Transmission of bird flu to zoo big cats. Infographic.

There is a recent story in the online news media of 20 ‘big cats’ (not all are classic big cats as the list includes four bobcats, one lynx and four pumas) contracting bird flu (H5N1) and dying. It is the biggest outbreak of bird flu in a cat zoo that I have read about. The big cats died between late November and mid-December at the Wild Felid Advocacy Center, USA, according to the center’s director, Mark Mathews.

The disease is zoonotic as we know meaning it transfers from one animal species to another including to the human-animal sometimes in a chain event. It can kill zoo cats quickly (see some detail on this at the end of the article).

Barn cats (semi-feral domestic cats) are particularly susceptible it seems as they can contract the disease by drinking raw milk from cows that are infected. At a Texas dairy earlier this year, 12 barn cats died after drinking infected raw milk as reported by the Guardian newspaper.

The disease transmits from animal species to animal species.

The infographic lists 6 possible routes for transmission to the cats in this Washington zoo. Which is the most likely?

The first route—ingestion of infected prey or meat—is often considered the most likely route for big cats in zoos to contract avian influenza. This is because:

1. Direct Exposure to the Virus: Feeding raw or undercooked meat from infected birds (such as poultry or wild avian species) provides a direct pathway for the virus to enter the animal’s system. Avian influenza viruses can survive in raw meat, especially if not properly handled or sourced from infected stock.
2. High Viral Load in Food: Meat from infected birds can carry a significant viral load, increasing the chances of transmission when consumed by big cats.
3. Documented Cases in Captivity: Similar outbreaks in other zoos and sanctuaries have often been traced back to feeding practices, making it a recurring theme in such cases.

However, while this is a highly plausible route, the precise cause can only be confirmed with an investigation that traces the source of the virus. Zoos generally employ strict sourcing standards, but lapses or contamination in the supply chain could lead to such occurrences.

Other routes, such as direct exposure to wild birds or environmental contamination, remain possible but are less direct and typically harder to establish definitively without detailed environmental and epidemiological data.

Question: How can domestic cats contract the disease?

Domestic cats can contract avian influenza, though it is relatively uncommon. The primary routes of infection for domestic cats are similar to those for big cats in zoos, with some specific contexts relevant to their typical environments:

1. Ingestion of Infected Birds or Meat

• Primary Route: The most common way domestic cats contract bird flu is by eating infected birds, particularly wild waterfowl or other avian species that carry the virus.
• Raw Meat: Feeding cats raw meat from infected poultry or other birds can also transmit the virus.

2. Direct Contact with Infected Birds

• Cats that hunt and catch wild birds can become exposed to the virus through contact with the bird’s feathers, saliva, or droppings.
• Stray or outdoor cats are more at risk because they have more opportunities to encounter infected wildlife.

3. Environmental Contamination

• Cats can pick up the virus from environments contaminated with bird droppings or secretions, such as gardens, yards, or water sources frequented by infected birds.
• The virus can persist on surfaces or in water, particularly in cooler climates, where it may remain infectious for extended periods.

4. Close Contact with Infected Animals

• Cats living in multi-animal households or near infected poultry might contract the virus through close contact. This includes exposure to other infected cats, birds, or contaminated surfaces.

5. Airborne Transmission (Rare)

• In rare cases, cats in close proximity to infected birds or other animals could inhale viral particles suspended in the air. This is more likely in confined spaces with poor ventilation.

Preventing Bird Flu in Domestic Cats

To minimize the risk:

• Keep Cats Indoors: Limiting outdoor access reduces the chances of contact with infected birds.
• Monitor Diet: Avoid feeding raw poultry or wild game. Ensure any meat is properly cooked.
• Control Hunting Behavior: Prevent cats from hunting wild birds by supervising outdoor time or using deterrents.
• Maintain Hygiene: Clean and disinfect surfaces that may come into contact with wild birds.
• Monitor Health: Be vigilant for signs of illness, such as respiratory distress, lethargy, or loss of appetite, and consult a veterinarian if symptoms appear.

By controlling exposure to infected birds and contaminated environments, the risk to domestic cats can be significantly reduced.

Question: How fast can avian flu kill zoo cats?

Avian flu can act rapidly in felines, including zoo cats, depending on several factors such as the strain of the virus, the health of the affected cats, and the level of viral exposure. Here’s what is known about the progression of the disease in cats:

Timeframe of Fatality

1. Rapid Onset of Symptoms: Infected cats can develop symptoms within a few days (1–7 days) after exposure. Clinical signs may include:
   • High fever
   • Respiratory distress
   • Lethargy and weakness
   • Neurological symptoms (such as seizures or disorientation)
   • Decreased appetite or refusal to eat
2. Progression to Severe Illness: If the infection is severe, symptoms can worsen rapidly. Death can occur within 2–5 days after symptoms appear, particularly in cases involving highly pathogenic strains like H5N1 or H5N6.
3. Acute Cases: Some cases have shown sudden deaths with minimal prior symptoms, indicating that the virus can overwhelm the immune system and cause multi-organ failure quickly.

Why Does It Kill Quickly?

• High Pathogenicity: Certain avian flu strains (e.g., H5N1) are highly virulent and can spread rapidly within the body, causing severe inflammation, organ damage, and respiratory failure.
• Host Susceptibility: Cats (especially big cats in zoos) may not have strong immunity against avian flu, making them more vulnerable to rapid disease progression.
• Viral Load: Higher exposure to the virus (e.g., eating infected birds or contaminated food) increases the severity of the infection.

Case Study References

In prior outbreaks affecting zoo cats or other felines:

• H5N1 infections in domestic cats showed that animals consuming infected meat could die within 2–10 days of exposure.
• At zoos, big cats like tigers and lions that consumed infected meat succumbed to the disease in as little as 2–5 days after showing symptoms.

Mitigation and Response

Swift veterinary intervention, including antiviral treatments and supportive care, might slow the disease progression in early cases, but the high virulence of avian flu often leaves little time to act. Surveillance and prevention are critical in minimizing the risk and impact of infections in zoos and domestic settings.

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