Abstract: The liver and spleen samples of 600 unhealthy chickens were collected randomly to investigate infection of MDV,CAV,REV and REOV in Shandong province using Dot blotting. The clinic tissues came from six different districts including yantai, binzhou, linyi, tai′an, liaocheng and qingdao of Shandong. The results suggested that the checkout ratios of the four virus are 5.17% (MDV)， 8.17% (CAV)， 1.17% (REV) and 2.5% (REOV) respectively which were lower than the former research; certain degree duale infection and triple infection were found out. The result indicated that the immunodepressive virus are well controlled except individual flock in which the rate of infection was higher than the sum of other flocks; there was a significant discrepancy of the immunodepressive illness in different flocks where the management level were uneven.

Key words: broiler; MDV; CAV; REV; REOV; Dot blotting