I was "Shown!"- Cases March On - Wastewater Raises Questions Officials Seem Strangely Helpless to Investigate
For now at least under laboratory conditions onward respiratory transmission of H5N1 to other cattle was NOT demonstrated
My last blog requested that someone “show me” a study disproving widespread oronasal transmission of H5N1 2.3.4.4b B3.13 in the dairy outbreak. This article takes a giant step forward in providing that evidence:
What the study at Kansas State shows is that at least with this early isolate in a small subset of animals under experimental conditions, experimentally infected animals fail to generate sufficient levels of virus via oronasal secretions for onward infection of contact animals. That is a very significant finding and is indeed “good news”. However, Dr. Richt goes on to state some caveats, including the size of the experiment and the proclivity of influenza virus to adapt itself for improved transmission over time. We all await more data from these experiments showing infectious dose administered, levels of shedding observed over the 8 days, any tissue changes observed, clinical signs including fevers, etc.
Additionally, the experiment itself actually demonstrates as expected that cattle are susceptible to oronasal infection with this virus. Even the biosecurity breaches that USDA proposed as routes of inter-farm spread in many cases would require some sort of oronasal infection to initiate disease. A refined estimate of minimum infective dose will be of great importance for epidemiologists to better assess theoretical biosecurity risks for onward oronasal transmission of this virus.
However, if the study’s conclusions hold over time in replicated studies and is maintained through future viral adaptations, the main conclusion regarding lack of onward respiratory transmission in cattle does provide a sense of relief to the beef industry in particular, where amplification of virus by milk production is not an aggravating spread factor.
We still have the real epidemiological problem of infected poultry flocks linked to infected dairy herds by phylogenetic clocking. Is there sufficient oronasal shedding of virus by cows to result in infected nearby poultry operations? Or, as the Michigan epidemiological study seemed to imply, is biosecurity in the poultry industry still sufficiently inadequate to allow H5N1 to “walk” onto these premises? These are not idle questions! I received an informal estimate that poultry losses to H5N1 2.3.4.4b B3.13 (dairy strain) in one state alone in 2024 could exceed $.25 BILLION.
I thought until Thursday-Friday that perhaps new cases were slowing up; however, Colorado reported 4 new cases and Iowa 2 new cases (again in Sioux County) to add to the 133 listed on the USDA case count site (USDA Dairy Cases), providing a total count of 139 herds to date in U.S. dairy herds. In addition, Minnesota on Friday reported 2 new infected turkey flocks in Otter Tail and Swift Counties, totaling just over 90,000 birds; it remains to be seen if either or both infections are the B3.13 strain of H5N1.
Finally, wastewater surveillance was again headlined in California and Illinois released a new H5N1 Avian Influenza (Bird Flu) Protocols (illinois.gov), apparently in response to ongoing positive findings in Influenza A Virus Wastewater Data | National Wastewater Surveillance System | CDC.
I can’t decide if Illinois and California public health officials are truly unaware of the most likely etiology of their summer wastewater influenza spikes or if they are under pressure to not investigate further. Early work in Texas back in March showed conclusively that milk processing plants are prime suspects for positive H5 findings, due to high daily volumes of product handled and regular cleaning and disinfection processes with small discharges of potentially virus-laden product into the sewage treatment stream. This discharge is highly unlikely to be a public health threat due to dilution and treatment effects, but it does provide valuable material for virus surveillance and sequencing.
These samples are very testable to determine if detections are indeed H5 and if they are the 2.3.4.4b B3.13 “dairy” strain. Rationalizing that it could be wildlife or mice or that dairy farms don’t drain into the wastewater basin is almost as nonsensical as saying positive results can’t originate from milk processing because farmer-suppliers haven’t reported infections! In reading through both the article and the Illinois protocol, it seems the bottom line may be that officials are only going to further investigate H5 spikes in “negative” states if farmers come forward first to report H5 in dairy cows?
I really dislike accusing agricultural interests of pressuring officials to “hide the ball”! Please prove me wrong and ask public health labs to sequence the sewage, while submitting any sick cow samples into the USDA H5N1 Dairy Program. Ask your state public health officials to test more retail pooled milk samples from your processing plants. What is left to gain by not actively looking for infection in any state when non-diagnosis puts all dairy farms at risk for unmonitored spread?
It’s H5N1 today, but this new open information paradigm is increasingly the norm for every production and disease challenge every organization faces. Regarding “unwelcome” data transparency, we haven’t seen anything yet! The wastewater sampling program will only grow in usage, and any research organization with a bit of financial backing can sequence retail milk or food, or effluent, or even air. There’s a new hole in the dike every day; how many fingers (and how much good will) do our traditional ag groups have left to plug leaks in their industries’ issues management plans??
John