In the classical swine fever outbreak in the U.K., what was the most likely way the virus spread to 16 different sites?

• A. VECTORS INCLUDING MOSQUITOES AND FLIES
• B. Feeding of infected pig swill (food waste)
• C. Movement of infected animals and potentially wildlife scavengers carrying dead infected animals to neighboring farms.
• D. Wild boar and feral pig reservoir hosts

Answer: (C)

When a highly contagious disease like classical swine fever spreads to many sites, the pattern often points to how the virus is moved between farms rather than to natural wildlife reservoirs or environmental vectors. The most likely route in the UK outbreak was the movement of infected animals between holdings, along with situations where wildlife scavengers carried dead infected animals from one site to another. This combination can rapidly connect many premises, seeding infection across a network of farms.

Vectors such as mosquitoes or flies are less likely to account for spread to 16 different locations in this context, and wild boar/feral pigs as reservoirs would require a substantial wild population and interaction with farms, which wasn’t the principal driver in that outbreak setting. Swill feeding could contribute, but the question’s pattern fits the farm-to-farm and carcass-related dissemination described here.