In the USA, there has been an outbreak of bird flu among dairy cows for some time now. So far, 33 farms have been affected in eight states.
The first case was reported on March 25. According to SVA, this is the first time that highly pathogenic bird flu has been confirmed after natural infection in cattle. A few weeks before the cases were discovered among ruminants, kittens in Minnesota had also been affected.
The affected dairy cows have lost milk production, ate less feed, were lethargic, dehydrated and had a fever. The milk from the sick animals must also have been thicker than usual and similar to colostrum. The faeces from the cows must also have been abnormally sticky or loose, writes SVA.
Not in Europe
In affected animal groups, morbidity is estimated to be around ten percent, but the symptoms are transient. Viruses have been found in both milk samples and throat samples. It has been established that it is the same variant of highly pathogenic bird flu H5N1 (clade 2.3.3.4b) that affected birds in the USA and Europe. However, SVA writes that the virus that affected the cows in the USA carries more gene segments from the American gene pool of influenza A virus. A genotype that has not been detected in Europe.
In the United States, they are working hard to investigate the infections and reduce the risk of spread between the states. From April 29, it will be mandatory to test the animals if they are to be moved between different states. And only those who can leave a negative test may be moved, the USDA writes.
Low risk to humans
The USDA has identified spread between cows in the same herd, spread from cow to poultry, spread between dairies in connection with livestock movements, and even cows without clinical symptoms have tested positive.
Furthermore, the USDA writes that it is important to remember that so far no changes have been found to the virus that would make it more transmissible to humans or between humans. However, cases among people who are in direct contact with sick animals are possible. For example, one person has been infected after being in contact with cattle in Texas. However, this one had mild symptoms, in the form of an infection in the eye mucosa. The US Centers for Disease Control and Prevention (CDC) believes that the risk to the public remains low. This is an assessment that the European Commission for Disease Control (ECDC) shares.
Good recovery
The USDA also writes that affected cows recover after treatment and that mortality is low. They also stress how important it is to have good biosecurity to limit the spread of disease for both cattle and poultry.
The US Food and Drug Administration writes that according to the knowledge available today, they believe that commercial milk production is safe due to the pasteurization process and that the milk from sick animals has been destroyed.
The article was published on Friday, April 26, 2024
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