Division 1

The polymerase chain reaction (PCR) is applied to detect the virus genome in blood, serum, tissues or organ samples. Small fragments of viral DNA are amplified by PCR to detectable quantities. A wide range of isolates belonging to all the known virus genotypes, including both non-haemadsorbing viruses and isolates of low virulence, can be detected by using primers from a highly conserved region of the genome. Since this test detects only a genome sequence of the virus, the PCR may be positive, even when no infectious virus is detected by virus isolation (e.g. in autolysed tissues or samples from convalescent pigs or from pigs which have recovered and become clinically normal).