Aeromonas Bacteria and Koi keeping Prevention In Koi keeping, there is now a far greater reliance on treating bacterial disease, rather than preventing it.  There is no product in any bottle or syringe that is a completely safe or successful cure for any form of bacterial disease. Prevention has to be seen as the only way to control the increase in the outbreaks of bacterial infection in Koi ponds.  When a constant battle with disease is taking place in their pond any hobbyist can feel despondent, and some do consider giving up Koi-keeping.  Preventing bacterial disease is easier with an understanding of the situations in which an outbreak is most likely to occur. The list below summarises the situations that can arise in which Koi require stability and when this is denied them, disease frequently results.   CAUSATIVE FACTORS IN BACTERIAL DISEASE OUTBREAKS Unhygienic filter maintenance methods are the prime causes of the outbreaks of bacterial disease. A pond with no bottom drains or a vacuum in regular use can allow harmful bacteria to flourish. A filter in which fish waste and decaying matter is able to accrue might create health problems. Netting, bagging, transportation, and rough handling, causes stress which triggers disease. Failure to quarantine new Koi can introduce Aeromonas and other diseases. The introduction of fish from unknown origins is a risk. A low level of dissolved oxygen in a pond allows disease to flourish, and fails to support Koi metabolism and pond biology. A new pond filter that fails to mature increases all health risks. Failure to test pond water parameters can lead to disease and mortalities, particularly prolonged periods of ammonia or nitrite exposure. Fluctuations in pH and other water chemistry parameters destabilise Koi. Failing to test for chlorine or chloramine in pond water is a common issue.  A dechlorination unit removes chlorine, chloramine needs neutralising with a tap water conditioning product. Overcrowding Koi increases the risk of environmental issues and disease. Mature Koi become bonded to their pond and if moved health problems often occur. A serious parasitic infestation can debilitate Koi making them susceptible to disease. Pond construction materials, heavy metals, plant toxins, acid rain can all trigger health issues. Temperature fluctuations and the inappropriate use of heat can upset the immune response. The use of numerous chemicals in attempts to cure an unknown health problem can make the original disease or condition worse. An inappropriate diet and under feeding weakens fish and predisposes them to disease. Aeromonas Avoiding every one of the trigger factors listed is impossible.  However, it is possible to minimise instability and stress in Koi if any of the potential triggers arise.  Aeromonas is a genus of bacteria that includes many species capable of causing disease in Koi. Aeromonas salmonicida and Aeromonas hydrophila are the best-known members of the genus, but it is the latter of these organisms that most concerns Koi-keepers.  The scientific community has mixed views regarding the capacity of Aeromonas hydrophila to cause disease. Some take the view it is an opportunistic pathogen causing only secondary disease in susceptible Koi. Others see it as capable of causing primary infection in its own right.  Aeromonas is not the only potential bacterium lurking in pond water ready to cause disease, but it is the most common. It can cause disease in a pond at a water temperature as low as 5°C (41°F) although the outbreak is usually less virulent. The higher the temperature the faster the bacterium multiplies, and more signs of disease such as ulceration or reddening of the body will be observed.  In certain types of disease, outbreak losses due to septicaemia can be anticipated if the water is over 65°F /17°C. Aeromonas can multiply at an amazing rate if the temperature and conditions are conducive. In just one day, one organism could generate well over 20 million more and even 30 million in an ideal situation. The pond and Aeromonas Each new bacterium will possess genetic material, enabling it to resist the chemicals former generations of the species were exposed to in the fight to eradicate them.  It is a fact Aeromonas know how to survive and flourish as part of the normal bacterial life of every pond. Strains of Aeromonas are found on the skin as well as inside healthy Koi. However, whether or not an outbreak of disease occurs, depends on their level, the pond conditions, and how healthy the fish are. Koi cannot evade harmful bacteria and it is the Koi-keeper who keeps disease at bay by pond with good pond management. Managing the pond is a far bigger task than just its maintenance, as it covers every decision from the pond design and its construction materials to every item of equipment needed to support the fish.  In addition, management involves knowing the origins of every Koi that will live in the pond and how well they were quarantined before purchase. Avoiding the use of chemicals to keep the pond as natural as possible, and preserving its biology, are all part of the balance that Koi need and good pond managers aim to achieve. Ulceration Although Aeromonas can present in several forms, this article covers the most common form of skin ulceration.  