OTOLOGIC AND SYSTEMIC MANIFESTATIONS OF EXPERIMENTAL INFLUENZA-A VIRUS-INFECTION IN THE FERRET

In an effort to further validate an animal model and to better define the mechanisms relating viral upper respiratory tract infections and a cute otitis media, we infected 10 ferrets intranasally with influenza A virus. Infection was monitored by cultures and antibody titers, illn ess was monitored by signs and temperatures, and otologic complication s were monitored by otoscopy, tympanometry, and eustachian tube functi on testing. All animals became infected, Forced-response test results showed progressive increases in the passive function variables offer i noculation. Inflation-deflation test results documented progressive im pairment of active tubal function, which was accompanied by the develo pment of middle ear underpressures. No otitis media was seen. The resu lts suggest that Influenza A virus infection results in progressive, s ubtotal occlusion of the eustachian tube lumen, which compromises the ventilatory function of the tube, thereby promoting the development of middle ear underpressures. These findings support the hypothesized pa thophysiologic relationship between viral upper respiratory tract infe ctions, eustachian tube dysfunction, middle ear underpressures, and ac ute otitis media. Given these pathophysiologic changes and previously documented physiologic similarities to the eustachian tube-middle ear system of human beings, we conclude that the ferret represents an appr opriate animal model for studying the pathogenic processes related to viral upper respiratory tract infections, eustachian tube dysfunction, and otitis media and for testing of potential prophylactic and therap eutic regimens.