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Re: [Killietalk] Emailing: Ogo wound
Let's try again. I don't think it's a bite, but rather a bacterial infection.
See this story, below:
DISEASES OF FISHES, Part 2. The Common Bacterial Fish Diseases
by Robert J. Goldstein, Ph.D. (copyright)
Almost all important freshwater and marine aquarium fish diseases are
Gram-negative. A few coldwater fish diseases are caused by Gram-positive
bacteria, but you won't see them unless you're a salmon or trout farmer. Why is this
important? It's important because antibiotics typically are effective on
Gram-positive or on Gram-negative bacteria, but not both. For example, the
penicillins and erythromycin interfere with cross-linkages of structural molecules of
the cell wall of Gram-positive bacteria, but have no effect on the walls of
Gram-negative bacteria. And the tetracyclines work on Gram-negative bacteria, but
not on Gram-positive species. People get both Gram-negative and Gram-positive
infections, so we need a broad array of antibiotics for our own public
health. However, tropical aquarium fishes are mostly infected by Gram-negative
bacteria, so penicillins, erythromycins, and similar drugs are next to useless.
Let's look at the most common aquarium fish diseases caused by
Dropsy and Sores
You've seen blood poisoning in fish. A better term is septicemia, which
means infection of the blood stream. In this disease, bacteria spread through
the tissues via the blood stream and lymphatic system to many organs, and often
shut down the kidneys and other important organs, preventing the fish from
maintaining its osmotic balance and causing it to go into shock and die.
Symptoms of a general or systemic infection in fish are sores on the body,
listlessness, and swelling (dropsy) which is the accumulation of fluids in the tissues
when the fish is no longer able to pump them out through the gills or kidneys.
Other symptoms can be localized lesions where the body is wounded from within,
develops an ulcer on the surface, then a boil which eventually breaks down
leaving an open wound. There can be abscesses inside, in all the organs,
including the liver and kidneys. The fish will not survive if the disease progresses
Lots of bacteria can cause these symptoms, but Edwardsiella has been
identified as the major cause of mass mortalities in warmwater aquaculture
facilities all over the world in both salt water and in fresh water. Edwardsiella
ictaluri has been found to cause disease in North American catfishes, walking
catfish, danio, and knifefish, and E. tarda has caused disease in catfish, carp,
salmon, flounder, eel, bass, mullet, tilapia, and yellowtail. Note that these
bacteria can affect cichlids, cyprinids, catfishes, and primitive fishes, or
just about every major group. There is no doubt that Edwardsiella species
affect aquarium fishes as well.
The treatment of choice for this and other Gram-negative bacterial
diseases is oxytetracycline in the food. The aquaculture rate is about 3 grams/100
pounds of food, and feeding the fish 1-3% of its body weight per day of
medicated food. Purchase medicated feed from a pet store or veterinarian.
Columnaris, Fin Rot, and Gill Rot
Fin rot and gill rot, and the related columnaris disease, were previously
thought to indicate infection with "myxobacteria," a vague concept. In fact,
those "myxobacteria" have been found to consist of a cluster of species in
three genera (Cytophaga, Flexibacter, Flavobacterium) of so-called yellow
bacteria because they form yellow colonies in culture. These three genera affect
coldwater, warmwater, freshwater and marine fishes, including goldfish and black
mollies. What does it look like? You've had fish hover at the surface, gills
flared, mouth open and gasping seemingly for oxygen, even coughing. There may be
mucus streaming from the gills. The changes in the gill tissues develop
slowly but inexorably and include fusion of the gill epithelium, and swelling of
the cells as the fish lose the ability to osmoregulate. The fish die of
The association of these bacteria with fin rot is less clear, and we
don't know if they are the cause of fin disease or simply secondary invaders after
the fin was damaged by a bite, a nutritional deficiency, or water pollution.
