Migration of Alaria marcianae (Trematoda) in domestic cats

The migration of Alaria marcianae was studied in domestic cats. Mesocercariae penetrated the stomach wall, entered the abdominal cavity, and penetrated the diaphragm within 3 hr. Direct penetration of the lungs via the thoracic cavity occurred within 6 hr. Also observed was a circulatory route to the lungs when mesocercariae were recovered from both the liver and the chambers of the heart. Upon entrance into the lungs, mesocercariae began to enlarge with sequential lappet formation, holdfast development, and penetration gland atrophy. By day 7, they were recognized as fully formed diplostomula. The diplostomula resided a minimum of 4 days in the lungs as they first appeared in the duodenum by day 11. Diplostomula were found in both the trachea and stomach, indicating that they reach the duodenum after being coughed up from the lungs and swallowed. Diplostomula recovered from the duodenum were indistinguishable morphologically from the most advanced lung forms. Maturation of the reproductive organs occurred in as little as 4 days as the first ovigerous specimens were seen on day 15. The bidirectional route to the lungs may be significant when viewed in light of the recent discovery of transmammarian transmission. If a hormonal stimulus is involved, it is conceivable that those mesocercariae in the circulatory system may be more readily influenced than those undergoing a somatic migration. This may account for why some larvae are diverted to the mammary glands in a pregnant mammal instead of the normal, maturative migration to the duodenum.