The new ASF quarantine zone includes the districts of Vecumi, Medneva and Skilbeni in the municipality of Vilaka.
The veterinary authority explained that the necessity to establish the new quarantine zone arose after the ASF virus was found in several wild boars in Vecumi.
As many as 400 wild boars in Latvia have tested positive for ASF this year. The last case of ASF in domestic pigs was reported on July 6.
African swine fever is an extremely dangerous and contagious virus infection affecting pigs.
The head of the Latvian Pig farmers' association (LCAA), Dzintra Lejniece, told BNS on Thursday that the only solution for limiting the spread of the disease is decreasing the number of wild boar in Latvia.
"We have to realize that there are no laws or borders for pigs, and they move as they please. We cannot do anything else but limit their numbers," said Lejniece.
She added that farmers are negatively affected by the wild boar population growth, and that she has heard that the boars rummage the farmers' fields and have become so numerous they don't fear walking up to the windows of people's houses.
Meanwhile, a spokesman for PVD, Edvīns Oļševskis, said, in an interview to Latvian Radio on Thursday, that ASF will reach Rīga in one to two years.