Avian influenza in cats

Cats with Avian Influenza exhibit symptoms that can result in death. They are one of the few species that can get Avian Influenza. The specific virus that they get is H5N1, which is a subtype of Avian Influenza. In order to get the virus, cats need to be in contact with waterfowl, poultry, or uncooked poultry that are infected.[1] Two of the main organs that the virus affects are the lungs and liver.[2]

History
See also: Global spread of H5N1 § Felidae (cats)

The H5N1 virus has been found in China, Thailand, Vietnam, Indonesia, Iraq, Austria, and Germany. Besides being found in domestic cats, the virus has infected a variety of wild cats such as the Asiatic golden cat, the clouded leopard, tigers, and leopards.[3]

H5N1 was first discovered in domestic and wild cats in Asia,[4] specifically in 2003 in the Thai zoo where two tigers and two leopards died. In 2004, the Thai zoo had 147 tigers that died or were euthanized.[5] This was then followed by an outbreak in Germany in 2006, where three stray cats were found to be either dying or dead during the peak time of the virus outbreak.[6]

Because the virus infects the lungs of cats, it is one of the preferred model animals to study the effects of H5N1 in humans.[3]

Virus

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.[6] 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.[3] Though there is no concrete evidence, there is a potential link between the transfer of the virus between poultry, wild birds, and humans.[7]

Once the cat is infected, after an incubation period of 2 to 3 days,[4] the virus can be found in the respiratory tissues, attached to the type II pneumocytes and alveolar macrophages,[3] 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.[8]

As of right now the H5N1 virus has not adapted to transfer in between mammals, but there is a fear that this can occur.[2]

Studies done with cats

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.[9]

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.[10]

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.[11]

Symptoms

A cat that is infected with a high dose of the virus can show signs of fever, lethargy, and dyspnea.[8] There have even been recorded cases where a cat has neurological symptoms such as circling or ataxia.[1] In a case in February 2004, a 2-year-old male cat was panting and convulsing on top of having a fever two days prior to death. This cat also had lesions that were identified as renal congestion, pulmonary congestion, edema, and pneumonia. Upon inspection, the cat also had cerebral congestion, conjunctivitis, and hemorrhaging in the serosae of the intestines.[12]

However, a cat that is infected with a low dose of the virus may not necessarily show symptoms. Though they may be asymptomatic, they can still transfer small amounts of the virus.[3]

Treatment and prevention

Cats can be protected from H5N1 if they are given a vaccination, as mentioned above. However, it was also found that cats can still shed some of the virus but in low numbers.[3]

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.[1] 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.[4]

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.[4]

References
  1. Thiry, Etienne; Addie, Diane; Belák, Sándor; Boucraut-Baralon, Corine; Egberink, Herman; Frymus, Tadeusz; Gruffydd-Jones, Tim; Hartmann, Katrin; Hosie, Margaret J.; Lloret, Albert (1 July 2009). "H5N1 avian influenza in cats. ABCD guidelines on prevention and management". Journal of Feline Medicine & Surgery. 11 (7): 615–618. doi:10.1016/j.jfms.2009.05.011. PMC 7128855. PMID 19481042.
  2. MARSCHALL, J; HARTMANN, K (1 August 2008). "Avian influenza A H5N1 infections in cats". Journal of Feline Medicine & Surgery. 10 (4): 359–365. doi:10.1016/j.jfms.2008.03.005. PMID 18619884. S2CID 29347001.
  3. Harder TC, Vahlenkamp TW (March 2010). "Influenza virus infections in dogs and cats". Vet. Immunol. Immunopathol. 134 (1–2): 54–60. doi:10.1016/j.vetimm.2009.10.009. PMID 19896216.
  4. Philippa J, Baas C, Beyer W, et al. (May 2007). "Vaccination against highly pathogenic avian influenza H5N1 virus in zoos using an adjuvanted inactivated H5N2 vaccine". Vaccine. 25 (19): 3800–8. doi:10.1016/j.vaccine.2007.01.121. PMID 17403559.
  5. Yee KS, Carpenter TE, Cardona CJ (July 2009). "Epidemiology of H5N1 avian influenza". Comp. Immunol. Microbiol. Infect. Dis. 32 (4): 325–40. doi:10.1016/j.cimid.2008.01.005. PMID 18448168.
  6. Starick, E.; Beer, M.; Hoffmann, B.; Staubach, C.; Werner, O.; Globig, A.; Strebelow, G.; Grund, C.; Durban, M.; Conraths, F.J.; Mettenleiter, T.; Harder, T. (1 April 2008). "Phylogenetic analyses of highly pathogenic avian influenza virus isolates from Germany in 2006 and 2007 suggest at least three separate introductions of H5N1 virus" (PDF). Veterinary Microbiology. 128 (3–4): 243–252. doi:10.1016/j.vetmic.2007.10.012. PMID 18031958.
  7. Kalthoff D, Globig A, Beer M (January 2010). "(Highly pathogenic) avian influenza as a zoonotic agent". Vet. Microbiol. 140 (3–4): 237–45. doi:10.1016/j.vetmic.2009.08.022. PMID 19782482.
  8. Belser JA, Tumpey TM (February 2013). "H5N1 pathogenesis studies in mammalian models". Virus Res. 178 (1): 168–85. doi:10.1016/j.virusres.2013.02.003. PMC 5858902. PMID 23458998.
  9. MARSCHALL, J; SCHULZ, B; HARDERPRIVDOZ, T; VAHLENKAMPPRIVDOZ, T; HUEBNER, J; HUISINGA, E; HARTMANN, K (1 August 2008). "Prevalence of influenza A H5N1 virus in cats from areas with occurrence of highly pathogenic avian influenza in birds". Journal of Feline Medicine & Surgery. 10 (4): 355–358. doi:10.1016/j.jfms.2008.03.007. PMID 18640861. S2CID 6326717.
  10. Giese, Matthias; Harder, Timm C.; Teifke, Jens P.; Mettenleiter, Thomas C.; Vahlenkamp, Thomas W. (1 March 2009). "The role of T cells in avian influenza H5N1 infected cats". Veterinary Immunology and Immunopathology. 128 (1–3): 343. doi:10.1016/j.vetimm.2008.10.282.
  11. Stittelaar, Koert J.; Lacombe, Valérie; van Lavieren, Rob; van Amerongen, Geert; Simon, James; Cozette, Valérie; Swayne, David E.; Poulet, Hervé; Osterhaus, Albert D.M.E. (1 July 2010). "Cross-clade immunity in cats vaccinated with a canarypox-vectored avian influenza vaccine". Vaccine. 28 (31): 4970–4976. doi:10.1016/j.vaccine.2010.05.028. PMID 20566392.
  12. Cardona CJ, Xing Z, Sandrock CE, Davis CE (July 2009). "Avian influenza in birds and mammals". Comp. Immunol. Microbiol. Infect. Dis. 32 (4): 255–73. doi:10.1016/j.cimid.2008.01.001. PMID 18485480.
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