A case of interstitial pneumonia associated with Pneumocystis carinii in afoal

Subacute interstitial pneumonia with diffuse alveolar damage, marked macrop hage infiltration, and intracellular Pneumocystis carinii cysts is describe d in a 3-month-old Swiss warmblood foal. Clinically, the disease was charac terized by sudden onset of respiratory distress with fatal outcome. Based o n serum immunoglobulin G (IgG), IgA, and IgM values, no humoral immunosuppr ession was detected. Spleen, thymus, and bronchial lymph nodes did not reve al lymphoid depletion, as assessed by immunohistochemical staining of CD-3- positive cells. Immunopathogenesis of pulmonary infections with intracellul ar agents in foals is discussed.