Treatment and Identification of Aeromonas and Vibrio in Aquariums and PondsInformation about Aeromonas, Furunculosis, & Vibrio in fresh and saltwater. Also symptoms or manifestations of these bacterial pathogens such as Septicemia, Pop-Eye, Intestinal, swim bladder and occasionally Dropsy. |
By Carl Strohmeyer Aeromonas and Vibrio are both anaerobic gram negative bacteria with similar manifestations such as infecting wounds, gastroenteritis, as well as being the primary bacterium cause of hemorrhagic septicemia. Other manifestations may include pop-eye and Dropsy. Aeromonas is more common in freshwater while Vibrio is more common in brackish and saltwater. Aeromonas salmonicida (commonly called Furunculosis ) is a variant of Aeromonas that is more common in coldwater, often affecting Koi and Trout. Please read further for more in depth descriptions and treatment/prevention methods for each. Vibrio:  Vibrio a lactose-fermenting, anaerobic, gram-negative, and slightly curved and rod shaped bacteria, opportunistic pathogen, is found in aquatic environments. Vibrio is more common in Saltwater. This organism causes wound infections, gastroenteritis, and is a common cause of “hemorrhagic septicemia” (see the picture below in the Aeromonas section for Septicemia), where the microorganism enters the blood stream, resulting in septic shock, rapidly followed by death in many cases (about 50%).A common symptom in marine fish and brackish fish is red patches or red streaked fins, especially in Yellow Tangs and Marine Angels. Kanamycin is very effective in the high pH applications where Vibrio is usually present. Another older but useful antimicrobial for treatment of Vibrio is Triple Sulfa and it also is effective in high pH environments. Pimafix and a tea made Usnea Lichen are natural treatments that have shown some effectiveness for Vibrio. Treatment of wounds with Mebromin or a 30 minute double dose dip with Methylene Blue OR Potassium Permanganate is also useful in treatment of Vibrio. Aeromonas:  One of the most common infections in freshwater fish is caused by the rod-shaped bacteria Aeromonas, which is also a gram negative, anaerobic, lactose-fermenting bacterium.This bacterial pathogen is common in goldfish and many Tropical Fish. This bacterial infection can show itself in a wide variety of symptoms. Affected fish may have shallow or deep ulcers somewhere on the body, but may exhibit other signs such as exophthalmia (pop-eye), areas of bloody spots, and a distended abdomen. Infected fish with open sores appear to spread the disease to other fish, and sub clinical carriers may exist, shedding bacteria in their feces.  Aeromonas infections are probably the most common bacterial disease to infect Tropical Freshwater Fish. Mortality rates are often low (10% or less) and losses may occur over a period of time (2 to 3 weeks or longer). In these instances, some factor; usually stress, has caused the fish to become more susceptible to the bacteria. Common sources of stress are poor water quality, overcrowding, or rough handling. It should be also noted that since Aeromonas is anaerobic, so improving oxygen levels and circulation is important for prevention and recovery. Aeromonas (along with Vibrio in brackish and marine) are common causes of hemorrhagic septicemia, where the microorganism enters the blood stream, resulting in septic shock, rapidly followed by death in many cases. Clinical signs of aeromonas septicemia range from sudden death with high morbidity in peracute cases to superficial to deep skin lesions. Skin lesions include variously sized areas of hemorrhage and necrosis and the base of the fins. These lesions may progress to reddish to gray ulcerations with necrosis of the underlying musculature. Ulcers may be observed in conjunction with a hemorrhagic septicemia which can produce non-specific lesions and clinical signs of exophthalmos (Abnormal protrusion of the eyeball), ascites (An abnormal accumulation of serous fluid in the abdominal cavity), and visceral petechiation (Small red or purple spots on the body), and a hemorrhagic and swollen lower intestine and vent. Anorexia and skin discoloration are also observed with the septicemia.  As noted above, Aeromonas (along with Pseudomonas Bacteria which is also gram negative but is aerobic) is one of the more common causes of bacterial “pop-eye” in fish.Aeromonas can also be a factor in swim bladder or intestinal problems, especially when food is allowed to decompose on the bottom of the aquarium where fish (especially goldfish) may come along and consume it; also soaking dry foods in water prior to feeding cuts down on intestinal Aeromonas infections. Generally for Swim Bladder infections simple baths described later in this article should be the first step as well as with holding food for a couple days, and increasing mineral/electrolyte levels in the tank.  When Aeromonas goes systemic (internal) it has been shown to be a major contributor to Dropsy (which is a kind of catch all diagnosis for bloating with distended scales usually caused by kidney and sometimes liver maladies). Prevention is the key here; *Soak dry foods so as to not introduce air into the intestines which can start an aeromonas infection in the intestines (gut) and swim bladder. *Good tank parameters including GH *Use antibiotics sparingly, many have side affects on the liver and kidneys such as Neomycin and Tetracycline. Kanamycin (which is gram negative) is a better choice, although Neomycin when fed as a part of a medicated food can be useful.  