Tumor
Symptoms:
Fish with tumor will usually remain unfazed unless the tumor itself begins to hinder its normal body functions. Tumor can come as barely noticeable bumps, black growths or even open bump that may look ulcerated.
Causes:
Please note this excerpt from the main scientific study may not apply much to the aquarium or pond environment due to various factors that we have to differentiate from the natural body of water where this study was supposedly conducted
however it gives us a general overview of how and why tumors exactly occur. The questions alone have baffled many aquarium enthusiasts especially those who keep goldfish, koi and hundred other cyprinids.
Types of Tumors Suitable as Impairment Indicators
A comprehensive review documented tumor epizootics from 41 different locations in North America (Harshbarger and Clark 1990). Additional analysis of this data indicated that 22 species of fish had populations with elevated tumor incidence associated with environmental contaminants, and that about two-thirds of these species were benthic or bottom-dwelling fishes (Baumann 1992a). A more recent review, specific to the Great Lakes, and dealing primarily with brown bullhead and white sucker, lists dozens of epizootics in both Canadian and U.S. waters (Baumann et al. 1996). Such tumors are generally categorized into three different groups by etiology: genetically induced, viral induced, and those caused by chemical carcinogens.
Genetically Induced Tumors
Some tumors have a genetic origin or etiology (Baumann 1992b). Hybrids fish species, such as platyfish/swordtail crosses, may be susceptible to tumors because of dilution of modifier genes (Anders 1967) or amplification of oncogene segments (Vielkind and Dippel 1984). Such fish exhibit a certain incidence of “spontaneous” cancers, but are also more susceptible to chemically induced cancers.
Field studies indicate that hybrids between common carp (
Cyprinus carpio) and goldfish (
Carassius auratus) in the Great Lakes develop gonadal tumors which appear to have a genetic basis (Harshbarger and Clark, 1990; Sonstegard 1977, Smith, 1998). Thus gonadal tumors in carp x goldfish hybrids are unsuitable for use in impairment assessments until a base incidence of “spontaneous” gonadal tumors can be determined.
There has also been a suggestion that bullhead in Great Lakes tributaries are crosses between black and brown bullheads, and thus could be more susceptible to tumors. However, genetic studies to test this hypothesis have not been conducted. Ohio EPA studies have recorded zero brown bullhead/black bullhead hybrids in Lake Erie waters or tributaries. In fact very few black bullheads have been recorded. Furthermore the differing tumor prevalence in different tributaries, and in particular the vastly differing liver tumor frequencies seen over time in single locations such as the Black River, preclude genetics as a major factor influencing tumor development in brown bullhead (Baumann, 1998).
Viral and Multifactorial Tumors
Certain tumors in fish have a viral origin. The classic example is lymphoma in northern pike and muskellunge (Mulcahy and O’Leary 1979, Papas et al 1977, Sonstegard 1976). External tumors having a known viral etiology affect many species including: epidermal hyperplasia in walleye (Smith et al 1992, Martineau et al 1990, Yamamoto et al 1985) and papilloma on Atlantic salmon (Carlise and Roberts 1977), rainbow trout (Roberts and Bullock 1979), white suckers (Baumann et al 1996, Premdas and Metcalfe 1994, Smith et al 1989 a,b, Cairns and Fitzsimmons 1988, Smith and Zajdlik 1987, Sonstegard 1977) and brown bullheads (Smith et al 1989a, Baumann et al 1996).
If external tumors are due to viruses alone, the tumor rate does not increase with age and these tumors can regress spontaneously (Premdas and Metcalfe 1994, Smith and Zajdlik 1987).
Since external tumors in walleye are known to have a viral origin, and since there have been no studies indicating an increased incidence in polluted waters, walleye skin tumors can not be used as indicators of impairment.
Recently scientists have succeeded in inducing lip papillomas in healthy white suckers by injecting cell-free filtrates from papilloma tissue of diseased white sucker (Premdas and Metcalfe 1994). Thus, at least some lip tumors present in white sucker have a clear cut viral etiology.
However, in other situations, pinpointing the underlying cause of a tumor as strictly viral in wild fish is not always possible. For example, with a few exceptions, prevalences of lip tumors in white sucker and brown bullhead are elevated in populations from industrialized Great Lakes areas (Baumann et al 1996 and Premdas et al), pointing to a multifactorial (chemical and viral) etiology. It is postulated that exposure to chemicals increases the incidence of tumors caused by viruses through immune suppression or enhanced viral replication. Thus, in certain situations, the presence of virally induced tumors may be an indicator of exposure to adverse levels of
chemicals in the aquatic environment.
