Trans-sialidase and sialidase activities discriminate between morphologically indistinguishable trypanosomatids

The expression of trans-sialidase and sialidase activities in the kinetoplastid protozoa was explored as a potential marker to discriminate between the morphologically indistinguishable flagellates isolated from human, insects and vertebrate reservoir hosts. By virtue of the differences observed in the ratios of these enzyme activities, a collection of 52 species and strains comprising the major taxa of these parasites could be separated into four expression types. Type-I parasites express comparable levels of both trans-sialidase and sialidase activities (Endotrypanum species and Trypanosoma lewisi). Type-II parasites express predominantly trans-sialidase activity (Trypanosoma cruzi and Trypanosoma conorhini). Type-III parasites express sialidase activity exclusively (Trypanosoma rangeli and Trypanosoma leeuwenhoeki). Type-IV parasites do not express either activity (Leishmania species and Trypanoplasma borreli). The measurement of trans-sialidase and sialidase activities thus permits the differentiation of parasites frequently found in the same insect vectors that are difficult to distinguish, such as T. cruzi and T. rangeli, or in the same sylvatic vertebrate and invertebrate hosts, such as Leishmania and Endotrypanum.