Parasitic and non-infectious diseases of wild and cultured coldwater fish. Case 1: Myxobolus cerebralis Rainbow trout (Oncorhynchus mykiss)

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1 This CD-ROM is intended for educational use, and copying or reproduction of its images and drawings is not permitted without written consent from their authors Parasitic and non-infectious diseases of wild and cultured coldwater fish Kevin Snekvik DVM, PhD, Dip ACVP Case 1: Myxobolus cerebralis Rainbow trout (Oncorhynchus mykiss) Washington Animal Disease Diagnostic Laboratory (WADDL) 1

2 Plasmodia Developmental stages Vegetative nuclei; generative cells Pansporoblasts Morphologic Diagnosis Spores Chondritis and osteitis, necrotizing, histiocytic, chronic, multifocal, severe with intralesional myxosporidia, head Cause: Myxobolus cerebralis Name the disease: Whirling Disease 2

3 Myxobolus cerebralis: Whirling disease Myxozoan (multicelluar organisms) Originally considered protozoan Cnidarian (sea anemones-nematocyst) Requires two hosts invertebrate host (tubifex tubifex) Sexual reproduction vertebrate host (salmonid fish) Asexual reproduction Two infective stages Myxospore (infects worm) Triactinomyxon (infects fish) Myxobolus cerebralis testing s 1956 Pepsin-Trypsin digest PCR Histopathology (spores within the cartilage is pathognomonic) Whirling Disease in the United States A Summary of Progress in Research and Management 2009 Case 2: Tetracapsuloides bryosalmonae Species: Mountain whitefish (Prosopium williamsoni) Location: Idaho Falls area 3

4 Pre-sporogonic stages Daughter cell Primary cell nucleus Cause: Tetracapsuloides bryosalmonae Name the disease: Proliferative kidney disease Clinical disease: Ascites, exophthalmia, pale gills, darkened skin Kidney (anterior and posterior), spleen, other organs Tetracapsuloides bryosalmonae: Proliferative kidney disease Location: Europe, North America Natural infections in salmon, trout, grayling, and pike Young of the year Summer water temp (>12-15 C) Survivors have strong resistance to reinfection Intermediate hosts: Bryozoan Fredericella sultana 4

5 Tetracapsuloides bryosalmonae: Life cycle Freshwater bryozoan Fredericella sultana Tetracapsuloides bryosalmonae: Proliferative kidney disease Brook Trout (Salvelinus fontinalis) Brown Trout (Salmo trutta) Multiple salmonid species, graying, Northern Pike (Esox Lucius) Pathogenic Histopathology: Presprogonic stages infect kidney interstitium, gills, liver, spleen, pancreas Primary cell contain 5-20 um diameter with foamy eosinophilic cytoplasm 1-3 nuclei 1-7 spherical daughter (secondary) cells Some daughter cells may have tertiary cells Adhered to vessels walls induce necrotizing vasculitis Histiocytic inflammation which may surround parasites (whorls) Sporulation occurs in renal tubules (lack hard valves) Tetracapsuloides bryosalmonae: Proliferative kidney disease Diagnosis: Presumptive diagnosis on Giemsa stained impression smears Case 3: Ceratonova shasta Formerly Ceratomyxa shasta Rainbow trout (Oncorhynchus mykiss) Confirmatory diagnosis: Histopathology PCR (small subunit ribosomal DNA primers PKX 3f/4r or PKX 5f/6r: Kent et al 1998) Biotinylated GS (Griffonia simplicifoia) -1 lectin staining Monocloncal Ab commercially available Ceratonova shasta After intestinal infection other visceral organs: Liver Gall bladder Spleen Heart Gonads Gills Muscle Kidney 5

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7 Ceratonova shasta Location: North America (California, Oregon, Idaho, Washington, British Columbia, Alaska) Natural infections in native chinook salmon (Oncorhynchus tshawytscha), coho salmon (O. kisutch), rainbow/ steelhead trout (O. mykiss), cutthroat trout (O. clarkia), pink salmon (O. gobuscha), chum salmon (O. keta), sockeye salmon (O. nerka), Dolly Varden (Salvelinus malma). Non native species infected : Atlantic salmon (Salmo salar), brown trout (S. trutta), brook trout (Salvelinus fontinalis) Ceratonova shasta: Life cycle Intermediate host: Polychaete worm Manayunkia speciosa Ceratonova shasta Diagnosis: Presumptive diagnosis on Giemsa stained impression smears or wet mounts of posterior intestine Confirmatory diagnosis: Spores on histopathology PCR (Palenzuela et al. 1999; Palenzuela and Bartholomew 2002 ) Note that spores only develop late in infection Case 4: Cryptobia(Trypanoplasma) salmositica Chinook salmon (Oncorhynchus tshawytscha) Location: Dungeness Hatchery Woo et al Clinical signs: severe anemia exophthalmia lethargy abdominal distention/ ascites 7

