MycobacteriosisBy Lance Ichinotsubo |
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| Symptons Oftentimes, a fish will arrive in what appears to be a seemingly good condition. Over a short period of time however, it begins to develop an emaciated appearance along the narrow, dorsal edge. A sunken belly becomes noticeable, although bloating (ascites) may also occur, due to fluid accumulation in the body cavity. Unilateral or bilateral exopthalmia (popeye) are common symptoms, as well as lifted scales, pale coloration, and in advanced, chronic cases, spinal curvature. All this soon leads to a loss of appetite, jerky swimming, greatly reduced reactions and reflexes. Ultimately, the affected fish becomes lethargic, seeking the corners of the aquarium, appearing to want to remain apart from it's tank-mates until it dies. Although nutritional deficiencies, drug-collection, and other environmental stresses may sometimes be implicated, this sad loss of a good specimen is typically caused by mycobacteriosis. It has been known as piscene tuberculosis in the past, perhaps due to the fact that the disease was first described from mycobacteriosis lesions in carp from a small lake in France. Polluted by biowaste deposited in the lake by a sanitarium on it's shores, human tubercular patients are suspected to have caused the emergence of piscene mycobacteriosis. This disease causes lesions and granulomatous tissue development, appearing gray-white, exhibiting a variety of sizes. Usually obvious in liver and kidney tissues, it has also been described from, spleen, mesentary, stomach, heart, gills and other organs as well as muscle tissue. Kidney tissue often appears to be specked throughout, because of the large quantity of lesions. Although past diagnosis have implicated the species mycobacterium marinum, several new species of this genus have recently been identified, most notably by Dr. Beverly Dixon, in her research within the University of California system. Clinically, acid-fast rod-shaped bacteria, which are gram positive, can been seen, measuring 1 - 5 micron long by 0.2 to 0.6 micron wide. A distinctive ubiquity makes this bacteria an ever-present danger to marine teleosts. As previously mentioned, external symptoms include emaciation, indicated by a general loss of body mass, particularly in the area just behind the nape, as well as the posterior, ventral abdominal region. Characteristically, the area anterior to this (just behind the pectoral region) displays a bulge which enlarges over time until death occurs. This bulge is a result of organ enlargement due to the formation of large quantities of granulomas in the liver, posterior and anterior kidney, which are sometimes visible with the naked eye, but usually seen under magnification (100 - 200 x). Cure Cure of this disease has been doubtful, at best. Some positive results have been reported from the use of tuberculin drugs, such as Isoniazid (in the past), and perhaps Kanamycin or Baytril currently. Unfortunately though, once symptoms become apparent, there typically is no reversal and therefore no cure as the appearance of visible symptoms seem to indicate a point of no return. Due to the fact that this disease appears to be highly contagious given the proper conditions, the cause of action recommended is to destroy the affected specimen. Aquarist Beware It is worthy of mention here that great care should taken when handling a suspected case of mycobacteriosis, especially when cuts or breaks in the skin of the handler, are present. This is because of the fact that although rare, the bacteria has to potential of infecting human tissue, causing a localized infection commonly on the elbow or knee, which unless properly treated for does not heal over extended periods of time. I know of at least five personal acquaintances who have been infected by Mycobacteriosis. In four of the five cases, diagnosis was not made for a long time, prolonging the infection. Only after the administration of proper medications over an extended period of treatment were these people cured. Of the fifth case, I was personally able to observe the wound early on. Upon recommendation to the attending physician to culture for mycobacterium, it turned out positive (marinum, to be exact). Cure was accelerated by prompt diagnosis, surgical excision of the affected area, and a treatment of sulfamethoxazole, then changing to Minocycline, for a period of 5 to 6 months, since (proportionately) more people are affected by mycobacteriosis than any of the other fish pathogens which can affect humans, one can generalize that it then is the most commonly encountered fish disease affecting humans. So, if you ever have an open sore or lesion which does not seem to heal. So what can be done about this problem you ask? As with all diseases, try to minimize stress, provide proper nutrition, and make available the best water quality possible. Remove any suspicious fish to a hospital tank for observation. Above all, quarantine, quarantine, quarantine. This is probably all that is within our power in an attempt to combat this disease, so try to prevent the bacteria from entering your systems to begin with. For more information and additional reading, please refer to the following references: Blasiola, George. 1991 Bassleer, Gerald. 1996 Gratzek, Dr. John B. 1992 Herwig, Nelson. 1979 Moe, Martin Jr. 1989 Post, Dr. George. 1983, 1987 Untergasser, Dieter. 1989. Veterinary Clinics. 1988. |
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