SOFIA (Reuters) - Bulgarian authorities said on Wednesday that they would cull another 17,000 pigs after detecting an outbreak of African swine fever at a breeding farm in the north of the country, the fifth hit by the fast-spreading virus this month.

FILE PHOTO: A pig rests at a farm near the village of Belotincy, 140 km (90 miles) from the capital Sofia, April 28, 2009. REUTERS/Oleg Popov/File Photo

The outbreak was detected at a farm in a village near the Danube town of Svishtov. More than 100,000 pigs have already been culled at four other farms in the past two weeks.

Industry officials fear that the virus could wipe out the Balkan country’s entire pig herd of about 500,000 and cause damages of up to 2 billion levs (931.4 million pounds).

Bulgaria has so far detected more than 20 outbreaks of African swine fever at industrial or backyard farms in the north of the country.

Officials said that, for the time being, they are not ordering the culling of all home-raised pigs but may have to do so if the instructions of the veterinary authorities are not strictly observed by the rural population.

“We may get to the worst possible scenario if the protective measures are not followed,” Agriculture Minister Desislava Taneva told reporters after a meeting at the president’s office.

“We need to keep the remaining 60 industrial pig farms clean from contamination,” she added.

On Monday, 20km sanitary zones around all registered industrial pig farms were set up. Home breeding of pigs without bio-security measures is not allowed in these zones.

Officials appealed to the people in the affected areas not to try to hide or sell their pigs.

Bulgaria is one of the poorest EU member states and almost every household in rural areas keeps home-raised pigs.

The country has also mobilised military and police forces to help to combat the highly contagious disease.

Analysts said that the price of pork in Bulgaria has increased by up to 30% in less than a month because of the swine flu outbreaks and could rise by a further 15% in the autumn.

African swine fever is lethal to pigs and wild boar but does not affect humans.