Maintenance of foals with combined immunodeficiency: causes and control of secondary infections.

Sixty-six cases of combined immunodeficiency (CID) in foals were studied to determine the most prevalent causes of infection and death. Lesions of the respiratory system were observed in 59 of the foals and were attributable to infection with equine adenovirus. Pneumocystis carinii, and bacteria. Significant lesions were also observed in liver, pancreas, intestines, heart, and kidneys. Maintenance of foals with CID for experimental purposes is directed at the prevention and control of these secondary infections. Adenovirus can be controlled by administration of horse plasma containing high titers of antiadenovirus antibody. Bacteria are controlled by appropriate antibiotic therapy. Pneumocystis carinii infection remains a significant problem in the maintenance of foals with CID.