Pathology of goats and sheep experimentally infected with Mycoplasma mycoides var. capri

Twenty goats and four sheep were experimentally infected with Mycoplasma mycoides var. capri and examined histopathologically. Death occurred or a moribund state developed in most of them within a week after parenteral inoculation with mycoplasmas. Histopathological examination revealed severe serofibrinous inflammation on the serosa and interstitial connective tissue at the site of inoculation. Marked inflammatory edema with infiltrating polymorphs was found in the early stage of infection. As the infection progressed, the lesion became a cellulitis; necrosis, sometimes with focal liquefaction, was a constant feature. Organization with infiltration by lymphocytes and histiocytes had begun in some tissues. Acutely infected organs had evidence of systemic involvement. Lesions included splenitis, lymphadenitis, meningitis, metastatic foci in the intestine and urinary bladder, and parenchymatous degeneration in the liver, heart, and kidneys. Mycoplasmas were isolated from many tissues of critically ill animals. Other goats which had received mycoplasmas by instillation escaped severe illness. Even so, mycoplasmas were isolated from one or two of their tissues at necropsy. The great variation in clinical and pathological response was apparently dependent upon the route of inoculation. Recovery of mycoplasmas from two contact control goats which remained healthy is suggestive of the clinically undectable carrier state. As other workers have reported, the clinical and pathological changes in sheep were similar to those in parenterally inoculated goats.