If diagnosis is based on clinical symptoms alone, malaria may easily be confused with any of several other diseases. For example, an enlarged spleen can also sometimes be caused by other less-prevalent tropical infections such as schistosomiasis, kala-azar (a type of leishmaniasis), and typhoid fever. For this reason the most reliable method of diagnosis is a laboratory test in which a trained technician is able to distinguish between the four species of parasites when a smear of blood from the infected person is examined under a microscope. The method has drawbacks, however. For example, the test is time-consuming, may fail ...(100 of 4093 words)