How do you treat this disease? Surprisingly, the treatment is simplicity
itself. For freshwater fishes, place the fish in a 1-5% sodium chloride dip
for one or two minutes. Or, put the fish in sea water until it shows signs of
distress, but no more than three minutes.
In classic columnaris disease, the fins seem to gradually erode down to
the nubs, and open sores develop on the body, growing until they penetrate all
the way to the body cavity. The causative agent has been called Chondrococcus
columnaris, Flexibacter columnaris, and today, Cytophaga columnaris. A marine
species causing columnaris disease is named Cytophaga maritimus.
Columnaris can be treated with medicated foods, or with nitrofurans or
copper in the water. Choices abound, but what is most promising is the
development of a vaccine consisting of infection with a harmless bacterium (Cytophaga
freundii) that confers immunity.
This is worse than it sounds. The genus Vibrio is made up of many species
of Gram-negative curved rods, the vast majority of them marine, but a few in
fresh water. Two examples are Vibrio comma, which causes cholera in man, and
Vibrio vulnificus, which is normally a fish pathogen but which can can kill an
immunodeficient person who is scratched or eats raw oysters.
Mostly the cause of marine fish diseases in aquaculture, Vibrio
anguillarum, V. ordali, V. damsela and several other vibrios can form hemorrhagic
lesions in the mouth, on the skin, around the eye, or inside within the muscles.
The wound on skin looks like it has a black ring around an inner white ring,
with a deep hole in the tissue in the center. Vibrios need iron. They secrete a
toxin which causes the blood cells to liquify and then absorb the iron from the
tissues and surrounding juices.
Despite the large number of ubiquitous species, pathogenicity is
uncommon, and is passed to offspring most often via plasmids. It can also be
transmitted across species lines by transfer of the plasmids by viruses. The species of
Vibrio is less important than whether it carries the plasmid conferring
The only treatment is a Gram-negative specific antibiotic in the food,
but this is difficult to administer because infected fish soon stop eating.
Nonetheless, it's worth a try, at least to save all the other fish in the same
water. Oxytetracycline, oxolinic acid, and sulphonamides are all effective at
times, but the best control is good water quality, avoidance of crowding, quick
disposal of fish with these symptoms, and sterilization of the aquarium if
Ulcers in freshwater fishes that look like saltwater Vibrio infections
(black and white rim around a necrotic hole) are usually due to Aeromonas
hydrophila, A. sobria, and A. caviae (Inglis et al., 1993). These Gram-negative
short rods are motile in culture, swimming with a long flagellum. The bacterium
has been isolated from fish, frogs, snails, shrimp, and alligators, and you can
bet it's in your fish tank. It is not clear whether the bacterium is a primary
cause of disease, a secondary invader, or an opportunist in either case
taking advantage of a poorly operating immune system due to parasites, stress,
nutritional deficiency, or bad water quality. The symptoms are caused by other
bacteria too, especially Pseudomonas fluorescens. In all cases caused by this
group of bacteria, the ulcers are shallow and bright red (bloody), rather than
deep and pale (in which the blood cells have been destroyed), as in the Vibrio.
Fin rot in Aeromonas and Pseudomonas infections may have brownish margins, and
dropsy may be associated with swimming or hanging sideways near the surface.
Most Pseudomonas are harmless freshwater bacteria, and they have an almost
identical marine relative, harmless or pathogenic, in the genus Alteromonas.
Medicated foods (oxytetracycline, nifurpirinol, chloramphenicol) are
useful, as is intraperitoneal injection with kanamycin, but antibiotic resistance
transmitted by plasmids is very common. Although the bacteria are usually
harmless, outbreaks of disease occur when a plasmid for pathogenicity is
introduced into the bacterial population.
Robert J. Goldstein, Ph.D.
Robert J. Goldstein & Associates, Inc.
8480 Garvey Drive
Raleigh, NC 27616 USA
tel (919) 872-1174
fax (919) 872-9214
e-mail rgoldstein at rjgaCarolina_com