Subclinical Infection With Avian Influenza A (H5N1) Virus in Cats

Michael Leschnik; Joachim Weikel; Karin Möstl; Sandra Revilla-Fernández; Eveline Wodak; Zoltan Bagó; Elisabeth Vanek; Viviane Benetka; Michael Hess; Johann G. Thalhammer


Emerging Infectious Diseases. 2007;13(2):243-247. 

In This Article


H5N1 virus-positive cats (1 and 2) and H5N1 virus antibody-positive cats (1 and 4) did not show any signs of influenza virus-associated illness after the swan had been placed in the animal shelter (days 1-50). Upper respiratory symptoms (laryngitis, bronchitis, and tracheitis) were evident in 30 cats, bronchopneumonia in 40 cats, diarrhea in 7 cats, mucosal lesions in 37 cats, and traumatic wounds and lesions in 10 cats. However, for each cat with clinical symptoms that might have been associated with influenza infection, another specific etiologic reason for illness could be documented. Pathomorphologic examination showed no lesions associated with respiratory infection in cats 1 and 4 or in any other cat that had died before day 50. Influenza A virus-specific nucleic acids were not detected in any organ sample tested by PCR. Likewise, all pharyngeal and rectal swabs obtained at the quarantine station were negative for influenza A virus by PCR. Antibodies against influenza virus A (H5N1) were detected in 2 cats (1 and 4, Table) with titers 256 on day 50 in both cats.

Cats 1, 2, and 4 had negative test results for FeLV and FIV, but all 3 cats had high antibody titers against FCoV. FCV was detected in the swab from cat 2, and a double infection with FCV and FHV-1 was detected in cat 4. Clinical, bacteriologic, and virologic tests identified infection with FeLV in 15 cats, FIV in 12 cats, and antibodies against FCoV in all but 1 cat. A total of 44 swabs showed positive results for FCV-specific nucleic acids, 4 for FHV-1; 13 samples showed a double infection with FCV and FHV-1. Some pathologic bacterial infections of the respiratory and digestive system were confirmed by swab cultures.

All veterinarians and staff members at the animal shelter and at the quarantine area were clinically monitored for any influenzalike symptoms. Because results of this monitoring were unremarkable and virus excretion by the cats was not detected, serologic tests were not conducted for these persons.


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