H5N1 FROM FERRET: SCIENCE & TECGHNOLOGY

H5N1 FROM FERRET: SCIENCE & TECGHNOLOGY

NEWS: Study shows fatal spread of H5N1 virus from ferrets to suckling kits

 

WHAT’S IN THE NEWS?

The H5N1 influenza virus (clade 2.3.4.4b) has spread across continents since 2020, causing large-scale mortality in birds, marine mammals, and cattle, with evidence of transmission via milk raising zoonotic concerns. Research in ferrets shows efficient transmission through milk but limited respiratory spread.

H5N1 Influenza Virus (Clade 2.3.4.4b): Emergence and Spread

Background of H5N1 Virus

Nature of H5N1:

  • Highly pathogenic avian influenza virus primarily infecting birds.
  • Transmitted among birds, especially migratory and wild species, via direct contact with infected feces or respiratory secretions.

Previous Assumptions:

  • Rarely infects mammals and unlikely to spread among them.
  • Poses occasional zoonotic risks, primarily through direct exposure to infected birds.

Global Spread of H5N1 Clade 2.3.4.4b (2020–2024)

Initial Emergence (2020):

  • First detected in Africa, Asia, and Europe.
  • Rapid spread caused extensive mortality in seabird populations.

Expansion to the Americas (2021–2023):

  • Spread to North and South America.
  • High-impact outbreaks in marine mammals along the coasts of Peru and Chile.
  • Over 30,000 sea lions and other marine mammals such as dolphins and otters succumbed to the virus.

Severe Impact on Argentina’s Elephant Seals:

  • Infected over 17,000 elephant seals, wiping out almost 97% of the pups.

Outbreaks in Cattle (2024):

  • First reported in Texas, U.S., in March 2024.
  • Virus spread to 616 dairy herds across 15 states, with California accounting for 402 herds.

Human Infections in the U.S.:

  • First farm worker infected in April 2024 following exposure to infected cattle.
  • By November 2024, 58 human cases reported in the U.S.

Infection Dynamics in Cattle

Mammary Gland Infection:

  • Virus localized in mammary glands of infected cows.
  • High levels of viral RNA and infectious virus detected in milk.

Potential for Transmission via Milk:

  • Raises concerns about milk being a medium for virus transmission to offspring and humans.

Research Findings on Ferrets

Study on Lactating Ferrets:

  • Aim: To investigate H5N1 (clade 2.3.4.4b) transmission through milk.
  • Method: Virus introduced into mammary glands of lactating ferrets at 2.5 weeks postpartum.

 

Key Observations:

Viral Load:

  • Increased viral RNA levels in milk and mammary gland tissue.
  • High viral RNA levels in oral and nasal cavities of suckling pups.

Disease Progression:

  • 100% mortality in ferret pups within four days of inoculation.
  • 100% mortality in lactating ferrets within six days of inoculation.

Respiratory Transmission:

  • Pups developed respiratory infections directly from H5N1-positive milk.
  • Transmission back to mothers observed through prolonged contact.

Significance:

  • Demonstrates active viral replication in mammary glands.
  • Highlights milk as a potential vector for virus transmission.

Comparison with H1N1:

  • H5N1 (clade 2.3.4.4b) causes more severe disease than H1N1 in ferrets.

Viral Spread Among Ferrets:

  • Efficient transmission through direct contact but not through respiratory droplets or fomites.

Concerns about Zoonotic Transmission

  • Increased Mammalian Susceptibility: Outbreaks in marine mammals, cattle, and ferrets challenge previous assumptions about limited mammalian susceptibility.
  • Human Infections: Direct exposure to infected animals remains the primary mode of human infection.
  • Potential for Broader Outbreaks: Zoonotic potential raises concerns about interspecies transmission and public health risks.

Key Studies and Findings

Nature Study (October 28, 2024):

  • Severe disease and 100% mortality in infected ferrets.
  • Efficient transmission through direct contact; limited airborne spread.

Preprint Study on Milk Transmission:

  • Viral RNA levels peak in milk during mammary gland infections.
  • Milk serves as a direct medium for virus transmission to offspring.

Implications and Future Directions

Animal Health:

  • Importance of monitoring and containing outbreaks in farm animals and wildlife.
  • Potential economic impact on dairy and livestock industries.

Human Health:

  • Need for surveillance among farm workers and people in close contact with infected animals.
  • Investigate zoonotic transmission pathways to mitigate public health risks.

Research Needs:

  • Further studies to understand mammary gland infections in different species.
  • Explore mitigation strategies to prevent virus spread via milk or other mediums.

Global Response:

  • Enhanced biosecurity measures to limit spread among animals.
  • Collaborative efforts to study interspecies transmission and develop vaccines or antiviral treatments.

Source: https://www.thehindu.com/sci-tech/science/study-shows-fatal-spread-of-h5n1-virus-from-ferrets-to-suckling-kits/article68895611.ece#:~:text=Viral%20RNA%20levels%20in%20the,the%20pups%2C%20the%20study%20notes.