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Nematode (Roundworm) Infections in Fish
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Summary
Nematodes, or roundworms, have been found in numerous species of fish. Because they are similar to other worm-like parasites of fish, proper diagnosis is important for effective treatment. Working with a fish health specialist will insure proper diagnosis and legal treatment or prevention. Producers of food and game fish have more limited options for the treatment of infected fish than will the producers of ornamental fish because ornamental fish are considered a low regulatory priority by the FDA.

Small numbers of nematodes may be present in fish without causing significant symptoms. In more severely infected fish, evidence of disease can inlcude emaciation (wasting or significant loss of body mass), nodules or masses present in skin or muscle, stunted growth, abnormal swimming, lethargy, or death.

Depending upon the species of fish and the species of nematode, fish may be final hosts (containing adult nematodes) or intermediate hosts (containing larval nematodes). Some species of nematodes that infect fish can be transmitted directly from one fish in the population to another (direct life cycle). Other species of nematodes require additional hosts to complete their life cycle, commonly an invertebrate host or a fish, bird, or mammal as final host. Consequently, correct identification of the nematode is critical for proper management of the disease.

Nematodes found within the gastrointestinal tracts of ornamental fish can be treated with appropriate dewormers. Nematodes found in other areas of ornamental fish cannot be removed through chemical means, and the fish in such cases must be culled. Control of intermediate or final hosts will help break the life cycles of these parasites. In addition, proper sanitation of ponds or tanks will help reduce the abundance of infective stages.


References:
  • Dick, T.A. and A. Choudhury. 1995. Phylum Nematoda. In Fish Diseases and Disorders, pp. 415-446, Chapter 11, Volume 1, Protozoan and Metazoan Infections, P.T.K. Woo (editor), CAB International, Cambridge, UK.
  • Carpenter, J.W., Mashima, T.Y. and Rupiper, D.J. 1996. Exotic Animal Formulary. First Ed. Greystone Publications. Manhattan, KS. 310 pp.
  • Hoffman, G.L. 1999. Parasites of North American Freshwater Fishes. Second Edition. Comstock Publishing Associates, Ithaca, NY.
  • Measures, L.N. 1987. Epizootiology, pathology, and description of Eustrongylides tubifex (Nematoda: Dioctophymatoidea) in fish. Canadian Journal of Zoology 66: 2212-2222.
  • Measures, LN. 1988. The Development of Eustrongylides tubifex (Nematoda: Dioctophymatoidea) in Oligochaetes. Journal of Parasitology 74(2): 294-304.
  • Noga, E.J. 1996. Fish Disease: Diagnosis and Treatment. Mosby-Year Book, Inc., St. Louis, MO, pp. 166-170.



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Footnotes
1. This document is Circular 91, one of a series from the Department of Fisheries and Aquatic Sciences, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First Published: December 2002.

2. Roy P.E. Yanong, Assistant Professor, Tropical Aquaculture Laboratory, Department of Fisheries and Aquatic Sciences, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Ruskin, FL 33570-3434.

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The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race color, sex, age, handicap, or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Service office.

Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / Christine Taylor Waddill, Dean

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Copyright Information
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