Flies, ‘Milk Snatching’ Among H5N1 Transmission Contributors in Dairy Cattle

By Lisa Schnirring

Though H5N1 avian flu outbreaks in dairy cattle and commercial poultry are at low levels in the United States, scientists continue to sort out how the virus spreads on farms, and two new pieces of information this week shed more light on potential spread in dairy cattle: contamination from house flies and “milk snatching”.

Over the last 30 days, the US Department of Agriculture (USDA) has reported only one detection in poultry, a game bird farm in Pennsylvania, and two detections in dairy cattle, which involved herds from California and Arizona. 

The decline in US detections appears to be part of a largely seasonal drop in cases. A new monthly update from the World Organization for Animal Health (WOAH), which covers activity in June, said though poultry outbreaks have decreased, with only 15 reported for the month, new outbreaks in wild birds are on the rise, especially in Europe. 

In the early days of H5N1 outbreaks in dairy cattle, movement of infected cattle and contaminated equipment were thought to play major roles in the spread of the virus. However, outbreaks continued to occur, despite curbs on moving dairy cows among states and stepped-up biosecurity measures on farms, raising ongoing questions and intense scientific investigations into other contributing factors.