Plasmodium ovale is a tiny parasite that infects humans through the bite of a mosquito.
Plasmodium ovale is a microscopic, one-celled parasitic animal, one of the four species of protozoa that are responsible for malaria, a disease that continues to cause widespread illness and death around the world. These tiny creatures can be introduced into the bloodstream of humans only through the bite of a female Anopheles mosquito that has picked up the protozoan in feeding upon an infected vertebrate.
Significance
Plasmodium ovale protozoa are seen throughout sub-Saharan Africa, as well as some islands in the western Pacific. In a July 2005 article for Clinical Microbiology Reviews, William E. Collins and Geoffrey M. Jeffrey of the Centers for Disease Control and Prevention said there also have been reports of the protozoa on the mainland of East Asia. Another CDC report, in the Jan. 11, 2006, issue of the Journal of the American Medical Association noted that Plasmodium ovale is the second most common cause of malaria in Nigeria, Africa's most populous nation.
Incidence in the United States
Malaria, caused by all four species of Plasmodium protozoa, is not widely diagnosed in the United States, according to the CDC. Of the roughly 1,300 cases diagnosed each year, virtually all of them are seen in people who have traveled recently to tropical areas where malaria is endemic. The CDC estimates that Plasmodium ovale accounts for only 2.3 percent of all U.S. diagnoses of malaria.
Function
Although all four forms of malaria are serious, the ovale strain of the disease is perhaps the mildest. After a bite from an infected mosquito, the protozoan usually travels through the bloodstream to the liver, where it gathers strength before causing systemic symptoms. It takes 12 to 20 days for the protozoa to establish itself sufficiently in a victim's system so that it can be diagnosed by blood cultures. However, even after the incubation period, ovale protozoa sometimes stay dormant in the liver for weeks or months before triggering an acute attack.
Symptoms
The classical malaria attack of chills, followed by fever, and ending with intense sweating as the fever breaks is rarely seen these days, according to the CDC. Instead, patients generally report a combination of symptoms that may include any of the following: body aches, general malaise, fever, chills, sweating, nausea, vomiting and headaches. In the United States and other countries where the disease is uncommon, the symptoms sometimes are misdiagnosed as influenza. Patients with ovale malaria may experience relapses months or even years after they recover from an initial attack.
Identification
Until recently the only way to definitively diagnose malaria was through microscopic inspection of a blood sample. This method of diagnosis remains the most widely used. However, in 2007 the U.S. Food and Drug Administration approved the Binax NOW malaria test that can produce a diagnosis within 15 minutes. Only a few drops of blood are needed for the test, which has an accuracy rate of 95 percent, according to the FDA.
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