Detection avian reovirus (ARV) by RT-PCR; from left DNA Marker 2+ (100–1000 bp, A&A, Gdańsk, Poland), NC—negative control, 1—liver, 2—spleen, 3—bursa of Fabricius 4—joints, 5—tendon, 6—tendon sheath, 7—heart, 8—kidney, 9—intestines; PCR product size 1100 bp.