How is H. americana transmitted and how does it affect all these body systems?
The life cycle of H. americana is indirect – it involves a snail. This is what happens. The egg of H. americana is passed in the feces of the dog and hatches almost immediately in water. The immature form swims around until it finds a snail. The immature form enters the snail where it matures into an infective form. These forms leave their snail host and swim in search of a dog or raccoon. But, they only leave the snail early in the morning. So, in this case the early dog gets the fluke – sorry, just had to include that. These forms only have one day in which to find a host before they die. Upon entering a dog, the infective forms enter the veins in the skin and are carried to the heart and lungs. By several routes, they migrate to the veins of the intestine and liver where they mature. A bulkier male worm mates with the very slender and petite female. She then moves into smaller and smaller veins and lays her eggs and then leaves. The contractions of the vessels and intestine actually
