DIAGNOSIS OF PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME USING INFECTED ALVEOLAR MACROPHAGES COLLECTED FROM LIVE PIGS

A highly sensitive method of detecting infection of live pigs with por cine reproductive and respiratory syndrome virus (PRRSV) was developed by testing alveolar macrophages collected by pulmonary lavage, Five p igs were exposed by oronasal inoculation or by contact to PRRSV when t hey were 10 (1 pig) or 14 weeks (4 pigs) of age. Diagnostic samples (a lveolar macrophages and sera) were collected from each pig just before exposure to PRRSV. During the next 9 weeks sera were collected at wee kly intervals and alveolar macrophages were collected at weeks 2 and 4 -9. Both sera and alveolar macrophages were suitable for detecting ear ly infection, but alveolar macrophages were clearly the better sample after longer intervals, Virus was last isolated from serum at week 4 ( from 1 of 5 pigs), whereas it was isolated from the alveolar macrophag es of 4 of the 5 pigs at week 4 and from at least 2 pigs at each of th e weekly intervals thereafter (i.e. weeks 5, 6, 7, 8, and 9 postexposu re). The most sensitive method of testing alveolar macrophages for PRR SV was cocultivation with MARC145 cells. None of the pigs had any clin ical signs after exposure to PRRSV or as a result of pulmonary lavage and there was no evidence that repeated pulmonary lavage caused anythi ng other than a mild, transient (mild hyperemia) tissue reaction.