| Summary |
One hundxei and sEuynine piglet were divided into four groups. The first group was consisted of 107 neonates; the piglet were vactina& with a dose of LPC vaccine either by intramuscular (I.M,) or subcutaneous (S.C.) or oral routes, They were deprived of the coicetnim from to6hours pcet vaccination. The 1? piglet in the sesond group were inoculate1 with LPC vaccine by intranasal (IN.) and oral routes, resjeztavely, at? weeks old. For the third grou 1? piglet were vaccinated by LM. at 3 and6weeks of age. Theother28 piglet inthefouthgroupwereleftuntreaIfor oontact inf&tion and served as challenge controL
All pigs, except for oontact infection, were challenged with AU) hog cholera virulent virus at 10 weeks of age. The result showed that those pigs which received prerxdostwn vaccination by LM. or S.C. and vaccinai at 3,6 weeks of age were refractory to the challenge. However, the most of pigs had one to two days of fever response about the 5th day post challenge. Some had a low viremia and lesions such as the scaring of splenic infarction, non-suppurative encephalitis, and endothelial proliferation in blood vessels. The timing for colost’imn intake aft farrowing seems had no influence on immune response, if the neonates were vaccinated kefore the sucldng of the colostum. Althouglr pigs vacdnael by oral or IN. at? weeks oki were refractory to the challenge, that ptxdostal vaccinated by oral route did not establish an effective immunity. The HC lesions incurred by the piglets, pmecolcetrally immunized and exposed to a virulent virus, warrant to ke discouraged due to increase in mnisdiagnosis from true hog cholera.
|