APVSにて発表しました。
Eradication of Aujeszky’s Disease from a Japanese farm using an adapted vaccination program
IntroductionSince 1991, we have been trying to eradicate Aujeszky’s Disease (AD). But, in Japan, vaccination is not compulsory, its use depends on a voluntary decision by veterinarians or farmers. We were asked to eradicate AD on one particular farm. We monitored the farm’s AD status by regularly examining serum samples for AD antibodies. Using these results, we recommended a whole herd vaccination program, advising on the choice of vaccine and its timing for piglets, sows and gilts. We finally succeeded in eradicating AD.
Materials and Methods
The farm: A typical Japanese 500-sow farrow-to-finish herd on a single site in the northern part of Japan.AD Neutralizing Test (NT): Serum samples were incubated for 1 hour with AD virus (200 TCID/ L). The maximum dilution was recorded for neutralization (CPE -ve) after five days incubation (37°, 5% CO2). Measurements >2 were taken to be positive, and those 2, negative. ELISA Test: The ADV (gI) ELISA Test Kit (IDEXX) was used which measured ADV infection, because the only vaccines available in Japan are marker vaccines. Vaccine: Porcilis Begonia, Suvaxyn Forte Vaccination Programs: Program 1. (between spring and autumn, 2005) Vaccination with AD live vaccine (gI-, tk-) Gilts: When acclimatized: 2 doses, 4 weeks apart Sows: All sows, one month before farrowing Piglets: Not vaccinated Program 2. (between autumn 2005 and summer 2006) Vaccination with AD live vaccine (gI+, tk-) Gilts: When acclimatized: 2 doses, 4 weeks apart Sows: All sows, 3 times per year, all at once Piglets: 2 doses at 60 and 90 days old Program 3. (from summer 2006 to present) vaccination with AD live vaccine (gI-, tk-) Gilts: Soon after arrival: 2 doses 4 weeks apart Sows: All sows, 3 times per year, all at once Piglets: Single dose at 90 days old
Results
Program 1: Only one sow was ELISA-positive, there were no other field infections in sows. But field infection was observed in pigs at 90, 120 and 160 days of age. Program 2: The number of AD-positive sows increased, and field infection was observed in pigs of all ages. The farmer considered that the program was failing, and asked us to improve it. Program 3: No rapid changes in field infection, but by the end of November 2008, most pigs were negative. There were only limited numbers of older sows showing AD infection.
Discussion
Though he was not confident at the start, the farmer became convinced that AD eradication was possible using this monitoring approach. Management measures, including the introduction of only AD-ve gilts, periodic monitoring and feedback to inform a proper vaccination program were effective in eradicating AD on this farm. Communication between farmer and consultant was the key to maintaining motivation. It has now been shown that, strongly motivated farmers in Japan can eradicate AD using an appropriate program of vaccination guided by regular disease monitoring.
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