Close this window to return to IVIS www.ivis.org Proceedings of the European Veterinary Conference Voorjaarsdagen Amsterdam, the Netherlands Apr. 22-24, 2010 Next Meeting: Apr. 27 29, 2011 - Amsterdam, the Netherlands Reprinted in IVIS with the permission of the Conference Organizers http://www.ivis.org
Reprinted in IVIS with the permission of the Organizers Part 1. Fish diseases IMost veterinarians handle fish only with knife and fork. In these four lectures I hope to interest you to start looking at fishes the most kept pet animal in a different way. Veterinarians are the persons to treat fishes. It is just as easy as treating any other (exotic) animal. The health of any animal is closely related to the health of its environment. This is even more the case with fish, where the environment plays a direct part in the levels of stress felt and their susceptibility to disease. Diseases Diseases in aquarium and pond fishes in order of importance are caused by water quality problems, parasites, bacteria, fungi, viruses and other causes like feeding mistakes, intoxications, problems of genetic origin, etcetera. Water quality problems are directly or indirectly the cause of many fish diseases. A too high level of ammonia (NH3) or nitrite (NO2-) - both are very toxic to fishes irritates the skin and gills and as a result extra mucus is formed. This irritation causes the fishes to scrape along the bottom, flash or even jump out of the water. Small wounds caused by scraping can become a port of entrance for parasites, bacteria or fungi. Too much oxygen or nitrogen may cause gas bubble disease where bubbles can be found under the skin, in blood vessels in the gills and sometimes in an eye. Parasites like the one celled ciliates Ichthyophthyrius multifiliis (ICH), Trichodina and Chilodonella can be found on the skin and gills usually separate, but sometimes more than one species is seen. Flagellates like Ichthyobodo (Costia) and Hexamita damage the skin externally and Hexamita may also cause intestinal problems. The skin worm Gyrodactylus and the gill worm Dactylogyrus are more celled parasites that irritate the skin and gills and hold onto the fish with large hooks. Larger parasites, crustaceans like Lernea, Ergasilus and Argulus (fishlouse) are visible with the naked eye and cause skin wounds with possible secondary bacterial infections. Bacteria like Aeromonas and Pseudomonas sp. are found on almost any fish. But especially when the immunity of fishes is lowered by any cause of stress these bacteria can become pathogenetic to fishes. They may even cause septicemia (seen as hemorrhages in the base of fins and all over the body). Columnaris bacteria and Myxobacteria sp.(rods) are quite frequently seen in skin scrape samples. Sometimes Mycobacteria sp.zoönotic bacteria (tuberculosis) are found. They are harmful to humans and can infect them through small wounds on hands or arms. Some Vibrio sp. are also zoönotic bacteria found in marine fishes. Always use gloves when handling fishes. The fungus Saprolegnia is seen in wounds as cotton like patches. Usually they are found secondary to another infection with parasites or bacteria and as a result of poor water quality. Viruses like Koi Herpes Virus (KHV), Spring Viremia of Carp (SVC) and Carp pox are seen in pond fishes (koi) and Lymphocystis in wild caught fishes. Mistakes in the composition of food may result in skeleton deformations. Vitamin deficiency may be caused by old food, or food not properly stored. Missing parts of fins or gill covers may be caused by a genetic defect. Husbandry Intoxication by incorrect use of a medication or from the outside like the use of herbicides or pesticides can result in mass mortality. Power failure may result in sudden death because of the lack of oxygen, lack of heat or lack of clean water from the filters. Poor husbandry like not checking the water quality regularly or not cleaning filters properly may result in fish losses. It is a mistake to think that clear water is water of good quality. Introducing new fishes without a proper quarantine period may cause illness or even death in the new or the already present fishes. 54 Abstracts European Veterinary Conference Voorjaarsdagen 2010
