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Eritrea’s Most Dangerous Snake: the Carpet Viper (Part Two)

Editor’s Note: The first part of this article by Dr. Theodore Papenfuss was published in the June 4, 2022 issue of Eritrea Profile, under the topic ‘What do you know about snakes in Eritrea?’

After dark, I walked out of the Barentu Tree Nursery at the edge of the town. Our vehicle was parked next to some houses by the gate. We had collected a few frogs from pools of water in the nursery. Two young men who lived nearby and worked in the nursery had helped us catch the frogs. As we were getting ready to leave, a young boy about ten years old came out of his house to see the frogs. Kaleab turned on his flashlight to show the boy our bucket of frogs. I looked down and saw a Carpet Viper, a hazardous snake, lying motionless on the ground only about two meters from Kaleab and the boy. I said, “Kaleab, do not move and tell the boy to stand still!”

The snake did not move while I got an empty bucket and a snake hook tool from the back of the Toyota Hilux. I used the snake hook to lift the Carpet Viper into the bucket. The snake was about 40 centimeters long. Carpet vipers are a small species; the maximum size is about 70 centimeters. The snake was uncomfortable with the light we were shining on the bucket. The typical behavior of this viper species is to form its body into a coil with its head up on the top while the snake moves the coiled body back and forth, rubbing the scales together. The rubbing makes a loud noise that sounds like someone cutting wood with a saw. Another name commonly used is “Saw-scaled Viper” because of the noise these angry vipers make. The name “Carpet Viper” is due to the colors of the body markings that look like an oriental carpet. They seem familiar in the tree nursery because many frogs, toads, lizards, and mice provide food for the snakes.

There is a well at the nursery, and the tree seedlings are watered daily. Our primary purpose in collecting Carpet Vipers from Barentu is to take tissue samples for future DNA studies. In addition, there is a need to find out if Eritrean Carpet Vipers are genetically closely related to Carpet Vipers in Sudan, South Sudan, Ethiopia, and northern Kenya. Finally, snakebites from venomous species are treated with an intravenous injection of antivenom. There may be a need to develop new antivenoms to treat Carpet Viper bites in Eritrea and neighboring countries.

In 1960 only two species of Carpet Vipers were scientifically recognized and given scientific names. All Carpet Vipers in Africa were named Echis ocellatus scientifically. The second species was the Indian Carpet Viper, scientifically called Echis carinatus for snakes found in the Arabian Peninsula, the Middle East, and the Indian subcontinent. This unfortunate early classification of Carpet Vipers contributed to the death of many who lived in Sub-Saharan Africa because suitable antivenoms had not yet been developed for Echis from a different region of Africa where these snakes lived. In addition, medical professionals did not know that there were considerable differences in the venom composition of Carpet Vipers from other countries.

Starting around 1960, scientists found significant regional differences in the chemical composition of Echis venom that was extracted for making antivenom to treat snakebites. Superficially all Echis look almost the same and have the same coiling behavior and the saw-like sound we observed in the Barentu snake. However, there were differences in scale numbers and scale shapes that can be seen under a microscope. Now, in 2022 there are 18 species of Echis, with 12 found only in Sub-Saharan Africa north of the Equator.

The only effective treatment for venomous snakebites is antivenom. The medical history of antivenom production started in India in the 1890s. An Indian doctor talked to a snake charmer bitten by a cobra but had no severe reaction to the bite. At that time, cobra bites were very often fatal. The snake charmer told the doctor that he had injected himself with tiny amounts of cobra venom over several years and was now immune to the toxin. He told the doctor that he had been bitten several times with no effects. The doctor and other medical professionals decided to try to produce an antivenom, which could be injected into humans to neutralize the venom.

Various experimental methods were tested, and by the 1920s, the best method was the production of antivenom using the blood plasma of domestic animals, usually horses. This method is still used over a century later. First, venom is extracted from snakes using a process called “milking,” where a trained person holds a snake behind his head and presses the mouth against a piece of plastic wrapped to a glass container. Then, when the snake opens its mouth and extends its fangs through the plastic wrap, the person presses the top of the head where the venom glands are located. This forces the venom out of the paired venom glands, and the poison is ejected through the hollow fangs into the glass container.

Kaleab is removing the liver from the carpet

The antivenom is injected into a horse, starting with a small amount of venom and gradually with larger and larger amounts once a week for about two months. The horse’s immune system reacts and produces antibodies that bind to and neutralize the venom. At this point, the horse is ready to have its blood harvested. Around 3 to 6 liters of blood are drained from the jugular vein. In a few weeks, the horse produces enough blood to replace the amount drained, and the process can be repeated. The antibodies are separated from the blood plasma and purified to use as antivenom for humans. When injected intravenously into a patient, the antibodies neutralize the venoms in the patient.

2021 WHO report estimates that there are 2.7 million snakebite envenomations (poisoning from snakebites) with between 81,000 and 138,000 human deaths each year with three times as many amputations and other permanent disabilities caused by venomous snakes worldwide. Many victims living in remote areas far from medical facilities die shortly after snakebite accidents and therefore are absent from hospital records.

Dr. Tekeste Fekadu is a surgeon at Orotto Hospital in Asmara. He was an EPLF Frontline Trauma Surgeon during the struggle for independence from 1976 to 1991. He published an article about venomous snakebites in Eritrea in the Journal of Eritrean Studies, Volume 7, June 2016.

This excellent article provides information on human snakebites in Eritrea from the colonial period until 2016. As a frontline surgeon, venomous snakebites were a significant concern for forwarding Surgical Units (FSU) and Front Line Hospitals (FLH) during a military engagement, especially in the lowlands of Gash-Barka and the arid Sahel mountains around Nakfa and Afabet. Quoting Dr. Fekadu, “It was common to see different types of snakes resting, sluggishly or swiftly moving, leaping across or coiling around branches of trees, stealthily creeping among rocks and in caves, and rarely, even lying beside combatants during nights.” Combat medics first treated snakebite victims at brigade clinics or division hospitals in combat zones.

The standard procedure for treating snakebites included immobilizing the bitten limb, tying a tourniquet above the bite site, and administering antibiotics and anti-pain medicines. No antivenoms were available. From 1979-1986 there were 104 cases of treated snakebite victims from the Sahel around Nakfa and Afabet. Unfortunately, there were 13 deaths (12.5%). After independence, reports are made to the Ministry of Health from health facilities in each Administrative Zone.

In Eritrea, there are two families of venomous snakes, vipers such as the East African Carpet Viper, and elapid snakes such as the Nubian Spitting Cobra. Depending on the type of snake, the toxins in the venom can cause different problems, like damage to the nervous system from a bite by Nubian Spitting Cobra or massive internal bleeding and tissue destruction from the bite of an East African Carpet Viper.

This ends part 2 of Eritrean snakes. I received new information this week about two new methods that are being studied to make antivenom that does not require the 100-year-old method of snake milking to make horse serum for human injection.

Dr. Theodore (Ted) J. Papenfuss

Museum of Vertebrate Zoology,

University of California at Berkeley

NCEA-Public-Diplomacy-Group- Online Quarterly Magazine


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