McFadyean reaction is seen in:

Ref: Harrisons 19th ed. pg. 261e2 \* McFadyean reaction is a special staining reaction, demonstrating a pink capsule around a blue cell, after staining with methylene blue, which is used as a presumptive diagnosis for anthrax in a blood smear.* Anthrax is caused by B. anthracis a Gram-positive, nonmotile, spore-forming rod that is found in soil and predominantly causes disease in herbivores such as cattle, goats, and sheep.