Non-pathogenic intestinal protozoa are single-celled parasites commonly found in the intestinal tract but never associated with illness. They reside in the large intestine of the human host. Both cysts and trophozoites of these species are passed in stool and considered diagnostic..A total of 284 children from a rural area in Mexico participated in the study. A fasting blood sample was collected from all children to determine concentrations of iron, zinc, vitamins A, C, D, and E. Intestinal parasitic infection was determined by a direct smear and Kato Kats technique from a stool sample. Approximately 20% of the population studied was infected with E. coli and 16% with A. lumbricoides
Asymptomatic human infections are usually diagnosed by finding cysts shed in the stool. Various flotation or sedimentation procedures have been developed to recover the cysts from fecal matter and stains help to visualize the isolated cysts for microscopic examination. Symptoms can range from mild diarrhea to severe dysentery with blood and mucus. In about 10% of invasive cases the amoebae enter the bloodstream and may travel to other organs in the body. Most commonly this means the liver, as this is where blood from the intestine reaches first, but they can end up almost anywhere in the body.