The skin lesions are created by metabolites or waste products of the Aeromonas bacterium.  However, if the disease is caught in time before what is termed bacteraemia has developed it is possible to control an outbreak with bactericides and topical treatment.  The aim is to stop bacteria entering the body through the open skin ulcer, and applying an iodine-based product as soon as an ulcer is spotted can help to prevent this.  Once disease has become systemic and is affecting Koi internally only antibiotics are effective or the fish will not survive. However, if the disease is caught in time before what is termed bacteraemia has developed it is possible to control an outbreak. The ulcer being open means vital fluids containing electrolytes are being lost from the body, and the use of salt at ½ an ounce per gallon can help to prevent this.  In cases of large or deep ulceration, the salt level can be increased to 1ounce per (Imperial) gallon after 24 hours. If ulcers have been left untreated for weeks it may be too late for some of the fish.  However, chloramine T cannot cure internal disease but it can lower Aeromonas in the pond water as well as limit cross infection and secondary disease. Hydrophila and Sobria Aeromonas Sobria is one of several subspecies causing disease in Koi.  It is frequently isolated in bacterial cultures either alone or with Aeromonas Hydrophila. Some bacterial species work as a team cleaning up after one another, as we can trust nature never to waste a nutritional resource.  From the laboratory, perspective Aeromonas hydrophila is a gram negative - oxidase positive rod with a singular polar flagellum. This means that the outer wall of this bacterium, unlike some others, will retain a specialist stain known as Gram’s stain that colours it blue.  A further aid to identification is the confirmed presence of the enzyme oxidase. The term rod refers to the shape of the organism and the flagellum is a tail like protuberance at one end, which gives the bacterium its motility.  Aeromonas species whilst normally aerobic have the capacity to live in both aerobic and anaerobic conditions, and we call organisms that can adapt in this way facultative.  This means that the bacterium can hide in poorly oxygenated ponds or filtration systems harbouring in decaying matter and becoming a source of disease when disturbed. The pond filter As I have stated in many articles including “Antibiotics in Koi-keeping” on this web site, filter hygiene is often misunderstood. Flushing to waste for several minutes after all filter-cleaning procedures helps to prevent harmful bacteria that has been harboured in the filter and disturbed during maintenance getting into the pond. Koi do not always develop antibodies against Aeromonas species for reasons that are beyond this article, and therefore the battle against bacterial disease can become a long-term one. It is common for an infection to appear to clear up using antibiotics and bactericides yet a new outbreak occurs the following year. Koi will not withstand the prolonged use of antibiotics as their major organs can be damaged by their side effects. Resistance to antibiotics plagues all branches of medicine and is now affecting the Koi industry and hobby.  Antibiotics are more effective with a managed course of treatment rather than haphazard use. Envirex biological pond cleaner is manufactured by LFH laboratories.  It contains microorganisms and enzymes to naturally lower harmful bacteria and waste matter in ponds. This can reduce the workload for the Koi-keeper in support of pond hygiene, whilst at the same time lowering the risk of all disease including Aeromonas.  We have successfully used Envirex in our research centre that has been home to thousands of Koi for over 30 years. The way forward It is possible to have a pond free of the risk of Aeromonas and other harmful bacteria.  Such a pond will have a fully biological filter system with the capacity to support more than the volume of Koi stocked. The owner of this hypothetical pond will be aware a borderline filter system is inadequate and could give rise to poor water quality when Koi are fed more in the warmer months.  The pond will have enough water volume to allow each fish room to thrive.  Fifty inches of Koi to a thousand gallons is an old statistic that still stands the test of time, and this can be exceeded a little with additional filtration.  This same pond will be stocked from a quarantine facility never by direct introduction and it will be hygienically maintained on a regular basis.  The Koi will be well fed on quality pellets and fresh foods in the summer. Chemicals will never be used routinely, only for a diagnosed health problem. Test kits will be used regularly to ensure the water quality is optimum all year round not just in summer. Dissolved oxygen levels will also be tested, as the wise Koi-keeper realises the vital role of oxygen in the well-being of Koi, and the biology of the pond they live in.  This pond is a possibility and only healthy Koi will ever live in it. March 2016