Cats and Avian Influenza (H5N1)
Written by Faith Morris, edited by Gary Whittaker
Despite being widespread in many animal species, cats are not generally thought to be susceptible to influenza—although they can, and do, get infected with influenza viruses from other species in more of a spill-over situation. One notable example of this was with a relatively low pathogenicity, avian-origin H7 influenza in the New York City shelter system in 2016 (1). Currently, we are experiencing a panzoootic of a different and much more concerning highly pathogenic avian influenza (HPAI), known as H5N1.
The first widely disseminating H5N1 case was found in geese in China in 1996 (2). Since then, we have seen this H5N1 spread worldwide, affecting a variety of wild birds and poultry. According to the World Health Organization (WHO), since the first recorded outbreak, “[there has been] an unprecedented number of H5N1 outbreaks among poultry and wild birds [as of 2021]” (4).
The first recorded feline case of H5N1 happened in December 2003. The virus infected tigers and leopards at a zoo in Thailand due to being fed contaminated meat (3). Since then, more cases of H5N1 have been recoded, notably in Poland in 2023—in this case thought to be through the feeding pet cats raw chicken from the human food supply. In South Korea, shelter cats were also infected, likely via raw/unpasteurized pet food. Notably, H5N1 can be extremely virulent in cats, with animals developing severe neurological signs.
However, felines are not the only mammals that have recently found to be infected with H5N1. As of March 2024, the US state of Texas reported that dairy cows had been infected with H5N1 (5). The virus in now though to be widespread in the US dairy industry, across multiple states, but with cows showing only limited clinical signs. Thus, H5N1 is no longer solely affecting bird populations and is now spreading across species.
The United States, Poland, South Korea, and France have all reported incidents of felines testing positive and dying of H5N1 (4). Of the cats reported to have H5N1, the overall source of infection has not been determined definitively, but they are suspected to have acquired the virus from “direct or indirect contact with infected birds or their environment, ate infected birds, or ate food that was contaminated” (4). The symptoms of felines that are infected with H5N1 can include “difficult breathing, bloody diarrhea, and neurological signs, with rapid deterioration and death in some cases” (4).
The most commonly circulating H5N1 virus is the so-called 2.3.4.4b genetic clade; a clade is a group of organisms that evolved from a common ancestor. It is believed that H5N1 can be transmitted from birds to cats because both species have alpha-2,6- and alpha-2,3-linked sialic receptors on their cell surfaces. For felines, these alpha-2,6- and alpha -2,3 receptors [are located] in the trachea and lung”, and for avian species, these receptors are found in the “lungs and intestines” (7). It is thought that the receptors and the evolution of the 2.3.4.4b clade are the two principal driving factors that allow avian to feline transmission, although other factors may yet be uncovered. The most recent reported case of H5N1 in felines comes from Texas, as “several cats from several dairy farms experiencing H5N1 virus infections in dairy cows, suggesting the virus spread to the cats either from affected cows, raw milk or wild birds” (8).
There have been no recorded cases of humans contracting H5N1 from felines (6). It is possible for humans to contract H5N1 through other means, but specifically, animal hospital staff members are more at risk of acquiring the virus than members of the general population. Proper protection and procedures should be followed when dealing with suspected H5N1 patients (4). The growing concern with felines and bovines getting infected from H5N1, as well as with wildlife in the vicinity (e.g. foxes and raccoons), is in the formation of newly established mammalian reservoir where the virus could evolve further and thus be able to spread more readily across species.
If you think your cats, and/or cattle have possibly been exposed to H5N1, please seek immediate medical attention and contact your state veterinarian.
References
- Roberts, E., Allen, C., Brennen, R., Swartz, A., Dines, B., Cigel, F., … Newbury, S. (2023). Discovery of Influenza A (H7N2) in a Cat After Admission to an Animal Shelter: A Case Report. Journal of Shelter Medicine and Community Animal Health, 2(1). https://doi.org/10.56771/jsmcah.v2.61
- Wan, X F. Lessons from Emergence of A/Goose/Guangdong/1996-like H5N1 Highly Pathogenic Avian Influenza Viruses and Recent Influenza Surveillance Efforts in Southern China.” Zoonoses Public Health. 2012 Sep; 59(0 2): 32–42.doi: 1111/j.1863-2378.2012.01497.x
- Understanding Evolution, https://evolution.berkeley.edu/teach-resources/clades-1-of-2-definition/ Accessed 15 June 2024.
