early onset of manifestations, polymorphonuclear leukocytosis and bite during September to March predicted poorer outcome. 45% of the victims were totally unaware of any kind of preventive measures, those who were aware of did not take any preventive measures.

KEYWORDS:snakebite prevention, antisnake venom, capillary leak.

INTRODUCTION: Approximately 10-15% of 3000 species of snakes found worldwide are poisonous1.In Kerala, around 104 species are known, and of which 37 are poisonous1. Snake envenomation is a medical emergency with mortality of up to 10%2.Proper and prompt management often prevents significant morbidity and mortality. Snakes cause injury to human beings only when they are provoked.Though no epidemiological studies are available, most of the snakebites are accidental which could be avoided if proper precautions are taken.Many studies are available regarding clinical and demographic details of snake envenomation, but there are no studies that have evaluated the awareness or lack of awareness of preventive aspects of snakebite3.Here is an attempt to study all snakebites including the suspicious bites with an aim to study all aspects of snake bite including the awareness and practice of preventive measures.


  1. To study the clinical and demographic profile of snakebites in North Kerala.
  2. To find the predictors of outcome, if any.
  3. To find out whether the victims were aware of preventive measures or not.
  4. To formulate guidelines for prevention of snake bite

MATERIALS AND METHODS: This was an observational study from March 2003 to February 2004, conducted in Calicut Medical College, catering to patients from 5 districts of north Kerala.Patients were selected from snakebite ICU of the department of Medicine, which admits all the adult patients with history of any envenomation.Patients were included if they had definite history of snake bite or of suspicious snakebite.They were evaluated and managed based on a standard protocol and were monitored round the clock.Patients included in the study were evaluated based on a proforma with detailed history and physical examination. Particular attention was given to occupation, educational status, whether they were definite about the bite, awareness about preventive aspects, whether the bite could have been avoided if some precautions had been taken, regarding the type of snake, tourniquet used and whether they were given treatment from outside.The treatment given and the basic investigations done were also recorded. The end point of the study was recovery and discharge, going against medical advice or the unfortunate event of death.

All patients were examined for features of envenomation; at the time of presentation, after 2 hours, at 4 hours and every 2-4 hours thereafter or more frequently if required.Bite mark with edema, blister, bleeding or necrosis was considered as local reaction.Tender lymph node enlargement and limb edema extending beyond the proximal joint were considered regional manifestation.Vomiting, neurological, hematological or capillary leak was considered as systemic manifestation.Capillary leak was identified by conjunctival edema (chemosis) and parotid enlargement. Patients having no evidence of any of local, regional or systemic manifestations were observed and discharged 24 hours after the presentation. Those with any of the manifestations were admitted and monitored.Polyvalent Anti Snake Venom (ASV) was givenwhen indicated but withheld for isolated local reactions as far as possible.All patients were given local cleaning with antiseptic and injection tetanus toxoid.If there was evidence of envenomation like local/regional reactions, neurotoxicity, prolonged whole blood clotting time or any features of envenomation snakebite was considered as toxic bite and if there was no manifestation, it was considered as nontoxic.Equality of means was compared using ‘t’ test and Chi square test was used for comparison of continuous variables.

Character / Toxic
(N=213) / Nontoxic
(N=671 / Total
1 / Female / 48 / 228 / 276
2 / Male / 165 / 443 / 608
3 / Mean Age / 34.33 / 32.6 / 32.84
4 / Low Socio Economic Class / 199 / 566 / 765
5 / Manual Laborers / 159 / 364 / 523
6 / Referred From Outside / 152 / 230 / 382
7 / Bite Inside House / 41 / 232 / 273
8 / Avoidable Bite / 129 / 280 / 409
9 / Unprovoked Bite / 10 / 80 / 90
10 / Presentation Within 6hrs of Bite / 116 / 468 / 584
11 / Tourniquet use / 141 / 402 / 543
12 / Expired / 28 / 0 / 28
13 / Improved And Discharged / 183 / 648 / 831
14 / Gone Against Medical Advise / 2 / 13 / 15
Table 1.Demographic profile of snakebite cases

OBSERVATIONS: There were 874 cases of snake bite with 213 toxic bites and the snakes were well identified in 349(40%). Of the total 213 toxic bites, Russell’s viper contributed to 54 (26%) cases. Of the 213 toxic bites there were 28 fatal cases (13%). Three cases each with identified viper and cobra bite had not shown any toxic manifestations. Of 49 pit viper bites 24 cases showed evidence of systemic envenomation and the remaining 25 had not shown any evidence of envenomation. Eryx conicus was the commonest nonpoisonous snake identified (92 cases).The demographic profile of the patients with snakebite cases is given in table 1.

