Patrick T. K. Woo

Natural anti-proteases in rainbow trout, Oncorhynchus mykiss and brook charr, Salvelinus fontinalis and the in vitro neutralization of fish α2-macroglobulin by the metalloprotease from the pathogenic haemoflagellate, Cryptobia salmositica

Natural anti-proteases (alpha 1-protease inhibitor (alpha 1-PI; alpha 1-antitrypsin) and alpha 2-macroglobulin (alpha 2-M)) were found in the blood of rainbow trout, Oncorhynchus mykiss and brook charr, Salvelinus fontinalis. The alpha 2-M inhibited Cryptobia salmositica proteases and was significantly higher in brook charr than in rainbow trout. Under in vitro conditions it took longer for the same number of parasites to neutralize the alpha 2-M in charr than in trout blood. The haemolysis which occurred when C. salmositica was incubated in the blood of rainbow trout was due to neutralization of alpha 2-M. This in vitro study also showed that it was the metalloprotease of C. salmositica that lysed red blood cells and the plasma of the two species of fishes initially prevented haemolysis by inhibiting the proteolytic activity. We suggest that the natural plasma alpha 2-M plays an important role in defence against cryptobiosis in fishes.

Diseases and disorders of finfish in cage culture

Overview of cage cutlure marine and brackish water - coldwater fishes freshwater - coldwater fishes marine and brackish water - warmwater fishes fresh water - warmwater fishes noninfectious disorders emerging infectious diseases.

In Vitro Attenuation of Cryptobia salmositica and Its Use as a Live Vaccine Against Cryptobiosis in Oncorhynchus mykiss

The present communication reports on the attenuation of a pathogenic hemoflagellate, Cryptobia salmositica Katz (Sarcomastigophora: Kinetoplastida) and its use as a live vaccine against cryptobiosis. The parasite was attenuated by continuous in vitro culture (at 10 C for 55 wk) in minimum essential medium. Attenuated (culture) forms are morphologically similar to virulent (blood) forms. They are however more slender and have a shorter anterior flagellum and a smaller nucleus and kinetoplast. The attenuated form returned to its normal size and multiplied when inoculated into naive Oncorhynchus mykiss. It produced a low parasitemia but did not cause disease (e.g., no exophthalmia or anemia) in fish. At four wk after infection, the vaccinated fish were challenged with the virulent parasite. They were protected from the disease, whereas the control (naive) fish, infected with only the virulent parasite, had the usual clinical signs (e.g., anemia, exophthalmia). No parasite was detected in any of 10 vaccinated fish at 22 wk after challenge with the virulent parasite. However, 5 of 9 fish infected with culture forms and 6 of 9 fish infected with blood forms still had detectable parasites at 26 and 22 wk after infection, respectively.

Cryptobia and cryptobiosis in fishes.

Publisher Summary Cryptobia is a flagellate with two flagella (one being attached to the body), a prominent kinetoplast, and a nucleus. The parasite has been reported on the body surface, in the digestive tract, and in the blood of fishes. The chapter helps to unify and clarify the relationship among the various groups of cryptobia and, as a result, to rekindle research interests in the often neglected ectoparasitic cryptobia and those in the digestive tract. It also brings together studies that would otherwise not be available to a more general readership. Some recent findings (e.g., a functional pulsatile vacuole in the blood forms of a haematozoic Cryptobia, an ectoparasitic phase in the life cycle, and direct transmission in an aquatic system) are perhaps good indications that there are more exciting discoveries waiting to be unraveled. Further new insights into the biology of flagellates may emerge when one starts to understand the metabolism and mechanisms that allow this organism to live both on and inside the host, in the blood, or digestive tract.

Immunological responses of fish to parasitic organisms.

