Aquatic animal models of human disease

Abstract

The study of disease is, at its core, the study of abnormal structure and function spanning levels of organization from molecules to cells to tissues to organisms (and including populations and ecosystems in the disciplines of epidemiology and epizootiology). Fish and invertebrates from marine and freshwater environments have long provided valuable models for the study of basic biological processes. Some of the earliest studies of non-self recognition and phagocytosis were conducted using sea urchins (leading to the 1908 Nobel prize for Mechnikov) while the principles of signal propagation in axons were elucidated from studies of the giant axon of squid (leading a Nobel prize in 1963 for Hodgkin & Huxley). Aquatic invertebrates and fishes have proved to be valuable model organisms based on specific physical features, such as giant axons, as well as by providing an evolutionary perspective on structure and function in higher vertebrate systems. Less recognized, however, are the contributions that these organisms have made to the study of disease. Historically, such studies have tended to fall into two very broad categories, natural versus laboratory experiments. Natural experiments are those in which spontaneously occurring disease states are discovered in wild or laboratory animal populations as a result of injurious environmental factors, infectious agents and/or mutations. Outbreaks, or epizootics, of these diseases often serve as a first warning of serious environmental problems, such as when flatfish with liver tumors were found in high numbers in Eagle Harbor in the Puget Sound area of Washington State, USA (Myers et al, 2003). This observation led to the detection of high levels of polycyclic aromatic hydrocarbons in sediments at this site, resulting in the designation of the harbor as a “superfund site” and the eventual remediation of the toxic sediments. In laboratory experiments disease states are induced under controlled circumstances, often in an attempt to determine the causes and mechanisms of spontaneously occurring diseases or to evaluate the potential injurious effects of toxins or drugs. Disease research on aquatic animals involves a wide variety of disciplines such as physiology, pathology, toxicology, immunology, microbiology, embryology, molecular biology and genetics working and a wide phylogenetic range of organisms. To bring together investigators working in such varied fields of disease research, a series of meetings focusing on use of aquatic organisms as models of human disease was begun in 2000. This special issue of Comparative Biochemistry and Physiology contains 16 manuscripts from a conference entitled “Aquatic Animal Models of Human Disease” held from September 29 to October 2, 2005, at the University of Georgia, Athens, Georgia. This volume joins similar special issues developed from the two previous meetings in this series held in 2000 and 2003 (Walter 2001; Schmale, 2004). The studies presented in this volume demonstrate that fish models can be used to investigate a wide range of disease related questions and can provide unique models for human disease processes.