Experimental infection of slaughter pigs with classical swine fever virus:transmission of the virus, course of the disease and antibody response

The spread of classical swine fever virus was investigated in an isolation unit containing four pens, each containing six slaughter pigs. One pig in t he middle pen of three adjacent pens was inoculated intramuscularly and int ranasally with the virus. The fourth pen was located in a separate compartm ent The pens were visited in a strict order to study, first, the effect of indirect contact via contaminated clothing and footwear on the spread of th e virus to adjacent pens and, secondly the airborne transmission of the vir us between compartments. The pigs were examined and blood samples were take n every other day for 62 days for virological and serological analyses. The virus was highly contagious for the five pigs that were in direct contact with the inoculated pig, but spread to the other pens only after all the pi gs in the originally infected pen had become viraemic. The spread of the vi rus was promoted by contaminated clothing and footwear, but airborne transm ission contributed considerably to the spread of the virus within the pigho use. The first clinical signs observed after the virus was introduced into a pen were decreased feed intake, increased mean rectal temperature and apa thy. Neither the clinical course of the infection, nor the pattern of seroc onversion observed over time, was affected by the differences in the intens ity of contact with the virus between the pigs in the different pens.