How is H. americana transmitted and how does it affect all these body systems?

Question

How is H. americana transmitted and how does it affect all these body systems?

Answer 1

Heterobilharzia americana is most commonly found in areas of mud flats of the Mississippi River and swampland in Louisiana. It infests dogs and raccoons.

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 f***s 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.

H. americana is unusual among flukes in that there are separate male and female forms.

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 veins and lays her eggs and then leaves. The contractions of the vessels and intestine actually push the eggs through the wall of the vessel, the wall of the intestine, and into the intestine's lumen. The eggs are then passed in the f***s.

Inflammation occurs at the site where the infective form enters. Pustules form and there may be itching.

An intense inflammation occurs in the intestine as the eggs pass through it. Diarrhea, with mucus and often blood, results. Dogs lose their appetite and may become emaciated. The wall of the intestine may become very thickened.

Cirrhosis of the liver can occur if the eggs are laid in its small veins and then enter the liver itself.

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