Avian influenza outbreaks in domestic cats: another reason to consider slaughter-free cell-cultured poultry?

Highly Pathogenic Avian Influenza H5N1 in Cats (Felis catus): A Systematic Review and Meta-Analysis

Introduction: Highly pathogenic avian influenza (HPAI) H5N1, a zoonotic virus primarily affecting birds, has shown increasing cross-species transmission, including to domestic animals such as cats. Recent reports of cat infections, often associated with contact with infected birds or the consumption of raw milk from H5N1-positive cattle, raise concerns about their role in viral adaptation and zoonotic transmission. Objective: To assess the global prevalence and characteristics of H5N1 infections in cats (Felis catus) through a systematic review and meta-analysis. Methods: Following PRISMA guidelines, we conducted a systematic search across PubMed, Scopus, and Web of Science up to 1 March 2025. Observational studies reporting the prevalence or seroprevalence of H5N1 in cats (Felis catus) were included. Data extraction and quality assessment were performed independently by four reviewers. Meta-analyses were conducted using a random-effects model, and heterogeneity was assessed via I2 statistics. Results: Twenty-one studies met the inclusion criteria, of which eight were included in the meta-analysis (n = 3586 cats). The pooled global prevalence of Felis catus infections due to H5N1 influenza was 0.7% (95%CI: 0.3-1.1%), with high heterogeneity (I2 = 86.5%). The prevalence varied by the diagnostic method, region, cat type, and time. Domestic cats and those in Africa had higher infection rates (20.0% and 32.0%, respectively). Case reports (n = 35) revealed a high mortality (74%), predominantly from clade 2.3.4.4b, with neurological and respiratory manifestations. Conclusions: Although the overall prevalence is low, H5N1 infection in cats is increasing, particularly in clade 2.3.4.4b. Their close contact with humans and other animals highlights the need for enhanced surveillance, diagnostics, and One Health strategies to mitigate zoonotic risks.

Molecular and ecological determinants of mammalian adaptability in avian influenza virus

The avian influenza virus (AIV) primarily affects birds and poses an increasing concern due to its growing adaptability to other hosts, heightening zoonotic risks. The adaptability is a key factor in AIV to infect multiple non-avian species, including humans, companion animals, aquatic mammals, carnivores, and other mammals. The virus is evolving through genetic mutations and reassortments, leading to the emergence of AIV strains with enhanced virulence and adaptability in mammals. This highlights the critical need to understand the genetic factors of AIV, including mutations in polymerase proteins, surface antigens, and other regulatory proteins, as well as the dynamics of AIV-host interactions and environmental factors such as temperature, humidity, water salinity, and pH that govern the cross-species adaptability of the virus. This review provides comprehensive insights into the molecular/genetic changes AIV undergoes to adapt in mammalian hosts including bovines, swine, equines, canines, and felines. The adaptive mutations in viral polymerase proteins, such as PB2-E627K, and receptor specificity shift facilitate the virus adaptability in mammals. Since AIVs interact with specific receptors on host cells, therefore the type and distribution of receptors are crucial in determining the host range of the virus and its adaptability by facilitating attachment and entry of the virus. This review examines sialic acid receptor distribution and binding patterns in various mammalian hosts, emphasizing how the presence and structure of specific receptors influence viral interaction, adaptation, and transmission. The review concludes that the differential distribution and expression of SA receptors are vital in the mammalian adaptability and tissue tropism of viral strains. Notably, during the adaptation to mammals, AIVs show a shift in preference from α-2,3 to α-2,6 receptors. This review further emphasizes the role of ecological determinants in the adaptation of viruses to mammalian hosts. Low temperatures, high humidity, and neutral to slightly acidic pH levels enhance virus stability, facilitating its persistence in the environment and spread among susceptible hosts. Overall, AIV remains a global health threat, necessitating coordinated efforts in research, surveillance, and public health strategies.

The Carbon Footprint of Diets with Different Exclusions of Animal-Derived Products: Exploratory Polish Study

Background/Objectives: Analyzing the carbon footprint of diets in various populations is important as it can help identify more sustainable food choices that reduce the overall impact of human activities on ongoing warming of the global climate. This pilot exploratory study analyzed the carbon footprint (measured in kg of CO2 equivalent, eq.) using food diaries collected from Polish individuals with varying levels of animal-derived product exclusion in their diets. Methods: The study employed a food diary method, where participants from four dietary groups (vegan, vegetarian, fish-eater, and meat-eater) recorded all meals and beverages consumed over a 7-day period, including portion sizes and packaging details. These diaries were then analyzed to assess dietary adherence and calculate carbon footprints, utilizing standardized CO2 equivalent emission data from publicly available databases. Results: The analysis revealed a decreasing trend in the carbon footprint corresponding to the degree of elimination of animal-derived products from the diet (R2 = 0.96, p = 0.0217). The mean daily footprint in the vegan group was 1.38 kg CO2 eq., which was significantly lower than in the vegetarian (2.45), fish-eater (2.72), and meat-eater groups (3.62). For each 1000 kcal, the meat-eater diet generated 39.7, 58.3, and 93.9% more CO2 eq. than in the case of fish-eaters, vegetarians, and vegans, respectively. Over a week, a group of 10 vegans had a total carbon footprint lower than vegetarians, fish-eaters, and meat-eaters by 42.9, 52.2, and 61.8%, respectively. Hard and mozzarella cheese had the highest contribution to the carbon footprint in vegetarians, fish, and seafood in fish-eaters, and poultry, pork, and beef had the highest contribution in meat-eaters. Conclusions: Dietary carbon footprints vary considerably by dietary pattern, with lower consumption of animal-derived products associated with lower emissions. Additionally, identifying specific high-impact food items within each diet may inform strategies for reducing environmental impact across various eating patterns.

Influenza in feral cat populations: insights from a study in North-East Italy

Influenza A virus (IAV) can cause high morbidity and mortality in domestic and wild avian species and it is able to infect mammals as well. IAV in cats is sporadic and self-limiting but the recent findings of high pathogenicity avian influenza virus (HPAIV) with genetic signatures of mammalian adaptation, in domestic cats, has raised new concerns about the potential role of cats in the virus ecology. The present study aimed to investigate the circulation of IAV in companion animals' shelters in North-eastern Italy. All samples were collected from feral cats living in feline colonies that were hosted in the companion animals' shelters for the requisite period to administer the veterinary treatments. Between 2021 and 2022, 389 oropharyngeal swabs and 279 sera were collected. All swabs tested negative for IAV and the only one ELISA positive serum sample resulted H5 positive by HI test with a titer of 1:80. Despite the sporadic occurrence of influenza in cats, continuous monitoring is crucial due to the evolving zoonotic nature of the virus.