Experimental Elaphostrongylus cervi infection in sheep and goats.

The pathogenesis and migratory life cycle of Elaphostrongylus cervi were studied in four sheep and six goats killed and examined 6 days to 5 months after inoculation with infective third-stage larvae (L3). Detailed histological studies demonstrated that the L3 followed a porto-hepatic, and probably also a secondary lymphatic, migratory route from the abomasum and small intestine to the lungs, with subsequent spread via the general circulation to the central nervous system (CNS) and other tissues. In addition, the results suggested that haematogenously spread L3, arrested in arterial vessels outside the spinal cord, migrated into the cord along the spinal nerves. During migration, the L3 caused focal inflammation and necrosis in the organs and along the spinal nerve roots, and infarcts occurred in the myocardium, kidneys and CNS. Nematode development took place in the CNS. During development, there was a gradual die-off of nematodes and patent infections were not observed. However, in one animal many mature nematodes were demonstrated in the CNS. In the nervous system, the nematodes caused encephalomyelitis, focal traumatic encephalomalacia, gliosis, meningitis, choroiditis, radiculitis and perineuritis. Two goats and one sheep displayed long-lasting paraparesis starting 6 weeks after inoculation. The signs apparently resulted from nematode-induced spinal nerve root lesions. From 19 weeks after inoculation the sheep also showed signs of severe brain disturbances due to traumatic and inflammatory lesions caused by adult E. cervi in the cerebral parenchyma. We conclude that E. cervi represents a potential cause of neurological disease in small ruminants grazing areas inhabited by red deer. This is the first report confirming the infectivity of E. cervi for domestic ruminants. Copyright 2000 Harcourt Publishers Ltd.