HOST SPECIFICITY IN MICROSPORIDIA
The host specificity of Microsporidia, obligate intracellular parasites of Metazoa and other eukaryotes (Ciliophora, Gregarinia) is analyzed in the present review. Previously it was assumed that all the species of microporidia were characterized by narrow host specificity and microsporidians from vertebrate and invertebrate hosts belonged to different taxa of the family rank or even higher ranks. In the end of the last century and in the beginning of the present century, the first evidence that microsporidia from blood-sucking mosquitoes do infect mammals and human and vice versa were obtained, together with the fact that microsporidia from warm-blooded animals are able to develop in blood-sucking arthropods. Recent studies showed that the same species of microsporidia can simultaneously infect fishes and crustaceans or humans and orthopteran insects. At present, only a single group of monophyletic narrow-specialized microsporidians of the family Amblyosporidiae is known, with the group of hosts limited to two arthropod familes: Culicidae (Diptera: Insecta) and Cyclopidae (Crustacea: Copepoda). All other phylogenetic branches include microsporidians revealed in different host species, including humans. Host variability is most diverse in representatives of the genera Anncaliia and Tubulinosema of the family Tubulinosematidae. Belonging of insect microsporidians to certain phylogenetic groups can predict their potential ability to infest humans. This circumstance must be taken into account during estimation of prospects of the use of these parasites in the control of population density of harmful arthropods, and also during the analysis of probable results of microsporidian epizooties in nature. Microsporidians developing in invertebrate and vertebrate hosts must not be treated separately in medical, veterinary, and agricultural practice.