Scientific proceedings: companion animals programme Reprinted in IVIS with the permission of the Organizers References: 1. Andrews C, Exell A and Carrington N. The Interpet Manual of Fish Health. 2002. Interpet Ltd Dorking UK (ISBN 1-84286-067-4), 208 pp. Good information about water quality and treatments, many pictures. 2. Baily M and Burgess P. Tropical Fish Encyclopaedia. A Complete Guide to Fish Care. 2000. Howell Bookhouse New York USA (ISBN 1-58245-166-4), 352 pp. Pocketbook with information 3. Bassleer G. De Nieuwe Wegwijs in Visziekten bij tropische siervissen en vijvervissen (+DVD-rom). 2e uitgave 2006. Bassleer Biofish Westmeerbeek België (ISBN 90-807831-6-1), 232 pp. Good information, (too) many pictures. 4. Brown L. Aquaculture for Veterinarians. 1993. Pergamon Press Ltd Oxford UK (ISBN 0080408362), pp 447. Excellent book, but no longer available 5. Lammens M. De koi dokter. 2004 Own edition (ISBN 9080856614) pp 176 Good information, many photographs, published in four languages 6. Wildgoose WH. BSAVA Manual of Ornamental Fish. 2nd edition 2001. British Small Animal Veterinary Association Quedgeley Gloucester UK (ISBN 0-905214-57-9), pp 304. Excellent book with much information. levels in the water sample from the filter and the one from the aquarium or pond. When both samples contain too much ammonia or nitrite, the biofilter is not functioning properly. Then one or more partly water exchanges are necessary to improve the living conditions for the fishes. The cause must be found and dealt with. Before any medication can be put into the water, the water quality has to be optimal. ph, temperature, hardness, oxygen and nitrate level are also important parameters. External problems When an external problem is suspected a scraping sample of the skin, fins and if possible gill can be taken and looked at under the microscope at low magnification. It is quite easy: anything that moves (parasites) should not be present. Be aware of very small parasites like Hexamita and Ichthyobodo (Costia) that have the size of red blood cells. Look at the edges of the mucus for parasites. Sometimes Myxobacteria can be seen as many rods together. Most skin scrapings can be taken without sedation. Hold the fish in a net and position it with one hand. A very active fish should be sedated. Always wear gloves when handling fishes. It is less damaging to the fish skin and it prevents you from being infected with (zoönotic) bacteria. CHAPTER 2 AquARium FiSH medic ine Part 2. Examination of fish When an appointment for a sick fish is made, ask the owner to bring two separate samples of water, one directly from the (bio)filter and one from the aquarium or pond. The first approach to a fish problem is taking the history from the owner. Examination of the patient Then look at the fish for abnormal swimming behaviour, abnormal colouration, abnormal body form, frayed fins, bulging eyes, wounds, tumours, etcetera. If possible observe the fish in its own aquarium or pond. Water samples From the water samples at least the ph, ammonia and nitrite level must be measured. Ammonia and nitrite are very toxic to fishes and should not be present. There should be a difference in the ammonia or nitrite Further investigation Other methods of examination are the use of ultrasound, taking radiographic pictures, taking blood samples or taking swabs from the edge of a wound for bacterial determination. Inoculate a sheepblood agar plate.a wide range of bacteria can be found, most of them are not pathogenetic. Have the plate tested for antibiotic sensitivity (antibiogram). Poor water quality can lead to the start of a bacterial or parasitic infection. Sometimes only improving the water quality is sometimes sufficient to cure the fishes without the use of an antibiotic drug. Raising the water temperature speeds up the recovery. Is more than one fish sick and no diagnosis from external examination is found, sacrificing one or two fishes could then be necessary to get a proper diagnosis. Post-mortem Further post-mortem investigation by a specialized laboratory is needed when a bacterial or viral infection is suspected. Parasites leave dead fishes rapidly and the internal organs of a dead fish decompose quickly It therefore is advisable to bring live fish to the laboratory. When Koi Herpes Virus is suspected the laboratory needs part of a gill and kidney in 97% alcohol to perform a PCR-test. Abstracts European Veterinary Conference Voorjaarsdagen 2010 55
