[Comparative pathomorphological studies of piglets infected with different strains of the pseudorabies virus].

Studied were morphologically the central nervous system and the internal organs of a total of 40 experimentally infected pigs-10 infected with the virulent strain B (5.2 C 10(6) PFU), 10 infected with the slightly virulent strain K (4.8 X 10(6) PFU), and 20 infected with the vaccinal mutant strain MK 25 (2.4 X 10(6) PFU), along with 4 control pigs. Histologically, all treated animals showed changes in the central nervous system characteristic of nonsuppurative meningoencephalitis. The lesions were more strongly expressed in the pigs infected with the virulent strain. Those of the animals treated with the MK strain presented changes that were similar to the changes observed in the pigs of the remaining two groups. By intensity and size, however, they were more slightly manifested and tended toward rapid limitation and lower frequence and dimension. The animals infected with strain K mad also changes in the lungs - interstitial pneumonia of lymphohistiocytis type. Those injected with the MK 25 strain presented numerous macrophages in the tonsils and lung lymph nodes, which was referred to as the morphologic expression of immunogenesis. The morphologic differences observed in the course of Aujeszky's disease in the individual test groups of pigs were due to the varying virulence and tissue tropism of the pseudorabic virus strains used. Studies revealed that the strongly virulent strains were predominantly neurotropic, while the slightly virulent ones were to a lesser extent neurotropic but were shown to be strongly pneumotropic.