Special Veterinary Pathology

SPIROCERCOSIS 

Definition

• The bright red coloured Spirocerca lupi adult worms are found in nodules in the wall of the oesophagus and aorta of dog, fox, wolf and cat

Pathogenesis

• Embryonated eggs passed in the faeces are ingested by intermediate host, coprophagus beetles in which the larvae develop.
• If the beetle is eaten by a transport host such as frog, snake, lizzard or birds they remain in them
• When the infected beetle or transport host is eaten by the final host, the larvae penetrate the stomach and through blood reach the wall of the aorta where they localize in the upper thoracic portion
• After a period of development, they move to the adjacent oesophagus and develop in cystic nodules.
• Through a small pore in the nodule, the eggs are released into oesophagus

Clinical signs

• Oesophagel obstruction may cause persistent vomition
• Sudden death due to rupture of aortic wall

Gross and microscopic lesions

• Principal lesions are produced by the adult worms localized in the aorta and oesophagus
• Nodules on the aortic wall initiates the formation of aneurysm which may rupture ending in fatal haemorrhges
• The intimal surface of the aorta may be roughened
• Nodules on the thoracic portion, oesophagus near the cardiac region of stomach may contain one or several worms.
• A granuloma with central worm surrounded by connective tissue and infiltration of neutrophils, macrophages, lymphocytes, plasma cells may be observed

Sprocercosis-Dog- Worm with eggs

• Eosinophils are usually absent.
• Exostoses of thoracic vertebrae may be due to the aberrant location of the larvae
• “Fibrosarcoma" and “osteosarcoma" near the spirocercal lesion is reported to be their metastasis.

Diagnosis

• Small gelatin capsule shaped eggs with the coiled larva inside
• Post mortem demonstration of lesions in the aorta and oesophagus