Re: [Killietalk] Emailing: Ogo wound

[Rjga at aol_com]

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 
Gram-negative bacteria. 

    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 
this far. 

    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 
suffocation.

    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.

    Ulcerative Necrosis 

    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 
pathogenicity. 

    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 
possible. 

     
    Hemorrhagic Septicemia
    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.
Environmental Consultants
8480 Garvey Drive
Raleigh, NC 27616 USA
tel  (919) 872-1174
fax (919) 872-9214
URL   www.rjgaCarolina.com
e-mail  rgoldstein at rjgaCarolina_com