Ascaris larvae as a cause of liver and lung lesions in swine.

In a previous paper the writers (1930) reported the occurrence of lesions in the lungs and liver of swine in the form of small pearly cysts under the pleura of the lungs and under the capsule of the liver. While practically each cyst isolated from the lungs contained a brittle, degenerated nematode larva, no parasites were discovered in several liver cysts which were subjected to a searching microscopic examination. More recently, the writers had an opportunity to examine a liver of a pig which had been killed at the Bureau of Animal Industry Experiment Station at Bethesda, Maryland. The liver showed lesions essentially similar to those noted on the previous occasion except that the lesions were more numerous and therefore more striking. From a number of the discrete pearly cysts, located underneath the capsule, degenerated nematode larvae, morphologically identical with those reported previously from the lungs of swine, were isolated for study. This finding completed the chain of evidence, already suspected from the earlier study, that small cysts in the liver and lungs of swine frequently encountered by veterinary inspectors and others in the course of post-mortem examination of these animals, are due to the encystment and ultimate degeneration of nematode larvae. While the lesions in the lungs are limited to the cysts themselves, those in the liver are more striking because the entire organ takes on a mottled appearance, due to the striking contrast between the normal color of this organ and the pale color of the cysts; the contrast is particularly marked when the cysts are numerous.