Avian Influenza (H5N1): Updated Case Definitions for Mammals

16 May 2024

Defra have updated their guidance on Influenza A (H5N1) infection in mammals, specifically the suspect case definitions and diagnostic testing criteria, to include a new case definition for ungulates including dairy cattle. Vets in small animal practice may wish to be aware as this will affect the suspect case definition relating to small animals.

The updated guidance is in response to the emerging situation in dairy cattle in the USA. The addition of the suspect case definition 3 which covers ungulates will impact suspect case definition 1 which relates to small animals (domestic cats, dogs and ferrets) in particular, the third criterion and specifically, if the animal has been on a dairy farm (dairy cattle, sheep or goats) where mammals fulfil case definition 3 or if it has consumed raw milk.

Information on the suspect case definitions is available here and information on the Guidance in full is available here.

Defra have reminded individuals that as Avian influenza (bird flu) viruses can also infect mammals, if an individual examines a kept or wild mammal or a test sample from any kept or wild mammal and suspects or detects the presence of avian influenza virus or antibodies to avian influenza virus, they must report it immediately; not to report it, is to break the law. To report cases, please call the following: