Canberra, Feb. 7 : The Giant feral pigs have outnumbered humans in Australia, with 24 million of the beasts compared to a human population of about 21 million - a phenomenon that is ruining city drinking water and triggering an official cull.

According to the Herald Sun, parasites from pig excrement have been found in surface-water catchments, and it is likely to cost millions of dollars to treat and purify the water.

“We rely on our surface water. It''s an important part of our water supply. The feral pig issue is something we don''t want to get worse,” Water Department director John Ruprecht said.

“If we let it get out of hand there could be consequences. Feral pigs can carry many diseases such as Murray Valley encephalitis, as well as pathogens,” he added.

The Western Australia government had stepped up the pig-cull campaign, under which the feral pigs, which reportedly weigh up to 120 kilograms, are being caught in traps and then shot.

Other pests that the department has identified as a problem include feral cats, foxes, rabbits, camels, goats, horses, emus and wild dogs.

Water Corporation spokesman Phil Kneebone said research by Murdoch University had shown that hunters were introducing pigs into the protected water catchments so they could hunt and kill them for sport. (ANI)