Persistence of hog cholera virus of low virulence in the central nervous system of piglets from well-managed farms

© 1999 Universidad Nacional Mayor de San Marcos. All rights reserved. The distribution of HOG cho lera virus (HCV) anti gen in the central nervous system (CNS) of 28 piglets with subclinical HOG cho lera (HC) infection from 1 O well managed f arms in the Department of Lima was studied. The pigs, aged 1 to 20 days, included animals with diarrhea (n=5), pneumonia (n=5) and retarded growth (n=6), as well as normal specimens (n=7) and others which died from trampling (n=5). The presence of viral antigen in lymphoid and/or nerve tissue was used as a criteria to identify the persistence of low virulent strains of HCV. Tissue samples from tonsils, spleen, and regional lymph nodes were taken to perform the immunofluorescence test (IF). The brain, including the pituitary gland, was fixed in formalin at 10% for subsequent viral identification using the immunoperoxidase test (IP). Viral antigen was present in tonsils, spleen, lymph nodes and CNS in 42.9% (12/28) of the animals sampled. In the CNS, HCV antigen was detected in both neurons and groups of neurons in different areas of the brain. All the pigs (12/12) showed viral antigen in the cerebral cortex, 83.8% (1 O/ 12) in the cerebellum, 41.7% (5112) in the thalamus and hypothalamus, 33.3% (4112), in the hyppocampus, 16.7% (2/12) in the medulla oblongata, and the 50% (6112) in the pituitary gland. No viral antigen was detected in the leptomeninges or choroid plexus. The frequency of antigenic detection was found to increase as the pigs aged. The results show that low virulent HCV is present in well managed pig farms in the Department of Lima and the strains persist in the CNS, pituitary gland, and lymphoid tissues. A high percentage of pigs with diarrhea and pneumonia had viral antigen suggesting the immunosupresive role of the HCV.