may be the main route of transmission

Milking procedures may be a major route of transmission of the highly pathogenic H5N1 avian influenza virus among dairy cows in the United States, according to a published study. Nature.

For a study conducted by a group of German and American scientists, Calves and dairy cows were experimentally infected with H5N1 virus variant 2.3.4.4b.which is currently circulating in cattle in the United States to obtain information on possible modes of transmission.

The team compared virus susceptibility and transmission in nine calves infected orally and nasally and three cows inoculated with the virus in their mammary glands. Infection of the calves resulted in a mild clinical picture with moderate viral replication but no transmission of the virus to other calves with which they were in contact.

However, dairy cows experienced severe mammary gland infection with fever, mastitis and a sudden decrease in milk production. In addition, there was a “dramatic increase in virus levels in the milk” but no signs of systemic infection or nasal discharge were found.

These results show, according to the study, that milk and milking procedures, rather than respiratory spread, are the likely primary modes of transmission. H5N1 in cattle.

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