Pathology of spleen and liver in turkeys inoculated with Escherichia coli.

Lesions of spleen and liver were studied by light and electron microscopy in 3-week-old turkeys inoculated intravenously with Escherichia coli. Spleen and liver of turkeys given avirulent E. coli were hyperaemic and had increased numbers of heterophils. Aggregates of heterophils were in the splenic red pulp and hepatic sinusoids. Turkeys given virulent strains of E. coli had intense heterophil infiltration in spleen and slightly increased numbers of heterophils in liver. In these spleens, reticular sheaths . (ellipsoids) contained large aggregates of heterophils, fibrin, and thrombocytes 2 to 8 hours postinoculation. Turkeys given virulent E. coli and killed in extremis had hypaeremic red pulp and fibrinopurulent exudates and haemorrhage in splenic white pulp. Livers of birds killed in extremis were turgid, friable and engorged with dark blood. Centrolobular hepatocytes were individualised and vacuolated. The dilated sinusoids contained fibrin, erythrocytes, heterophils and bacterial colonies. Phagosomes of hepatic macrophages contained up to 10 structurally normal bacilli, whereas heterophils contained bacilli with altered cell walls. Thrombi, composed of thrombocyte aggregates and fibrin, were common in small hepatic veins. These studies indicate that early bacteraemia with virulent E. coli leads to intense fibrinopurulent splenitis. Progressive bacteraemia is associated with pooling of blood in viscera, intravascular coagulation, and venous thrombosis and bacterial colonisation in liver.