LIFESCI 3AA3 Lecture Notes - Lecture 18: Ascaris Lumbricoides, Ascariasis, Ascaris
9 Dec 2018
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Document Summary
One of most common nematode (roundworm) infections worldwide. Reside in small intestine (up to 35 cm) Uses active muscle contractions to wrap and tuck itself into the intestinal walls to prevent being excreted. Produces a pepsin inhibitor to prevent host enzymes from digesting it. Eggs have 3 protective epidermis coatings: outer protein layer, middle chitinous shell and inner membrane. Infection due to soil or contaminated food (poor sanitation) containing ascaris eggs; leads to ascariasis which protects egg from digestive enzymes. Complete digestive system (feeds on digestive food of the host) Males are smaller than females and have a curled tail. Mating happens through 2 openings cloacal and gonopore openings. Giovanni grassi (1800s) italian physician and zoologist; first to demonstrate infectivity of ascaris lumbricoides: took embryonated eggs from feces of corpses and ate them, then found the eggs in his feces. Shimesu koino (1900s) japanese pediatrician, consumed 2000 mature eggs to see life cycle.
