Comparison of immunohistochemistry and Ziehl‐Neelsen staining for detecting the distribution of Mycobacterium avium subsp avium in naturally infected domestic Pekin ducks (Anas platyrhynchos domestica)

In order to detect the distribution of Mycobacterium avium subsp avium (MAA) in naturally infected domestic Pekin ducks, immunohistochemistry (IHC) and Ziehl‐Neelsen (ZN) staining were used and compared. Six organs, the liver, spleen, lung, kidney, duodenum and pectoralis muscle, were collected from naturally infected Pekin ducks. Paraffin embedded tissues were examined, and the results were compared. Statistical analysis was performed using Chi‐Square test. The results showed that the detection rates by IHC were similar with ZN staining in liver, lung, spleen and pectoralis muscle, but the detection rates by IHC were much higher than ZN staining in kidney and duodenum (p = .013, p = .0044). The liver (87.5%) and lung (81.3%) had the highest detection rates. Acid‐fast bacilli (AFB) were primarily found intracellularly in six organs using ZN staining. Similarly, the MAA antigens in those selected organs were also detected in the cytoplasm with different cell types. Specifically, MAA antigen was distributed in epithelioid macrophages and necrotic centres within the liver, lung, spleen and kidney, while they were observed in macrophages of the lamina propria and duodenal glands and degenerative myocytes in the pectoralis muscle. This comparative study provides an important insight into the distribution of MAA in infected domestic ducks and indicates that the detection rate by IHC was higher than that of ZN staining.