Tissue tropism of Nosema ceranae. Tissues such as hypopharyngeal gland, salivary gland, alimentary canal, malpighian tubules, muscle, and fat body were dissected and examined for the presence of N. ceranae by PCR method. For electrophoresis gel, numbers 1–6 indicate hypopharyngeal gland, salivary gland, alimentary canal, malpighian tubules, muscle, and fat body, respectively; letter N indicates negative control, and letter P indicates positive control. The size of PCR fragments is indicated on the right of the gel.