PARIS (AFP) - Tens of thousands of people will unnecessarily die of snakebites unless an affordable new source of antivenom is found, Doctors Without Borders has warned, with stocks of a French-produced drug running out.

Pharmaceutical company Sanofi stopped production of the drug, Fav-Afrique, at the end of last year, the medical volunteer group, known by its French acronym of MSF, said.

The last batch will expire next June.

An effective replacement will not be available "for another two years," MSF warned in a statement issued to coincide with a symposium in Basel, Switzerland on Tuesday (Sept 8), entitled: "Time to improve snakebite management in the tropics."

"The absence of a safe and effective antivenom that is active against multiple toxins from June 2016 until at least the end of 2018 will translate into countless deaths," it said.

"Until alternative treatments are found, Sanofi needs to ensure the interim production of the Fav-Afrique antivenom." Fav-Afrique acts against the venom of 10 different snake species, among the most dangerous in Africa.

About five million people are bitten by snakes every year, of whom about 100,000 die, according to the World Health Organization (WHO).

Some 300,000 people per year lose limbs or suffer other permanent disabilities after snakebites.

The UN's health body lists snakebites as a "neglected" public health issue.

"Poor data on the number and type of snakebites, leading to difficulty estimating needs, combined with deficient distribution policies, have contributed to manufacturers stopping production or increasing the prices of antivenoms," says a WHO factsheet.

"Poor regulation and the marketing of inappropriate antivenoms, has led to a loss of confidence in the available antivenoms by clinicians, health managers and patients, which has further eroded demand" and pushed up prices.

Antivenom treatment can cost as much as US$500 (S$700) per patient, according to MSF.

Sanofi said Fav-Afrique could no longer compete with cheaper alternatives flooding the market from Asia, Latin America and Africa, but MSF warned these versions were less effective and did not cover snakebites by such a wide range of species.

The pharmaceutical giant said it "regretted" having to stop production, but stressed it had been warning of the impending situation for years.

"This situation, essentially a failure of the market, has clearly shown how price pressures can lead to choices being made to the detriment of reliability and, potentially, quality, of drug supply, with impacts on public health," it said in a statement.

MSF warned of a "real crisis".

"The global health community, donors, governments and pharmaceutical companies should accept responsibility for their share of the neglect of snakebite as a public health emergency and take immediate, appropriate and collaborative action," it said.