An outbreak of Classical Swine Fever (CSF) has been confirmed near Porto, Brazil, in the northern state of Piauí. The outbreak occurred in a backyard farm and does not affect international trade because it took place outside the region that is considered “free from CSF.”
The outbreak affected 65 animals, of which 56 became ill and 32 were culled. In response, the state government declared a 180-day animal health emergency by a decree published Jan. 6. Control measures implemented include quarantine, zoning and movement controls. Additional measures are planned or underway, including stamping out affected animals, cleaning and disinfection, enhanced surveillance within and outside restricted zones, and traceability activities, officials say.
The outbreak was detected through passive surveillance and the source of infection remains unknown, reports Beacon, a program at Boston University’s Center on Emerging Infectious Diseases (CEID). Epidemiological investigations are underway to identify possible transmission pathways or links to other outbreaks.
The disease was reported to the World Organization of Animal Health (WOAH) by the Federal Agricultural Laboratory of Minas Gerais on Dec. 31, following a reverse transcription polymerase chain reaction test, reports Eurocarne.
This is not the first time this region has experienced CSF outbreaks. Piauí reported two CSF outbreaks in November 2023 and 13 in March 2024, with additional cases detected in the neighboring state of Ceará.
“The recurrence of CSF in Piauí underscores a persistent animal health risk within Brazil’s non-free zone, where the virus continues to circulate despite eradication in approximately 95% of the country’s pig production areas,” Beacon reports. “Repeated outbreaks in northeastern states indicate ongoing viral circulation, likely driven by gaps in backyard pig biosecurity and/or undetected transmission chains.”
CSF is a highly contagious pestivirus that affects both domestic and wild pigs. Transmission occurs primarily through direct contact with infected animals, contaminated feed and fomites. It can also spread through vectors such as ticks. The virus can persist in the environment for extended periods, particularly in organic matter, and can survive in frozen or chilled pork products, facilitating long-distance spread through contaminated meat.
The incubation period typically ranges from five to 15 days, during which infected animals may shed virus before showing clinical signs, complicating early detection and containment efforts. Clinical presentation ranges from acute forms with high fever, hemorrhages and rapid mortality to chronic forms with reproductive failure and immunosuppression, though the acute hemorrhagic form with high lethality is most common.
CSF is currently not present in the U.S.