The most common site was lower limb with the right (354) and left (357) having equal incidence. In case of upper limb, there was right side predominance (right 90 and left 47). 26 cases had their bite on other parts of the body.

Seasonal and diurnal variation of snake bites:Seasonal variation was observed in snakebites, more so with nontoxic bites. Fifty percent of the nontoxic bites occurred March to June. The distribution in cases of toxic bites had more or less uniform incidence over the whole year.Snakebites occurred throughout the day, but the maximum (63%) was between 6pm to 10 pm.


Nontoxic bites(Total Number= 661):Pain was the commonest symptom in nontoxic bites, and was present in 414 (63%). Bite mark was seen in 420 (64% of nontoxic) cases. 248 (37.5% of nontoxic bite) cases had not seenthe snake. Only in 121 (18.5% of nontoxic bite) cases they were sure of identifying the snake and bite marks were present.

Bites with Toxic manifestations: (Total number = 213): Symptoms:Pain at the site was the commonest symptom present in all cases of toxic bite. Vomiting was present in 134 (63%) cases. Hematemesiswas present in 48 (22%) cases, bleeding in 37 (17%), diplopia in 29 (14%) and giddiness in 29 (14%) cases.

Local and regional manifestations:Bite marks were seen in 196 (92%) cases. Other local reactions included local necrosis in 17% of toxic bites, bleeding from the bite marks in 17% and bullae in 8% of toxic bites. Tender regional lymphadenopathy was observed in 127 (60%) cases. 36 (17%) cases had local swelling involving more than half of the limb. Isolated local/regional manifestation without signs of envenomationwas present in 24 cases (11% of toxic cases).

Neurotoxicity:Ptosis was observed in 78 (37%) and ophthalmoplegia in 76 (36%) cases. Single breath count was reduced to less than 30 in 82 (40%)cases, 74 cases had single breath count less than twenty. 9 (4%) cases had respiratory distress, three cases had respiratory arrest requiring mechanical ventilatory support and one of them, an 80 year old lady with Krait bite who was referred for respiratory distress died in spite of ventilatory support within hours of presentation to snake bite unit.

Hemotoxicity:Prolongation of whole blood clotting time to more than 20 min was the commonest bedside evidence of hemotoxicity (69 %), followed by bleeding gums and hematuria (22%). Altogether there were 149 patients who had features of hemotoxicity. A 75-year-old man who was bitten by Russell’s viper had prolonged clotting time, died due to intracranial bleeding one day after the bite in spite of ASV administration. Out of 149 cases having Hemotoxic features, evidence of capillary leak was observed in 40 cases (26%of hemotoxic bites, 29 male and 11 female). Russell’s viper was identified in 14 cases and saw scaled viper in 1 case; rest of the cases had not identified the snake but had features suggestive of viper bite. The median age of these patients was 30 years. Three of them belonged to middle socioeconomic class and the rest (37 cases) belonged to the lower socioeconomic class. 75% of the total cases with capillary leak occurred during September to February half year and (25% of the total cases with capillary leak in March to August.

