Page 719 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

694 CHAPTER 3

VetBooks.ir Management solution through the chest tube and then allowing
free flow drainage by gravity. Alternatively, fluids
Broad-spectrum antimicrobial therapy is required.
Antimicrobials commonly used are penicillin com-
sally in the thorax and allowed to drain through
bined with an aminoglycoside, ceftiofur or trim- can be infused through a separate tube placed dor-
ethoprim–sulphamethoxazole. Metronidazole is the ventral chest drain. Additional therapy should
commonly used to provide added efficacy against include NSAIDs (following restoration of hydra-
anaerobes. Bacterial culture and antimicrobial sen- tion) to control pain and inflammation. More severe
sitivity testing should be carried out to verify drug pain may be managed by butorphanol, morphine or
selection. In many cases, prolonged antimicro- fentanyl. Common complications include laminitis
bial treatment is required, necessitating transition and thrombophlebitis for horses with indwelling i/v
to an oral antimicrobial after the initial period of catheters.
treatment. In chronic cases, thoracostomy with or without
If pleural fluid is present, pleural drainage is rib resection, may be performed to facilitate large
also indicated to facilitate optimal response to sys- volume lavage and increased drainage of purulent
temic antimicrobial therapy and to alleviate clini- material. However, care must be taken to ensure that
cal signs associated with pleural fluid accumulation. the lung has adhered to the body wall, or that the
Drainage can be performed using a cannula, large normal fenestrations of the mediastinum are closed,
bore intravenous catheter or indwelling chest tube, so that bilateral pneumothorax does not occur during
depending on the character and volume of the pleu- the procedure. Prolonged rest and good nutritional
ral fluid. Thoracocentesis may be a single event, or support are essential to a satisfactory recovery.
chest tubes with a one-way valve to permit ongo-
ing drainage may be left in place. Intravenous fluid Prognosis
therapy is also indicated if large volumes of pleural Survival and return to previous athletic function
fluid are to be removed or if signs of endotoxaemia are largely dictated by the severity and duration of
or dehydration are evident. For horses with very cel- the disease. Prognosis for survival is usually good
lular or flocculant pleural fluid, pleural lavage can if early diagnosis and aggressive treatment are
be achieved by infusing a sterile physiological fluid provided. In contrast, horses with fibrinous locula-
tion and abscess formation, or those with extensive
pulmonary necrosis evident on ultrasonography,
3.153 typically have a poorer prognosis for long-term
survival (Fig. 3.153).

PNEUMOCYSTIS JIROVECI
(FORMERLY P. CARINII)

This unicellular eukaryote (currently classified as a
fungus) is a respiratory tract commensal that causes
interstitial pneumonia in immunocompromised
foals (such as foals with severe combined immuno-
deficiency) or foals with other causes of pneumonia,
especially R. equi, between 6 and 12 weeks of age.
It rarely causes pneumonia in older foals or adult
horses, and affected individuals are immunocom-
promised. Infection is difficult to diagnose because
Fig. 3.153 Appearance of the chest wall of a horse the organism cannot be cultured. P. jiroveci cysts
with pleuropneumonia as seen at necropsy. A thick can be identified within macrophages from bron-
layer of fibrin (‘fibrin peel’) is present covering the choalveolar lavage (BAL) samples. Special stains
parietal pleura. such as calcofluor white stain and Grocott–Gomori