8 Cryptobia (Trypanoplasma) salmositica Blood smear Woo et al Kinetoplast Cryptobia (Trypanoplasma) salmositica Vector: Piscicola salmositica (freshwater leech) Cryptobia multiples in crop and accumulate in crop and proboscis sheath Transmission: transmitted by blood sucking leeches and direct transmission between fish. Principal natural reservoir: Sculpins No clinical disease Cryptobia (Trypanoplasma) salmositica Histopathology: Focal hemorrhages, congestion of blood vessels, occlusion of capillaries by parasites, edema of glomeruli. 1-2 weeks pi: Generalized inflammatory reaction of reticuloendothelial system- liver, gills, spleen 3 weeks pi: Vasculitis and mononuclear cell infiltrates 4 weeks pi: Extra vascular localization of parasites and tissue necrosis Variation of disease in Pacific salmon Chinook salmon: 100% Coho salmon: essentially no disease 8

9 Case 5: Sanguinicola sp. Arctic char (Salvelinus alpinus) Location: Private production hatchery in WA state Increased mortality of 1 month duration that developed with onset of summer and warm water temperatures Veterinarian: Dead spots in gills 9

10 Sanguinicola sp. Location: Freshwater and marine environments Disease: In North American: Large scale mortalities rainbow trout and brook trout Frequent seen in low levels in multiple pacific salmon Sanguinicola sp.: Life cycle Cercaria Disease from secondary bacterial or fungal infections Miracidium Modified from: Bullard and Overstreet, Potential pathological effects of blood flukes (Digenea: Sanguinicolidae) on pen-reared marine Fishes. Published in the Proceedings of the 53rd Gulf and Caribbean Fisheries Institute, Fort Pierce, Florida (2002), p Copyright 2002, Gulf and Caribbean Fisheries Institute. Case 6: Paramoeba pemaquidensis Atlantic salmon (Salmo salar) Location: Puget Sound, Washington Clinical history: Fish sluggish, congregate at surface or corners of sea pen and swim with open opercula Paramoeba pemaquidensis (Amoebic gill disease) British Columbia, Canada; WA, CA, USA; Australia Reported to be an opportunistic pathogen, but environmental conditions/ health status that promotes proliferation is unknown Epithelial hyperplasia with characteristic large interlamellar vesicles/ cysts Disease only typically seen in summer (water temp C) with mortalities reaching 50% Susceptibility: Younger > older Treatment: low salt or fresh water bath 10

11 Case 7: Trichophyra piscium Salmon Case 8: Neascus sp. Trout Metacercaria Case 9: Nanophyetus salmincola Chinook salmon (Oncorhynchus tshawytscha) Metacercariae in fish Oxytrema snail (release cercaria) 11

12 Nanophyetus salmincola Neorickettsia helminthoeca Salmon poisoning disease Vomiting, diarrhea, fever, swollen lymph nodes 14 days from eating raw fish 90% mortality if not treated Case 10: Phoma herbarum Cutthroat trout (Oncorhynchus clarkii) Location: Columbia basin hatchery, Moses Lake, Washington State Water temperature 59ºF (15ºC) System Freshwater flow through Necropsy: anemia, thick leathery swim bladder granulomatous lesions in the kidney 12

13 Phoma herbarum Histopathology Lesions typically start in anterior swim bladder or pneumatic duct- spread through viscera Histiocytic to granulomatous inflammation Epithelial hyperplasia of swim bladder Hyphae um long and 2-3um wide Lightly pigmented (Fontana-Mason positive) Special stains: PAS or GMS Phoma herbarum Cutthroat trout (Oncorhynchu clarkii) Plant saprophyte Natural infections in salmon, trout Fry and fingerlings Clinical signs Abnormal swimming / ataxia (loss of equilibrium) Swollen vents Hemorrahagic fin and skin lesions Phoma herbarum Diagnosis: Culture (Sabouraud dextrose agar) Light buff to light pink fungal plaques that change to black with formation of pycnidia that produce hyaline unicellular conidia Case 11: Walleye dermal sarcoma Walleye (Sander vitreus) Angler caught walleye from Nelson Reservoir, MT with multiple tumors Tissue submitted as a biopsy by MT Fish, Wildlife and Parks History: Curious if tumors were lymphocystis 13

14 Walleye dermal sarcoma Type C retrovirus (walleye dermal sarcoma virus) Seen across North America Lesions present in fall, last over winter and regress in spring summer in association with inflammatory response Case 12: Thyroid carcinoma Rainbow trout (Oncorhynchus mykiss) Sample from a barren, 2 year old brood fish Pond crew noticed growths on the gill arch while sorting fish Mass at base of gill arch where tongue enters mouth No to limited virus shedding in fall -> heavy virus shedding in summer coincides with spring spawn Virus has been shown to transmit in cell free inoculation of tumor filtrates and waterborne exposure 14

15 Thank you! 15