Pakistan tackles snakebite envenomation

[KARACHI] Kasturo Hathi was lopping down leafy fodder for his goats on a bright day in November when a saw-scaled viper bit him on his finger. Through the shock and excruciating pain he managed to swing his axe and bring down the shimmering, black and white reptile. 

Hathi survived because the species of the snake that bit him could be identified and because there was a vehicle handy to drive the five hours it took to move him from his village of Kohliweri to the nearest government-run hospital at Nagarparkar town, which stocks antivenom.  

Nagarparkar, nearly 450 kilometres from the port city of Karachi, lies in the foothills of the Karoonjhar hills bordering the Indian state of Rajasthan. The area is snake-infested and responsible for a fair share of the 40,000 people who are reportedly bitten by snakes in Pakistan each year. A fifth of these cases turn fatal.

In the absence of any scientific survey of snakes and snake species, this figure is questionable, says Amina Najam, senior scientific officer at the biological production division of the National Institute of Health in Islamabad, which has been manufacturing antivenom for 40 years.

“Most snakebites occur in very remote rural areas and we do not know how many [victims] are able to reach the hospital in time or if the reporting in hospitals is accurate,” says Najam.

“Hathi reached here in time and was just bitten once,” says Shankar Lal, Nagarparkar hospital’s medical superintendent who has over two decades of experience in treating snakebite victims.

“We used six vials (10 cubic centimeter) of antivenom on him over three days before his blood started coagulating and he was allowed to go home,” Lal says. Viper venom interferes with blood-clotting — a property exploited by pharmaceutical companies to manufacture blood thinners. Left untreated, the victim typically dies from internal bleeding or suffers permanent kidney failure.

Because Lal was certain that it was a saw-scaled viper he was confident in devising a sure-shot treatment plan. The distance between the fang marks and Hathi’s description of the rustling sound of the viper’s scales rubbing together were added confirmation. 

Had it been a cobra, a species common in the Tharparkar region, the treatment would have been very different. “Cobra venom is neurotoxic, and it can cause a cardiac arrest, blindness or stop the brain from working,” says Lal.

Allergenic antivenom

Administering the wrong type of antivenom not only results in treatment failure but also causes severe allergic reaction or even a fatal anaphylactic shock, says Chaman Sharma, a medical superintendent at the Mithi District Hospital, which serves Tharparkar. 

But doctors closely watch for adverse reaction from antivenom and are ready with adrenaline, antihistamine and cortisone. “We keep all of these drugs ready in the event of adverse reaction,” says Lal. The district hospitals are also equipped with ventilators and blood dialysis equipment which may become necessary.

The smaller hospital in Nagarparkar town stocks six months’ worth of polyvalent antivenom, capable of neutralising the venom of the Big Four — the Indian cobra, the common krait, Russell’s viper and the saw-scaled viper. To keep the refrigerator going and maintain the cold chain in a remote area with uncertain power supply, the hospital uses solar power and a diesel backup.  

According to Najam, the NIH scientist, the country’s antivenom production levels are estimated to be around 20,000 vials per year, which is insufficient for Pakistan’s needs. “A patient may need anywhere between two to five or even more vials," she tells SciDev.Net.

“By 2019 we should be able to produce over 100,000 vials and stop our dependency on import of antivenom from India,” says Najam. “We may even be able to export antivenom,” she adds.

“The Indian variety is not very potent and at times we have to administer as many as 26 vials or more to a single snake-bite victim,” says Sharma. That can be expensive, since each imported vial costs US$11 against the US$9 for a locally manufactured one.

Venom potency variation

Indian scientists say the potency of antivenom depends on several factors. “Ecological and environmental factors, gender, age and temperature affect the composition and potency of snake venom,” Kartik Sunager, a scientist at the Centre for Ecological Sciences at the Indian Institute of Science, tells SciDev.Net.

India recognises intraspecies variation and encourages collection of snake venom in each of its states for the manufacture of antivenom to be used locally. Efforts are also on to standardise antivenom made by different Indian manufacturers.

But in both India and Pakistan the mainstay of snakebite treatment is polyvalent antivenom which is made by injecting horses with venom from the Big Four and using the resulting antibodies.

Lal believes that snakebite prevention is far better than cure. “In the olden days, villagers were careful to slip on leather leggings, especially when moving about in the dark, but this practice has been abandoned because a false belief has grown that snakebite is now easily treated in Pakistan,” he says.

It was an hour after sunset when 27-year-old Kewal Churo, while returning home with his herd of goats, felt the sharp fangs. "It happened within seconds. I felt the bite on my left heel and glimpsed the grey and white snake, about a foot long, slithering away."

"I ran home and my father wound a rope tightly around my lower leg for a tourniquet,” recounts Churo. Because his village was not very far from the Mithi District Hospital, he could be brought in for medical treatment within an hour on a motorbike. The other option was to go to a traditional healer.

But, modern medicine has been elbowing out traditional healers. Kheemo Chand, 87, has not used his skills for two decades. "In my time I cured thousands of cases, even those from neighbouring towns and districts. Not a single person died on my watch."

Dismissing Chand’s claims, Sharma a the district hospital says most snakes found in Pakistan are not venomous. According to the IUCN, of the 72 snake species found in Pakistan, only 14 marine and 12 terrestrial snake species are poisonous.  

Najam says the NIH follows WHO standards to produce polyvalent antivenom that treats most poisonous snake bites. "We have never had a complaint from any part of the country saying the antivenom has not worked on a victim treated in time," she said.

Traditional healers, known as bhopas in Tharparkar, treat snakebite in a variety of ways. "These include applying a concoction made of herbs found in Karoonjhar hills, casting spells and sucking the poison out of the wound," said Chand.

Roop Chand Kanji, a snake charmer from Tharparkar's Jogi tribe keeps snakes as pets. Kanji uses herbal medicine made from a secret family recipe passed down generations. For the more serious cases, he places the precious manka (a black oval shaped stone that he claims is the fossilised head of an ancient snake) on the wound to suck out the venom. "It’s rare and extremely valuable," he says.   

Kanji says he never charges for his services but people feel obliged to gift him clothes, goats and food — which he accepts gladly.

More than medical science it is the free treatment for snakebite offered at the government hospitals that is elbowing out the Jogis and Bhopas. Churo's father was clear why he brought his son to a health facility. "Hospital treatment is free; we would have had to pay the bhopa in kind!"

This piece was produced by SciDev.Net’s Asia & Pacific desk.