In the US, the first known case of highly pathogenic avian influenza in a dairy herd in Wisconsin has been confirmed via routine national milk testing.
On 14 December, the US Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) National Veterinary Services Laboratories (NVSL) announced that a detection of highly pathogenic avian influenza H5 clade 2.3.4.4b has been confirmed in a dairy cattle herd in Wisconsin. This marks the first known case of HPAI in cattle in Wisconsin.
The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) has identified a case of highly pathogenic avian influenza in a dairy herd in Dodge County. The DATCP states that the affected farm has been quarantined, and any cattle exhibiting signs of illness will be separated for further treatment.
The departments have said that while dairy cattle have been infected since the start of the outbreak in March 2024, APHIS has seen cases in only a small number of states this year.
The current detection of avian influenza in Wisconsin was confirmed as a result of routine National Milk Testing Strategy testing, not pre-movement surveillance, the USDA stated.
Avian influenza biosecurity
The USDA’s highly pathogenic avian influenza eradication strategy remains a top priority – biosecurity is still key to mitigating the risk of disease introduction or spread between premises. APHIS recommends enhanced biosecurity measures for all dairy farms. Producers should immediately report any livestock with clinical signs, or any unusual sick or dead wildlife, to their state veterinarian.
The organisation further highlights that bird flu detected in dairy cattle does not pose a risk to consumer health or affect the safety of the commercial milk supply. It adds that the US Food and Drug Administration is confident that pasteurisation is effective at inactivating the highly pathogenic avian influenza virus.
In addition, dairies are required to send only milk from healthy animals into processing for human consumption; milk from impacted animals is being diverted from the commercial milk tank or destroyed so that it does not enter the human food supply.
Further tests
Additional on-farm investigations, diagnostic testing, and epidemiological data collection is being carried out to better understand the detection and prevent further disease spread. APHIS will also complete genetic sequencing and announce final results when available.
Since the start of the outbreak in March 2024 in dairy herds in Texas and Kansas, there have been more than 1,000 confirmed cases across 18 states. Despite its slow progression in recent weeks, the virus still poses a threat as California has a confirmed case in the last 30 days.