Septic Arthritis in the Foal

Incidence and risk factors Septic arthritis is a common consequence of bacteremia and septicemia in foals. In one study, septicemia was the most common cause of death (30%) in foals under 7 days of age. In the same study, septic arthritis was identified as the cause of death in 12.5% of foals aged 8 to 31 days.1 Establishment of infection depends on several factors including host defense, virulence of the organisms, and local joint factors. In foals, host defense is mainly associated with passively acquired immunity.2 Failure of passive transfer is the highest risk factor for development of septicemia in foals. The incidence of disease resulting from FPT has been reported to be as high as 78%.3 Organisms virulence is related to the ability to establish infection. Attachment factors, ability to resist phagocytosis, or resistance to cell killing all contribute to establishment of infection. Local joint factors that may predispose to establishment or maintenance of infection include low blood flow, particularly in end-loop capillaries, or poor blood supply, which is more a factor in bone. Although not commonly used in foals, certain intra-articular medication such as corticosteroids, hyaluronan, and polysulfated glycosaminoglycans have been associated with a higher risk for septic arthritis potentially by decreasing articular defense.