Abstract:
A proportion of Babesia rossi infections in dogs are classified as complicated and one of the most lethal complications is acute
lung injury (ALI) and acute respiratory distress syndrome (ARDS). Most dogs that die succumb within 24 hours of presentation.
The pulmonary pathology caused by B. rossi in dogs has not been described. The aim of this study was to provide a thorough
macroscopic, histological and immunohistochemical description of the lung changes seen in dogs naturally infected with B.
rossi that succumbed to the infection. Death was invariably accompanied by alveolar oedema. Histopathology showed acute
interstitial pneumonia characterised by alveolar oedema and haemorrhages, with increased numbers of mononuclear leucocytes
in alveolar walls and lumens. Intra-alveolar polymerised fibrin aggregates were observed in just over half the infected cases.
Immunohistochemistry showed increased numbers of MAC387- and CD204-reactive monocyte-macrophages in alveolar walls and
lumens, and increased CD3-reactive T-lymphocytes in alveolar walls, compared with controls. These histological features overlap to
some extent (but far from perfectly) with the histological pattern of lung injury referred to as the exudative stage of diffuse alveolar
damage (DAD) as is quite commonly reported in ALI/ARDS.
