EFFICACY OF AN INACTIVATED VACCINE FOR PREVENTION OF REPRODUCTIVE FAILURE INDUCED BY PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS

This report describes the results of experiments with an inactivated o ily vaccine containing per dose about 10(5.5) median tissue culture in fectious dose (TCID50) of the Spanish strain of porcine reproductive a nd respiratory syndrome (PRRS) virus grown in porcine alveolar macroph ages (PAMs). In order to evaluate the efficacy of the vaccine, two exp erimental infection routes were tested in sows: subsequent intranasal (I.N.) and intravenous (I.V.) (out of a total of 93 piglets born to 7 sows, 16% were mummified, 18.2% were weak and died within 48 h of birt h, 37% were stillborn, 5.3% died between 2 and 7 days of age, 22.5% Li ved for more than one week) and intranasal alone (out of a total of 65 piglets born to 5 sows, 0% were mummified, 22.5% were weak and died w ithin 48 h of birth, 40% were stillborn, 4.6% lived for more than one week). I.N. alone was selected to evaluate the efficacy of the vaccine because this is the natural route of infection. A number of experimen ts were conducted to test the immunogenicity of the vaccine. In genera l, after challenge with the homologous strain, protection in vaccinate d sows was high (at least 70% of the piglets were born alive and healt hy), whereas protection in unvaccinated sows was low (only 10% of the piglets were born alive and healthy). Vaccinated animals devoid of ant ibodies by immunoperoxidase monolayer assay (IPMA) at the time of chal lenge were still protected at experimental infection. (C) 1997 Elsevie r Science B.V.