USDA Map Now Tracking Domestic Cats With H5N1

 

#18,089

Yesterday the USDA updated their map/list of HPAI H5N1 in mammalian wildlife, with an unusually large jump in cases.  Most (n=16), we learn from the following notice, are domestic cat infections going back to March of this year.  

While many of these feline infections have come from direct exposure to dairy cattle or raw milk, over the past week we've seen reports from two states (South Dakota and New Mexico) of 4 H5N1 feline deaths not linked to diary barns. 

Additionally, one case from Montana is listed, which has yet to report HPAI H5 in cattle. 

We've seen earlier reports of domestic cats infected with H5N1 - both in the United States (see here & here), and in many other countries (see Poland, South Korea, and France).  

These events are undoubtedly badly under-reported, both here in the United States, and around the world. 

First, there is great disparity in the reporting of mammalian wildlife with HPAI H5 (see map above). Only 26 states have reported finding cases, and while New York and Michigan lead with 27 reports each, 7 of the reporting states (Arizona, Florida, Illinois, Missouri, Ohio, Rhode Island, and Vermont) have only reported a single incident.

Why the clear majority of the reports have come from northern states isn't clear, although it may come down to differences in climate and terrain (swamps vs. forests vs. deserts), and the fact that some states may be looking harder than others.

Mammals - including domestic cats - often die in remote and difficult to access places where their carcasses are quickly scavenged by other animals, meaning most never discovered or tested. And of course, some of these animals are likely to survive the infection, and are never tested. 

With so much H5 circulating in the wild, one of the concerns is the potential for companion animals (primarily cats) to bring avian influenza from the wild into the home (see A Brief History Of Avian Influenza In Cats). While the risk is considered low, it is not zero. 

In late 2016, New York City reported that hundreds of cats across several city-run animal shelters contracted avian an LPAI H7N2 (see NYC Health Dept. Statement On Avian H7N2 In Cats).

Studies later showed that two shelter workers were infected while 5 others exhibited low positive titers to the virus, suggesting possible infection (see J Infect Dis: Serological Evidence Of H7N2 Infection Among Animal Shelter Workers, NYC 2016). 

While dogs are also susceptible to H5N1 (see Microorganisms: Case Report On Symptomatic H5N1 Infection In A Dog - Poland, 2023), they tend to have milder (often asymptomatic) infections.

We recently reviewed the CDC's Updated Advice On Bird Flu in Pets and Other Animals, which warned the public to avoid contact between their pets (e.g., pet birds, dogs and cats) and wild birds. 

And of course, knowing what we know now,  you should never feed pets raw milk. 

Given the unusual amount of H5 virus still circulating in North America this late in May - and the unknowns provided by the recent introduction of H5N1 to American livestock - taking a few extra precautions over the summer would seem prudent until we know more about the threat we are facing.