Pathogenicity and transmission of bovine-derived HPAI H5N1 B3.13 in pigs
A new study published in bioRxiv examines the pathogenicity and transmissibility of the bovine-derived HPAI H5N1 B3.13 virus in pigs. The HPAI H5N1 virus has been detected in dairy cattle, with significant outbreaks across multiple U.S. states, leading to human infections primarily through direct contact with infected cattle. The study aimed to assess the ability of the B3.13 virus to infect pigs, which are known "mixing vessels" for influenza viruses. The virus was administered to pigs via oro-respiratory routes.
The B3.13 virus replicated in the lower respiratory tracts of infected pigs, producing infectious virus but demonstrating limited viral shedding compared to other known strains, such as those adapted for mink or swine. Pathologic changes were primarily observed in the lungs, but the disease remained self-limiting. A mutation in hemagglutinin (HA) associated with mammalian adaptation was detected but did not reach significant levels. Sentinel pigs placed in close contact with infected pigs did not exhibit seroconversion, indicating a lack of virus transmission despite shared environmental exposure.
These findings raise concerns regarding the potential for bovine-derived viruses to replicate and evolve in pigs. However, the limited pathogenicity and lack of transmission observed in this study suggest that the B3.13 virus is not currently a high-risk candidate for generating novel reassortant influenza viruses with pandemic potential.