Chemosis and periorbital edema were present in all the 40 cases with capillary leak and all were presumably due to viper bite. Parotid enlargement was present in 39 (26% of the total hemotoxic bites). In 30 (20% of the total hemotoxic bite) cases, the central venous pressure was low (<6 cm of saline). Nine patients of the total hemotoxic bite developed evidence of ARDS, 31 cases of the total hemotoxic bite developed ascites, and 10 cases developed pleural effusion.A 28-year-old woman developed pancreatitis 1week after Russell’s viper bite, was treated conservatively and was discharged after 20 days.27 patients of the hemotoxic bite had been given dialysis support.7 cases received hemodialysis alone, 13received peritoneal dialysis alone and 7received both peritoneal and haemodialysis.26 patients of the total hemotoxic bite were given blood or blood products transfusions., Of the 9 cases with ARDS8 died, only one survived, who was a 40-year-old woman, was discharged after 30 days of admission. Of the total 40 cases with capillary leak syndrome 23 died. Median dose of ASV given for cases with capillary leak syndrome was 20 vials.Russel’s viper alone was the cause in those with renal failure wherever snakes were identified. Russell’s viperwas identified in 14 cases with renal failure; others with renal failure also had features of Russell’s viper bite. Three patients expired due to renal failure in the absence of capillary leak syndrome. None of these patients had identified the snake, but features were suggestive of viper bite..

Treatments given: 210 out of 213 patients with toxic features were given anti- snake venom(ASV). Median dose of ASV was 15.5 vials. Antibiotics were given to 203 (95% of the total toxic bite) cases, Neostigmine to 51 (25% of the total toxic bite), steroids to 63 (30% of the total toxic bite), blood or blood products had to be given in 39 (19% of the total toxic bite) and dialysis support to 40 (19% of the total toxic bite) cases. Majority (170) of patients received intravenous fluid more than 100mL per hour. Twelve (6% of the total toxic bite) cases had to be given mechanical ventilation.Doses of ASV given to patients ranged from 1 vial to 35 vials median dose being 15 vials.

Investigation results: 154 out of 213 toxic snakebite cases had a total count of more than 10, 000/mm3 and of these 110 cases had polymorphs more than 80%. Eighty patients out of 213 toxic cases had a total count more than 15, 000/mm3 (22 Russell’s viper 2 cobra and 2 krait were identified) and 22 out of total 28 deaths occurred in this group. 11 cases had hemotoxic features, 10 cases had mixed hemo and neurotoxic and 1 case had neurotoxic feature.A 22-year man with unidentified snakebite presented with mixed toxic feature developed capillary leak syndrome in a day. He had a total count of 73900/mm3with69 % polymorphs, Hemoglobin of 19.6g/dLand creatinine of 1.3 mg/dL. Peripheral smear showed neutrophilia with toxic granules. He expired in a day in spite of peritoneal dialysis.

Complications:There were 83 patients with at least one complication. Acute renal failure (59 cases) was the commonest complication encountered followed by capillary leak syndrome (40 cases), both were more common with viper bite (14 identified viper bites, rest were presumed viper bite).. ARDS requiring ventilatory support (10 cases of total 213 toxic snake bite), and cellulitis (7 cases of total 213 toxic snake bite) were other common complications occurred with viper bite. Reaction to anti snake venom was seen in 17 cases.

Cause of death:Capillary leak syndrome contributed to majority of the mortality, i.e. 23 out of 28 (82% of the total death). Acute renal failure without features of capillary leak was the causein 3 patients who died.A difference in mortality rate in different months was also observed. There were17 deaths out of 78 admissions (15 viper bite) in a 4 months period from November to February (winter months) compared to 2 deaths out of 66 admissions (26 viper bite) in the following 4-month period (summer). There were 9 deaths out of 69 admissions (13 viper bite) from July to October (monsoon). Details are given in table 2

Month / No Of Death / No of Admission / No Of Viper Bite / Mortality Rate
March / 0 / 9 / 0 / 0%
April / 0 / 12 / 7 / 0%
May / 1 / 28 / 13 / 3%
June / 1 / 17 / 6 / 6%
July / 3 / 23 / 8 / 13%
August / 2 / 15 / 1 / 13%
September / 3 / 19 / 3 / 16%
October / 1 / 12 / 1 / 8%
November / 7 / 29 / 4 / 24%
December / 6 / 30 / 6 / 20%
January / 2 / 8 / 4 / 25%
February / 2 / 11 / 1 / 18%
Total / 28 / 213 / 54 / 14%
Table 2: Month Wise Distribution Of Mortality Due To Snakebite

Hospital stay:Median duration of hospital stay was 4 days with a range of 1 to 60 days. Those who expired had median stay of 3 days. Median duration of hospital stay for patients with local envenomation was 3 days, those with neurotoxicity 4 days, those with hemotoxicity 4 days and those with mixed Hemo and neurotoxicity 5 days.


