Although oral exposure to H5N1 highly pathogenic avian influenza viruses is a risk factor for infection in humans, it is unclear how oral exposure to these virus results in lethal respiratory infections. To address this issue, we inoculated ferrets and hamsters with two highly pathogenic H5N1 strains. These viruses, inoculated directly into the stomach, were isolated from the large intestine and the mesenteric lymph nodes within 1 day of inoculation and subsequently spread to multiple tissues, including lung, liver, and brain. Histopathologic analysis of ferrets infected with virus via direct intragastric inoculation revealed lymph folliculitis in the digestive tract and mesenteric lymph nodes and focal interstitial pneumonia. Comparable results were obtained with the hamster model. We conclude that, in mammals, ingested H5N1 influenza viruses can disseminate to nondigestive organs, possibly through the lymphatic system of the gastrointestinal tract.Since 1997, over 500 cases of human H5N1 influenza A virus infection have reported, with more than 300 deaths worldwide (WHO [http://www.who.int/csr/disease/avian_influenza /country/cases_table_2011_01_13/en/index.html]). These viruses remain enzootic in birds in many countries, posing a serious pandemic threat. Contact with sick birds is the most common risk factor for human infection; however, some patients are known to have consumed raw duck blood prior to the onset of their influenza-like illness. This fact highlights the importance of reports that some mammalian species, including domestic cats, leopards, tigers, and dogs, have been infected with H5N1 viruses after consuming virus-contaminated meat (5,9,10,14,16,17).Many patients infected with H5N1 viruses, regardless of the exposure route, develop viral pneumonia. During the early phase of human H5N1 infection, viruses are rarely isolated from the upper respiratory tract (1, 4), probably because the receptor molecules for H5N1 viruses, namely, oligosaccharides terminating with sialic acid (SA) bound to galactose by ␣-2,3 linkages (SA␣2,3Gal), are abundant predominantly on the cells of the lower respiratory tract in humans (15, 19). Therefore, we posed the question, How might H5N1 viruses reach the lower respiratory tract, the site of severe infection in most humans, after oral exposure?Among the several reports of oral H5N1 infections in mammals, particularly felines (5, 9, 10, 14, 17), an experiment in cats by Rimmelzwaan et al. (14) suggests two possible routes of virus entry following oral H5N1 virus exposure: the blood and the intestinal lumen. However, the latter possibility was not experimentally demonstrated in the study by Rimmelzwaan et al. since viral exposure through the respiratory tract after the consumption of virus-infected raw chicken was not excluded.Therefore, we designed our study to investigate the intestinal viral invasion route. Our results with ferret and hamster models implicate the digestive tract in H5N1 virus invasion in mammals. MATERIALS AND METHODS Viruses.A/Vietnam/UT3062/04 (UT30...

ABSTRACT. A six-year-old female Labrador retriever dog was suffering from osteomyelitis in her hindlimb. A puncture wound caused by a rotted bamboo stick was presumed as the source of infection. The dog suffered from pre-existing aortic stenosis, but otherwise exhibited no significant abnormality in her systemic conditions excluding claudication of the left hindlimb. The results of cytology and pathological examinations of biopsy samples revealed the diagnosis of mycotic osteomyelitis in this dog. Mycological and DNA tests showed the pathogen as the mushroom Schizophyllum commune. Antibiotic sensitivity testing also revealed susceptibility to itraconazole, which was used to successfully treat the dog. This is a rare case of canine basidiomycosis with S. commune as the etiologic agent.

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