Angiostrongyliasis : Life cycle and transmission

In the rat, the first-stage larvae migrate to the brain and mature to the adult stage. The young adult worms migrate to the surface of the brain and penetrate the venous system to reach their final destination in the pulmonary arteries of the rat. After mating, eggs deposited by female worms hatch in small branches of the pulmonary arteries. The first-stage larvae enter the bronchial lumen and pass up the trachea. They are swallowed and passed in the rat’s faeces. When these are consumed by a snail, infection of the mollusk will ensue. Many different snail species can be infected, including Pila snails (e.g. Thailand, local cuisine) and the giant African land snail (Achatina fulica). [For the detection of larvae in snails, shells are crushed and the bodies are homogenized and digested in pepsin-hydrochloride solution at 37° for 1 hour. The solution can then be examined with a light microscope]. Humans (and rats) become infected through eating raw slugs or snails, soiled lettuce contaminated with mollusk slime, infected planarians or eating a carrier host (infected land crabs, shrimps or freshwater prawns). Inside man, the neurotropic third-stage larvae pass from the intestinal tract to the meninges. They die 1-2 weeks after arriving in the human brain.

Category: Medicine Notes