Recognition of Pneumocystis carinii in foals with respiratory distress

Five 3-month-old foals presenting with fever and respiratory disease were found to have pulmonary abscesses with patchy to diffuse alveolar and interstitial pneumonia on post-mortem examination. All affected foals had evidence of Rhodococcus equi infection and had few to abundant Pneumocystis carinii cysts in the sections of affected lung. Of the 5 foals examined radiographically, 3 had a distinct reticulonodular (miliary) pattern which may aid in the ante-mortem diagnosis of P. carinii pneumonia (PCP). Leukocyte counts of foals with PCP were significantly greater than in the control group of foals with uncomplicated bacterial pneumonia. Foals with PCP tended to be more tachypnoeic than the control foals and 4 of the 5 PCP+ foals appeared dyspnoeic before death. The ante-mortem recognition of PCP may be expedited by bronchoalveolar lavage and successful treatment of foals with PCP may require the administration of adequate levels of potentiated sulphonamides.