Special Veterinary Pathology

ANAPLASMOSIS

Synonym: Gall sickness

Definition

• Anaplasmosis is an acute or chronic rickettsial disease especially of adult cattle characterized by anaemia, extreme weakness, high fever and icterus without haemoglobinuria caused by Anaplasma marginale or A. centrale

Transmission

• The disease is transmitted by ticks, biting flies or mosquitoes

Pathogenesis

• They invade erythrocytes as initial bodies and develop inside and infect other red blood corpuscles
• It does not cause haemolysis but the infected erythrocytes are phagocytosed by the reticulo endothelial cells in the spleen
• Hence, no haemoglobinuria is not seen

Clinical signs

• Young animals are quite resistant
• In adult, rise in temperature, depression, fall in production, anaemia, icterus and dehydration

Haematology

• Fall in total erythrocyte count with anisocytosis, poikilocytosis and punctate basophilia may be observed
• Haemoglobin content and packed cell volumne are also reduced

Gross lesions

• Severe anaemia with pale mucous membrane and icterus
• Spleen is greatly enlarged and reddish in colour
• Liver is also enlarged with rounded edges and the gall bladder is distended wih granular bile
• Petechiae of epicardium and catarrhal gastroenteritis are evident

Microscopical lesions

• Hyperplasia of bone marrow and extramedullary haematopoiesis in spleen and liver is observed

Diagnosis

• A.marginale is a coccoid form seen at the periphery of erythrocytes and is a virulent form while A.centrale is usually seen towards the centre of the cell and causes a milder disease

A.marginale -Coccoid form in the periphery of erythrocyte

• Complement fixation test and fluorescent antibody technique (FAT) may be employed