Attempts were made to study the stabilization of the Lapinized Hog Cholera Liquid Vaccine. The results were summarized as follow :
Lapinized Hog Cholera Liquid Vaccine was produced from spleens and lymph nodes of rabbits infected with LPC strain of hog cholera virus. The fresh prepared vaccine had a 50% protective dose of 104•5 PDs0/gm when titrated in pigs, where as the vaccine after nine-month preservation in refrigerator at 2-5°C. had only a level of 10'·"PD50/gm. (table 1)
Rabbits inoculated with 10-5 dilution of fresh vaccine still showed a typical curve of fever reaction. The virus titer of the vaccine dropp-ed to 1Q3.i•RID.;0/gm. after an inter val of nine months when titrated in rabbits. (table 2)
Two to four rabbits were intravenously inoculated with 2 ml. of vaccines at various duration of preservation, respectively. Temperature of each rabbit was checked twice a day, in the mo:-ning and afternoon, for ten days. Typical fever reaction (temperature rise up to 41.1 °C. or higher) were observed in 14 out of 16 rabbits (87 .5%). The temperature curve was almo;t the same as that of control group. (tabl:! 3)
This typic:il curve of fever reactio:i caused by vaccine inoculatio:1 was not influenced by duration of vaccine preservation. The temperature rose to peak ( 41-41. 8°C. ) o the 2nd or 3rd day, then declined to normal range on the 4th day after inoculation. A second fever (40.1-41°C) was observed at 5 or 6 days after the inoculation. The first peak of fever was higher than the second. This phenomenon was called "diphasic temperature curve" Twelve out 16 rabbits showed this reaction. (Figure 1)
The Lapinized Hog Cholera Liquid Vaccine preserved in refrigerator (2-5 C. ) were tested for potency at various durations, i, e, from one week to nine months. All inoculat-ed and control pigs were challenged with the virulent blood (ALD strain) at dose of 105 MLD on the 10 th day post-inoculation. All pigs were observed for clinical signs for 3 weeks. All the vaccinated ones survived, wereas the controls died of the challenge. (see table 3)
The PH of the fresh prepared vaccine was 5.4. No any PH change was noted during various times of the nine months preservation.