The effect of vaccination with the PAV-250 strain Classical Swine Fever (CSF) virus on the airborne transmission of CSF virus

The airborne transmission of Classical Swine Fever (CSF) virus to susceptib le pigs, as well as the effect of vaccination with the CSF virus PAV-250 st rain was investigated on this mode of transmission. Experiment I: four pigs were inoculated with the ALD CSFV strain (10(4.3) 50% TCID) by the intramu scular route, and at the onset of fever, they were introduced into an enclo sed chamber. At the end of the experiment surviving pigs were sedated, anes thetized and euthanatized. Experiment II: four pigs were previously vaccina ted with the CSF virus PAV-250 strain, and at 14 days post-vaccination they were challenged with the CSF virus ALD strain. In both experiments, four s usceptible pigs were exposed to infectious aerosols by placing them in a ch amber connected by a duct to the adjacent pen containing the infected anima ls and were kept there for 86 hs. In Experiment I, pigs exposed to contamin ated air died as a result of infection with CSF virus on days 14, 21 and 28 post-inhalation. These four pigs seroconverted from day 12 post-inhalation . CSF virus was isolated from these animals, and the fluorescent antibody t est on tonsils was positive. In Experiment II, a vaccinated pig exposed to contaminated air did not seroconvert, nor was CSF virus isolated from lymph oid tissues. However, mild fluorescence in tonsil sections from these pigs was observed. In conclusion, CSF virus was shown to be transmitted by air a t a distance of 1 m to susceptible pigs. Vaccination with the PAV-250 CSF v irus strain protected the pigs from clinical disease under the same conditi ons.