Comparative Epidemiology of Myxozoan Diseases

Abstract

Epidemiological studies are crucial to understand infectious diseases in both captive and free-ranging fish. Such studies on myxozoan fish parasites are rare or incomplete, owing to the complexity of myxozoan life cycles, confounding environmental factors and difficulties of data collection. Here we discuss how epidemiological data can be gathered for myxozoans and then compare the epidemiology of seven economically and/or ecologically important myxozoan species: Myxobolus cerebralis; Ceratonova shasta; Tetracapsuloides bryosalmonae; Henneguya ictaluri; Enteromyxum leei; Kudoa thyrsites; and Parvicapsula pseudobranchicola. These species were selected due to their representation in the literature, breadth of habitats and range in life histories. Specifically, we synthesise epidemiological information in relation to: life cycles; habitat types; distribution; fish host disease characteristics; actinospore and malacospore prevalence in water, infectivity and longevity; parasite transmission modes; infection prevalence and mortality in invertebrate and fish hosts; seasonality and environmental and biotic factors. We also consider available treatment and control strategies and how progress may be made in understanding myxozoan epidemiology by incorporating new research approaches.