Toxins in fish

In general, nonconventional protein foods must be competitive with conventional plant and animal protein sources on the bases of cost delivered to the consumer, nutritional value to humans or animals, functional value in foods, sensory quality, and social and cultural acceptability. Also, requirements of regulatory agencies in different countries for freedom from toxins or toxic residues in single-cell protein products, toxic glycosides in leaf protein products, pathogenic microorganisms, heavy metals and toxins in fish protein concentrates, or inhibitory or toxic peptide components in synthetic peptides must be met before new nonconventional food or feed protein products can be marketed. 

Reports implicating paralytic shellfish toxins in fish kills are summarized in Table I. The first instance in which it was suspected that these toxins were the cause of a fish kill occurred in May 1968... 

Table VI. Paralytic Shellfish Toxins in Fish Tissues Following Oral Dose of Toxins at 2000 g/kg...

FDA (Food and Drug Administration). (2001a). Natural toxins. In "Fish and Fishery Products Hazards and Controls Guidance," 3rd ed., pp. 73-82. Center for Food Safety and Applied Nutrition, Office of Seafood, Washington, DC. 

Lagana, A. et al., Sample preparation for determination of macrocyclic lactone myco-toxins in fish tissue, based on on-line matrix solid-phase dispersion and solid-phase extraction cleanup followed by liquid chromatography/tandem mass spectrometry, J. AOACInt., 86(4), 729, 2003. 

Bioconcentration factor (BCF), which describes the affinity of the pesticide for aquatic organisms and measures the accumulation of toxins in fish relative to the water in which they swim. 

Park, D.L., Evolution of methods for assessing ciguatera toxins in fish. Rev. Environ. Contam. Toxicol., 136, 1, 1994. 

Despite frequent occurrences of ciguatera toxins in many parts of the world, this poisoning is rarely fatal, because of the low concentration of the toxin in fish flesh. Maybe for this reason very few specific regulations exist for ciguatera toxins [6]. In some areas, public health measures have been taken that include bans on the sale of high risk fish from known toxic locations. Such bans have been used in American Samoa, Queensland, French Polynesia, Fiji, Hawaii, and Miami. The bans were apparently with some success but with attendant economic loss [38]. 

Hokama, Y. Shirai, L. K. Iwamoto, L. M. Kobayashi, M. N. Goto, C. S. Nakagawa, L. K. Assessment of a rapid enzyme immunoassay stick test for the detection of ciguatoxin and related polyether toxins in fish tissues. Biol. Bull. (Woods Hole, Mass.), 172 144-53. 1987. 

Pathogens and Toxins in Fish. FDA estimates that contaminated shellfish cause over 100,000 illnesses and cost the country around 200 million annually. In addition, several species of fish at the top of the food chain accumulated mercury to such high levels that they posed a hazard to pregnant women and small children. ... 

Saponin can also be used in fishing a toxin, it is introduced into streams to stupefy fish and make them easy to catch.)... 

Assays of ciguatoxin. Determination of ciguatoxin levels in fish was carried out in many laboratories by mouse assays. Enzyme immunoassay to screen inedible fish has been proposed by Hokama (9). No specific chemical assay has been developed, as information on functional groups suitable for fluorescence labeling is not available. Analyses conducted in the authors laboratory on remnant fish retrieved from patients meals indicated that ciguatoxin content as low level as 1 ppb could cause intoxication in adults. An extremely high sensitivity and a sophisticated pretreatment method will be required for designing a fluorometric determination method for the toxin. 

Distribution. The first indication of the occurrence of palytoxin in fish was presented in 1969 (16). The filefish Altera scripta belonging to family Monacathidae was traditionally known in Okinawa, Japan, to contain a toxic substance in the gut and, thus, to kill pigs when fed to them. The presence of fragments of Palythoa sp. in the guts and the resemblance in solubility between the fish toxin and palytoxin led the authors to a conclusion that the toxic principle in the filefish viscera was palytoxin. Incidence of human intoxication due to eating the filefish was not confirm. ... 