Abstract The piscine immune system is well developed and is normally quite efficient in protecting healthy free ranging fish from parasitic diseases. However, when fish are cultured in high numbers and are stressed by adverse environmental factors (e.g. heavy metal pollution, low dissolved oxygen, nutritional deficiencies, and/or overcrowding), parasites may have the advantage and the risk of disease outbreak increases in the fish population. We know very little about innate immunity against parasites. Hence it has not been considered a viable strategy to protect fish from diseases. The alternative pathway of complement activation is the protective mechanism in certain fish species against hemoflagellates (Cryptobia salmositica and Cryptobia catostomi). This mechanism also operates in some resistant individuals (in a susceptible fish species) against C. salmositica. Complement is also involved in innate parasiticidal activities against adult intestinal tapeworms (Acanthobothrium quadripartitum) and encysting larval stages of digeneans (Diplostomum spathaceum and Cryptocotyle lingua). It is suggested here that more studies be conducted to elucidate the mechanism(s) of innate immunity in nonsusceptible host species, and also to follow the heredity of parasite resistant factor(s) in individuals that belong to an otherwise susceptible host fish species. The innate nonspecific cytotoxicity of leukocytes of flounders, infected with the copepod, Phrixocephalus cincinnatus, was significantly depressed compared to those from uninfected flounders. The target cells for the leukocytes were murine cells; future studies should include parasites as target cells to determine the importance of the depression on disease resistance in copepod-infected fish. Fish that survive Amyloodinium ocellatum, C. salmositica, Cryptobia bullocki, Trypanosoma danilewskyi, Ichthyophthirius multifiliis, Myxidium lieberkuehni, a myxosporean parasite (PKX), and D. spathaceum infections are generally protected from disease when they are later exposed to the same parasite. Complement fixing antibodies and/or cell-mediated immunity are important in acquired immunity against C. salmositica, C. bullocki, T. danilewskyi, I. multifiliis, Diplostomum spathaceum, Cryptocotyle lingua, and Posthodiplostomum minimum. A live C. salmositica-vaccine has been developed. The vaccine has fewer polypeptide bands and a few of the remaining polypeptides are antigenically different from those in the virulent strain. It does not cause disease in fish but has remained protective. Fish are assumed to, or are known to, respond immunologically to numerous other parasitic infections. These include: Cryptocaryon irritans, Myxosoma cerebralis, Gyrodactylus bullatarudis, Dactylogyrus vastator, Neobenedenia melleni, Telogaster opisthorchis, Ligula intestinalis, Diphyllobothrium, Caryophyllaeus laticeps, Pomphorhynchus laevis, Anguillicola crassus, and Larnaea cyprinacea. However, the precise role of the immune system in these infections has yet to be determined. In general, there are little antibody and cell-mediated responses during early myxosporean infections because the parasite antigenically mimics host tissues. The proliferative type of inflammation is the principal defense when spores are formed, resulting in parasite encapsulation. Melanomacrophages ingest spores in tissue and transport them to kidneys, spleen, or liver where they are encapsulated and destroyed. Also, cestodes are thought to adsorb host antigens on their body surface to evade the host immune system. The extent and the mechanism of host tissue mimicry by parasites, presumably to avoid or reduce the host immune response, are both fascinating and in need of more careful study in the future. Not much is known about immunodepression due to parasitic diseases in fish. This is an important phenomenon because it generally increases the susceptibility and mortality of infected fish when they are exposed to another pathogen. Also, it will adversely affect vaccination programs carried out against other pathogens. Immunodepression has been found in C. salmositica, Glugea stephani, and PKX infections. It is suggested here that other parasitic infections should be closely examined for their effects on the piscine immune system. It is also beneficial to more closely evaluate the interactions of multiple infections (microbial and parasitic) and their effects on the fish.

The effects of short-term acute cadmium exposure on blue tilapia,Oreochromis aureus

SynopsisDisease-free blue tilapia,Oreochromis aureus, exposed to cadmium (0.5 ppm and 10 ppm) showed very significant and dramatic decrease in food consumptions. Food consumptions returned to near normal 21 days after fish were returned to cadmium-free water. Along with anorexia there were decreases in body weights during the period when fish were exposed to cadmium. Fish in cadmium-free water that were pair-fed to cadmium-exposed fish (0.5 ppm) did not gain weight but there were no decreases in body weights. Cadmium was still in tissues 34 days after the fish were placed in cadmium-free water and the accumulation was highest in the kidney; this was followed by liver, brain, gill filaments and muscles. The accumulations of the heavy metal (in kidneys and gills) were significantly higher in fish exposed to high than low cadmium levels. There were no differences in complement levels (haemolytic acitivity) in cadmium-exposed and cadmium-free fish. However, cadmium-exposed fish did not produce detectable haemagglutinating antibodies against sheep red blood cells while cadmium-free fish responded well to the antigen. The anorexia in cadmium-exposed fish contributed to the depression in antibody production.