Bite by Russell’s viper had significantly higher mortality than any other snake. Out of the 54 identified viper bites 14 died while 169 non-viper bites only 14 died. Vomiting was associated with higher mortality risk. Presence of regional or systemic manifestation and development of any of the complications also made the patients at higher risk of death. Those who had developed manifestations within 6 hours had a higher mortality risk than those who developed it after 6 hours. Bites on the lower limbs had an increased risk of mortality compared to those in other parts. It was also observed that an increase in mortality occurred during the months from September to February (21 deaths out of 109 admissionswith established toxicity) as compared to March to August (7 deaths per 104 admissions). Those who needed steroids, Neostigmine, dialysis support, blood transfusion also were at a higher risk of mortality (Table 3).

The investigational parameters associated with higher mortality were high total leukocyte count, high polymorphs, thrombocytopenia, and high blood urea, prolonged clotting time and reduced single breath count. Hemoglobin and Serum Creatinine values did not predict the risk of mortality and complications. After considering various parameters, those given in Table 3 predict the risk for mortality.

Character / Discharged (n=185) / Expired (n=28) / Odd’s ratio
Present / Character
Absent / Character
Present / Character
Definite bite / 143 / 42 / 27 / 1 / 7.9
Viper bite (identified) / 40 / 145 / 14 / 14 / 3.6
Vomiting / 107 / 78 / 27 / 1 / 14.6
Regional Lymphadenopathy / 102 / 83 / 25 / 3 / 6.8
Neurotoxicity (SBC<30) / 51 / 134 / 23 / 5 / 12
CT>20 / 119 / 66 / 27 / 1 / 15
Steroids / 41 / 144 / 23 / 5 / 16
Neostigmine / 41 / 144 / 11 / 17 / 2.3
Delay 6hrs / 109 / 76 / 22 / 6 / 2.6
Admission in Sept -March / 88 / 97 / 21 / 7 / 3.3
Table 3: Mortality Risk Factors Of Snake Bite Cases

The total dose of ASV given did not differ in those who expired and those who were discharged. There was no significant difference in mortality among patients receiving less than 10 vials, 11 to 20 vials or more than 20 vials.Treatment or receiving ASV from outside had no significant difference in mortality. Walking after bite (117 out of 213 toxic cases) did not alter the mortality-pattern.

DISCUSSION: Snakebite is a common medical emergency in North Kerala, there were 874 cases in a year attending Calicut Medical College, which is a tertiary care center, and teaching institution. This constitutes both toxic as well as nontoxic snakebites and might grossly be an underestimate because many of the cases especially nontoxic cases might not have reached the Calicut Medical College. There were 661 (75.6%) non-toxic and 213 (24.4%) toxic snakebites that occurred during the period of March 2003 to February 2004.

The age group most affected is 20 to 40 years since the young males are often outdoors as workers21% of the toxic bites and 39% of nontoxic snakebites occurred inside house. This indirectly indicates the poor living condition of the victims affected. They might be benefited by adopting precautionary measures, improvement in living conditions and the hygiene of the house.

Most common site of snakebite was in the lower limbs, and in cases of bites in the upper limbs there was significant difference between right and left (in 90 cases right and in 47 cases left) indicating indirectly that the bites occurred due to provocation of the snakes by touching it due to lack of precaution on the part of the victim. Higher mortality in bites on the lower limb might be due to less chance for immobilization as compared to other parts of the body.

Almost half of the victims were not sure of the snakebite, half walked after the bite. In case of toxic cases, 117 out of 213 patients walked after the bite, though this has not contributed to an increased mortality. More than half of total patients (141 of 213 toxic bite) used tourniquet. 47% of all snakebite victims thought bite could have been avoided, had they taken some precautions but had not taken adequate precautions to prevent snakebite in spite of knowing its importance. Remaining 53% of the total cases were not aware of any preventive measures. Early development of manifestations was found to be associated with a higher mortality.Such early manifestations could be due to higher dose of venom injected. None of the patients who presented after 48 hours of snakebite had died.