Question

some parasites can cause digestive tract infections and some have the ability to form cysts. Please explain how a cyst may play a role in the ability of the parasite to cause disease.

Answer 1

The cysts are eggs that have a hard covering for the survival of the organism outside a host or inside a host, cysts have ability to give birth to whole parasites; many parasites are able to make cysts.a typical example is given below:

1. Entamoeba histolytica - The active (trophozoite) stage is found only in the host and in fresh loose feces; cysts can survive outside the host in water, in soils, and on foods, especially under humid conditions. The infection can occur when a person eats anything that is infected with E. histolytica cysts, swallows something, such as water or food, which is contaminated with E. histolytica, or swallows E. histolytica cysts (eggs) usually picked up from contaminated surfaces or fingers. The cysts are usually killed by heat and by freezing temperatures, and survive for only a few months outside of the host. When cysts are swallowed they cause infections by excysting (releasing the trophozoite stage) in the digestive tract causing further infection, trophozoite can bore into membrane of intestine and cause bloody diarrhoea and loss of water, it can become invasive if it gets into the blood stream and invade liver, lungs, brain or even lungs. Cysts can survive and remain inactive (dormant) for a long period of time inside the host as well and is usually resistant to typical antiamebic antibiotics.