Transmammary Infection of Paratenic and Definitive Hosts with Alaria marcianae (Trematoda) Mesocercariae

Transmammary infection with Alaria marcianae mesocercariae was demonstrated using mice as model, paratenic hosts. Prenatal transmission was ruled out because neonates removed immediately postpartum from infected dams were never infected. Mesocercarial distribution in virgin females and in females examined immediately postpartum showed no marked preference for the mammary glands. In contrast, infection of neonates that were allowed to suckle on infected dams was absolute, and the number of mesocercariae in the mammary glands of postparturient dams that suckled their young was increased significantly. These experimental observations were coupled with other observations on paratenic hosts to outline the pathways open to mesocercariae in gravid hosts. The term amphiparatenic host is coined for those host species that are paratenic hosts as adults, but as juveniles can serve as definitive hosts.