Reprinted in IVIS with the permission of the Organizers the head. A large fish can be injected with a pentothal solution 60 mg/kg intra-cardially. Welfare of fish is a hot item today and we have the obligation to take good care of all fishes, of a large koi as well as of a small guppy. Too often people say: my fish is dead, tomorrow I will buy a new one. Knowing that a goldfish may live up to 25 years I believe that the average age reached is only about six months. Husbandry mistakes, overfeeding, impulse buying and ignorance are the cause of too many fishes dying well before their time. Research has shown that fishes feel pain, so we should prescribe and apply analgetic medications as for any other animal. Surgery Fishes can undergo surgery. To anesthetize a fish usually a compound like Benzocaine, 2-Phenoxy-ethanol or oil of cloves can be mixed with the water. The fish is sufficiently deep under anesthesia when it does not react upon pressing the base of the tail with thumb and forefinger. Then it can be lifted out of the water and put on a wet towel with a second towel covering the head and tail. A fish can stay out of the water for two to three minutes, when kept wet. Surgery is performed to remove skin tumours, to do wound repair or to extirpate an eye. Abdominal surgery is also possible. A flow of water is sent through the mouth over the gills with a small pump or by hand with a large syringe. The fish rests on its back in a sort of foam rubber trough. When it starts to struggle it is put back in the anesthetic solution and when quiet lifted out again. Standard solution: Sedation: Anesthesia: Euthanasia: Benzocaine 50 grams in 1 liter ethanol 25 mg/l = 5 ml st.sol in 10 liter 50 mg/l = 10 ml st.sol.in10 liter 250 mg/l = 5 ml st.sol. in 1 liter 2-Phenoxyethanol 10 ml in 1 liter warm water 10 ml standard sol. in 1 liter 20 ml standard sol. in1 liter 100 ml standard sol. in 1 liter After surgery the fish is transferred to a separate tank in clean water from its own aquarium or pond. When moving the fish over a bubbling air stone it recovers in a few minutes. Four to five times overdose of anesthetic is sufficient to euthanize a fish. After about ten to twenty minutes the fish is lifted out of the water and a cut is made behind Part 3. Treatments of fish disease Water quality is the number one cause of fish disease problems. Therefore regularly checking water parameters as the ph, ammonia and nitrite levels is necessary. Clean the filters regularly and replace one quart of the water at least every 14 days. Siphon sediment and food rests off the bottom and remove sick or dead fish as quickly as possible. Parasites all have different life cycles. Some cycles are direct, from one stage to another and back to the first stage, others need one or more hosts. Some fish parasites like Ichthyobodo, Ich (White spot) and Chilodonella are more harmful than others like Trichodina. The condition of the fish as well as the number of parasites seen in a skin or gill scraping sample are important. Not every parasite or bacterium has to be killed, because a healthy fishes in good condition always carry some bacteria and parasites without causing them any harm. Eggs from parasites are usually not affected by anti-parasitic medications. Therefore egg laying parasites like Dactylogyrus (gill worm) need repeated treatments. From the White spot parasite only the free swimming stages of the parasite are susceptible to anti-parasitic drugs. To speed up the life cycle of ICH the water temperature can be raised to about 29ºC, if possible. Ich parasites irritate the fish and a device should be put in the pond or the aquarium to facilitate the fishes to rub themselves against it to remove some of the mucus and parasites. Increasing the water flow makes it more difficult for the free swim- 56 Abstracts European Veterinary Conference Voorjaarsdagen 2010
Scientific proceedings: companion animals programme Reprinted in IVIS with the permission of the Organizers ming stages to attach to a fish. These three methods can help to eliminate the parasites besides the use of a medication like FMC, salt or formalin. Most ciliate and flagellate infections can be treated with FMC (a combination of 1 liter formalin + 3.5 grams malachite green + 3.5 grams methylene blue) dosage 1 ml in 50 liters water, or sea salt (iodine free salt) 3-5 grams/ liter or formalin 0.2 ml/l 30 minutes in a separate tank (aerate extra). Raising the water temperature to 28ºC will kill Chilodonella parasites. The internal parasite Hexamita can be treated with metronidazole 7.5 mg/liter three times every third day. More celled organisms like Gyrodactylus and Dactylogyrus can be treated with praziquantel 20 mg/l bath 45-90 minutes, sea salt 5 grams/l or 30 grams/liter 2 minutes or with formalin 0.3 ml/l 30 minutes (aerate extra). Treatment for Dactylogyrus must be repeated (eggs). The larger parasites Ergasilus, Argulus and Lernea can be treated with Lufuron (a flea killer). Crush 1 tablet 499 mg (large dog) and