in favourable conditions the embryonated eggs of ascaris can remain viable for about 6 years in moist soil. can you find the reason for this?
Answers
Answer:
Ascaris lumbricoides is the largest intestinal nematode of humans. Females are up to 30 cm long; males are smaller. Three types of eggs may appear in feces: fertilized, unfertilized, and decorticated.
Multiplication and Life Cycle : Adults in the small intestine produce eggs that pass in feces, embryonate in soil, are ingested, and hatch. The larvae migrate from the intestine to the lung and back to the intestine, where they mature.
Pathogenesis: Migrating larvae cause eosinophilia and sometimes allergic reactions. Erratic adult worms may invade other organs. Heavy infections can impair nutrition.
Host Defenses: Resistance increases with age; the mechanism is not clear.
Epidemiology : Egg viability is supported by warm, moist soil. Transmission is favored by unsanitary disposal of feces. Prevalence is highest in children.