Highly Pathogenic Avian Influenza (HPAI) Detections in Livestock

In recent weeks, the agricultural community in the United States has been on high alert following the confirmation of Highly Pathogenic Avian Influenza (HPAI) in domestic livestock across several states. As of April 5, 2024, the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS) has confirmed HPAI in dairy milking cattle herds in Texas (8), Kansas (3), New Mexico (2), Idaho (1), Michigan (1), and Ohio (1).

What is HPAI?

Avian influenza, commonly referred to as bird flu, is a highly contagious viral infection that primarily affects birds, including domestic poultry and wild birds. The virus exists in several strains, with some strains causing mild illness and others leading to severe outbreaks with high mortality rates among infected birds. Of particular concern is Highly Pathogenic Avian Influenza (HPAI), which can cause severe illness and high mortality rates in poultry populations.

Transmission of avian influenza among birds primarily occurs through direct contact with infected birds or their secretions, including respiratory droplets and feces. Wild migratory birds, particularly waterfowl, are natural reservoirs for avian influenza viruses and can carry the virus over long distances during seasonal migrations. Domestic poultry can become infected through contact with contaminated water, surfaces, equipment, or through exposure to infected wild birds.

How did the cattle contract HPAI?

Wild migratory birds are believed to be the source of the virus, with transmission occurring through contact with contaminated feces, saliva, or respiratory secretions. In particular, water sources can become contaminated after contact with an infected bird, leading to transmission in other animals drinking from that source. Transmission can also occur if cattle share pasture or living spaces with infected birds, as cattle may graze in contaminated areas. However, the spread of the illness among the Michigan herd raises concerns about the possibility of HPAI transmission between cattle.

Is this the same strain that has been affecting poultry in recent months?

Tests conducted so far indicate that the HPAI strain identified in dairy cows belongs to the H5N1 subtype, specifically the Eurasian lineage goose/Guangdong clade 2.3.4.4b. This is consistent with the strain that has been circulating among wild birds and commercial poultry flocks in recent months.

Is HPAI a threat to humans?

HPAI can infect humans under certain circumstances. On March 27, a farm worker on a commercial dairy farm in Texas tested positive for HPAI after exposure to infected dairy cattle. The patient reported conjunctivitis and received antiviral treatment with oseltamivir. This is the first reported incident of HPAI spreading from cows to humans, and the second confirmed case of HPAI in humans in the US. The first case was reported in April 2022 in Colorado in a person who had contact with infected poultry.

The CDC has issued a Health Alert Network Health Advisory, and recommends that people with job-related or recreational exposures to infected birds, cattle, or other animals are at higher risk of infection should take appropriate precautions. Precautions for farmers, poultry workers, and livestock owners include wearing PPE (N95 filtering facepiece respirator, eye protection, and gloves) and thoroughly washing their hands after contact or going into any buildings that have had sick or dead birds or other animals, feces, or litter from potentially infected animals.

Since 1997, more than 900 sporadic human cases of HPAI A(H5N1) have been reported in 23 countries, with more than half of these cases resulting in death. However, human cases have decreased substantially since 2015. Clinical illness with HPAI infection ranges from mild (e.g. conjunctivitis and upper respiratory symptoms) to critical disease (e.g. pneumonia, multi-organ failure, and sepsis) and death.

How can transmission be prevented?

Preventing the transmission of avian influenza to livestock and mitigating the risk of outbreaks require comprehensive biosecurity measures and proactive surveillance efforts.

Implementing biosecurity measures on farms may include regularly disinfecting equipment and limiting contact with wild birds and other animals. First, regularly cleaning and disinfecting all equipment, tools, and vehicles used on the farm can prevent cross-contamination between animals. Then, securing poultry houses with proper fencing and netting and keeping feed and water sources covered can prevent contamination by wild birds or other animals.

Furthermore, regular monitoring of bird populations for signs of illness, coupled with prompt reporting of suspected cases to veterinary authorities, can facilitate early detection and rapid response to outbreaks. By training personnel to recognize clinical signs associated with avian influenza and promptly reporting suspected cases to veterinary authorities or public health agencies, outbreaks can be caught before they spread to livestock or humans.

Finally, real-time monitoring of water sources, such as drinking water or ponds or lakes near livestock facilities, can help identify potential sources of contamination and mitigate the risk of avian influenza transmission. By continuously testing for the presence of avian influenza in water sources available to livestock, contamination can be caught before it infects cattle herds. Moreover, if contamination is found, interventions like improved sanitation practices, installation of physical barriers to deter wild birds, and treatment of water with disinfectants can be implemented promptly.

Conclusions

As the situation continues to evolve, it is imperative for stakeholders across the agricultural sector to remain vigilant and collaborate closely with regulatory agencies and public health authorities. Timely reporting of suspected cases, adherence to biosecurity protocols, and proactive surveillance efforts are crucial in containing the spread of HPAI and safeguarding animal and human health.

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