At least 116 Infected Herds across 12 States
#18,139
Despite the reassuring title, the big news from Germany's Friedrich-Loeffler-Institut (FLI) statement yesterday is that it isn't just the North American B3.13 genotype of H5N1 that is able to infect cattle, as they have successfully infected a cow using a local strain of the virus.
As we've discussed previously (see here, here, and here), this is not an entirely unexpected result. Cattle have been experimentally infected with earlier clades of H5N1, and the current clade 2.3.4.4b viruses have shown an enhanced ability to infect mammals.
The fact that we haven't seen other H5N1 outbreaks in cattle does suggest the spillover process into cattle is likely both complex and rare - but since most countries aren't testing cattle for the virus - there could be other outbreaks we are not aware of.
First the statement from the FLI, after which I'll have a brief postscript.
Avian influenza: No evidence of H5N1 infection in dairy cows outside the USA
06/20/2024 Short Messages
– German virus isolate can replicate in cow's udder after experimental infection
The Friedrich-Loeffler-Institut (FLI) is currently conducting an infection study on the susceptibility of dairy cows to the highly pathogenic avian influenza virus H5N1 (HPAIV H5N1, avian influenza virus). As a first interim result, not only the US isolate but also a recent H5N1 virus from a wild bird in Germany was able to multiply very well in the udder. Following direct infection of the udder through the teats, the dairy cows in both cases showed clear signs of disease such as a sharp drop in milk production, changes in milk consistency and fever.
The FLI's risk assessment for avian influenza, including recommended measures, is not affected by this interim result, as the possibility of infection with other HPAIV H5 strains has already been taken into account in the current version of the assessment. Both the risk of the US HPAI H5N1 strain (B3.13) entering German cattle herds, including dairy farms, and the risk of cattle becoming infected with HPAI H5 viruses circulating in Europe are considered to be very low for Germany.Nevertheless, increased vigilance is recommended and HPAI H5 should also be considered in investigations, especially in the case of unclear and frequent cases of disease in dairy herds. In contrast to the USA, there is no evidence of similar cases of HPAIV H5N1 infection in Germany or other countries worldwide.
Direct infection of the udder by the virus seems to be of particular importance. Since the first detection of the pathogen 27 years ago in many countries, particularly in Asia, there has been possible contact of ruminants such as water buffalo and cattle with the faeces of infected wild birds, but no similar infection events have ever been observed. The exact circumstances that led to the outbreak in the USA are still unknown.
As a precautionary measure, the FLI has already tested around 1,400 bovine serum samples from cows from regions in Germany particularly affected by avian influenza for antibodies and around 350 tank milk samples from different regions for virus genomes using PCR, with negative results in each case. Further analyses of tank milk samples up to a total of around 1500 will follow. B
Once the FLI infection study has been completed and analysed, the results will be published. The timing cannot be estimated at this stage, but the FLI will provide information in due course.
Three weeks ago, the UK's rationale for not testing their cattle (see UK HAIRS Risk Statement On Avian Influenza (H5N1) In Livestock) for HPAI was that the H5N1 genotype B3.13 had never been seen in Europe or the UK.
It will be interesting to see if this report changes their next assessment. Or that of other countries.
To be fair, there are finite resources available to deal with H5N1. Last week we saw an example of its dire economic impacts in Finland's Food Agency To Curb Services & Lay Off Animal Disease Investigators, which undoubtedly factored into their decision to offer H5N1 vaccines to farmers and veterinarians.
While we could get lucky, and the virus could still attenuate or recede, right now it appears to be on a winning streak.
At the same time, our ability to continue playing an ever-escalating game of `whack-a-mole' with this rapidly spreading and continually evolving virus appears to be declining. As they say, we live in interesting times.
Stay tuned.
