Tropism of Mycoplasma gallisepticum for Arterial Walls ( encephalopathy / turkey / tylosin / pleuromutilin / brain )

The fatal encephalopathy associated with M. gallisepticum strain S6 in turkey poults was completely curable by treatment with tylosin or pleuromutilin. The lesions of cerebral polyarteritis disappeared after therapy. Polyarthritis developed in some birds after recovery from encephalitis. Immunofluorescent studies revealed that intravenously injected organisms became localized as microcolonies within the walls of cerebral and periarticular arteries, and in the glomeruli. Turkey IgG deposition was demonstrated on the glomerular basement membranes, but not in the arterial lesions. The results suggest that the pathologic changes caused by this microorganism are due to selective localization and growth in arteries. Infection of turkeys by the S-6 strain of Mycoplasma gallisepticum is associated with extensive and remarkably selective lesions of polyarteritis nodosa, affecting almost exclusively the arteries of the brain (1, 2). Except for the relative paucity of polymorphonuclear leukocytes, the lesions are morphologically similar to the necrotizing arteritis associated with experimental serum sickness. Living Mycoplasma is required for the production of arteritis; organisms disrupted by freeze-thawing or killed by heat are ineffective. Prior treatment with tetracycline provides complete protection against the disease (2). A neurotoxic factor, specific for turkey, has been demonstrated in concentrated suspensions of live Mycoplasma; antibiotic treatment also protects against this