Treatments of Aeromonas in tropical freshwater aquariums include: Pimafix and/or Melafix for mild infections (especially mild wound infections), Kanamycin for more serious infections (this can be combined with Nirofurazone for an even stronger combination treatment). Gel Tek Neomycin is an excellent medicated food that delivers neomycin internally to infections (although this is primarily a gram positive antibiotic, so it should be combined with a gram negative antibiotic such as Kanamycin for better results).Another antibiotic worth considering is Minocycline which is found in Maracyn Two (do not confuse this with Maracyn One which contains Erythromycin which is rarely effective for Aeromonas). Aquarium Salt or Cichlid Salt can also be added at a rate of 1 tablespoon per 5 net gallons of water as an additional treatment to those above and the baths below (however sodium chloride rarely replaces these treatments, only compliments). Please see this article for more about the use of Aquarium Salt: “Aquarium Answers; Salt in Freshwater Aquariums” For ulcerations I also recommend medicated baths of about 30 minutes using either Methylene Blue or Potassium Permanganate at double normal in tank strength using tank water for this bath, then disposing of the bath water after completion. Potassium Permanganate is the slightly better choice for external infections of Aeromonas (as it has more antibacterial properties due to oxidation properties). Methylene Blue is the better choice for internal manifestations of this bacterial pathogen such as Swim Bladder, intestinal, Dropsy or Pop-Eye due to its effectiveness in tissue penetration. In fact in Swim Bladder and intestinal Aeromonas infection the MB Bath (along with possibly 1-2 teaspoons of salt and ¼ teaspoon of Epsom salt per gallon of bath water), followed by changes in water in the main aquarium, changing diet and/or withholding food for 2 days (dry foods should be soaked for 5 minutes prior to feeding), establishing a GH level of at least 100 ppm (for Calcium, Magnesium) and 1 tablespoon of salt per 5 gallons may be all that is necessary for treatment. If this does not remedy the problem then treatment with medications such as Kanamycin and possible Neomycin based foods such as Gel Tek Neomycin Furunculosis:  In Coldwater freshwater fish the similar pathogen is Aeromonas salmonicida also known as furunculosis. Treatment in Coldwater can be difficult as many treatments are not as effective below 65 degrees F. Also Nirofurazone , which is one of the treatments of choice in coldwater is less effective at the higher pH most coldwater fish prefer.In higher pH applications Triple Sulfa and Kanamycin can also be effective. And on some strains of Furunculosis, Tetracycline has shown occasional effectiveness. Another treatment in coldwater is Oxytetracycline, which works much better if soaked in the food and is especially useful when treating the water such as in a pond is undesirable. A newer treatment preferred by many Koi keepers is KoiZyme (formally known as LymnoZyme). This is a formula of natural bacteria, enzymes, and micro nutrients that reduce the Aeromonas (and Pseudomonas) bacteria present in the water. It does not attack the bacteria directly, rather is out competes the Aeromonas bacteria for nutrients. Melafix is an organic treatment shown to be effective for Aeromonas, especially in pond applications. Treatment of wounds with Mebromin or a 30 minute double dose dip with Methylene Blue is also useful in treatment of Aeromonas. Outside reference for Furunculosis: Furunculosis and Other Diseases Caused by Aeromonas salmonicida (PDF) Summary: It is important to note that both Aeromonas and Vibrio pathogens are opportunistic bacteria that are more virulent in poor water conditions. It is important to affect a cure that water conditions are improved during treatment and not worsened by the treatment itself, which is why I do not recommend Tetracycline be used in display tank treatments of this disease as Tetracycline lowers red blood cell counts and binds calcium in the water which is essential for healing. Regular partial water changes between treatments, stable pH and a proper functioning bio filter are all essential for effective cure and prevention. I recommend good water parameters as prevention and to speed recovery during infections. Here are a few parameters to consider: *Ammonia/ Nitrites- 0 ppm * Nitrates - under 40 ppm for freshwater/ 20 ppm for saltwater *KH (Alkalinity)- 50 to 150 for freshwater (depending on the fish kept)/ 240 + for saltwater For more about prevention I recommend this article: “Aquarium Disease Prevention” Further references: http://ag.ansc.purdue.edu/courses/aq448/diseases/bacteria.htm FOR MORE AQUARIUM MEDICATION AND TREATMENT INFORMATION For more aquarium information and articles (pond too), please visit this site:   
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