Abstract
In vertebrate hosts, malaria parasites produce specialized male and female sexual stages (gametocytes). Soon after being taken up by a mosquito, gametocytes rapidly produce gametes and, once mated, they infect their vector and can be transmitted to new hosts. Despite being the parasite stages that were first identified (over a century ago), gametocytes have remained elusive, and basic questions remain concerning their biology. However, the postgenomic era has substantiated information on the specialized molecular machinery of gametocytogenesis and expedited the development of molecular tools to detect and quantify gametocytes. The application of such highly sensitive and specific tools has opened up novel approaches and provided new insights into gametocyte biology. Here, we review the discoveries made during the past decade, highlight unanswered questions and suggest new directions.
Highlights
In vertebrate hosts, malaria parasites produce specialized male and female sexual stages
Primaquine treatment can clear all gametocytes remaining after treatment with artemisinin-based combination therapy (ACT) and sulphadoxine–pyrimethamine [23]. 2008 Quantitative genotype-specific and sex-specific reverse transcriptase (RT)-PCR for P. chabaudi reveals: genetic variation for patterns of sex-ratio variation observed throughout infections; sex-ratio patterns correlate with host anaemia, and total parasite and gametocyte density; and genotypes increase their investment in male, relative to female, gametocytes in response to the presence of co-infecting genotypes
Concluding remarks Over the past decade, molecular methods have superseded traditional microscopy because they have enabled, for the first time, gametocytes at low densities to be readily quantified and gametocytes produced by parasites of different genotypes in multi-genotype infections to be distinguished
Summary
Malaria parasites produce specialized male and female sexual stages (gametocytes). Over the past decade [10], the continued development of molecular techniques has provided assays that are sensitive enough to: (i) detect and quantify gametocytes at low densities [9,11–13]; (ii) differentiate gametocytes at early and late stages of development [14]; (iii) quantify gametocytes produced by different parasite genotypes in multi-genotype infections [15,16]; (iv) determine the expression pattern of sexual-stage-specific genes [17]; and (v) distinguish between male and female gametocytes, including those produced by different genotypes in multi-genotype infections [18].
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