Introduction:
Snakebite is an important occupational hazard affecting farmers, plantation
workers, herders and fishermen. Open-style habitation and the practice of
sleeping on the floor also expose people to bites from nocturnal snakes,
with children being at a particularly high risk. In rural Nepal, snakebite is an
important public health problem. The agriculturally prosperous terai region
with hot climate, high seasonal rainfall, lush natural vegetation, high density
of rodents, rich reptiles and amphibian flora make an ideal habitat for snake
to live and increase availability of marshy land to undergo hibernation. The
abundance of snake and human activities, mainly agriculture, increases the
man– snake encounter leading to snakebite. Nocturnal snakebite is also
common in Nepal due to the sleeping habit.
Snakebite is a life threatening medical emergency and survival of the
victims depends much on the appropriate first aid measures and immediate
transportation to the nearest health center where the facility to administer
anti-snake venom and supportive care is available. In developing countries
where snakebite is mostly prevalent, traditional faith healers, snake
charmers and religious man (Dhami) treat many snakebite victims. In
rural population of Nepal, the doctor population ratio is far from accepted
norms and most of the trained health workforce are based in urban areas.
Therefore, the people of rural areas often seek health care from practitioners
of indigenous medicine. Most of the death related to snakebite occurs
before reaching the treatment center, either during transportation or at the
village. Doctors or health workers at primary care level as well as some of
the district and provincial level hospital do not treat snakebite, likely due
to inadequate training on snakebite management during medical schools
resulting in lack of confidence on management of snake envenoming.
Magnitude of the Problem:
Globally, the actual incidence and mortality associated with snakebite
envenoming is poorly known, in part due to the lack of reliable information.
In Nepal, WHO estimates that 20’000 people are bitten by snakes each year,resulting in over 1000 deaths . Nevertheless, existing epidemiological data
remain fragmented, and several studies suggest that the true burden of
snakebite is much higher. A hospital-based retrospective survey conducted
in 10 hospitals of eastern Nepal reported 4078 cases of snakebite (407/
hospital/year) including 379 with signs of envenoming. The mortality in
envenomed patients varied considerably among the centers from 3% to 58%
(mean=21.37%) . Similarly, high numbers of snakebite cases were reported
from the districts of western development region, eastern and central Nepal.
The highest figures reported so far come from a community-based survey
conducted in southeast Nepal in 2002 which revealed annual incidence and
mortality rates of 1,162/100,000 and 162/100,000, respectively.
An ongoing study “Snake-byte: a nationwide cross-sectional community
incidence study to assess and predict the impact of snakebite on human and
animal health in Nepal” is likely to provide better statistics of snakebite in the
community and outcome of snakebite including its economic impact. The
mortality related to snakebite envenoming varies. It may be related to quality
of care of the patients, access to mechanical ventilatory support, health care
knowledge and skill to timely and appropriately administer antivenom and
intubate patients when indicated, inability to identify serious adverse effects,
lack of standard protocol for management of snakebite, etc.
Clinical Manifestation of Common Venomous Snakes Of Nepal:
Snake venom is a complex mixture of toxins. Composition of venom varies
from one species to another. Even in same species, the venom composition,
may vary according to geographical location and age of the snake. Therefore
the clinical features may differ in severity although bitten by same species.
After the bite of a snake, victims may have following consequences:
- No clinical manifestation except bite mark. This may be due to bite by non-venomous snakes or bite by venomous snake without injection of venom (Dry bite)
- Local manifestation in the part of body that has been bitten.
- Systemic manifestation due to systemic absorption of venom. This may be neurotoxicity or hematotoxicity depending on the envenoming species.
- Signs and symptoms due to traditional treatment for example; local gangrene due to tight tourniquet, pain abdomen, vomiting etc. due to congestion of chilies, herbal medicine etc. Tight tourniquet/s may cause pain, swelling and congestion that may be confused with local envenoming.
Note: Not all bites by venomous snakes are accompanied by the injection of venom, and
therefore not all patients bitten by a venomous snake will develop symptoms and signs of
envenoming. However, when envenoming does occur, it can be life-threatening.
Recommended First Aid Treatment for Snake Bite:
Reassurance:
- The victim may be very frightened and anxious. Reassure victim that most of the suspected snakebite are caused by nonvenomous snakes. Reassure victim on that snakebite is a treatable condition.
Immobilization:
- Immobilize the bitten limb with a splint or sling. Any cloth or bandage may be used for this, as done for fracture limb. Any form of movement causing muscle contraction like walking, undressing will increase absorption and spread of venom by squeezing veins and lymphatics.
- Pressure immobilization (PIB) is believed to delay in spread of venom to systemic circulation and PIB method is commonly recommended by many experts in pre-hospital management. However, the pressure-immobilization technique demands special equipment and training and is not considered practicable for general use in Nepal. Searching for the material to apply pressure immobilization may cause delay in seeking much needed health care for treatment of envenoming.
- Moreover, envenoming by cobra and vipers snakes causes local tissue damage and localization of toxin by PIB may worsen tissue damage. n Pressure pad immobilization has been found to be useful in Myanmar. It’s applicability in Nepal is not known. Remove rings, jewelries, tight fittings and clothing and avoid any interference with the bite wound to prevent infection, increase absorption of venom and increase local bleeding.
Rapid Transport
- The victim should be transported to the hospital where he can receive the medical care.
- The most common cause of death due to snakebite envenoming in Nepal is due to respiratory paralysis (and rarely shock due to bleeding from Russell’s viper envenoming). In one of the community- based study, 80% of the patient with envenoming died even before reaching snakebite treatment center or hospital. Rapid transport using motorcycle has been found to decrease mortality in Nepal. The victim is seated and held between driver and pillion rider.
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