Trypanosomatids Are Much More than Just Trypanosomes: Clues from the Expanded Family Tree

• Published in: Trends in parasitology Vol. 34; no. 6; pp. 466 - 480
• Main Authors: Lukeš, Julius, Butenko, Anzhelika, Hashimi, Hassan, Maslov, Dmitri A., Votýpka, Jan, Yurchenko, Vyacheslav
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-06-2018
• Subjects: diversity; endosymbiosis; phylogeny; trypanosomatids; virus; trypanosomatids; phylogeny; diversity; virus; endosymbiosis
• ISSN: 1471-4922; 1471-5007
• DOI: 10.1016/j.pt.2018.03.002

Trypanosomes and leishmanias are widely known parasites of humans. However, they are just two out of several phylogenetic lineages that constitute the family Trypanosomatidae. Although dixeny – the ability to infect two hosts – is a derived trait of vertebrate-infecting parasites, the majority of trypanosomatids are monoxenous. Like their common ancestor, the monoxenous Trypanosomatidae are mostly parasites or commensals of insects. This review covers recent advances in the study of insect trypanosomatids, highlighting their diversity as well as genetic, morphological and biochemical complexity, which, until recently, was underappreciated. The investigation of insect trypanosomatids is providing an important foundation for understanding the origin and evolution of parasitism, including colonization of vertebrates and the appearance of human pathogens.
Dixenous trypanosomatids, such as the human Trypanosoma parasites, infect both insects and vertebrates. Yet phylogenetic analyses have revealed that these are the exception, and that insect-infecting monoxenous lineages are both abundant and diverse.
Globally, over 10% of true bugs and flies are infected with monoxenous trypanosomatids, whereas other insect groups are infected much less frequently. Some trypanosomatids are confined to a single host species, whereas others parasitize a wide spectrum of hosts.
Many trypanosomatids are themselves infected with viruses and bacteria that have been acquired from insects, terrestrial invertebrates, and fungi. At least two lineages contain bacteria; these endosymbiotic events occurred independently and evolved differently.
Genomes and transcriptomes of monoxenous trypanosomatids will bring new insight into the origins of parasitism and how trypanosomes and leishmanias evolved their capacity to infect humans and other vertebrates.