- Influenza A (H5N1) in Cats – Poland., World Health Organization, July 2023, who.int/emergencies/disease-outbreak-news/item/2023-DON47
- Current H5N1 Bird Flu Situation in Dairy Cows.” Centers for Disease Control and Prevention, https://www.cdc.gov/bird-flu/situation-summary/mammals.html. Accessed 15 June 2024.
- Technical Report: December 2023 Highly Pathogenic Avian Influenza A(H5N1) Viruses.” Centers for Disease Control and Prevention, https://www.cdc.gov/bird-flu/php/technical-report/h5n1-122923.html. Accessed 15 June 2024
- Coston, M. Virology Journal: Receptor Cells in Minor Poultry Species., 1 Jan. 1970,https://afludiary.blogspot.com/2010/12/virology-journal-receptor-cells-in.html
- Considerations for Veterinarians: Evaluating and Handling of Cats Potentially Exposed to Highly Pathogenic Avian Influenza A (H5N1) Virus in Cats.” Centers for Disease Control and Prevention, https://www.cdc.gov/bird-flu/hcp/animals/index.html
Cats and COVID
contributed by Faith Morris
Throughout the COVID-19 pandemic and even today, there is controversy on the extent and impact of human-to-animal and animal-to-human transmission of SARS-Cov-2. The American Veterinary Medical Association (AVMA) made a statement regarding such concerns—that under natural conditions, it is rare for cats to get SARS-CoV-2 (AVMA Accessed 26 Mar. 2024). However, as felines live near their owners, it may be possible for humans to transmit the respiratory infection to cats without clinical signs. If we can find a direct correlation, it will open the doors to new ways of looking at transmission across species.
Our research article SARS-CoV-2 serosurvey of health, privately owned cats presenting to a New York City animal hospital in the early phase of the COVID-19 pandemic (2020-2021), takes a much closer look at the potential risk of indoor domesticated felines getting infected with SARS-CoV-2. This work was prompted by early findings that cats share high similarity to humans in their angiotensin-converting enzyme 2 (ACE2), the SARS-CoV-2 receptor. ACE2 is a receptor binding interface (RBD) that is widely present throughout the body. This enzyme is found in the heart, lungs, kidneys, and small intestine of humans. For felines, the enzyme can be found in the gastrointestinal mucosa (Hamming, I, et al 2004). ACE2 is important for understanding if/how SARS-CoV-2 can be transmitted to another animal species. As a respiratory virus, SARS-CoV-2 attaches to ACE2 to gain access to cells.
In collaboration with a veterinary practice in New York City (Choi et al. 2024) we sampled a population of 79 cats serologically, using a sensitive immunoassay, Multiplex Immunofluorescence (mIF), whcih is both highly specific and sensitive, and is a test that works by tagging antibodies of viral proteins that are found in plasma. mIF was modified to tag biomarkers in felines (Sheng W et al. 2021). Our test was set to look for Spike S1, Spike S2, RBD, and N protein in SARS-CoV-2. Because mIF uses plasma for its test, all of the felines in the study only had to give 2mL of blood to test for SARS-CoV-2. Of the 79 felines that were used in this study 44% were confirmed to be positive (Choi A et al. 2024) in the fall of 2020, a very high level considering the public health lockdown.
The research article opens up a new way to look at viral transmission events across species. In the article, they were able to show that felines can indeed get COVID-19, but more research should be done to determine transmission routes between humans and animals, and the impact of this on society.
References
- Hamming, I, et al. “Tissue Distribution of ACE2 Protein, the Functional Receptor for SARS Coronavirus. A First Step in Understanding SARS Pathogenesis.” The Journal of Pathology, U.S. National Library of Medicine, June 2004, www.ncbi.nlm.nih.gov/pmc/articles/PMC7167720/#:~:text=We%20have%20shown%20that%20ACE2,show%20this%20brush%20border%20staining.
