Pathway of mesocercariae of Alaria marcianae (Trematoda) through the mammary glands of lactating mice.

Lactating mice were infected with mesocercariae of Alaria marcianae to demonstrate more precisely how these parasites migrate within the mammary glands. The infected dam that first transmitted larvae to all of her young was necropsied and her mammary glands removed and sectioned serially. Mesocercariae penetrated the dense connective tissue surrounding the lobules. Within the stroma the larvae migrated along tracks of fat cells and were consistently found in pools of milk created from the destruction of alveoli. These pools of milk led directly into the large lactiferous ducts. It was notable that no mesocercaria was found in the lactiferous or galactiferous ducts indicating that clearance from these vessels was rapid. No larva was found in any blood vessel nor was any significant hemorrhage demonstrable. Lack of an inflammatory response surrounding the worm was characteristic, although large numbers of neutrophils were scattered diffusely throughout the lobules, and multiple, proliferative lymph nodules were present.