JPC SYSTEMIC PATHOLOGY
MUSCULOSKELETAL SYSTEM
April 2019
M-P06 (NP)

Signalment (JPC# 3121691):  Adult female guppy (Poecilia reticulata) from a pet store

HISTORY:  The fish was euthanized following a prolonged period of anorexia and weight loss. 

HISTOPATHOLOGIC DESCRIPTION:  Scaled skin with subjacent skeletal muscle: Extending through the multifocally eroded and ulcerated scaled skin, further extending through the dermis and multifocally into the variably affected subjacent skeletal muscle, and multifocally expanding the submesothelial space of the coelomic cavity by up to 300um, are numerous ciliate trophozoites.  Ciliate trophozoites are 30 to 40 um diameter, ovoid, with a thin cell wall lined circumferentially by cilia of equal length and distribution, cytoplasm that contains variably sized eosinophilic globules, one irregularly oval to elongate deeply basophilic macronucleus, and occasionally a contractile vacuole.  Trophozoites are frequently admixed with a small amount of eosinophilic cellular and karyorrhectic debris (necrosis), minimal fibrin, edema, and rare hemorrhage as well has low to moderate numbers of granulocytes and few lymphocytes (most significant in the areas of cutaneous ulceration/erosion).  Individual rhabdomyocytes are surrounded, separated, and rarely replaced by ciliate trophozoites, and are often characterized by one of the following:  shrunken with irregularly sized sarcoplasm (atrophy); pale, swollen, vacuolated sarcoplasm with loss of cross striations (degenerate); or hypereosinophilic, fragmented sarcoplasm with nuclear pyknosis, karyolysis, or karyorrhexis (necrotic).

Liver, hepatocytes:  Hepatocellular cytoplasm is frequently expanded by single varisized vacuoles which often peripheralize the nucleus (lipid).

Intestine:  Within the intestinal lumen is a cross section of a 350um diameter adult cestode with a 3um brightly eosinophilic tegument bounding a spongy parenchyma containing basophilic calcareous corpuscles and a uterus with many 10-20 um thin walled eggs.

MORPHOLOGIC DIAGNOSIS

  1. Scaled skin, skeletal muscle, and coelomic cavity: Ciliated trophozoites, numerous, with associated mild to moderate granulocytic inflammation, rhabdomyocyte degeneration and necrosis, and erosive to ulcerative dermatitis, etiology consistent with Tetrahymena corlissi, guppy, (Poecilia reticulata), Cyprinodontiform.
  2. Liver: Hepatic lipidosis, diffuse, marked.
  3. Intestine: Adult cestode.

ETIOLOGIC DIAGNOSIS:  Tetrahymenal coelomitis, myositis, and dermatitis

CAUSETetrahymena corlissi

SYNONYMS:  Guppy disease; spectacle eye; tetrahymeniosis; “tet disease”

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS:

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Gardiner CH, Fayer R, Dubey JP. An Atlas of Protozoan Parasites in Animal Tissues. 2nd ed. Washington, DC: Armed Forces Institute of Pathology; 1998:16-17.
  2. Leibowitz MP, Zilberg D. Tetrahymena infection in guppies, Poecilia reticulata Peters: parasite characterization and pathology of infected fish. J Fish Dis.  2009:32(10):845-855.
  3. Noga EJ. Fish Disease: Diagnosis and Treatment. 2nd Ames, IA: Wiley-Blackwell; 2010:140-141.
  4. Roberts RJ. The parasitology of teleosts. In: Roberts RJ ed. Fish Pathology. 3rd Philadelphia, PA: W.B. Saunders; 2003:272-273.
  5. Sharon G, Pimenta Leibowitz MP, Kumar Chettri J, Isakov N, Zilberg D. Comparative study of infection with Tetrahymena of different ornamental fish species. Jour Comp Pathol. 2014; 150:316-324.
  6. Stidworthy MF, Garner MM, Bradway DS, et. al. Systemic scuticociliatosis (Philasterides dicentrarchi) in sharks.  Vet Pathol.  2014;51(3):628-632.


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