DISEASES O F MARINE FISHES
11
seems little doubt, however, that a common infectious agent is involved
in many of the outbreaks reported, since Vibrio anguillarum has been
isolated repeatedly (Bergman, 1909; Schaperclaus, 1927 ; Nybelin,
1935b). Two types, A and B, of the Vibrio have been identified, and a
toxin has been demonstrated. V . anguillarum has also been found to be
pathogenic to cod and plaice (Dannevig and Hansen, 1952; Bagge and
Bagge, 1956; Ljungberg, 1963), pike (Schaperclaus, 1928; Ojala, 1963),
and trout, Salmo trutta L. (Smith, 1961).
Other Vibrio diseases of marine and fresh-water fishes have been
reviewed by Rucker (1959). He suggested that Vibrio infections may
be much more prevalent than had been previously recognized, pointing
out as examples that Vibrio infections often kill Pacific herring,
Clupea pallasi Val., held as live bait, and that a study by Biickmann
(1952) disclosed that almost half of a sample of 117 European plaice
had natural Vibrio infections.
Bacterial dermatitis, sometimes accompanied by ulcerations and
fin rot and usually associated with Pseudomonas, has been reported
from wild populations of marine fishes. Pseudomonas ichthyodermis
infections have been observed by Wells and ZoBell (1934), ZoBell and
Wells (1934), and Hodgkiss and Shewan (1950). ZoBell and Wells
reported evidence of the infection in killifish, Fundulus parvipinnis
Girard, in their natural habitat on the Pacific Coast, and stated that
90% of these fish died of the disease when brought into aquaria during
the summer. Other species, such as gobies, Gillichfhys mirnbilis Cooper,
blennies, Hypsoblennius gilberti (Jordan), and smelt, Atherinops afinis
(Ayres), also exhibited lesions. Characteristics of the disease included
an initial whitish spot on the body surface which expanded rapidly,
disintegration of melanophores, raising and sloughing of scales, minute
hemorrhages and death. Smears from lesions revealed almost pure
cultures of Pseudomonas ichthyodermis, but there was no evidence of
systemic invasion, nor could the organism be demonstrated in the
blood. Reinfections from cultures were made repeatedly; initial lesions
occurred within 18 hours and death within 14 days. Mortality of fish
infected from cultured pathogens was not as high as that of fish infected
directly with material from lesions. The pathogen was described as a
motile, Gram-negative, non-spore-forming, halophilic bacillus, with a
temperature optimum for infectivity, growth and virulence in the
region of 20°C. A significant finding was that fish kept in water above
30°C did not become infected and that badly diseased fish recovered
rapidly if acclimated successfully to water of 32-35OC.
Hodgkiss and Shewan (1950) described an intramuscular lesion in
plaice and obtained presumptive evidence that Pseudomonas ichthyo-
11
seems little doubt, however, that a common infectious agent is involved
in many of the outbreaks reported, since Vibrio anguillarum has been
isolated repeatedly (Bergman, 1909; Schaperclaus, 1927 ; Nybelin,
1935b). Two types, A and B, of the Vibrio have been identified, and a
toxin has been demonstrated. V . anguillarum has also been found to be
pathogenic to cod and plaice (Dannevig and Hansen, 1952; Bagge and
Bagge, 1956; Ljungberg, 1963), pike (Schaperclaus, 1928; Ojala, 1963),
and trout, Salmo trutta L. (Smith, 1961).
Other Vibrio diseases of marine and fresh-water fishes have been
reviewed by Rucker (1959). He suggested that Vibrio infections may
be much more prevalent than had been previously recognized, pointing
out as examples that Vibrio infections often kill Pacific herring,
Clupea pallasi Val., held as live bait, and that a study by Biickmann
(1952) disclosed that almost half of a sample of 117 European plaice
had natural Vibrio infections.
Bacterial dermatitis, sometimes accompanied by ulcerations and
fin rot and usually associated with Pseudomonas, has been reported
from wild populations of marine fishes. Pseudomonas ichthyodermis
infections have been observed by Wells and ZoBell (1934), ZoBell and
Wells (1934), and Hodgkiss and Shewan (1950). ZoBell and Wells
reported evidence of the infection in killifish, Fundulus parvipinnis
Girard, in their natural habitat on the Pacific Coast, and stated that
90% of these fish died of the disease when brought into aquaria during
the summer. Other species, such as gobies, Gillichfhys mirnbilis Cooper,
blennies, Hypsoblennius gilberti (Jordan), and smelt, Atherinops afinis
(Ayres), also exhibited lesions. Characteristics of the disease included
an initial whitish spot on the body surface which expanded rapidly,
disintegration of melanophores, raising and sloughing of scales, minute
hemorrhages and death. Smears from lesions revealed almost pure
cultures of Pseudomonas ichthyodermis, but there was no evidence of
systemic invasion, nor could the organism be demonstrated in the
blood. Reinfections from cultures were made repeatedly; initial lesions
occurred within 18 hours and death within 14 days. Mortality of fish
infected from cultured pathogens was not as high as that of fish infected
directly with material from lesions. The pathogen was described as a
motile, Gram-negative, non-spore-forming, halophilic bacillus, with a
temperature optimum for infectivity, growth and virulence in the
region of 20°C. A significant finding was that fish kept in water above
30°C did not become infected and that badly diseased fish recovered
rapidly if acclimated successfully to water of 32-35OC.
Hodgkiss and Shewan (1950) described an intramuscular lesion in
plaice and obtained presumptive evidence that Pseudomonas ichthyo-