#18,598
Yesterday the avian flu world was roiled by a statement released over the weekend from the Nevada Department of Agriculture, which announced 4 new dairy herds infected with HPAI H5 (see below), along with a slightly vague and confusing description of the genotype.
"Preliminary results show this detection to be consistent with a strain that has also been detected in wild birds in all North American flyways."Curiously, not the expected `bovine' B3.13 strain. At the same time, the screenshot from the USDA livestock list below states: `The genetic sequence for all cattle cases and the alpaca case is influenza A, H5, clade 2.3.4.4b, genotype B3.13'
The `Bovine' B3.13 strain has only rarely been detected in birds, and for months agricultural officials have insisted that the H5 virus was not being transmitted to new herds by birds, but rather have all stemmed from a single spillover event in Texas.
Nevada Department of Agriculture taking additional action to prevent the spread of avian influenza
Contact
Ciara Ressel
Public Information Officer
775-353-3603
cressel@agri.nv.gov
SPARKS, Nev. - January 31, 2025
The Nevada Department of Agriculture (NDA) in conjunction with the U.S. Department of Agriculture (USDA) Wildlife Services is taking additional action in an effort to prevent the spread of avian influenza. Dairy cattle premises in Nye and Churchill Counties have been placed under quarantine due to detections of Highly Pathogenic Avian Influenza (HPAI). The USDA National Veterinary Services Laboratory is continuing testing to confirm what strain of virus has been detected in Churchill County. Preliminary results show this detection to be consistent with a strain that has also been detected in wild birds in all North American flyways.
"The challenge with this virus is that it may be spread through contaminated clothing worn and equipment shared between animals, but birds carrying the disease can also infect domestic animals and livestock," said NDA Director J.J. Goicoechea, DVM. "We cannot stress enough how important it is to keep equipment clean, practice good animal health safety practices, and bolster biosecurity measures to prevent the spread of disease."
The USDA Wildlife Services will begin surveillance and testing wildlife for HPAI to better determine which strain and how it is spreading. The NDA has been conducting surveillance on milk silos to detect the virus before dairy cows may begin showing signs of symptoms, as part of the National Milk Testing Strategy.
To help prevent the spread of HPAI, the NDA and USDA Wildlife Services will begin removing non-native European starling populations in Churchill, Pershing and Lyon Counties. Due to their large numbers, the birds are a nuisance population and spread disease and contaminate food and water sources for animals, putting them at risk of HPAI, salmonella, E. Coli infections and other diseases. The removal of these starling populations is critical to mitigating the spread of disease.
In the event that the public finds dead or dying birds during the removal, Wildlife Services recommends handling the birds with single-use gloves and disposing of them in the trash, as they may be carriers of HPAI. While the pesticide used in the removal of starlings is not harmful to pets, due to the risk of HPAI, it is recommended that pets be kept away from the dead birds. The dead birds do not need to be reported. Residents unable to dispose of the starlings may call the USDA at (775) 851-4848 and provide the location of the birds by address.
European starlings are a non-native invasive species that cause a great deal of economic damage to agricultural interests across the nation. While not commonly associated with HPAI H5, they have been implicated as potential carriers of the virus.
A study published in the EID Journal in October of 2007, entitled Role of Terrestrial Wild Birds in Ecology of Influenza A Virus (H5N1) gives us this perspective.
Abstract
House sparrows, European starlings, and Carneux pigeons were inoculated with 4 influenza A (H5N1) viruses isolated from different avian species. We monitored viral replication, death after infection, and transmission to uninfected contact birds of the same species. Sparrows were susceptible to severe infection; 66%–100% of birds died within 4–7 days. High levels of virus were detected from oropharyngeal and cloacal swabs and in organs of deceased sparrows. Inoculation of starlings caused no deaths, despite high levels of virus shedding evident in oropharyngeal swabs. Least susceptible were pigeons, which had no deaths and very low levels of virus in oropharyngeal and cloacal swabs.
Nearly a decade later, researchers found that starlings were also susceptible to HPAI H7N9 (see USGS : Experimental Challenge Of European Starlings With Avian H7N9). In both studies, starlings could be infected, and could carry and shed the virus, without succumbing to the virus.
That said, whether they have any solid evidence of carriage of the virus by starlings in Nevada is unknown.
Admittedly, all of this could boil down to less-than-precise communications. The USDA still maintains (as of yesterday) that ALL cattle infections have been due to genotype B3.13, while Nevada suggests differently.
They clearly can't both be right.
Presumably this mystery will be solved when sequences are uploaded to GISAID and the genotype is identified by independent researchers. Given the less-than-timely release of avian flu information of late, exactly when that will happen is hard to say.
While much of the world has banked on the idea that only the B3.13 genotype (which has only been detected in North America) is capable of infecting livestock, there have been other studies suggesting those hopes may be misplaced.
- Last summer, in Germany: FLI Statement On Experimental Infection Of Dairy Cows With European H5N1 Virus, we saw researchers were able to successfully infect cattle with European genotypes of the virus.
- Their full results were published in Eurosurveillance: Strain-dependent Variations in Replication of European clade 2.3.4.4b Influenza A(H5N1) Viruses in Bovine Cells.
- Last June we looked at a cautionary letter - published by Chinese researchers in the Journal of Infection - that warned that similar spillovers could occur anywhere in the world.
If it can happen once, the stars can probably align again.
Whether we are `there' or not, remains to be seen. But the hallmark of HPAI H5 is that it continues to evolve, and to surprise. We underestimate it at our own peril.
Stay tuned.
