March and April, 1997

Danish PRRS control program

Dear Editor:

I think the article that appeared in the December 6, 1996 issue of Animal Pharm may be of interest to many veterinarians in the AASP. The article concerns the use of a modified-live virus PRRS vaccine in a national PRRS control program in Denmark.

The article relates that the Danske Slagterier (DS), the Federation of Danish Pig Producers and Slaughterhousese, has decided to stop their PRRS control program, which was using the Boehringer Ingelheim modified-live (MLV) PRRS vaccine. This decision was prompted by a number of reports of passive vaccination--where PRRS had spread from vaccinated to unvaccinated animals in the same herd.

The program began in July 1996 when the vaccine was approved for use in Denmark, but after several months of use they witnessed the spread of PRRS in a number of vaccinated sow herds.

The DS decided to stop the program because clinical symptoms of PRRS had been recorded in 30%-40% of vaccinated sow herds. So it appears that the national PRRS control program has come to an end because the MLV PRRS vaccine was to be its main tool.

The article states that the decision to discontinue the PRRS control program maybe a shock to many outside of Denmark, but because of the problems mentioned above, the situation had changed dramatically. The DS began the program knowing that it would stop it if things did not go according to plan. At present, they feel there is no vaccine available to take the place of the Boehringer product.

The vaccine, however, can still be used under commercial conditions in Denmark.

I think perhaps there are some lessons to be learned here concerning the widespread use of MLV vaccines in livestock when in many instances the inactivated vaccines will immunize just as well as the MLV vaccine and at much less risk to the animal population.

--Kenneth J. Groninga, DVM
Grand Laboratories, Inc.
Iowa Falls, Iowa