Central nervous disease and blindness in Nankeen kestrels (Falco cenchroides) due to a novel Leucocytozoon-like infection

Abstract

The histopathological and electronmicroscopic features of a novel parasitic infection causing seasonal epizootics of central nervous disease in Nankeen kestrels (Falco cenchroides) from Western Australia is described. Thorough necropsy, haematological and transmission electronmicroscopical examinations were performed on thirteen affected kestrels between 1996 and 1999. All had an extensive vasculocentric granulomatous meningoencephalomyelitis, pectenitis and proliferative arteritis with endothelial parasitic cysts measuring 40 to 60 μm in diameter. Arterioles in the brain, optic papillae, pecten and kidney were most consistently affected. In some birds there was severe haemorrhage from the pecten. Less commonly, parasitic cysts were seen in the arterioles of the lung, liver, heart and intestines. Endothelial schizonts contained many spherical merozoites measuring 1 μm in diameter that were also present free within the lumen of affected arterioles. Haematological examination in three of seven affected kestrels tested demonstrated rare, basophilic intracytoplasmic inclusions in leucocytes with distorted nuclei consistent with Leucocytozoon-like gametocytes. Day-old chickens inoculated with brain homogenate failed to develop similar lesions.