mix in 3750 liter water or acetic acid 1-2 ml/l 30-40 seconds dip 4 times every other day. It kills all crustacea. Some medications like formalin are more toxic in soft water with a high temperature and a low ph. Preferably use pure substances when a bath treatment is necessary. Internal parasites like Ligula can be treated with Praziquantel 5 mg/kg fish orally, repeat after 2 weeks. Capillaria and Camellanus with a Levamisole bath 3-5 mg/l, repeat after two weeks. Metronidazole is used against internal Hexamita: 30 mg/kg fish 5 days in food. Bacterial infections should be treated according to an antibiogram. Sometimes more than one bacterium sp. is present. Most of them are not pathogenetic. In that case do not use an antibiotic, but improve the water quality and try to find out where the bacterial infection came from. Using an antibacterial medication in the water may help killing bacteria in skin wounds or ulcera. Preferably this should be done in a separate tank with better observation possibilities of the fishes. Catching and injecting is easier and less bath medication and less water for changes is needed. The healing of a sick fish from a pond improves considerably in water with a higher temperature. An antibiotic drug can be mixed in the food as long as the fish will eat. Larger fishes can be injected. Examples of antibiotic medications are oxytetracyclin, florfenicol, trimethoprim sulfa and flumequine. These substances and also formalin and malachite green can kill bacteria in the biofilter. Filters should then be isolated and not be reconnected until after the medication has been removed from the water. Do not stop the water flow through a biofilter. FMC is used against a fungus infection like Saprolegnia. But usually improving the water quality will have the infection disappear without the use of a medication. No treatment against virus infections is possible. Some countries use a vaccine against Koi Herpes Virus, but the use of live vaccines in this country is not allowed. Problems like gas bubble disease can be prevented by decreasing the flow of oxygen into the water or checking defective pumps sucking false air. Deficiencies in the food are not easily discovered. All medications are potentially toxic substances and overdoses can kill fishes. Lower vertebrates and some plants are more susceptible to medications than most fishes. Treating sick fishes in a marine or fresh water aquarium with many different species of animals, lots of plants and many hiding spots may be impossible unless the affected fishes can be caught and treated in a separate tank. In order to reduce the use of antibiotic medications in fishes it is sometimes possible to treat a fish disease problem by raising or lowering the water temperature or the ph. Reducing the amount of food or even to withholding it for a few days may also help. Exchanging half of the water for some consecutive days or a few times a week helps to improve the condition of the fishes. Surgery can be performed on a fish that floats upside down with a swim bladder problem. Sterile quartz gravel is put into the abdomen to counterbalance the fish. CHAPTER 2 AquARium FiSH medic ine Abstracts European Veterinary Conference Voorjaarsdagen 2010 57
Reprinted in IVIS with the permission of the Organizers Part 4. Prevention of fish diseases We have discussed fish diseases in part 1, examination of fishes in part 2, treatments of fish disease in part 3 and now we have a look at the prevention of fish diseases. Actually this is the most important part. The aquarium and water quality First of all the aquarium or the pond must not be too small. It is easier to maintain a good water quality in a large volume of water than in a small tank. Another important fact is that everything in a pond or aquarium grows or increases. Plants grow, fishes grow, waste products increase. Fish hobbyists like to see many fishes, so when one or more fishes have died they are tempted to buy more new fishes than just one. The pond or aquarium itself and the filtration system however do not grow and that can result in a filtration problem. All filtration systems should have an overcapacity to remove the toxic substances ammonia and nitrite from the water. Ammonia is excreted for 95% by the gills and with oxygen and Nitrosomas bacteria it oxidizes into nitrite. Nitrite with Nitrobacter bacteria is oxidized into nitrate. Nitrate is less toxic and is used as food for plants. Regularly check the water for the presence of ammonia or nitrite. A normal ph is between 7.5 and 8.5, ammonia 0, nitrite 