For such a potentially big problem, we’re received disappointingly little official information about H5N1 influenza on dairy farms in the US. The more we know, the better we can plan for containment and control, wherever it pops up next. If information isn’t being gathered or isn’t being shared, our ability to address this problem is significantly compromised. It was therefore really nice to see some details from Michigan State University about the H5N1 outbreak on one Michigan dairy farm, but also concerning to see that the situation may not be as straightforward as we were hoping based on the information available to date.

This is how the story went for this Michigan dairy farm:

Widespread fever in the cows was the initial finding. It was detected quickly since most cattle on the farm have a monitoring bolus (in their rumen) that tracks things like body temperature, among other things. Temperature increases of 4-5^oF were typical. Shortly after the temperature spike, rumen activity decreased. (The rumen is the largest of the cow’s four “stomachs;” as the cow goes, so does the rumen, so a decrease in rumen activity indicates that something is off with the cow). Fever typically persisted for 2 days. The cows were mostly treated with aspirin and IV fluids.

After the problem was identified, the farm staff tried to contain it. Milk has been implicated as the main route of spread, so the farm started washing all the milking equipment after the affected cows were milked. Unfortunately that didn’t help, and it eventually spread to all the groups of milking cattle on the farm.

• The subsequent spread to other groups on the farm could indicate that the routine equipment washing procedure was not adequate to stop the spread, or that the virus had already spread before they changed their procedures, or that there are other routes of spread. Some people have said that this indicates milk is not the main route of spread, but I think that’s a bit premature. We need to keep investigating. Some people online are using this as a “gotcha” moment to say that USDA is hiding respiratory spread, but I don’t think there’s enough detail here to make any conclusions like that either.

Over the first 9 days of illness, milk production decreases were fairly mild. Daily milk yield per cow dropped about 5 pounds (with the average cow on the farm normally producing 95-100 pounds of milk). However, by day 12, milk production had dropped by 21 pounds per cow, the somatic cell count (an indicator of inflammation in the udder) increased, and many cows became severely dehydrated. This is more severe than the general descriptions provided to date.

Overall, they suspect that 40% of cattle on the farm were infected.

• 40% affected is surprisingly low for flu. With all groups having one or more infected cow, I’d expect pretty much all the cows to get infected. I wonder how many of the “unaffected” cows actually had mild disease that simply wasn’t detected.

Unsurprisingly, the impact on farm management was severe. A lot more work was required to manage so many sick cows.

• That also increases the risk to farm workers, since it means more cow-to-human contact, and that contact is mainly with sick cows. They had to stop breeding cows because they were too busy managing the sick milking cows, which will presumably have at least some long term impact on farm operations.

Some abortions occurred in pregnant cows; it’s suspected that this was because of the high fevers.

• Flu isn’t something we typically link to spontaneous abortion, but anything causing severe disease can do it. That’s another aspect of disease severity that hasn’t been previously reported in this outbreak.

The good news is all the farm workers remained healthy.

• It’s not clear whether there was any surveillance for mild or subclinical infections, but no illnesses were reported. Since the farm is providing detailed information, I assume that their assurance of no human illness (so far) is pretty solid.
• The US CDC recently issued guidelines for working with infected animals, including cattle. They’re pretty standard from a control standpoint, but I also look at them and say “not gonna happen” on a standard, busy and potentially hot farm. In this case, “the farmer encouraged them to wash their hands frequently and avoid touching their face and eyes. All employees were offered safety eye wear or face shields.” That’s probably as good as we’re going to get.

Cost to this 500-cow dairy herd was estimated as $30,000-40,000 USD.

• That may not seem like a massive number, but if it’s your family farm, that’s a big chunk of income, and you also lost money while having to work a lot harder and in a higher risk situation. It also doesn’t include long term costs from any ongoing loss in milk production, and other impacts on farm operations, such as missed breedings. Some cattle will be culled because of sustained impact on milk production despite apparent recovery from infection. That’s not been reported before either.

We need to remember that people on farms are people. They have to work and live through this. If it’s a family farm where there’s an even closer association with the animals and more direct dependence on income, it’s even harder. The farmer in this case was quoted as saying “It has been a lot of work, stressful on the cows and frankly overwhelming.” I suspect that’s an understatement of the potential impact on the mental health of farm personnel.

The article states “[The farmer] believes it is important for the industry to understand the disease. He knows that his is not the only farm to get HPAI and hopes that the more we can learn from his experience, the better we can prevent more herd infections, reduce the impact and potentially be better prepared against other diseases.”

• We need more people like this. They managed a new and potentially scary problem to the best of their ability and were willing to tell their story. That’s too rare. We also need more groups like the MSU Extension Service who will write about events like this, so we understand more about this outbreak. A lot of questions remain and a few new questions and uncertainties have come up based on this information, but information is power. We need good information to plan and to contain. There’s been too much hiding of information, unwillingness to share, and unwillingness to cooperate (at many levels), and that’s compromised our ability to respond.

We need to thank people like this and support people/farms/veterinarians/government officials who are willing to stick their necks out to provide critical information, despite the risks (social, political, economic or other).