H5N1 Avian Flu Spread Under Study

By Scout Nelson

Though H5N1 avian flu outbreaks in US poultry and dairy cattle remain low, scientists are carefully investigating how the virus spreads on farms. The USDA recently confirmed only one poultry detection and two cattle detections in the past month, showing a seasonal decline in cases.

However, concerns remain as the virus continues to spread in wild birds globally. Earlier theories focused on infected cattle movements and contaminated equipment as primary causes. But outbreaks kept occurring even after stricter controls, leading scientists to look for other sources.

One surprising find came when scientists detected H5N1 in a house fly sample from California. Experts believe flies might carry the virus on their bodies, potentially spreading it around farms. Though there's no proof flies can infect animals or people directly, this discovery highlights the need for stronger farm biosecurity.

Past studies, including a 2006 report from Japan, suggested that flies could move the virus after contacting infected material. Other suspected virus carriers include rodents and poultry dust. Experts warn that until the exact spread routes are known, controlling outbreaks will remain difficult.

Another key study from China explored how H5N1 infects dairy cows. Researchers found the virus enters cows’ mammary glands through the teats, especially when cows self-nurse or share milk—a behavior known as “milk snatching.” Calves can also spread the virus during nursing.

Experiments showed that virus entry through the nose affected only the respiratory tract, while direct teat exposure infected the mammary gland. The study also noted that certain tissues in cows allow the virus to survive and spread.

Scientists tested two vaccines in cows—an H5 inactivated vaccine and a DNA-based vaccine—both gave complete protection against H5N1, even after direct exposure.

Experts continue monitoring the situation and emphasize the importance of biosecurity and vaccination in preventing outbreaks and protecting animal health.

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