Significant concentrations of cyanotoxins have been found to accumulate in the tissues of macroinvertebrates such as mollusks and crustaceans, presenting an indirect route of exposure for invertebrates, fish, and aquatic mammals at higher trophic levels (Negri and Jones 1995). In natural systems, mortality among benthic invertebrate herbivores is probably low because most bloom-forming bacteria are planktonic and only periodically come into contact with the benthos. Nevertheless, Kotak et al. (1996) determined that enhanced mortality of snails at the end of a bloom cycle in Canadian lakes was due to consumption of Microcystis cells that had formed a scum on the surface of macrophytes. Oberemm et al. (1999) found that aqueous microcystins, saxitoxins, and anatoxin-a all resulted in developmental delays in fish and salamander embryos. Interestingly, more severe malformations and enhanced mortality were observed when larvae were exposed to crude cyanobacterial extracts than to pure toxins applied at natural concentrations (Oberemm et al. 1999). 

Unlike EH and GTr activities, the production of AFL from AFB by trout hepatic enzymes was observed to increase in fish fed the higher casein diets (Table III). AFL has been shown to be carcinogenic (30) and mutagenic (53) and may be oxidized back to AFB by trout hepatic enzymes (54). It has been suggested that AFL represents a reserve pool of toxin in vivo (35, 55) and that its production is indicative of a sensitive animal species (56, 57). If AFL does indeed represent a reserve pool of AFB in trout, then its increased production by fish fed high levels of casein may predispose these particular animals to the induction of cancer. 

Lewis et al. [714] combined HPLC with Tandem Electrospray Mass Spectrometry (i.e., HPLC-ESI-MS-MS) for the determination of sub-ppb levels of toxins in extracts of fish. 

Phycotoxins accumulate in fish and shellfish because of the natural feeding habits of the respective organisms, rather than because of food handling or processing practices. The toxins causing the diseases discussed in this chapter are heat stable (Australia New Zealand Food Authority, 2001 Committee on Evaluation of the Safety of Fishery Products, 1991). Complete inactivation of saxitoxin (associated with PSP) requires at least ten minutes of exposure to 260°C dry heat. Brevetoxins (associated with NSP) were inactivated (i.e., to levels below the limit of assay detection using Japanese medaka [Oryzias latipes]) by exposure to 500°C heat for 10 to 15 minutes (Poli, 1988). Complete inactivation required 10 minutes exposure to 2760°C dry heat (Wannamacher, 2000). 

Kotaki, Y., Oshima, Y. and Yasumoto, T., Analysis of paralytic shellfish toxins in marine snails, Bull. Jpn. Soc. Sci. Fish., 47, 943, 1981. 

Food stored in a proper way and in proper conditions is not a vehicle of C. botulinum. Unlike non-proteolytic strains, proteolytic strains will not grow in refrigeration temperatures. The number of spores in meat and poultry is rather low, much higher numbers are observed in fish. If stored at 3 to 5°C, vacuum-packed, not very sour meat products usually remain safe for consumers up to 21 days. Botulin toxin was not detected in raw rockfish fillets or red snapper homogenates after being stored for 21 days at 4°C. None of 1074 samples of commercially packed fresh fish stored for 12 days at 12°C contained botulin toxin (Lilly and Kautter, 1990). 

Among fish we find some of the most potent toxins in animals. We dis-tinguish passivelj toxic fish from actively toxic fish. The former simply have toxins in their tissues, typically taken from some other source such as their diet. The latter produce the poison and have evolved apparatus to discharge, deliver, or inj ect the... 

Yamamori, K., Nakamura, M., Matsui, T., and Hara, T. J. (1988). Gustatoiy responses to tetrodotoxin and saxitoxin in fish a possible mechanism foravoiding marine toxins. Canadian Journal of Fisheries and Aquatic Science 45,2182-2186. 

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