Acquired immunity against Trypanosoma danilewskyi in goldfish, Carassius auratus.

Two groups of goldfish maintained at 20 degrees C were experimentally infected with two different sized inocula of Trypanosoma danilewskyi. One group was inoculated with 380,000 trypanosomes/fish and the other with 3800. Forty and 90% of the fish, respectively, survived. All surviving fish challenged 190 days post-infection were protected from re-infection. The plasma of these fish when inoculated into another group of fish also protected them from infection. Finally, trypanosomes incubated in vitro in immune plasma at 20 degrees C for 2 h were not infective; however, incubations at 5 degrees C or for 1 h were not as effective.

Giardia lamblia in children in day-care centres in southern Ontario, Canada, and susceptibility of animals to G. lamblia

In 1982, Giardia lamblia cysts were found in the faeces of eight of 97 children (two to five years old) in day-care centres in Guelph, Ontario, Canada. None of the infected children showed any of the classical signs of giardiasis. The survey was repeated in 1983 in the Kitchner-Waterloo area, Ontario. In this survey nine of 147 children were infected with G. lamblia. Experimentally established Giardia-free colonies of mice, hamsters, rats, cats (adults and kittens) and dogs (adults and puppies) could not be infected with Giardia cysts from clinical and non-clinical patients. Also, kittens, hamsters, and mice could not be infected by trophozoites from an axenic culture. However, five-day-old suckling rats can be infected with G. lamblia. Also, the Giardia-free rats and dogs are susceptible to their own Giardia (G. simoni and G. canis respectively). This proves that cats and dogs are not reservoirs of G. lamblia and consequently are not responsible for the spread of the infection in the human population.

Fish parasites: pathobiology and protection.

1. Neoparamoeba perurans 2. Amyloodininium ocellatum 3. Cryptobia salmositica 4. Ichthyophthirius multifiliis 5. Miamiensis avidus and related species 6. Perkinsus marinus and Haplosporidium nelsoni 7. Loma salmonae and Glugea anomala 8. Myxobolus cerebralis and Ceratomyxa shasta 9. Enteromyxum scophthalmi and related species 10. Henneguya ictaluri and related species 11. Gyrodactylus salaris and G. derjavinoides 12. Pseudodactylogyrus bini and P. anguillae 13. Benedenia seriolae and Neobenedenia spp. 14. Heterobothrium okamoti and Neoheterobothrium hirame 15. Diplostomum spathaceum and related species 16. Sanguinicola inermis and related species 17. Bothriocephalus acheilognathi 18. Anisakis simplex 19. Anguillicoloides crassus 20. Argulus foliaceus 21. Lernaea cyprinacea and related species 22. Lepeophtheirus salmonis and Caligus rogercresseyi.

Anorexia reduces the severity of cryptobiosis in Oncorhynchus mykiss.

Cryptobia salmositica multiplied more rapidly and caused a more severe disease with a higher mortality (65%) in rainbow trout (Oncorhynchus mykiss) fed a 52% protein diet than in fish fed 37 or 22% protein diets (25 and 30% mortalities, respectively). Also, plasma protein was significantly higher in fish fed a 52% protein diet than in fish fed 37 or 22% protein diets. Anorexia in infected trout was related positively to parasitemia and was most significant at 4 wk postinfection. During the chronic phase of the infection, food consumption increased with declining parasitemia. It is hypothesized that anorexia lowers plasma protein level, which reduces the multiplication rate of parasites, thus decreasing the severity of the disease.