Relationship of Leeches and Blood Parasites

Leeches are a group of organisms belonging to the class Hirudinea within the phylum Annelida, with over 650 species that can live in marine, freshwater, and terrestrial environments. Some predatory species among them feed by consuming other Annelida species, various invertebrates, snails, and insect larvae. Most leeches, however, are ectoparasites that primarily feed on the blood of vertebrates and mammals, including fish, frogs, turtles, snakes, snails, and crustaceans. A small number of leech species are known as "medicinal leeches" and have been used for therapeutic purposes from the past to the present. It is known that leeches can transmit a large number of viral and bacterial agents during their blood-sucking feeding, and it has also been reported that they are vectors of many Trypanasoma species seen in fish and blood parasites such as various Haemogregarina and Haemococcidios. The presence of ricketsial agents such as Bartonella spp. and Ehrlichia spp. has also been shown in various molecular studies. Until now, the studies about leeches as vectors of blood parasites are not at a adequate level. Therefore, in this review, it is aimed to present the information and the results of some laboratory studies performed so far in order to shed light on the studies to be carried out on the subject.