Avian Influenza and the Gut Microbiota

Avian influenza is a constantly relevant topic among infectious disease experts and health authorities. Clarifying its implications is essential for maintaining alertness levels, while understanding its transmission mechanisms helps develop new prevention strategies.

In the following paragraphs, we’ll explain what avian influenza is and why it poses a threat to human health. We’ll then focus on the role of the gut microbiota in the immunity of farm animals, as well as the One Health approach to infectious risk mitigation.

H2: What is Avian Influenza and Why Is It a Threat?

Avian influenza is a zoonotic infectious disease caused by certain subtypes of influenza A viruses. These viral agents infect poultry species (like chickens, hens, and turkeys), causing major outbreaks in farms. Under certain conditions, avian flu can also infect humans. Therefore, it represents a significant public health concern—not only due to the economic damage from livestock culling but also because of the potential for a severe pandemic.

H3: Highly Pathogenic Avian Influenza Viruses

Avian influenza viruses are classified into highly pathogenic (HPAI) and low pathogenic (LPAI) viruses. HPAI viruses cause severe infections with very high mortality in affected birds. Symptoms affect both the respiratory and gastrointestinal systems, along with loss of appetite, lethargy, and swelling. Egg production may decrease or stop entirely. Disease severity varies depending on the individual bird’s susceptibility. A-H5N1 and A-H5N8 are examples of highly pathogenic strains.

LPAI viruses, such as A-H9N2, tend to cause milder symptoms but can be more severe when birds are co-infected with other pathogens or under environmental stress.

H3: Transmission Mechanisms Between Animals and Humans

When a virus typical of a specific animal group (e.g., birds) gains the ability to infect humans, it’s called a species jump or spillover. This is facilitated by the high mutability of influenza viruses, although not all genetic changes are the same. One mechanism, antigenic drift, occurs frequently in influenza A and B viruses and is due to replication errors in viral genetic material. These small changes are associated with seasonal flu variants. A second, less frequent mechanism called antigenic shift happens when two different type A viruses recombine inside the same host. This can produce a novel and highly pathogenic virus, potentially leading to a pandemic.

Currently, human avian flu cases mostly arise from direct contact with infected animals, and human-to-human transmission remains rare. However, future recombination events could increase the virus’s infectivity in humans.

H2: The Gut Microbiota and Its Immune Function

The gut microbiota is a diverse community of “good” microorganisms living in our intestines. It performs many functions, including significant modulation of the immune system. Certain by-products of microbial metabolism (SCFAs) can influence immune cell differentiation, promote anti-inflammatory responses, and enhance antimicrobial factor production. Additionally, live microbiota components compete with pathogens in the gut, reducing nutrient availability and altering the pH of the microenvironment.

The gut microbiota isn’t unique to humans—other mammals and birds also have it, albeit with structural differences. Soon we’ll examine its health value in farm animals, especially in relation to avian flu prevention.

H3: Microbiota in Farm Animals and Health Impact

Despite compositional differences, farm animals also benefit from a balanced gut microbiota. Conversely, a qualitative-quantitative imbalance (dysbiosis) negatively affects overall well-being, just as in humans. In farms, this results in reduced productivity and financial losses.

H3: Microbiota Alterations and Susceptibility to Viral Infections

Microbiota imbalance increases animals’ vulnerability to viral infections such as avian flu. A balanced microbiota, on the other hand, helps suppress the pathogen. How? Animal studies suggest multiple mechanisms. First, live microbiota components may directly inhibit viral replication and prevent viral entry into host cells. The microbiota may also affect viral particle stability, reducing infection rates. Other mechanisms involve immune modulation—on both immune cells (e.g., lymphocytes) and molecular factors (e.g., IFN-I), ultimately strengthening host defenses.

H2: Animal Surveillance to Prevent Avian Flu

Preventing avian influenza outbreaks requires proper farm management, starting with biosafety protocols and nutritional strategies. Here’s a closer look:

H3: Health Surveillance and Biosafety in Farms

Health surveillance and biosafety are essential elements in farm operations. The former is managed by the company’s occupational physician and aims to protect workers’ health. Biosafety includes measures to reduce infection risk and may leverage innovative technologies to curb aerosol transmission of viruses.

Both measures are mandatory requirements in professional settings and must be consistently applied across the entire production cycle. These protocols are adapted to the type of farm and follow national regulations. Poultry farming, in particular, has seen multiple avian flu outbreaks with serious economic and health consequences. As such, surveillance and biosafety must be rigorous and are key aspects of prevention.

H3: Diet and Microbiota Modulation

The animals’ diet plays a vital role in maintaining gut health. Feed composition greatly influences microbiota care and modulation. Various natural methods—proven safe and effective—can promote gut health and support microbial balance. These include plant extracts, essential oils, probiotics, enzymes, and prebiotic fibers. Probiotics are live microorganisms added to feed to enhance microbiota balance when administered in adequate amounts. Prebiotic fibers are non-digestible substances that serve as food for microbiota components.

H2: The One Health Approach: Integrating Human, Animal, and Environmental Health

The One Health approach to infectious disease control emphasizes the interconnection between human, animal, and environmental health. In recent years, avian influenza has spread more widely, correlating with globalization, air pollution, and intensive poultry farming. This calls for comprehensive epidemic risk management across multiple sectors and disciplines.

H3: Examples of Multidisciplinary Strategies

Diverse techniques address critical points of infection control. Analyzing the gut microbiota of farm animals, for instance, is an early intervention strategy to detect microbial imbalances and disease biomarkers. A network of specialized labs and standardized testing methods would be ideal.

Ecological farming methods and strict biosafety and veterinary interventions must be implemented. In parallel, it’s important to regulate transport and trade procedures to minimize risky contact—especially between humans and animals and between wild and farm animals.

Health authorities must play an active role by enforcing control procedures and offering targeted training programs for workers. Understanding basic concepts—such as contagion modes, epidemic dynamics, and workplace hygiene—is crucial for infection mitigation.

H3: Collaboration Between Health, Veterinary, and Environmental Agencies

Ultimately, the One Health model depends on collaboration among professionals from different fields. These professionals must interface transparently, handling interconnected aspects of disease prevention. The environment—shared by humans and animals—is central to collective well-being. Healthy livestock protects human health, whereas weakened animals facilitate viral outbreaks. Veterinary and environmental sectors must offer care and early warnings, while health agencies must monitor regulation enforcement.

H2: Conclusions: Prevention and Research as Key Tools Against Avian Flu

To combat avian flu in the long term, prevention must progress alongside scientific research. Ideally, prevention strategies will evolve and improve with new evidence—ensuring a proactive, informed approach to health security.

FAQs

What is the current status of avian flu in Italy?

Between September 2024 and March 2025, over 50 avian flu outbreaks were reported in Italy, mostly affecting chicken and turkey farms in Lombardy and Veneto.

What’s the link between epidemics, avian flu, and China?

Following COVID-19, China remains a hotspot for viral outbreaks due to frequent risky human-animal interactions. Live wild animal markets—still present in China and across Asia—are a major concern.

How are the gut microbiota and the immune system connected?

A balanced gut microbiota supports immune defenses in both humans and animals—indirectly through immune modulation and directly by outcompeting pathogens and altering intestinal pH.

Is there a vaccine for avian flu?

Yes, vaccines for avian flu exist for livestock. For humans, widespread vaccination is only considered in case of a declared pandemic risk.