It is conventionally assumed that malarial relapse is caused by hypnozoites, via schizogony in hepatocytes. In regard to malaria (as opposed to other diseases), the word “relapse” is nowadays used to refer specifically to renewed parasitemia and illness that originates from presumed hypnozoites in the liver.
A valid alternative term for “hypnozoite” is “dormozoite”. However, it is the former word that has become ubiquitous in the literature; and consequently, use of the name “hypnozoite” is preferable.
The apicomplexan hypnozoite was discovered by Mehlhorn and Markus (1976), when electron microscopy revealed the sporozoite-like nature of a known and apparently dormant extraintestinal stage of Cystoisospora (synonym: Isospora), an organism closely related to Plasmodium. It was a few years later that plasmodial hypnozoites were recognized for the first time, in the laboratory of W. A. Krotoski in New Orleans, USA. These were hypnozoites of the relapsing simian...
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