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Parasitemia is a condition in which parasites are present in a person's or animal's blood. In evaluating a medical condition, the term parasitemia may be used to indicate the number of parasites infecting the person or animal. It may also be used to determine the degree to which the person or animal suffers from an infection caused by parasites.
Measuring parasitemia can be important in diagnosing a patient with a parasitic infection. It may also be critical during treatment and prognosis evaluation. For example, curing a patient of certain types of parasitic infections requires lowering his parasitemia to a level of zero. This is particularly true of chronic phases of parasitic infection.
Often, parasitemia is measured using an optical microscope. This type of microscope is frequently called a light microscope because it employs visible light and lenses to help users see the samples they are analyzing. An optical microscope enables users to see very tiny samples. Sometimes polymerase chain reaction (PCR), a molecular biology technique, is used to analyze parasitemia. PCR involves the amplification of deoxyribonucleic acid (DNA), which is genetic material, and the generation of copies of DNA sequences, which are letters used to represent DNA strands. It is commonly used not only in diagnosing diseases, including some parasitic infections, but also in genetic research and testing.
Often, parasitemia is discussed in relation to malaria, a disease that is spread through the bites of some mosquitoes. This infection occurs when an infected mosquito bites a person or animal and transmits parasites of the following species: Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae. Blood smears can be used in the microscopic analysis and diagnosis of malaria. Thick smears are considered more sensitive for identifying parasitema and screening for the presence of malaria parasites while thin smears can be good for identifying malarial parasite species and figuring out the quantity of parasites that are present.
To analyze parasitemia using thick and thin blood smears, a doctor pricks the patient’s skin to obtain drops of blood. For a thick smear, a drop of blood is placed on a slide made of glass. This type is better for detecting parasitemia because the sample of analyzed blood is larger than that of a thin blood smear, and the amount of parasites may be low at the time of testing, requiring a larger blood sample. With a thin blood smear, a drop of blood is spread around an area of the slide, allowing laboratory scientists to have an easier time discovering the species of the parasite and the percentage of red blood cells that are infected by it.