A few examples of harmful protozoa are listed below along with the symptoms they cause and how to prevent becoming infected.

Protozoan	Symptoms	Prevention
Cryptosporidium parvum	Diarrhea.  May also cause vomiting, headache, fever and stomach cramps.  Can be fatal to those in poor health.	Use an approved water filter, an approved brand of bottled water or boil water for 1 minute.  Avoid drinking water from lakes and rivers.
Plasmodium (causes malaria)	Fever, headache and vomiting.  Can be fatal.	Spread by mosquito bites.  The use of DDT in the U.S. and many other countries brought malaria under control.  It is still a problem in many Third World countries though.
Toxoplasma gondii	Does not cause symptoms in most people.  Can cause fatalities in unborn children and in AIDS patients.	Thoroughly cook all meats,  be careful handling cat litter, feed cats commercial cat food, cover sand boxes when not in use and wash all fruits and vegetables before eating.

Common Properties | Bacteria | Virus | Protozoa | Fungi