Among all species of leeches, only true leeches especially jawed leeches are known to attack humans. These
species are either freshwater or land dwellers. Freshwater leeches of medical importance may be divided
into two groups: leeches which attack the mucous membranes (endoparasites), and those that attack
the skin (ectoparasites). Some species of the former group have been incriminated in causing halazoun,
while many species of the latter group were used in bloodletting. Leeches may be potential transmitters of
human pathogens. The land leeches are much less fearsome than the aquatic leeches. However, the harm
which land leeches cause to man and his domestic animals may be such that some infested foci become
almost uninhabitable. This review summarizes current knowledge on the public health significance of
true leeches as human parasites and their medical uses, and the recommended methods of prevention
and control.