UPDATE COMMENTARY: Acquisition of novel insights has been taking place (reflected especially in 2018 reports) in relation to where plasmodial parasites go in the mammalian body. This new understanding has led to the hypnozoite hypothesis of relapse in malaria becoming partly out of date insofar as it is now a theory that is (in the way it has been applied since 1980) too restrictive. To elucidate:
Miles Markus's blog
Was P.G. Shute’s “X Body” the same plasmodial stage that is now called a “hypnozoite”? The short answer is “No”. The malariologist who has just put this question to me has suggested that the whole reply (see below) be made available in the MalariaWorld Newsletter, considering the current topicality of the enigmatic hypnozoite; particularly in regard to the concept of malaria eradication.
As shown by the record of historical events listed in Table 1 in a recent review of biological concepts in recurrent vivax malaria, the question of a hypnozoite-independent, non-circulating origin(s) of recurrences was first raised approximately 7 years ago. (Link to the paper and Table 1 [click here]). More specifically, parasites in bone marrow as a possible contributing source are discussed in this 2018 article, the matter having initially been debated in a 2017 publication cited therein.
Aspects of the eradication-related parasitology of this topical subject are covered in a 2018 paper that has been published online. It is "in press" for a special journal issue. (Link to the article [click here]).
The occurrence of Plasmodium vivax in bone marrow/spleen has been reported by various authors (including Baro, del Portillo, Lacerda, Marti, Obaldia, Siqueira and Wirth). It is not apparent from the title, but some of the implications hereof are discussed in the 2017 article on “Malaria Eradication and the Hidden Parasite Reservoir” (click here).
A new blood-stage parasite question has arisen. Are erythrocytic forms in bone marrow/spleen part of the hidden Plasmodium vivax reservoir? Do they cause or contribute to renewed or increased peripheral parasitaemia? (Link to the article on the subject [click here]).
What has happened to various hypnozoite-associated (in one way or another) personalities from the late 1970s and the 1980s, when the malarial hypnozoite was "accidentally" discovered, is not widely known. People occasionally enquire about these individuals. Some, such as M.R. Hollingdale, R.E. Sinden, G.A.T. Targett and M.B.
Are hypnozoites the only source of relapse-like, recurrent Plasmodium vivax malaria? They might not be. See explanation here [click] (however, note from the website link provided in a response to the blog, the new angle re erythrocytic parasites that was published online on 30 March 2017).
When analysing results obtained in genetic epidemiological studies, how can homologous recurrences of Plasmodium vivax malaria be explained? Link to a blog on the subject [click] (but see, via the website given in one of the blog responses, the new analysis concerning erythrocytic parasites that was published online on 30 March 2017).