Two months ago, the World Health Organisation’s (WHO’s) 71st World Health Assembly in Geneva adopted a resolution “to accelerate and coordinate global efforts to control snakebite ‘envenoming’ — the life-threatening disease that follows the bite of a venomous snake”.
Between 1.8 million and 2.7 million people are bitten worldwide every year, between 81,000 and 1,38,000 of them die, and four or five times that number are disabled, according to the WHO. In India, which was a signatory to the resolution, some 50,000 die every year; however, the WHO fears this estimate may be just 10% of the actual burden. In 2017-18, 1.96 lakh cases of snakebites were recorded, with West Bengal, Maharashtra and Tamil Nadu reporting the biggest numbers.
This June, Maharashtra approved the setting up of a National Venom Research Centre, and asked the Centre to aid the public sector Haffkine Institute in its work on snake species and poisons. Of the 300-odd species of snakes found in India, 52 are venomous, but all their poisons are different.
The high case burden, poorly trained doctors, and lack of anti-snake venom (ASV) makers hobble India’s battle against snakebites. Biological E Ltd, VINS Bioproducts Ltd, Bharat Serums and Vaccines Ltd, and Premium Serums and Vaccines Pvt Ltd, are India’s only private ASV manufacturers; the nearly 120-year-old Haffkine Bio-Pharmaceutical Corporation Ltd is the only government-owned maker. In 2015, Sanofi stopped producing ASV saying it cost too much.
“ASV manufacture requires a series of forest department permissions. Horses are needed for the test, for which a large space is necessary. Private companies do not find all this financially feasible,” Subhash Shankarwar, general manager at Haffkine, said.
Licensed snake catchers need clearance to trap snakes in the wild, and a separate licence is issued to keep them in captivity for 90 days. The snakes are “milked” every week to collect a multipurpose enzyme secreted by the animals’ salivary glands. The diluted venom is administered to horses to immunise them; they are then bled to collect the antibodies that are generated. The plasma is separated, purified and converted into powder or liquid form to produce ASV. The manufacturing process can take a year.
“Each manufacturer has its own protocol, which is why the quality of ASV differs… We need uniform guidelines,” said Sampada Mehta, MD, Haffkine Bio-Pharma. Haffkine produces 24 lakh vials annually — Maharashtra purchases 3.8 lakh, West Bengal 3.5 lakh, Tamil Nadu 1.4 lakh, and Odisha 1.2 lakh. Overall, India produces some 1.5 million vials of ASV every year, Haffkine Institute director Dr Nishigandha Naik said — which is a third of the estimated annual requirement.
Lack of research
A decade ago, Sri Lanka stopped importing ASV from Haffkine citing inefficacy, a company official said. “We are noticing that the potency of ASV is reducing in the last few years. There is need for research to understand which combination works best,” Dr Naik said.
Doctors say locally produced ASVs are the most effective. A snake’s venom changes with terrain, diet and environment. But most manufacturers source their venom from Irula Cooperative Venom Centre in Tamil Nadu, which houses a large number of snakecatchers. This explains why, to treat a saw-scaled viper’s bite in Tamil Nadu, less than 10 vials may be required, while in Maharashtra it could be 30-80 vials, and in Jammu and Kashmir, over 80. The cost of treatment in a private hospital can be huge — a Russell’s viper’s bite requires 30-40 vials, which could cost upwards of Rs 20,000.
In a study of 1,686 snakebite cases from 2013-16 in Maharashtra’s tribal Palghar district, researchers found poor training among doctors, and high wastage of ASV. The research, funded by the Tribal Health Research Forum of the Indian Council of Medical Research (ICMR), showed that “in most cases, primary health centres referred patients elsewhere and the golden hour was lost”, principal investigator Dr Rahul Gajbhiye said.
Dr Himmatrao Bawaskar, who specialises in scorpion and snake bites, said doctors often miss the small mark left by the bite of a krait, the species responsible for 40% of snakebite deaths in India. “In most cases, doctors do not identify the bite mark as it is small, and the victim is attacked while asleep. Within hours, the victim develops neuroparalysis,” Dr Bawaskar said. MBBS courses should have a separate chapter on snakebites, he said.
Dr Smita Mahale, director of the National Institute of Research in Reproductive Health, which is supporting the Maharashtra government in training doctors, said, “In 2009 and 2016, snake bite protocols were drafted by the central government. But the training is yet to cover all doctors.”
Monovalent vs polyvalent
A monovalent ASV, made from the venom of one species, can treat the bite of only that species. It is more efficient, but the purpose is lost if the snake is not identified correctly. A polyvalent combines the venoms of India’s four most common poisonous snakes — cobra, common krait, Russell’s viper, and saw-scaled viper. More venom is wasted in the manufacture of the ASV, and more vials are required to treat the patient.
India currently manufactures only polyvalent ASV. It needs to train doctors to identify snakes by their bites before switching to the production of monovalent ASVs.