Tick-borne microsporidiosis: ticks as a neglected source of human microsporidian infection?

Ticks, ectoparasites of humans, domestic and wild animals, are vectors of many diseases of great economic and medical importance. Besides already known viral, bacterial and protozoan pathogens, microsporidia have also been identified. These have long been associated with serious infections in immunocompromised individuals, but also occur in immunocompetent ones, and often cause life-threatening complications of common diseases. Although food or water contaminated from wild or farm animals that serve as a reservoir for zoonotic infections is considered the main transmission route of microsporidia, the possible involvement of bloodsucking vectors has never been studied. According to the results of previous and our pilot studies microsporidia are ranked among the most common pathogens detected in Ixodes ricinus ticks in the Czech Republic and the possible involvement of ticks in the transmission of microsporidia has been suggested. Moreover, it appears that tick feeding may facilitate transmission of infection by concentrating microsporidia in sites of inflammation induced by the tick.