[The pathology and pathogenesis of experimental Mycoplasma hyorhinis infection of piglets with and without thermomotoric stress. 1. Pathologico-anatomic, histologic and immunomorphologic study results].

The effect of an experimental Mycoplasma (M.) hyorhinis infection (3 times intranasal instillation of 3-5 ml bouillon with 10(7) Colony forming units [CFU]/ml) in combination with a standard thermomotoric stress (swim-test) was studied in piglets using pathomorphological, immunomorphological and microbiological methods. The 92 piglets were divided into the following 5 groups: swimmers with infection (S-I; n = 19); swimmers without infection (S; n = 19); control piglets with infection (K-I; n = 21); controls without infection, but direct (K1; n = 16) or indirect contact (K2; n = 17) with experimentally infected animals. The experimental or spontaneous infection (direct or aerogenous infection) with M. hyorhinis caused in 30.4% of the piglets an acute or subacute, catarrhal-purulent bronchopneumonia with an interstitial component. Incidence and intensity of pneumonia were significantly higher in the groups with thermomotoric stress (independent from the mode of infection) than in the non-stressed groups. The M. hyorhinis pneumonia was characterized by a limited expansion and a trend to restitution. The causal agent (M. hyorhinis) was demonstrated with immunomorphological methods (immunofluorescence and PAP) in the ciliary zone of the nasal, tracheal and especially on the bronchial mucosa, and occasionally in the bronchioles and alveoli.