Multifactorial anemia associated with leech transmitted trypanosomes in wild fishes: A comparative review

Trypanosomes are flagellated protozoan, classified under the family Trypanosomatidae and known to cause serious disease conditions in all vertebrate animals under terrestrial and aquatic environments. The ubiquitous nature of the piscine parasite, warrants several vectors to accomplish their digenic lifecycle, involving arthropods and annelids. Sleeping sickness, Nagana, Chagas disease, Surra, Dourine, Mal de Caderas, Avian and Piscine trypanosomosis are associated with man, cattle, camels, horses, birds and fishes respectively, with tsetse flies, mosquitoes and leeches identified as respective vectors. Anemia, nervous disorders, abortion and loss of condition are principal pathologic manifestations. Hemolytic anemia is common to all species, due to accelerated erythrocyte destruction. However, in fish, other salient factors predispose and complicate the anemia observed. Anemia from heavy leech blood meal, and severe bleeding at the site of bite constituted multifactorial nature in fish. Leeches are equipped with specialized organs and biologically active substances for attachment, piercing and sucking blood from the host with mild pain sensation. These factors are considered and compared with trypanosomosis in other animals.