0, nitrate maximum 20 mg/l. Oxygen level at least 6 mg/l. Aquarium and pond water should not be too soft or too hard to provide a buffering capacity. Clear water does not indicate that the quality is good. It may contain invisible toxic substances. The fish population in the pond or aquarium should not be used as a yardstick to determine the water quality. Test the water parameters. In a very warm summer bacteria in the biofilter need extra oxygen to survive; do not just aerate the pond, but also the biofilter. Cleaning filters properly is necessary because large waste particles can obstruct the water flow through the filter and the filtration process stops. Too much water pressure when cleaning the filter may flush the filter bacteria. It takes a long time to have them grow back again in sufficient numbers. Number of fishes How many fishes can be kept in an aquarium or pond? 10 Cm fish length (without the tail) in 50 liter, 100 cm fish in 1000 liter. Or 500 grams fish per m2, in 50 cm deep water with a good functioning biofilter. Koi: one adult koi (40 cm) in 1000 liter, one jumbo koi (70 cm) in 2000 liter. New aquarium syndrome Be aware of the so called new aquarium syndrome when starting a new aquarium or pond filter. When many fishes are put in an aquarium or pond before the biofilter is functioning properly these fishes can die within a few days due to ammonia or nitrite intoxication. To start a biofilter a small amount of food and a few small hardy fishes can be put in the water and the bacteria in the biofilter will start to grow and duplicate. This process may take from three weeks to six months, depending on the water temperature. Ammonia is produced first, a few weeks later nitrite is formed and finally nitrate is present. When nitrate can be measured the biofilter functions properly and until that time no new fishes should be put into the aquarium or pond. Do not put too many fishes at once in the water, the biofilter bacteria cannot cope at once with the extra load of waste material. Exchange part of the water every two weeks to remove a surplus of nitrate and to replenish the evaporated water. Water testing should be done more frequently (at least the ph, ammonia and nitrite levels) when new fishes are introduced or after cleaning the filters. Introduction of new fishes New fishes should be kept at least two to three weeks (koi at least six to eight weeks) separately in a quarantine tank. This tank must not have any contact with the show aquarium or garden pond. The tank should have the size of a small pond or aquarium with a biofilter plus the possibility to increase the water temperature to about 29ºC, an airstone and it should have a hiding place made of a polystyrene plate partly covering the water surface, plus a net to prevent the fishes jumping out of the tank. Observe the fishes frequently, especially at feeding time. After a week some water from the aquarium or pond can be added to the quarantine tank, observe the fishes then extra. Should a problem arise it can be dealt with quicker and more easily. Use separate nets and filter material so no infections can be transferred from one location to the other. Even a few drops of water on your fingers can infect other fishes. Clean and disinfect nets and other used materials when a disease has been diagnosed. When a fish shows abnormal behaviour try to catch it and put in a separate treatment tank. As long as the 58 Abstracts European Veterinary Conference Voorjaarsdagen 2010
Scientific proceedings: companion animals programme Reprinted in IVIS with the permission of the Organizers quarantine tank is not used this tank can be used to host a sick fish. The size of the tank should be so large that at least three of the biggest fishes can be kept in there for a number of weeks. CHAPTER 2 Fish and stress Fishes are very sensitive to stress. Anything out of the ordinary can cause stress. Catching fishes, transportation, introducing new fishes or plants, rapid temperature changes, aggression between species, loud noises and banging are examples for causing abnormal behaviour. Even small stress factors over a longer period may suppress the immune system and make these fishes more susceptable to infection with bacteria, parasites and viruses. AquARium FiSH medic ine First aid to a fish problem: 1. Exchange 1/3 to 3/4 of the water 2. Give extra oxygen or air 3. Stop or reduce feeding 4. Remove sick and dead fish immediately 5. Look for the cause of the problem and try to solve it Abstracts European Veterinary Conference Voorjaarsdagen 2010 59