Objective Fish Trypanosoma, caused by the blood parasite Trypanosoma spp., can infect both freshwater and marine fish around the world. With some sudden outbursts of fish Trypanosoma in aquaculture recently, there are huge economic losses. This article aims to summarize all available information about fish Trypanosoma in order to provide suggestions for controlling and preventing it.

Analysis  This review highlights the recent progress on studying taxonomy, prevalence, pathogenesis, and control of trypanosome. Instead of old characters for classification, molecular systematics and multi-locus gene analyses are favored. Studies in epidemiology indicate that fish trypanosomes affect a diverse array of hosts, such as Cyprinidae, Percidae, and Cichlidae, with varying levels of parasitemia leading to anemia, injuries to various organs due to the kinds of parasite species. At the same time, specific symptoms include anemia and damage to several organs. Trypanosomes may cause immunological disorders or inflammation if these processes happen with something mis-regulated, while through expressing genes like TcaCRT calcium binding proteins (Calbindin), they avoid the use of complement to attack and thus survive the attack of host's immune systems and make a difficult survival situation for the host when co-infected with other parasites. In diagnostics, conventional methods such as blood smears are being supplanted by more precise and sensitive molecular techniques, including PCR, qPCR, LAMP, and MIRA-colloidal gold rapid tests, which greatly improve detection capabilities. Even now, no effective medication and prevention approaches have been found yet. Some antimicrobial peptides can be used for controlling infection and creating new drugs for treating diseases because they are found in the bodies of mammal to enhance cellular immunity with effects like regulating iron levels and killing off parasites or bacteria (such as hepcidin).

Prospect  To learn about the entire mechanism related to parasitic agent, investigation on genome, transcriptome and so on that contain the molecular details would lead us closer to discovering some machinery that allows them to thrive in their environment and cause illness which can allow people to find the suitable targets in order to eliminate pathogen without negative side effects, making people better know this disease as well as creating necessary medical and diagnostic tools for better combating and understanding infestation. For example, some target genes can first be determined via techniques like knockout and knockdown through precise genetic manipulation using gene-edited ways (such as CRISPR/Cas9) and further suitable ones could then be produced as low-toxic effective drugs or vaccines.