Rhodococcus equi has been recognized as an equine pathogen since 1923 and is a worldwide pathogen in foals. Up to now, there has been one report on R. equi infection in an Arabian foal in Turkey. We report here two cases of R. equi pneumonia diagnosed in Turkish foals. R. equi was isolated from pure cultures obtained from lung abscesses of two dead foals which were sent to the laboratory from distinct stud-farms in the Izmit district, Turkey, due to the increasing mortality of foals with pneumonia. These isolates were analyzed by plasmid and protein profiles: one isolate had an 85-kb type I virulence plasmid and the other was considered avirulent. Virulent R. equi strains possessing an 85-kb type I or an 87-kb type I were isolated from one of the stud-farms with the problem. These results indicate that the stud-farm was contaminated with virulent R. equi.

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One hundred and eight foals were necropsied and examined for Rhodococcus equi infection from 1992 to 1998 in Hokkaido and Aomori, Japan. Fifty-four of 108 cases had been clinically diagnosed as having R. equi pneumonia, whereas the remaining 54 were diagnosed with non-R. equi pneumonia (23 foals), arthritis (6 foals) and other diseases (25 foals). Pathologically, 104 foals were shown to have suppurative pneumonia with abscesses, and the remaining 3 had intestinal involvement without pulmonary lesions and one had osteomyelitis. Based on the pathology and bacteriology, 108 were classified into 5 disease types: pneumonia (44 cases; suppurative bronchopneumonia), enteritis (3 cases; ulcerative enteritis associated with suppurative lymphadenitis of the intestines), mixed (25 cases; pneumonia, enteritis, and intestinal lymphadenitis), transitional (35 cases; pneumonia and intestinal lymphadenitis), and osteomyelitis (1 case). Eighty-three of the 108 foals (25 foals died due to non-infectious causes) were analyzed for age distributions at the first clinical examination and death. About 75% (62 foals) of the foals showed clinical signs within 2 months of age, peaking at 40 days, and the mean age at the clinical examination was 53.6 days. About 81% (67 foals) died within 3 months of age, peaking at 60 days, and the mean age at death was 77.2 days. About 57% (47 foals) died within 2 weeks after the first clinical examination, and mean days for treatment were 21.7. Mean ages at the clinical signs and death of the 83 foals were compared statistically according to breed, sex, birth month, and disease types, but the difference was not significant. Bacteriologically, virulent R. equi was isolated from lesions of all the 108 foals. Virulent isolates from the foals bred at Hokkaido and Aomori contained an 87-kb type II or a 90-kb plasmid with a different ratio. From this surveillance, it is clear that R. equi infection in foals is still one of the most important diseases in horse-breeding farms in Japan.

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Culture cells from a horse were stimulated by LPS and cytokines, and nitric oxide (NO) production was rendered detectable by a fluorescent measurement reagent. Increase of NO production was observed over time in the LPS-and cytokine-stimulated cells after the addition of l-arginine, a substrate for NO. NO production was observed to increase slightly over time, even in cells not stimulated by the addition of l-arginine. The addition of l-NMMA (an i-NOS inhibitor) along with l-arginine to the LPS-and cytokine-stimulated cells was found to markedly suppress NO synthesis. Enhancement of fluorescence intensity depended on LPS levels, suggesting that NO production may also depend on LPS levels.

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In order to understand the distribution of Emericella nidulans (E. nidulans), the main causative agent of guttural pouch mycosis, in the environment of Thoroughbred stable, fungal isolation was carried out from samples collected from a racehorse training center and racehorse-breeding farms. E. nidulans was isolated mainly from bedding straw at the training center stables and from straw and hay for bedding and feed at the breeding farms. Isolation rates from rice and wheat straw before use tended to be higher than those from the same materials while in use. Results of this study suggested that the main habitat of E. nidulans in the stable included straw and hay for bedding or feed and that these materials were often contaminated with fungi before use.

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