Pied Currawong (Strepera versicolour) with ‘Black and White Bird Disease’

Registry Case Number TARZ-9586.1

HISTORY

This male nestling (weight 217g) bird was found on the ground in the middle of a street in Mosman, NSW. Parents around, but rescuer concerned this bird would end up on the road again.  The bird was euthanased.

GROSS PATHOLOGY

External examination:  No lesions are visible.

Hydration: good; Muscle mass: good; Fat deposits: absent

Internal examination:  The pericardial sac is filled with clear straw-coloured fluid.  There are multiple small foci of epicardial haemorrhage.  There is a semicircular region of pallor and friability along the cranial 1cm of each liver lobe.  The ventriculus is filled with ingesta (insects).

HISTOLOGY

The tissues are very well preserved.

Lesions are not evident within the following tissues: oesophagus, trachea, kidney (B),eyes – fragmented (C), oesophagus, trachea (D).

The following observations are notable:

Throughout each tissue, blood vessels contain moderate numbers of leucocytes with eccentric, semilunar nuclei and the cytoplasm is largely displaced by large oval basophilic organisms that have a very small nucleus.

Heart (A):  There is multifocally extensive acute myocardial degneneration to necrosis along with numerous foci of myocardial and epicardial haemorrhage.  The foci of necrosis are characterised by pale, eosinophilc myocytes that lack striations and any nuclear detail.  Heterophils are scattered through some of these foci.  In other foci the myocytes have pale or hypereosinophilic granular cytoplasm.  There are mild multifocal perivascular clusters of mononuclear cells within the myocardium and epicardium near the greater vessels.  A small number of coronary vessels have slightly thickened eosinophilic walls.

Skeletal muscle (A, B):  There are multifocal clusters of mononuclear cells around blood vessels and scattered within the muscle bundles. In some foci the infiltrates appear to replace small portions of the muscle.

Proventriculus and ventriculus (A):  There are moderate multifocal mononuclear cell infiltrates within the lamina propria.  A cross section of a nematode parasite is present within and overlying the proventricular mucosa.  Multifocally there are perivascular aggregates of mononuclear cells.  Some of the blood vessels within these aggregates have plump endothelium.

Testis (B):  Spermatogenesis is not evident within the spermatic cords and there are sparse Leydig cells.

Liver (B):  There is a focus of subcapsular coagulation necrosis of the hepatic parenchyma.

Spleen (B):  The tissue contains some perivascular lymphoid cell cuffs but no discrete follicles.  There is a thick layer of reticuloendothelial cells surrounding penicillar arterioles.

Bursa of Fabricius (B):  The bursa is very well populated with lymphocytes.  Moderate numbers of tingible body macrophages are evident within the follicles, and there are also scattered cells with pyknotic and karyorrhectic nuclei.

Thymus (B):  The tissue is well populated with lymphocytes, but moderately affected by euthanasia artefact.

Small intestine (C):  The serosa between two loops of intestine is focally proliferative and contains small and large mononuclear cells with variable quantities of cytoplasm.  Blood vessels in this focus have markedly plump and vesicular nuclei.  A small quantity of protein coats the serosal surface above this focus.

Duodenum (D):  The serosa contains multifocal scattered and perivascular cuffs of small lymphocytes.  The intestinal lamina propria contains scattered mononuclear cell clusters.

Pancreas (D):  A focal mononuclear cell aggregate is present within the pancreatic parenchyma near the hilus.

Brain – sagittal section (D):  There are moderate, multifocal meningeal and perivascular infiltrates of mononuclear cells.  In some areas the perivascular mononuclear cell cuffs are 3-4 cells thick and contain lymphocytes and macrophages with brown, granular cytoplasmic pigment.  Affected blood vessels often have plump endothelium.

Lung (D):  The tissue is congested and consolidated.  Red cells are evident within parabronchi, but this may represent post mortem artefact.

DIAGNOSIS

Euthanasia

Hydropericardium

Meningoencephalitis – multifocal, moderate, non-suppurative

Myocardial necrosis – acute, extensive

Epicardial and myocardial haemorrhage – extensive

Myocarditis – multifocal, non-suppurative

Myositis – multifocal, non-suppurative

Coelomitis – multifocal, non-suppurative

Hepatic necrosis – acute, focal

Splenomegaly

Pulmonary congestion and consolidation

Thin

Proventricular nematodiasis

Leucocytozoonosis

COMMENT

This bird had interesting lesions of fluid around its heart and haemorrhage around and in the heart muscle.  Thus tissues were collected for histology.  The collection of lesions in this bird, such as haemorrhage and necrosis in the heart, nonsuppurative inflammation in the heart, brain, skeletal muscle and coelomic membranes is consistent with a syndrome that we have previously seen in magpies and currawongs in 2003 and 2006 – Black and White Bird Disease.  This syndrome is thought to have a viral aetology, but no virus has grown in culture from swabs and tissue samples of affected birds.