title: Surgical removal of an anal cyst caused by a protozoan parasite (Thelohanellus kitauei) from a koi (Cyprinus carpio).
abstract: METHODS
  An 8-month-old koi (Cyprinus carpio) fish was examined at the animal hospital at Seoul National University for anal obstruction.
  
  
  RESULTS
  The affected fish was lethargic and anorexic, appeared depressed, and had a nodular obstruction at the anus. A biopsy specimen from the anal mass was submitted for histologic examination, which revealed a number of protozoa. On the basis of the morphological characteristics of the spores and the location of the plasmodia (ie, vegetative form of the parasite), a diagnosis of a cyst containing Thelohanellus kitauei was made. Thelohanellus kitauei is a protozoan parasite that affects freshwater fish by producing cyst-like tumors that may cause intestinal obstruction. Thelohanellus kitauei infection with cystic disease has been reported to affect Cyprinus spp worldwide.
  
  
  RESULTS
  The cyst was removed surgically. After surgery, low-concentration tricaine methanesulfonate immersion was used for sedation and antimicrobial treatment was administered. The surgical wound healed completely, and the fish was clinically normal 14 months after surgery.
  
  
  CONCLUSIONS
  The successful outcome in this fish suggested that surgical removal may be a viable option for treatment of T kitauei infection in koi fish. The results of morphological analyses provided basic information on the relationships between tissue tropism and Thelohanellus spp.
authors.affiliation: Laboratory of Aquatic Animal Medicine, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Sang Phil
authors.initials: SP
authors.lastname: Shin
authors.forename: Hyang
authors.initials: H
authors.lastname: Jee
authors.forename: Jee Eun
authors.initials: JE
authors.lastname: Han
authors.forename: Ji Hyung
authors.initials: JH
authors.lastname: Kim
authors.forename: Casiano H
authors.initials: CH
authors.lastname: Choresca
authors.forename: Jin Woo
authors.initials: JW
authors.lastname: Jun
authors.forename: Dae Yong
authors.initials: DY
authors.lastname: Kim
authors.forename: Se Chang
authors.initials: SC
authors.lastname: Park
mesh_terms: D000818:Animals; D001004:Anus Diseases / Q000469:parasitology / Q000473:pathology / Q000601:surgery / Q000662:veterinary*; D002347:Carps; D003560:Cysts / Q000469:parasitology / Q000473:pathology / Q000601:surgery / Q000662:veterinary*; D005393:Fish Diseases / Q000469:parasitology* / Q000473:pathology / Q000601:surgery; D055764:Myxozoa / Q000302:isolation & purification*; D010273:Parasitic Diseases, Animal / Q000469:parasitology* / Q000473:pathology / Q000601:surgery