Experts from Michigan, led by wildlife rehabilitator Erica Zuhlke, admitted two fox kits last April. According to observations, the animals, which came from Macomb County, had high fevers and frequent seizures. After the diagnosis, one of them immediately died.
Zuhlke's team theorized that the condition of the foxes was induced by a secondary rodenticide, or that their parents consumed a poisoned rodent. After two weeks, a separate case was identified in St. Clair County, also involving a fox kit that had similar symptoms. After a day, Lapeer County confirmed the fourth case.
Avian Influenza in the US
A picture taken on January 10, 2018 shows a red fox (Vulpes vulpes) in its enclosure at a wildlife park in Frankfurt/Oder, eastern Germany.
Zuhlke, who is also the founder of Attica's nonprofit organization Critter Crossing Rehabilitation, explained in a report by MLive that the bizarre phenomenon was eventually confirmed as an impact of the current avian influenza pandemic.
The analysis was made possible through the help of the Michigan Department of Natural Resources and the Michigan State Veterinary Diagnostic Lab. The local authorities submitted samples from the affected red fox kits to the state's veterinary facility to test for 'highly pathogenic avian influenza.'
All three cases from the kittens were announced as 'non-negative.' The examination was backed up by a separate testing procedure from Iowa's National Veterinary Services Lab, which also found the samples positive for the deadly avian flu.
The pathogens of the disease were detected from the samples extracted from the nose, mouth, throat, as well as brain tissues of the small red foxes. Alongside the swab tests, the carcass of the animals was screened through a postmortem examination to find contributing information about the disease.
The tragic cases in Michigan were the first confirmed avian flu-related deaths among the state's wild mammals.
The Minnesota natural resources department explained last Wednesday, May 11, that they also confirmed a case of a fox that tested positive for the disease. Alongside the US, Canada also reported a pair of young foxes in the province of Ontario. Parts of Europe also had similar accounts, including the Netherlands, which had an infected fox last year.
HPAI H5N1 Disease in Mammals
State wildlife expert and veterinarian Megan Moriarty said that the virus, known as HPAI H5N1, is commonly passed through transmission from birds to mammalian species. These cases could also be detected in infections from other mammals when an outbreak occurs, but are likely to be isolated cases at most, the expert added.
Today, there are still no hints as to how the foxes have been infected, but it is highly possible that they were exposed or even consumed infected avians such as the common waterfowl.
The department said that the HPAI strain that manifested this year poses a more aggressive infection and inflicted more deaths to wild birds as well as domestic poultries compared to the records from the outbreak last 2015.
About nine Michigan counties have already confirmed approximately 69 cases of the disease in wild birds. Most populations included in the infected avians were bald eagles, ducks, Canada geese, and snowy owls.
Wild birds could be asymptomatic and could carry the infection during migration across regions. Chickens and other domestic avian species incur the most fatal impacts and fastest spread of the flu, the department said.
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