Propagation of Encephalitozoon cuniculi in tick cell lines supports the plausibility of possible tick-mediated transmission of this microsporidian

Microsporidia, obligate intracellular parasitic fungi, are increasingly associated with asymptomatic infections. One of the most prevalent zoonotic species, Encephalitozoon cuniculi, has been detected in Ixodes ricinus ticks. Nevertheless, the capacity of microsporidia to replicate within tick hosts remains unresolved. We used tick cell lines IRE11, IRE/CTVM19 and IRE/CTVM20 along with mammalian line Vero E6 for in vitro testing of E. cuniculi propagation. We evaluated the spore number using quantitative RT-PCR and documented the presence of microsporidia in host cells microscopically. We reported successful growth of Encephalitozoon cuniculi in tested tick cell lines, with IRE/CTVM19 providing the most suitable conditions for E. cuniculi propagation, reaching up to 1459 % increase of the inoculum. Moreover, the parasitophorous vacuoles containing developmental stages of microsporidia were observed in all cell lines. Our data support the plausibility of tick-mediated transmission, providing novel insights into the epidemiology of microsporidia.