We last looked in at the USDA's list of mammalian wildlife infections with H5N1 three weeks ago when the number sat at 176 (excluding recent reports in domestic cats here, and here), with Red Foxes and skunks make up more than 60% of the detected infections.
Since the majority of wildlife detections of H5N1 have come from peridomestic animals in urban or suburban settings, it makes sense to protect your cat and dog when they are outside. The CDC has some advice on keeping your pets, and yourself, safe from the virus.
Why nearly all of the reports to date 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 often die in remote and difficult to access places where their carcasses are quickly scavenged by other animals, meaning most never discovered or tested. Those that are reported likely only represent a small fraction of actual infections.
This week the USDA updated their list of mammals infected with H5 avian influenza, bringing the total to 191 (not including the domestic cats mentioned above). The list below only reflects positives reported since May 1st.
Although the increased number of spillovers of HPAI to mammalian hosts is concerning, the `saving grace' has been that we've seen very little evidence of mammal-to-mammal transmission of the virus (possible exceptions being farmed mink and marine mammals).
This is considered important - particularly with zoonotic diseases like avian flu - because long chains of infection can lead to adaptive mutations, which can make the virus even better suited for a specific host.
But since much of what goes on in the wild is hidden from view, just because we aren't seeing it doesn't mean it isn't happening. Scavengers - like feral cats, foxes, vultures, and raccoons - may be creating unseen chains of infection in the wild.
Among those scavenger species who are also at risk from the virus are critically endangered California Condors, whose population had declined to just 23 known survivors by the early 1980s. While it has made a dramatic recovery since then (roughly 500 either captive or in the wild), their survival is not guaranteed.
Over the past 6 weeks we've been following H5N1's impact on this endangered species (see here and here), including an investigation into the feasibility of vaccinating them against the H5 virus. The vaccine is currently being trialed in vultures, and if that is successful, they will try in on captive Condors.
The US Fish and Wildlife Service has posted an update on the impact of H5N1 on California Condors, and the good news is, no new deaths have been reported since our last update.
California Condor HPAI Response Update - May 26, 2023
May 26, 2023
The U.S. Fish and Wildlife Service’s Incident Command Team, in collaboration with partner agencies, continues to respond to Highly Pathogenic Avian Influenza (HPAI), also known as bird flu, in the Southwest flock of California condors.
Partners and stakeholders have initiated vaccine trials and are working to improve the ability of flock managers in swiftly responding to potential future HPAI outbreaks through management of the flocks, and facility and infrastructure improvements. The Incident Command will provide updates on the incident in this format on a routine basis until further notice.
On May 16, HPAI vaccination trials began with 20 vultures and eight controls as surrogates for the condor to determine safety and effectiveness of the vaccine. All vultures that received the vaccine appear to be in good health with no vaccine site reactions. A blood draw was conducted this morning, May 26, as part of a preliminary check and will be analyzed at the USDA’s Southeast Poultry Research Center for HPAI antibodies to evaluate immune response. It is too early to detect effectiveness of the vaccine, but we hope to observe some level of immune response.
Depending on the results of this trial, the second step will be to implement the trial on 25 captive California condors. Trial design was collaboratively developed by the Service, USDA APHIS and U.S. Geological Survey.
Status of HPAI in the Southwest Flock as of May 26, 2023
Changes are indicated in bold in our reporting below.
Mortality:Total mortality: 21 condors
Deceased and recoverable: 17 condors
Deceased and unrecoverable: four condors
Breeding pairs impacted:(Continue . . . )
Eight breeding pairs (13 individuals deceased)
Rescues:Number of condors in care: five condors
HPAI Results:Total condors tested: 21 condors
Confirmed HPAI positive: 19 condors (17 deceased, two in care at Liberty Wildlife)
Confirmed HPAI negative: two condors in care at Liberty Wildlife
Vaccination trials:Birds vaccinated: 20 vultures
Field monitoring continues to ensure the Arizona-Utah flock remains healthy.
Rescued condors 757, 982, 1061 and 1108 are in care at Liberty Wildlife and partners will determine when it safe to release them back in the wild.
Flock managers across the range of the California condor are adapting strategies to avoid congregation of birds through discontinuation of communal feeding sites and watering areas.