14
CARL J. SINDERMANN
hoferi-which is discussed in detail in various sections of this paper,
fungus diseases of marine fishes are almost unknown.
Half a century of sporadic study in Europe and North America
has provided evidence that one of the most serious fungus pathogens
of fishes, marine or fresh water, is Ichthyophonus hoferi. Systemic
infections, found in mackerel in England (Johnstone, 1913 ; Sproston,
1944), rainbow trout in Germany (Plehn and Mulsow, 1911), herring
and mackerel in Canada (Sindermann, 1958), can result in widespread
mortalities in these arid other species. Epizootics of the disease are
characteristic of herring, Clupea harengus, of the western North
Atlantic (Cox, 1916; Fish, 1934 ; Scattergood, 1948). Six such outbreaks
have been reported since 1898 (Sindermann, 1963). Drastic reduction
in herring abundance due to disease has been documented, and the
postulation made that this disease may be the most important single
limiting factor to population growth of herring in the western North
Atlantic.
Whether a single species, or a complex of related forms (Schaperclaus, 1953b ; Sprague, 1965), Ichthyophonus is known as a menace to
aquarium fishes in Europe (Lederer, 1936), as an introduced pathogen
in trout hatcheries of western United States (Rucker and Gustafson,
1953), as a long-recognized pathogen of wild salmonids in western
Europe, and as a pathogen of many other marine and fresh-water
fishes. Reichenbach-Klinke (1954, 1955a) has assembled a list of more
than 80 species that have been found to be infected by the fungus.
The disease is systemic, with foci of infection in the heart, viscera
and lateral somatic muscles (Fig. 3). A simple sequence of life history
stages, described from herring (Sindermann and Scattergood, 1954),
involves multiple germination of heavy-walled spores, hyphal invasion
of host tissues, formation of " hyphal bodies " and sequential germination of these entities. The disease has been reported in Atlantic herring
in chronic and acute phases. Acute infections were characterized by
massive tissue invasion, necrosis and death within 30 days. Chronic
infections exhibited cell infiltration, progressive connective-tissue
encapsulation of spores and accumulation of melanophores. The
disease was rarely arrested completely, however, and deaths occurred
in most fish within six months. During the most recent epizootics,
infections averaged about 25% of all herring sampled, and many cases
were acute. Enzootic prevalence was usually well under 1% and
infections during this phase have been chronic in all cases examined.
Transmission of the disease has been achieved by feeding massive
spore doses, derived either from cultures or from diseased fish. Increase
of experimental spore doses resulted in increasing numbers of chronic
CARL J. SINDERMANN
hoferi-which is discussed in detail in various sections of this paper,
fungus diseases of marine fishes are almost unknown.
Half a century of sporadic study in Europe and North America
has provided evidence that one of the most serious fungus pathogens
of fishes, marine or fresh water, is Ichthyophonus hoferi. Systemic
infections, found in mackerel in England (Johnstone, 1913 ; Sproston,
1944), rainbow trout in Germany (Plehn and Mulsow, 1911), herring
and mackerel in Canada (Sindermann, 1958), can result in widespread
mortalities in these arid other species. Epizootics of the disease are
characteristic of herring, Clupea harengus, of the western North
Atlantic (Cox, 1916; Fish, 1934 ; Scattergood, 1948). Six such outbreaks
have been reported since 1898 (Sindermann, 1963). Drastic reduction
in herring abundance due to disease has been documented, and the
postulation made that this disease may be the most important single
limiting factor to population growth of herring in the western North
Atlantic.
Whether a single species, or a complex of related forms (Schaperclaus, 1953b ; Sprague, 1965), Ichthyophonus is known as a menace to
aquarium fishes in Europe (Lederer, 1936), as an introduced pathogen
in trout hatcheries of western United States (Rucker and Gustafson,
1953), as a long-recognized pathogen of wild salmonids in western
Europe, and as a pathogen of many other marine and fresh-water
fishes. Reichenbach-Klinke (1954, 1955a) has assembled a list of more
than 80 species that have been found to be infected by the fungus.
The disease is systemic, with foci of infection in the heart, viscera
and lateral somatic muscles (Fig. 3). A simple sequence of life history
stages, described from herring (Sindermann and Scattergood, 1954),
involves multiple germination of heavy-walled spores, hyphal invasion
of host tissues, formation of " hyphal bodies " and sequential germination of these entities. The disease has been reported in Atlantic herring
in chronic and acute phases. Acute infections were characterized by
massive tissue invasion, necrosis and death within 30 days. Chronic
infections exhibited cell infiltration, progressive connective-tissue
encapsulation of spores and accumulation of melanophores. The
disease was rarely arrested completely, however, and deaths occurred
in most fish within six months. During the most recent epizootics,
infections averaged about 25% of all herring sampled, and many cases
were acute. Enzootic prevalence was usually well under 1% and
infections during this phase have been chronic in all cases examined.
Transmission of the disease has been achieved by feeding massive
spore doses, derived either from cultures or from diseased fish. Increase
of experimental spore doses resulted in increasing numbers of chronic