Melioidosis in a koala

Abstract

A 4-year-old female koala (Phascolarctos cinereus ) was seen on the ground about 40 hours after capture and release for routine survey purposes. It died shortly afterwards.
A 5-month-old infant koala in its pouch was alive but died 36 hours later despite regular feeding with a milk supplement. PM examination of the adult revealed congestion and haemorrhage in lymph nodes, lungs, myocardium, kidneys and adrenal glands as well as ecchymotic haemorrhages on most serosal surfaces.
Histological changes included necrotic foci in liver and spleen. A brown pigment which is a feature of normal koala liver was present in hepatocytes generally. Distinctive eosinophilic intranuclear hepatocyte inclusions were present which were unrelated to necrotic foci. Occasional bacterial colonies were associated with the necrotic foci. Gram negative bacteria were seen in liver, spleen and lung sections. Escherichia coli and Pseudomonas pseudomallei were isolated from liver and kidney samples. Enterobacter cloacae was isolated from the liver and P. putida and Streptococcus sp. from the lung. The adult koala was serologically negative for melioidosis using the complement fixation test but 8 (16%) of 50 free-living koalas in the same colony were positive, although apparently healthy.
Histological examination of the infant koala liver revealed small foci of necrosis; no bacteria were visible and no bacteria were cultured.