Group #1  Large Animal Osteomyelitis, adult with hematogenous spread

History:  With adult animals, hematogenous spread is not as likely than as in foals; 
however if it does occur, it is likely to be a systemic infection that arises from a focal 
point such as the respiratory tract, UTI, or other local infection which progresses to a 
systemic infection. Reasons for this include an immunosupressed animal, or an 
overwhelming infection. Exogenous infection can also develop into a hematogenous 
infection with time. 

Physical Findings: Lameness and swelling with one or multiple tissues (bones, joints) 
infected; possible walled off abscesses which allow a constant supply of bacteria into the 
vascular system. Anemia of chronic disease may be present, as the animal sequesters iron 
to prevent bacteria growth in the body. A purulent exudate may be present in infected 
joints. Arthrocentesis of the affected joint(s) may yield a positive culture for bacteria, 
increased cellularity, increased protein. The infections will not be focused in the area of 
the growth plates as in foals, because in adult animals the growth plates have already 
closed. 

Specialty exam findings:  Radiographs may yield evidence of bone destruction and new 
bone formation, soft tissue swelling, with possible sequestrum formation. A positive 
culture may be obtained from bone biopsy, or joint fluid analysis. Blood test values have 
been discussed above. Positive blood culture may also be diagnostic with a 
hematogenous spread. 

Management Plan: Very similar to case #3, including a culture and sensitivity of the 
bacteria. The animal should be placed on a broad spectrum antibiotic until the sensitivity 
results are obtained, and then adapt the systemic antibiotic treatment accordingly. After 6 
weeks, re-culture and re-radiograph. May need to drain / lavage individual joints, or even 
administer intra-articular antibiotics (gentamicin) to aid response in severely affected 
joints. In severe cases, arthrotomy may be required. Since this is an adult animal, you do 
not have to worry about regional perfusion of growth plates.

Prognosis: Fair to good with treatment and no dead bone fragments; with chronic 
infection the prognosis is guarded until the dead bone is removed, then fair.