The anatomical location of neural structures most optimally sampled for pseudorabies (Aujeszky's disease) in sheep.

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Since its description by Aladar Aujeszky in 1902, pseudorabies (Aujeszky’s disease) has become recognized as a worldwide disease in which pigs, the natural host, are a source of infection for ruminants. Virus and characteristic microscopic lesions in sheep have been localized to specific neurologic structures. A nonsuppurative encephalitis and a necrotizing encephalitis have been reported from spontaneous pseudorabies outbreaks in sheep flocks; lesions were in the cerebral cortex, cerebellum, and brain stem. In experimental infections, histologic lesions and virus were localized in neural structures associated with the route of inoculation. Nonsuppurative ganglionitis and encephalitis were in the trigeminal ganglia and medulla oblongata of experimental sheep inoculated by the conjunctival, oral, and intranasal routes. A virus-induced neuronal necrosis was found in the cervicothoracic ganglia of sheep in natural and experimental pseudorabies virus (PrV) infections. Sheep inoculated intratracheally with aerosolized PrV had histologic lesions, viral antigen, and virus in the medulla oblongata and in trigeminal, cranial cervical, and cervicothoracic ganglia. 16 This report illustrates the location of neural structures that contain lesions and virus in experimental and natural infections of sheep. Six adult ewes were euthanized and dissected to expose the cranial cervical ganglia, cervicothoracic ganglia, brain stem, and trigeminal ganglia. These tissues were easily obtained with standard necropsy instruments and without significantly altering necropsy protoco1s and prosection time. The cranial cervical ganglia (Figs. l-4) are bilaterally symmetrical sympathetic ganglia at the cranial end of the sympathetic trunk. These grayish to pale brown, fusiform neural structures are approximately 8 mm long and 6 mm wide and are embedded in the adipose tissue of the retropharyngeal area. Each ganglion lies ventral to the posterior foramen lacerum, ventromedial to the tympanic bulla, medial to the jugular process of the occipital bone, and on the lateral aspect of the rectus capitis ventralis muscle.’ The cranial cervical ganglia are excised prior to removing the head. After removing or reflecting the tongue, pharynx, larynx, trachea, and esophagus, the rectis capitis ventralis muscles are identified and then transected at the level of the atlantooccipital articulation. The cranial cervical ganglia are found by first locating the exposed ventral ovoid space at the atlantooccipital articulation. The space is formed cranially by the caudal aspect of the occipital bone at the ventral edge of the foramen magnum and caudally by the ventral edge of the cranial atlas. After this space is identified, the rectis capitis