Synovial sepsis in neonatal foals

Synovial sepsis is associated with substantial morbidity and mortality (Martens et al, 1986); it is defined as infection of the synovial joint by pathogens and can occur with or without multisystem disease. In neonatal foals, synovial sepsis is frequently associated with haematogenous spread of infection. Once infection is established in a synovial joint the resulting inflammatory response can result in deleterious effects on the articular cartilage and joint. Rapid diagnosis and initiation of suitable antimicrobial treatment is vital for a positive outcome. The mainstays of treatment are broad spectrum systemic antimicrobial therapy and lavage of the infected joint. In neonatal foals, treatment is further complicated by physiological differences and comorbidities that affect the distribution and elimination of drugs.

Septic arthritis can occur as the result of a periarticular infection, inoculation of the joint by a puncture wound, iatrogenic causes or by haematogenous spread (Hardy, 2006). In foals, haematogenous dissemination of bacteria is the most common route of transmission. The presence of bacteraemia and septicaemia is an important risk factor, with septic arthritis reported to occur in 14–38% of neonatal foals with sepsis (Gayle et al, 1998; Corley at al, 2007). Another factor that plays an important role in the development of joint infection is the foal's immune defence, which relies upon passively acquired immunity. Failure of transfer of passive immunity is the highest risk factor for the development of bacteraemia in foals, and therefore plays an important role in the development of septic arthritis (Robinson, 1993).