Is it realistic to talk about a future where we have eliminated highly pathogenic avian influenza (HPAI) in the U.S. dairy herd?
In a recent webinar hosted by National Milk Producers Federation (NMPF), an overview was shared of what the road map could look like to this future state as well as the collaborative work ongoing to reach this desired point in time.
Testing continues
Jennifer Siembieda, D.V.M., of USDA Animal and Plant Health Inspection Service (APHIS) veterinary services shared updates on national dairy processing plant silo monitoring, first implemented in several states in late 2024. New cases in the last 30 days have been detected in California and Nevada through the testing program. Siembieda added that 10 more states are left to be fully enrolled in the program, with a goal of having these 10 on board by the end of February. A monthly surveillance report will be produced on testing data collected.
Stage four of the testing strategy is state disease absence or elimination, as can be found in the five-stage road map. Colorado and Mississippi have both reached stage four through milk testing.
“Mississippi did state specific testing. Not having a large dairy industry, they sampled every farm on a weekly basis and were able to reach stage four status,” Siembieda added.
Each state has a choice on silo testing or individual on-farm bulk tank testing, which is the route that each state has taken to achieve this level.
Multi-state studies
As research continues, Jason Lombard, D.V.M., of Colorado State University updated attendees on shedding of HPAI, the presence of clinical signs in positive cows, and transmission rates. Lombard and his team have completed studies in California and Colorado, tracking transmission of the disease within herds and across herds. The studies have noted rapid spread throughout herds across different pen groups.
“I think that if we were looking at purely transmission through milking machines, I don’t think it would move as fast as it is moving. Could it be in the parlor in other ways? I think it could move through aerosols in the parlor because there is a lot of milk and water that is splashed around,” said Lombard.
When speaking further on transmission, they have not found a herd that remained negative in the vicinity of other positive herds. “If a big risk factor is how close you are to another infected farm, that means that some of the biosecurity practices we are implementing may not necessarily be as effective as we want them to be,” Lombard shared. “We may have to think about aerosol transmission – which doesn’t have a lot of data to support it other than anecdotal. In talking to folks on the ground in California and Colorado with herds at the initial onset of the disease, that’s what they will tell you they were thinking it looked like. Not that other routes of transmission aren’t important, but it seems like aerosol is rising,” he concluded.
Routes to vaccines
The avenue to get a vaccine on the market for HPAI was discussed by David White, D.V.M., of NMPF. “There are currently eight field studies ongoing for vaccines. We do not have data back from those; we are still waiting on the manufacturers for some of that. All studies are at various stages of completion,” said White.
“We have defined the reasonable expectation of efficacy, so we can move these products into the conditional licensure pipeline,” he added. “None of this means the vaccine use in cattle has been approved in the U.S., and that’s still true.”
