Pollution in the Mekong River in Southeast Asia has pushed freshwater dolphins in Cambodia and Laos to the brink of extinction, the World Wildlife Fund (WWF) has said.
"There are only 64 to 76 Irrawaddy dolphins in the Mekong," the WWF said Wednesday. It said toxic levels of pesticides, mercury and other pollutants were found in more than 50 calves that have died since 2003.
"Necropsy analysis identified a bacterial disease as the cause of the calf deaths," WWF veterinary surgeon Verne Dove said in a press statement. "This disease would not be fatal unless the dolphins' immune systems were suppressed, as they were in these cases, by environmental contaminants."
Dove said: "these pollutants are widely distributed in the environment and so the source of this pollution may involve several countries through which the Mekong River flows."
The Mekong flows from China through Laos, Cambodia, Thailand and Vietnam.
"The Mekong River dolphins are isolated from other members of their species and they need our help," said WWF Cambodia country director Seng Teak, adding that the mammals "can show remarkable resilience" if their habitat is protected.
The WWF said it was investigating how contamination had entered the Mekong River, and called for a cross-border health plan for the dolphins.
The Mekong River Irrawaddy dolphin, which inhabits a 190- km (118 mile) stretch in Cambodia and Laos, has been listed as critically endangered since 2004.