White spots of the liver in pigs experimentally infected with Ascaris suum.

To make clear the relationship between Ascaris suum infection and the appearance of white spot lesions on the surface of the liver in pigs, three groups of pigs were inoculated orally with embryonated A. suum eggs and observed clinicopathologically. Group A of three pigs were inoculated 21 times with 100 eggs each of the nematode, group B of three pigs 4 times with 50,000 eggs each for 10 weeks, and group C of two pigs 2 times with 50,000 eggs each at a one-week interval. All the pigs were sacrificed at the same time 1 week after the final inoculation. Such signs of the nematode infection as dyspnea, coughing and fever appeared in all the pigs of groups B and C seven days after inoculation to continue for several days. In addition, peripheral blood eosinophilia was recorded in these animals 7 or 14 days after inoculation. At autopsy, mesh-worked white spots, some compact and others lymphonodular, were observed on the surface of the liver in all the pigs of the three groups. Main white spots were mesh-worked and lymphonodular in the pigs of group A. They were severe and compact in group B. Therefore, they were rough to the touch. In group C mesh-worked white spots fused with one another and covered the surface of the liver. These white spot lesions observed were morphologically very similar to those found in the field conditions. Complement-fixating antibodies reacting to adult A. suum antigen were detected only in sera from the pigs of group B. Moreover, antibodies involved in the intradermal reaction of immediate type were found in the pigs of groups A and B.