Sequential Pathology of Genital Tract in Chickens Experimentally Infected with Mycoplasma gallisepticum

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Abstract
Unsexed day old White Leghorn chicks hatched from eggs pretreated with erythromycin were infected via the yolk sac with a 48 h broth cluture of pathogenic M. gallisepticum (S6). Of the 57 experimental female birds 14 had gross lesions in the oviduct, characterized by the presence of grayish-white caseous plugs of various sizes in a segment or throughout the length of the oviduct. Of the infected female birds 46 had microscopic lesions, detected primarily as mild heterophilic infiltration, lymphocytic aggregates, lymphoid follicles, diffuse lymphocytic infiltration, pleocellular response or a combination of any of these depending on the stage and extent of infection. The caseous plugs were formed by tissue debris, fibrin, necrotic heterophils and sometimes a few lymphocytes and macrophages. Changes that accompanied the necrotic exudate were atrophy of the mucosa, hypertrophy of the oviduct wall or sometimes necrosis of the folds of mucosa. No significant gross and microscopic lesions were detected in ovaries, although 3 of the 33 infected male chickens had histological lesions in the testes. Gross and microscopic changes of mycoplasmosis were also found in the respiratory tract. M. gallisepticum could be consistently reisolated from oviduct(s) up to 5 weeks PI [post-innoculation]; thereafter, isolations were intermittent. From the ovaries or testes the organism could be isolated consistently up to 1 wk PI only. Agglutinins were detected in the sera of infected chickens as early as 1 week PI, when the mean titer was 1:5; it reached a maximum of 1:128 at 6 wk PI. Thereafter the titer gradually declined, but the demonstrable agglutinins were present until 25 wk PI.