Bird flu thought to have killed Californian cows
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There are signs of bird flu being much more severe in dairy cows in California, perhaps linked to very hot weather in the state's Central Valley, which has the highest dairy farming density in the USA.
Since last March, bird flu has been found in more than 300 dairy herds in 14 states, and since the end of August, it has infected 120 herds in California, the top milk-producing state. It was recently spreading in California at a rate of 15 farms per week.
There is an estimated 20% cut in production for some California dairy farmers, compounded by a recent milk price cut from $24 to $21 per hundredweight.
The Milk Producers Council, which represents dairy families throughout California, has warned fourth-quarter dairy industry output could plummet due to bird flu spreading rapidly in the state, which accounts for about 40% of the USA's milk production. This could have "an explosive impact" on dairy prices (with the state's all-year-round production, the last quarter is usually the lowest producing, but only by a small percentage).
Infected herds in California are seeing cow mortality rates as high as 15% or 20%, compared to only 2% in other states, the Reuters news agency was told by Keith Poulsen, director of the Wisconsin Veterinary Diagnostic Laboratory.
Farms that might normally lose one or two cows per month have had hundreds die, said Anja Raudabaugh, chief executive of Western United Dairies, which handles 75% of the state's milk production.
Cows suffering from the virus have fever, reduced milk production, and other symptoms. Due to the increased death toll, rendering plants struggled to process all the dead animals, and wildlife scavenging on carcasses, sometimes left lying around for days, may be facilitating the spread of bird flu. Recent temperatures in the main dairy areas exceeding 35C have exacerbated the situation.
To protect their herds, dairy farmers are advised to strictly quarantine new or returning cattle (including contract-reared heifers or show animals) for 30 days, paired with pre-movement testing, which is available for free. The isolation area must be separated from resident cows. Early segregation of infected animals can greatly limit within-herd spread.
Cleaning and disinfecting shared livestock transport vehicles before and after farm entry is seen as critical.
Employees should not be shared with other dairy or poultry operations, and their farm-specific boots and coveralls should never leave the dairy.
Delivery vehicles (feed, milk tankers, rendering) should not cross farm vehicle paths. Because infected milk is a primary method of disease spread, processors may have to dedicate certain milk tanker trucks for infected farms.
It is also recommended for workers to use personal protective equipment, such as eye protection (face shields or safety goggles), respirators (N95 masks), and gloves. These are being supplied for free to farms by milk processors such as Western United Dairies, and agencies such as Tulare County Health, and the Tulare Agricultural Commissioner.
The virus has also infected 25 Americans this year. All but one had exposure to infected cows or poultry. All those infected experienced only mild flu symptoms.
Of the 11 infected in California, most were from the Central Valley's Tulare County, the number one dairy farming county in the USA.
Dairy farmers are obliged to not deliver milk from sick cows for food processing, but consumers have been assured there is no safety concern with milk from infected cows, as long as it is pasteurised.
Meanwhile, a small-scale research study of only six lactating cows that had bird flu injected into their udders showed how devastating the disease could be. They had severe illness, including lethargy, high fever, inflammation, and reduced feed intake, and four had to be humanely euthanised.
Their milk production fell by about 90%, and the milk quality deteriorated. “There is an incredible amount of virus in the milk,” said Juergen Richt, a professor at Kansas State University who took part in the research.
In three of the cows that were inoculated with a flu strain from wild birds, a viral mutation quickly emerged that is associated with spread to other mammals.
“We have to consider the small number of animals in these studies as not being perfect models of disease in a herd with hundreds or thousands of animals,” said Keith Poulsen of the Wisconsin Veterinary Diagnostic Laboratory.
He was not associated with the study, and warned: “We need more herd investigations to understand more fully how the virus is moving from animal to animal and from farm to farm.”
Meanwhile, the avian flu also continues to spread in poultry farms, with last week's new cases including a Utah layer farm with 1.8 million birds, and a Washington state farm with nearly 840,000 birds.
