The Cumberland Livestock Health and Pest Authority in Camden believes illegal pig hunters have released feral pigs and are obstructing organised pest control programs.

Ranger Steve Parker said there was an isolated population of feral pigs that had been released along the Nepean River foreshores.

The pigs are destroying native vegetation, farming crops and the Nepean River corridor. Their presence also increases the possibility of transferring diseases to humans.

Feral pigs are a pest under the Rural Lands Protection Act. The authority has implemented control programs using trapping, poisoning or shooting to eradicate them.

Ranger Parker said he believed that illegal pig hunters were transporting and releasing the declared pests into the area.

The hunters may also be interfering with the authority's traps, releasing trapped feral pigs and removing surveillance cameras.

Over the past year the authority has captured and eradicated about 60 feral pigs.

Mr Parker said tested pigs showed positive results for zoonotic diseases, which can be transmitted from animals to humans.

Feral pigs also have a high likelihood of carrying other exotic and serious diseases.

Mr Parker said the Menangle and Nipah viruses were potential risks in the area because Penrith has a significant bat population. Feral pigs can become infected with these viruses if they eat infected dead bats and bat droppings.

Menangle Virus can also be transmitted to humans. The Nipah Virus devastated Malaysia in 1999, causing human deaths and destroying the $400-million pork industry.

``Under the Rural Lands Protection Act it is an offence to transport and release feral pigs or keep them in captivity, with penalties of up to $22,000. ``We don't want to tarnish the reputation of law-abiding pig hunters but there are minority groups that have an attraction to illegal hunting.''

Any information about local illegal pig hunting should be given to the police.