, AND OTHER -BORNE PARASITIC ZOONOSES

Terry A Dickl, Brent R Dixorr' and Anindo Choudhury'

1 Department of Zoology, University of Manitoba, Winnipeg Manitoba, Canada, R3T 2N2; 2 Bureau of Microbial Hazards, Directorate, Health Protection Branch, Health and Welfare Canada, Ottawa, Ontario, Canada KIA OL2.

Abstract. Fish-borne parasitic zoonoses such as anisakiasis and occur infrequently in Canada and more work needs to be done on the interactions and transmission dynamics of marine and freshwater anisakids in North America. The diphyllobothriid tapeworms are primarily restricted to the northern Canada. Problems with the specific identification of these parasites from their fish hosts prompted the development of a series of nucleic acid probes. Use of the polymerase chain reaction proved to be quick, accurate and requires little skill, once developed.

INTRODUCTION problems caused by these parasites. There is little difficulty in distinguishing between larval There is an increasing awareness of the worms of the genera Pseudoterranova, Anisakis, importance of fish-borne parasites as human and ContracaecumlPhocascaris, from fish, pro- pathogens by consumers in North America. Such vided the worms are complete. However L) parasites include Diphyllobothrium, the anisakids larvae of Contra caecum osculatum, C. spiculi- and two fresh water trematodes. New sources of gerum and Phocascaris spp. are almost im- fresh fish supply from cultured fish, semi- possible to differentiate and aspects of their intensive (ponds) and intensive (marine and transmission dynamics and potential patho- freshwater cage culture), have added to the genicity to humans remain unclear. Anisakis logistic problems of inspection. Superimposed simplex and A. physeteris L) larvae are also on these are the potential effects of warming of difficult to separate. There is considerable the temperate region and the desire of humans overlap in the distribution of the anisakids in to preserve remaining natural resources such as Canadian waters (Margolis and Arai, 1990) fish eating birds and which serve as which adds to the problem. Little is known primary hosts of these parasites. about Contracaecum spp. in Canadian fresh- This paper will emphasize the Canadian water systems. Recently, semi-intensive stocking situation with respect to fish-borne zoonoses, programs with rainbow , for example, particularly anisakiasis and diphyllobothriasis, and resulted in very heavy infections in the viscera will discuss some of the unresolved and potential and flesh and a 10-fold increase over 3 years, new problems and methods of identification. thus rapidly altering the parasitofauna of a pristine system by attracting piscivorous birds (Dick et ai, 1987). There are at least three DISCUSSION of Contracaecum reported from pelicani form birds in North America (Deardorff and Anisakid roundworms Overstreet, 1980) and their impact on inshore A large volume of literature exists on fisheries is unclear. anisakids in fish and their pathogenicity to Diphyllobothriid tapeworms humans (Desowitz, 1986; Hafsteinsson and Rizvi, 1987), and a recent case of human Of the 12 species of Diphyllobothrium re- infection from Alberta, Canada (Kowalewska- ported in North America, three species are Grochowska et al, 1989) reinforces the health known to infect humans in Canada; D. latum

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and D. ursi utilize mammals as the primary host mise but the use of restriction digest profiles of while D. dendriticum utilizes a bird host (An- genomic DNA require extensive procedures that derson et al, 1987). It is generally believed are time consuming. Use of specific DNA that larval plerocercoids can be differentiated on probes are good but require the extraction of the basis of their morphology but considerable DNA prior to hybridization with a radiolabelled morphological variability among individual ple- probe. Amplification of a specific sequence of rocercoids in fish makes species identification DNA has considerable promise as small amounts tentative, at best. The location of plercercoids of DNA can be used and the time to diagnose in the viscera (D. dendriticum) and in the is about 4-5 hours. We have developed ribo- musculature (D. latum) generally holds as a somal DNA probes from the intergenic spacer distinguishing feature but from our experience, regions, sequenced this DNA, synthesized D. dendriticum often occurs in the flesh in specific primers which were used in the poly- both salmonid and coregonid . Positive merase chain reaction (PCR) to accurately identification of plerocercoids is only possible identify D. latum and D. dendriticum plero- by obtaining adult worms from experimentally cercoids. We are able to obtain sufficient DNA, infected hosts. Gulls are likely the primary hosts by amplification from pieces of parasite tissue, of D. dendriticum while the natural primary host to serve as a template for the PCR. Future of D. latum in Canada is less well understood identification methods will incorporate this but generally thought to be aquatic mammals technology as it is quick, accurate and requires or . It is also not clear how the North little specialized skill once the primers and American D. latum compares with the Eurasian methods have been developed. species which infect humans.

Larval trematodes REFERENCES Clinostomum complanatum and Metorchis conjuctus are considered potential human Andersen K, Cheng HL, Vik R. A review of fresh- pathogens in Canada. Clinostomum, usually water species of Diphyllobothrium with redes- criptions and the distribution of D. dendriticum considered a yellow parasite, has recently (Nitzsch, 1824) and D. ditremum (Creplin, 1825) caused heavy infections in fillets of pond from North America. Can J Zool 1987; 65:2216- (semi-intensive) cultured (Szalai 28. and Dick, 1988). Human infections of M. conjuctus, are from wild freshwate~ fish and Deardorff TL, Overstreet RM. Contracaecum multi- papillatum (= C. robustumy from fishes and occur infrequently. There has been one case only birds in the Northern Gulf of Mexico. J Parasitol in the last 10 years (Naiman et ai, 1980). 1980; 66:853-6. This parasite is restricted to northern Ontario, Manitoba and Saskatchewan' in central Canada. Desowitz RS. Human and experimental anisakiasis in the United States. Hokkaido Igaku Zasshi 1986; 61:358-71. deVos T, Szalai AI, Dick TA. Genetic and morpho- DIAGNOSIS logical variability in a population of Diphyllo- As stated earlier, problems in identification bothrium dendriticum (Nitzsch, 1924). Syst Parasitoll990; 16:99-105. arise at the species level or when only pieces of worms are available. Methods other than Dick TA, Papst MH, Paul HC. Rainbow trout morphological, such as isozyme and molecular ( gairdneri) stocking and Contracaecum biology techniques have been developed to spp. J Wild Dis 1987; 23:242-7. overcome such problems in identification of Hafsteinsson H, Rizvi SSH. A Review of the larval anisakids and diphyllobothriids (Orecchia sealworm problem: biology, implications and et al, 1986; deVos et al, 1990). Isozymes require solutions. J Food Protect 1987; 50:70-84. considerable care in the handling of specimens, Kowalewska-Grochowska K, Quinn J, Perry I, often not the case for the material one receives Sherbaniuk R. A case of anisakiasis - Alberta. for diagnosis. Molecular techniques show pro- CanDis WkJyRep 1989; 15:221-3.

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Margolis L, Arai HP. Synopsis of Vertebrates of G, Bullini L. Electrophoretic identification of Canada, Parasites of Marine Mammals. Alberta larvae and adults of Anisakis (: Agriculture, Health Division. 1990: 26pp. Anisakidae). J Helmithol 1986; 60:331-9. Naiman HL, Sekla L, Albritton WL. Giardiasis and Szalai AI, Dick, TA. Helminths of stocked rainbow other intestinal parasitic infections in a Manitoba trout (Salmo gairdneri) with special reference to residential school for the mentally retarded. Can Clinostomum complanatum. J Wild Dis 1988; Med Assoc J 1980; 122:\85-8. 24:456-60. Orecchia P, Paggi L, Mattiucci S, Smith JW, Nascetti

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