Myxozoans on the Move: Dispersal Modes, Exotic Species and Emerging Diseases

Abstract

Increased global connectivity and shorter transportation times translate to a higher probability and frequency that hosts and their parasites will be introduced to foreign locations and will arrive viable. However, myxozoans are heteroxenous with two obligatory hosts and two free-living life stages, so even if a parasite is introduced, a myriad of factors must align for establishment to occur. Associated with successful introductions are ecological and economic impacts. Unless there is an established monitoring program, it is difficult to detect the emergence of a myxozoan before clinical signs become overt. In this chapter we examine features of myxozoan parasites that promote or impede dissemination and establishment. We present examples of modes of myxozoan introduction and dispersal, both natural and human-mediated. We review known and novel species responsible for emerging diseases, and recently identified species that have the potential to cause disease. We conclude by outlining strategies to understand and limit myxozoan introductions.

Proteomic Analysis of the Parasitic Cnidarian Ceratonova shasta (Cnidaria: Myxozoa) Reveals Diverse Roles of Actin in Motility and Spore Formation

“…Myxozoans (myxosporeans) are unique within the Cnidaria, in that they are spore-forming parasites whose life cycles alternate between vertebrate (mostly fish) and invertebrate (mostly annelid) hosts. They are among the most common fish parasites (Mackenzie and Kalavati, 2014); however, they can also infect other vertebrate groups such as amphibians, reptiles, birds, and even terrestrial mammals (Hallett et al, 2015;Hartigan et al, 2016b, and references therein). Transmission occurs via two types of waterborne spores: myxospores, which are produced in the fish host and infect the invertebrate host, and actinospores, which operate in the opposite direction (Wolf and Markiw, 1984;Bartholomew et al, 1997;Canning and Okamura, 2003;Lom and Dyková, 2006).…”

Molecular diagnostic based on 18S rDNA and supplemental taxonomic data of the cnidarian coelozoic Ceratomyxa (Cnidaria, Myxosporea) and comments on the intraspecific morphological variation

“…The global aquarium market moves millions of ornamental fish worldwide and is the primary mode for international transport of cnidarian myxosporean parasites (Hallett et al 2015). As such, there is a fundamental need for constant monitoring to enable diagnosis and timely control of infections by this parasite group in aquarium fish (Mathews et al 2018).…”

A new Myxobolus (Cnidaria: Myxosporea) infecting the ornamental catfish Corydoras schwartzi from the Purus River in Brazil

“…There are, however, few published surveys of myxosporeans in Amazonian ornamental fish. Thus, further studies are necessary not only to increase our knowledge of the diversity of myxosporeans, but furthermore to evaluate their pathogenicity, taking into account that the Amazon Basin is the most important source of wild-caught freshwater fishes for the global aquarium trade and considering that increased global connectivity with shorter transportation times, favor hosts and their parasites arriving in a viable state to new environments (Hallett et al 2015).…”