Freshwater drum from some areas in Lake Erie are known to have an increased prevalence of pigment cell tumors (chromatophoromas) (Harshbarger and Clark 1990; Baumann, Okihiro, and Kurey unpublished data). These tumors are found with increasing frequency as the length of the fish increases (Black 1983b). A lower frequency of such tumors exists in the Ohio River. At this time, no cause, either viral or carcinogen, can be assigned to these tumors. In Japanese waters (Kimura et al. 1984) similar tumors in related drum species have been correlated with chemical carcinogen exposure. However, without similar evidence for freshwater drum, such chromatophore tumors in this species cannot currently be used to assess impairment in single species studies. This species, along with all others found in the lake effect zones of Ohio tributaries and Ohio Lake Erie nearshore will be assessed as applicable in the DELTs index results (see section 6.6 and 6.7).
Chemically Induced Tumors
Tumors caused by chemical carcinogens most often affect the liver although lesions have been induced in the skin and numerous other tissues by laboratory exposure (Black, 1983; Hawkins et al. 1989). No liver tumors in any fish have ever been proven to be of viral origin. Nor are epizootics of cancer in non-hybrid, wild fish populations likely to have a purely genetic basis (Baumann 1992b). All thirteen species of benthic fish listed by Harshbarger and Clark (1990) as having had liver tumor epizootics have also had populations from unpolluted areas with documented tumor frequencies below one percent. Furthermore, in five carcinogen laboratory studies reviewed by Baumann (1992b), large numbers of control fish (of three different species) all had less than a one percent incidence of spontaneous liver tumors.
Chemical induction of liver tumors in fish has been done experimentally with a variety of carcinogens via injection, waterborne exposure, and diet (Baumann 1992b). Both skin and liver tumors were induced in brown bullhead by exposure to extracts of sediment from the Buffalo and Black Rivers which contained carcinogenic polynuclear aromatic hydrocarbons (PAHs) (Black et al. 1983 and Black et al. 1985). Massive field studies have statistically correlated tumor frequencies in English sole with PAH in sediment in Puget Sound (Malins et al. 1984 and Myers et al. 1990). Similarly, a large number of field studies at freshwater locations have linked liver tumors in benthic fish with carcinogens, primarily PAH, in sediment (Vogelbein et al.1990, Baumann 1992a and Baumann et al. 1996). A number of laboratory experiments (Balch et al 1995, Hinton 1989, Metcalfe 1989, Metcalfe et al 1988, 1990, 1995, Hendrick 1985) clearly indicate that the chemicals have the potential to be direct acting carcinogens in fish.
One long-term series of studies in the Black River, Ohio has demonstrated a decline in liver tumors in brown bullhead following a decline in PAH in the river sediment (Baumann and Harshbarger, 1995). After remedial dredging in 1990, buried PAH contaminated sediment wasre-exposed and liver tumor prevalence again increased dramatically (Baumann and Harshbarger 1998). Such fluctuations in an effect which tracks similar fluctuations in the purported cause is one of the strongest epizootiological arguments for a cause and effect relationship.
The most recent literature review on Great Lakes tumor data states that there is sufficient data to warrant the conclusion that high tumor prevalences in suckers and bullheads from the Great Lakes are associated with exposure to chemical contaminants (Baumann et al. 1996). Suckers and bullheads are inshore species that do not migrate extensively. Therefore, the health of these species reflect the impacts of localized aquatic environment conditions on fish health.
Conclusion
In short, the causes of the tumor are by various reasons which we can diagnose if we look back to the history of the fish and the aquarium itself especially as there are indeed numerous products that are carcinogenic to all forms of life, not limited to just human beings. This in itself is rather complex as there are numerous variables that could possibly influence the health and welfare of the fish.
Treatment:
The treatment for tumors has been largely debated. Whether some incidents involved were simply ulcers mistaken for tumors, it remains baffling how tumors can be exactly treated however for those with tumors growing as bumps or lumps visible on the skin of the fish, a surgery may be conducted to remove the tumor if it is suspected to hinder the normal body functions of the fish. If the tumor is found in the gill area for instance, this is a rather critical case as the dramatic growth of the tumor could suffocate the fish to death if it hinders gill movements.
For surgery details, click here.
Goldfish Tumor Removal
Just as a warning, you may need to ask for further queries before attempting this. Fish surgeries are by far one of the trickiest procedures. It is best advised not to perform such unless you are confident and careful you can do it otherwise leave this to the fish vets to deal with. Even vets that do not necessarily specialize in fish may lenda helping hand to you however you need to plan this carefully with the fish vet how the procedures should be done properly without killing the fish.
Reference:
www.epa.gov/glnpo/lakeerie/buia/lamp6.pdf
