Causes
The most common way a cat can obtain H5N1 is by consuming an infected bird. This has been studied in the 2006 and 2007 cases in Germany and Austria where the strains between the cat and the infected birds were not different between the species. A cat is able to then transfer the virus via the respiratory tract and the digestive tract to other cats. However, studies suggest that a cat cannot transfer the virus to a dog, and vice versa, while sharing a food bowl. Though there is no concrete evidence, there is a potential link between the transfer of the virus between poultry, wild birds, and humans.
Once the cat is infected, after an incubation period of 2 to 3 days, the virus can be found in the respiratory tissues, attached to the type II pneumocytes and alveolar macrophages, as well as the intestinal tissues. There have also been some cases where the virus has been found in the brain and other systems in the body.
As of right now the H5N1 virus has not adapted to transfer in between mammals, but there is a fear that this can occur.
Treatment & Prevention
Cats can be protected from H5N1 if they are given a vaccination. However, it was also found that cats can still shed some of the virus but in low numbers.
If a cat is exhibiting symptoms, they should be put into isolation and kept indoors. Then they should be taken to a vet to get tested for the presence of H5N1. If there is a possibility that the cat has Avian Influenza, then there should be extra care when handling the cat. Some of the precautions include avoiding all direct contact with the cat by wearing gloves, masks, and goggles. Whatever surfaces the cat comes in contact with should be disinfected with standard household cleaners.
They have given tigers an antiviral treatment of Oseltamivir with a dose of 75 mg/60 kg two times a day. The specific dosage was extrapolated from human data, but there hasn't been any data to suggest protection. As with many antiviral treatments, the dosage depends on the species.
Research
One epidemiological study that was performed in Germany and Austria on 171 cats found that less than 1.8% of this population had H5N1. In this same sample population of cats, less than 2.6% had antibodies to H5N1. Even though Germany and Austria are among the countries that have had naturally occurring cases, this study shows that very few cats have contracted the disease.
There have also been studies looking at the T cells, specifically CD4 and CD8, in the cat after viral infection. Though the mechanism is not fully known, there seems to be an inverse relationship with the amount of T cells present and the amount of infected cells.
Another study to test whether the ALVAC recombinant canarypox virus could prime the immune system in cats was performed. This vaccine has the same hemagglutinin as the H5N1 virus, and therefore worked on preventing death from two different strains of the virus, HPAIV A/Vietnam/1194/2004 and HPAIV A/Indonesia/05/2005. However, some of the cats that were vaccinated did exhibit hyperthermia and weight loss, and all of the cats did have some disease change (assuming lesions) in their lungs. All of the cats, except one, still excreted the virus even after being vaccinated.
