Evaluation for immune system failures in horses and ponies.

Between January 1973 and September 1979, 2,092 horses and ponies were evaluated for immunologic disorders. A total of 418 abnormalities were detected in 416 (20%) of the animals tested. Disorders encountered were failure or partial failure of colostral immunoglobulin transfer from mare to foal (228 cases), combined immunodeficiency (159 cases), selective immunoglobulin M deficiency (19 cases), agammaglobulinemia (3 cases), transient hypogammaglobulinemia (2 cases), and lymphosarcoma (7 cases). Four conclusions were drawn from the study. (1) Immunologic abnormalities occur commonly in horses and ponies. (2) Failure and partial failure of passive transfer were the most common disorders, involving 19.7% of surveyed foals at risk. (3) Combined immunodeficiency remains a disease limited to Arabian horses. (4) Considering the high frequency of immunologic disorders in horses and the availability of diagnostic tests for the disorders, older animals with recurrent infections as well as all newborn foals should be evaluated for immune disorders.