Page 1387 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

1362 CHAPTER 14

VetBooks.ir complication in septic foals or it may develop as Minimal radiographic signs are evident initially,
with typical septic synovial fluid identified on
a result of bacteria seeding from a focal infection
(e.g. the umbilical remnants) or from the digestive
arthrocentesis.
and respiratory systems. The increased blood flow • E type: There is infection in one or more
to rapidly growing bones, the presence of trans- joints and the adjacent epiphysis in slightly
physeal vessels for the first few weeks, and the older foals (3–4 weeks), with acute-onset severe
slow flow and low oxygen tensions in the terminal lameness. The stifle and tarsocrural joints are
metaphyseal and synovial vessels, allow dissemina- most commonly affected, with joint distension,
tion of pathogenic bacteria in the joint itself, or the considerable periarticular swelling and deep
nearby bony epiphysis/physis, during transient or bone pain. Bone changes are often evident on
persistent bacteraemia. Spread of bacteria can also appropriate radiographic views. These cases
occur into a joint from adjacent infective foci in carry a more guarded prognosis.
the epiphysis/physis or soft tissue, and vice versa. • P type: Infection occurs in the physis and
Traumatic wounds involving synovial structures or metaphysis, usually at a single site (Fig. 14.27).
iatrogenic infections after joint injections are less The adjacent joint may become infected by local
common causes of joint sepsis in foals. Multiple or vascular spread, or there may be sympathetic
joints and/or the physes/epiphyses may be involved. inflammation in the joint (non-septic effusion).
The most commonly isolated bacteria are similar This is less common than the S type and can
to those recorded in septicaemic foals (i.e. E. coli, occur from 1 to 12 weeks of age. There may be
Actinobacillus equuli, Salmonella spp., Klebsiella spp., swelling and pain on palpation over the physis,
Streptococcus spp. and Staphylococcus spp.). In older with or without joint distension. Radiographic
foals, Rhodococcus equi may also lead to bone infec- changes occur quite quickly, but repeated series
tion in the epiphysis and physis and/or, in some may be necessary to identify some cases. In some
foals, to an immune-mediated non-septic synovitis. foals there is a prior history of systemic illness
Foals that have FTPI, prematurity/dysmaturity or such as diarrhoea or pneumonia. The distal
adverse peripartum events are at the highest risk for physes of the long bones appear most vulnerable
development of septic arthritis/osteomyelitis. Once to this type.
infection is localised and established in the joint or • I type: Infection enters the joint from infected
bone, there is a marked exudative septic inflamma- periarticular soft tissues, such as a periarticular
tion leading to rapid ischaemic necrosis of affected abscess. It appears to affect the upper limb joints
tissues. This leads to rapid bone and/or cartilage (i.e. the coxofemoral and femorotibial joints).
degeneration with soft-tissue fibrosis and, in the Early detection of the soft-tissue infection will
bone, abscess formation. help prevent this serious complication.
• T type: This is a rare form involving infection
Clinical presentation of the small cuboidal bones of the tarsus and
There are five different types of disease presentation, carpus. Collapse of these bones allows the
classified according to the anatomical site affected, infection to spread to the joint or joints. It is
the aetiology of the initial infection, the subsequent a separate condition from the more common
clinical signs, radiographic changes and necropsy aseptic collapse of the cuboidal bones seen in
findings. Clinical differentiation in some cases may premature and dysmature foals (see p. 1341).
be difficult. There is joint swelling, moderate to severe
lameness and radiographic changes.
• S type: There is a septic synovitis without
bone involvement. The foal is less than The clinical signs will vary depending on the type
14 days old, with one or more swollen/painful of sepsis that is involved, but signs usually include
joints, and acute-onset severe lameness acute, moderate to severe lameness, which rapidly
(Fig. 14.26). There may be systemic illness. worsens, and some degree of joint effusion and/or