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EQUINE VETERINARY EDUCATION / AE / APRIL 2018


previous antibiotic therapy. Post-mortem examination of hepatic tissue also identified acid-fast bacteria within multiple focal microgranulomas and macrophages. Germinal epithelium compatible with Echinococcus cysts was also seen.


Post-mortem histopathology of lung tissue revealed


severe, necrotising, granulomatous pneumonia. Moderate numbers of acid-fast bacilli were seen throughout the parenchymal tissue. In the alveolar tissue, parasitic protoscolices were seen as a result of cyst rupturing during post-mortem examination or processing. Splenic tissue also contained acid-fast bacilli (Fig 5) evident within granulomatous, mineralising lesions with central necrotic zones.


Fig 3: Post-mortem examination of a 4 cm echinococcus cyst within hepatic parenchyma as seen on ultrasound in Figure 1.


Microbiology and additional testing Paraffin embedded fixed 10 lg sections of spleen were submitted to Leeds Teaching Hospital for mycobacterial polymerase chain reaction (PCR; EliTech MTB Q-PCR Alert kit) and were positive for Mycobacterium tuberculosis complex DNA. Further specification PCR analysis was performed using the GenoType MTBC assay (Hain Lifescience), which identified M. bovis.


Discussion a)


Clinical discussion The predominant clinical signs in this case included chronic weight loss and intermittent fever with more recent changes in mentation attributed to HE. Bile acid and ammonia concentrations were not measured in this case. A diagnosis of HE was made on the basis of extreme elevations in hepatobiliary enzymes in conjunction with clinical signs of weight loss, obtunded demeanour, anorexia, hypersalivation and ataxia. These nonspecific signs are frequently reported in cases of severe hepatic impairment (West 1996; Nout 2011). An objective diagnosis of HE can be established by demonstrating hyperammonaemia, elevated serum bile acids, c-glutamyl transferase, aspartate transaminase and sorbitol dehydrogenase enzymes (Mair 1997); however, other


b)


Fig 4: a) Post-mortem examination of the spleen revealing multiple, caseous Mycobacterium bovis granulomas <4cm diameter. b) Splenic granulomas seen in cross section.


© 2017 EVJ Ltd


Fig 5: Ziehl–Neelsen staining of splenic tissue sampled post- mortem revealing multiple positively staining mycobacteria. A similar staining of mycobacteria was seen on the ante-mortem liver biopsy samples submitted.


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