Snakebite
is one of the most neglected of all tropical diseases, with nearly 5 million
people bitten by snakes each year and fatalities globally up to 30 times higher
than that of land mines and comparable to AIDS in some developing countries. It
has been estimated that more than 75 percent of snakebite victims who die do so
before they ever reach the hospital so a new approach may dramatically reduce
the number of global snakebite fatalities, currently estimated to be as high as
94,000 per year.
Such a fast, accessible, and easy-to-administer treatment for venomous
snakebite may be coming. Not soon, the regulatory process allows no shortcuts
and clinical trials are expensive, but it is in the works.
Researchers have reported on a pilot study geared toward developing a universal
antidote for snakebite. Last summer, the team tested the effectiveness of a
nasally administered antiparalytic drug on mice injected with high doses of
Indian cobra (Naja naja) venom. Mice injected with otherwise fatal
doses of venom outlived and in many cases survived after being treated with the
antiparalytic agent, neostigmine.
Although the mice in this experiment were each treated only once to maintain a
consistent protocol, a nasally administered antidote could, in practice, be
administered multiple times without needles. Inhibitors of other types of venom
could be combined with those working against paralysis to form a complete
antidote. With many combinations for potential testing, the team is now working
intensively with chemist and snake venom expert, Dr. Sakthivel Vaiyapuri of
Reading University in the United Kingdom, a co-author on the report.
Separate
groups of mice were given varying doses of venom (all above lethal limits) and
then treated with the antiparalytic treatment at two different time intervals:
within 1-2 minutes after envenomation and 10 minutes after envenomation. 10 of
15 mice given the lowest dose of venom, followed by the treatment within 10
minutes, survived and later exhibited completely normal behavior, while 100
percent of control mice died. In groups given higher doses of cobra venom (2 to
5 times the lethal dose) all mice succumbed, but those treated with a single
dose of neostigmine survived significantly longer than the controls.
"Antivenom is necessary, but not
sufficient to manage this problem. Its limitations are fairly well known at
this point and we need a better bridge to survival. It's ironic that virtually
every medical organization and practitioner wears the snake symbol, yet we have
no real effective treatments for the people getting bitten," says Dr.
Matthew Lewin of the California Academy of Sciences. "Ninety-eight percent
of snakebite victims live in poverty, which is perhaps why funding and
innovation are lacking. The bottom line is that no one should die from a snake
bite in the twenty-first century, and we're optimistic about this promising
step."
The team initially demonstrated the potential
of this novel snakebite treatment during an experiment conducted in April of
2013 at the University of California, San Francisco. In that experiment, a
healthy human volunteer was paralyzed, while awake, using a toxin that mimics
the effects of the venom of cobras and other snakes that disable their victims
by paralysis. The experimental paralysis progressed from eye muscle weakness to
respiratory distress in the same order typically seen in snakebite victims. The
team then administered the nasal spray and within 20 minutes the patient had
recovered. The results of that experiment were published in the medical journal Clinical
Case Reports.
In late June of 2013, Samuel, Dr. C. Soundara
Raj, and colleagues at TCR Multispeciality Hospital in Krishnagiri, Tamil Nadu,
India accelerated the recovery of a snakebite victim on life support using this
method. After receiving 30 vials of antivenom, the standard treatment for
venomous snakebites, the female patient remained weak and suffered from facial
paralysis. Within 30 minutes of treatment with the antiparalytic nasal spray,
the patient's facial paralysis was reversed. Two weeks after being treated, the
patient reported having returned to her daily activities.
Citation
Matthew
R. Lewin, Stephen P. Samuel, David S. Wexler, Philip Bickler, Sakthivel Vaiyapuri,
and Brett D. Mensh 2014. Early treatment
with intranasal neostigmine Reduces Mortality in a Mouse Model of Naja naja (Indian Cobra) Envenomation,” Journal of Tropical Medicine, vol. 2014, Article ID 131835, 6 pages, 2014.
doi:10.1155/2014/131835