Impact of H5N1 infection on dairy cows
The article titled "The impact of highly pathogenic avian influenza H5N1 virus infection on dairy cows" published in Nature Communications, presents a comprehensive study on the effects of HPAI H5N1 virus infection in dairy cattle. While historically known for causing high mortality in poultry, recent outbreaks have shown the virus's capacity to infect mammals, including dairy cows. This study investigates a significant outbreak on a large dairy farm in Ohio, examining clinical outcomes, production parameters, risk factors, seroprevalence, and the economic impact on the affected herd.
The H5N1 outbreak occurred in a 3,876-head dairy farm in Ohio in spring 2024, following the introduction of cows from Texas. Clinical signs were recorded in 20% of cows, predominantly manifesting as mastitis with decreased rumination and sharp drops in milk yield.
Clinically affected cows had a 6-fold higher risk of death and a 3.6-fold higher risk of early removal compared to unaffected cows. Affected cows suffered an average milk loss of ~900 kg per cow over 60 days. Rumination time and milk production decreased sharply before the onset of clinical signs, serving as early indicators of infection.
Risk Factors: Multiparous cows and cows in later lactation stages were at higher risk. No significant association was found with breed, baseline milk production, or somatic cell count.
Serological testing revealed a high seroprevalence (89.4%), with most infected cows showing no clinical signs. However, only clinically affected cows exhibited significant milk production losses.
The estimated direct cost per clinically affected cow was ~$950, leading to a total herd-level loss of ~$737,500 over the outbreak period. Costs included reduced milk yield, deaths, and premature removals.
The study highlights the severe economic and production impacts of H5N1 infection in dairy cattle, emphasizing the importance of early detection (using rumination and milk production monitoring) and biosecurity measures.