- “SARS-COV-2 in Animals.” American Veterinary Medical Association, www.avma.org/resources-tools/one-health/covid-19/sars-cov-2-animals-including-pets. Accessed 26 Mar. 2024.
- Sheng W, Zhang C, Mohiuddin TM, Al-Rawe M, Zeppernick F, Falcone FH, Meinhold-Heerlein I, Hussain AF. Multiplex Immunofluorescence: A Powerful Tool in Cancer Immunotherapy. Int J Mol Sci. 2023 Feb 4;24(4):3086. doi: 10.3390/ijms24043086. PMID: 36834500; PMCID: PMC9959383.
- Putlyaeva, Lidia. Overview of SARS-CoV-2 Life Cycle. 18 July 2021. Studying SARS-CoV-2 with Fluorescence Microscopy, NIH, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8234815/. Accessed 14 Mar. 2024.
- Choi A, Stout AE, Rollins A, Wang K, Guo Q, Javier AJ, Kennedy M, Wagner B, Whittaker GR. SARS-CoV-2 serosurvey of healthy, privately owned cats presenting to a New York City animal hospital in the early phase of the COVID-19 pandemic (2020-2021). bioRxiv [Preprint]. 2024 Feb 15:2024.02.13.580068. doi: 10.1101/2024.02.13.580068. PMID: 38405835; PMCID: PMC10888843.
Do cats pose a risk to our Health?
February 14, 2024
Cats—both big and small—are an enormous part of our lives and have significantly contributed to history and society as we know it. However, we need to keep in mind that the animal companions that we hold near and dear could also pose a health risk.
New feline coronavirus blamed for thousands of cat deaths in Cyprus
Now, researchers have identified a possible culprit: a new strain of feline coronavirus that has coopted key RNA sequences from a highly virulent dog pathogen called pantropic canine coronavirus (pCCoV). The findings, posted as a preprint on bioRxiv by collaborators in the UK and Cyprus, could help explain how severe illness managed to spread so widely among cats on the island; see https://www.biorxiv.org/content/10.1101/2023.11.08.566182v2
“They’ve done a great job in identifying what looks to be a very interesting and concerning virus,” says Gary Whittaker, a virologist at the Cornell University College of Veterinary Medicine ( see; https://www.science.org/content/article/new-feline-coronavirus-blamed-thousands-cat-deaths-cyprus) . Although canine-feline coronavirus crossovers have been reported before, he says, this is the first documented case of a cat coronavirus combining with pCCoV, apparently leading to a “perfect storm of both disease and transmissibility.”
Managing Microbes: Antibiotic and Anti-viral Stewardship
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Antimicrobial stewardship isn’t just about antibiotics. Viral evolution is rapid in response to outside pressures and advances in antiviral drugs mean it is increasingly important that we understand how to be good stewards of these important antimicrobials.
Getting to the heart of the matter
March 24 2021
Its been a year since SARS-CoV-2 was documented in tigers in the Bronx Zoo. In the intervening time, data has been trickling in on how COVID-19 affects cats. We share what we’ve been watching and our thoughts on what may be coming next.
COVID-19 and Wildlife: A One Health Perspective
Dec 9 2020
People aren’t the only species that can be infected with COVID-19. What can we do to prevent spill-over into wildlife populations? Keeping our feline companions indoors helps keep them out of harms way while safeguarding native species.
Nov 13 2020
Much ado about mink
What’s happening with Denmark’s mink farms and what does it mean for the SARS-CoV-2 pandemic? Laura Goodman and Gary Whittaker tackle the problem of mutant viruses in this week’s blog.
Nov 1 2020
Rethinking feline coronavirus outcomes
Dr. Alison Stout writes a compelling letter to JAVMA outlining the similarities between FIP and COVID-19. Although the viruses that cause these diseases are distinct, some of the outcomes are strikingly similar. Approaching the pandemic from a one heath perspective can enhance our understanding of coronaviral infections and lead to advances in human and animal health. SARS-CoV-2 is not limited by species bounds and we should not limit our understanding of this global crisis to the human sphere.
This letter to the editor was published in JAVMA on November 1, 2020. It is openly available on Cornell’s eCommons where it has been reprinted with the permission of the AVMA.