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Highly Pathogenic Avian Influenza A Clade 2.3.4.4b Virus Infection in Domestic Dairy Cattle and Cats, US, 2024
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In 2021, the Eurasian strain of highly pathogenic avian influenza A (H5N1) — clade 2.3.4.4b — was detected in North America. The authors of this study described H5N1 infection in dairy cattle and cats in Texas and Kansas — noted in February and March — reflecting the continued spread of clade 2.3.4.4b. Infected dairy cattle experienced nonspecific systemic illness, reduced feed intake and rumination, abrupt decline in milk production, and abundant viral shedding in milk. The devastating effect of this infection was observed among cats fed unpasteurized colostrum and milk from affected cows, with an approximately 50% mortality rate.
- These findings suggest cross-species mammal-to-mammal transmission of H5N1, emphasizing the importance of continued surveillance in domestic production animals to prevent the spread of this virus and mammal-to-mammal transmission.
abstract
This abstract is available on the publisher's site.
Access this abstract nowWe report highly pathogenic avian influenza A(H5N1) virus in dairy cattle and cats in Kansas and Texas, United States, which reflects the continued spread of clade 2.3.4.4b viruses that entered the country in late 2021. Infected cattle experienced nonspecific illness, reduced feed intake and rumination, and an abrupt drop in milk production, but fatal systemic influenza infection developed in domestic cats fed raw (unpasteurized) colostrum and milk from affected cows. Cow-to-cow transmission appears to have occurred because infections were observed in cattle on Michigan, Idaho, and Ohio farms where avian influenza virus-infected cows were transported. Although the US Food and Drug Administration has indicated the commercial milk supply remains safe, the detection of influenza virus in unpasteurized bovine milk is a concern because of potential cross-species transmission. Continued surveillance of highly pathogenic avian influenza viruses in domestic production animals is needed to prevent cross-species and mammal-to-mammal transmission.
Additional Info
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Highly Pathogenic Avian Influenza A(H5N1) Clade 2.3.4.4b Virus Infection in Domestic Dairy Cattle and Cats, United States, 2024
Emerging Infect. Dis. 2024 Apr 29;[EPub Ahead of Print], ER Burrough, DR Magstadt, B Petersen, SJ Timmermans, PC Gauger, J Zhang, C Siepker, M Mainenti, G Li, AC Thompson, PJ Gorden, PJ Plummer, R MainFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
Spillover — Highly Pathogenic Avian Influenza
While visiting my uncle’s dairy farm as a child, I could usually be found in the hay loft with the barn cats. I delighted in watching my cousins squirt milk from a cow into the eager mouth of a cat, several feet away. This pastoral remembrance reflects the common space of cows, people, and cats in dairy operations, and it raises the specter of virus spillover events — when viruses leap from one species to another.
A very concerning paper has emerged, ahead of its scheduled July publication date, which details a dual spillover event at a dairy operation in Texas. Cows became infected with highly pathogenic avian influenza (HPAI). Their milk production dropped, but the cows — for the most part — did not develop significant symptoms. However, cats fed raw milk from the affected cows did not fare so well. About half of the cats died after developing severe neurological symptoms and copious nasal and ocular discharge.
In an incredible diagnostic sleuthing effort by the farmers, veterinarians, state agricultural agents, and scientists at the Iowa State University Veterinary Diagnostic Laboratory and the US Department of Agriculture National Veterinary Services Laboratories, evidence was assembled for a very compelling story of spillover. The methods detailed in this paper describe a compendium of histological and molecular virologic methods. In a summary of the results, cows demonstrated acute multifocal neutrophilic mastitis. Milk samples and mammary glands demonstrated high levels of influenza A (H5N1). Cats had multifocal meningeal hemorrhages and microscopic lesions consistent with severe systemic virus infection. Lesions were found in the brain, lung, heart, and retina; all were positive for HPAI, and virus levels were very high in brain tissue. Finally, whole genomic sequencing indicated high concordance among influenza viruses from the cow, milk, and cat specimens.
Cross-species mammal-to-mammal transmission of HPAI raises a red flag regarding this virus’ ability to spill over. Significantly, cow-to-human transmission has already been documented at a Texas dairy facility. This study is the first to demonstrate interspecific influenza transmission through milk. Although pasteurization will inactivate the influenza virus, an estimated 4.4% of American adults consume raw cow’s milk on a regular basis. High and continued vigilance — despite our fatigue in the wake of the recent COVID-19 pandemic — is essential. Influenza viruses have tremendous pandemic potential. Attention across species using One Health approaches is of vital importance.