Page 713 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

688 CHAPTER 3

VetBooks.ir are most commonly discrete or diffuse, but ‘mili- other than a stiff gait. In contrast, osteomyelitis
is extremely painful and causes severe lameness.
ary’ abscesses can occur. In the abdomen, abscesses
develop mainly in the wall of the jejunum, caecum
may progress to cause neurological signs.
and colon, and in mesenteric lymph nodes, but they Affected bones may fracture. Vertebral abscesses
may occur in any of the abdominal viscera. In the
skeleton, R. equi causes osteomyelitis in long bones Differential diagnosis
and vertebrae. Other causes of juvenile pneumonia should be
considered, including acute interstitial pneumonia,
Clinical presentation bacterial bronchopneumonia (Streptococcus zooepi-
Clinical signs occur in foals between 1 and 6 demicus, S. pneumoniae, Actinobacillus spp., Pasteurella
months old. Disease in younger and older foals or spp., Klebsiella spp. and Bordetella bronchiseptica), para-
adults is rare. Clinical signs are usually insidious sitic bronchopneumonia and Pneumocystis jiroveci
in onset and slowly progressive, although some (formerly P. carinii) infection in immunosuppressed
foals present with acute-onset severe pulmonary individuals.
disease. Microbiological surveys of foals sug-
gest exposure occurs within the first 2 weeks of Diagnosis
life, with clinical signs appearing several weeks R. equi is the most significant cause of pneumonia
later. Clinical signs include pyrexia, depres- in foals between 1 and 6 months old. Affected foals
sion, anorexia, coughing and variable nasal dis- develop leucocytosis characterised by neutrophilia and
charge. Depending on the extent of pulmonary an increase in plasma fibrinogen. Ultrasonography
disease, there may be wheezing and crackling and radiography allow for detection of pulmonary
on auscultation. Pulmonary consolidation may abscesses (Fig. 3.144). Diagnosis cannot be made
be detectable by auscultation and percussion if based on imaging alone, as another common cause
extensive. Extrapulmonary signs are present in up of bacterial pneumonia in foals (Streptococcus zooepi-
to two-thirds of necropsied animals. Abdominal demicus) can cause similar clinical signs and lung
abscesses cause pyrexia, depression, diarrhoea, abscesses. Definitive diagnosis is achieved by dem-
colic and weight loss. Synovitis, seen commonly onstration of septic airway inflammation on cytol-
in the tarsocrural and stifle joints, may present ogy (Fig. 3.145) and R. equi on bacterial culture of
as marked joint effusion, with minimal lameness tracheal aspirate samples. Polymerase chain reaction

3.144 3.145

Fig. 3.144 Thoracic radiograph of a foal with R. equi Fig. 3.145 Cytology of tracheal aspirate fluid
infection. Multifocal abscesses (arrows) are visible from a foal with R. equi infection. Variably preserved
as opacities within the lung field. (Photo courtesy neutrophils are the predominant cell type. Intracellular
John Prescott) rod-shaped bacteria are visible (arrows). (Photo courtesy
Dorothee Bienzle)