the primary hosts of this parasite are birds such as herons or ducks , and its second intermediate hosts are freshwater fish such as carp , crucian carp , or loach . the parasite becomes a metacercaria inside the second intermediate host by forming a globular film around its body and waits for an opportunity to infect the final host . although infections in humans are extremely rare , if a person consumes a raw freshwater fish infected by the larvae of this parasite , the larvae will excyst in the stomach , migrate through the esophagus , and attach to the throat and mature , causing parasitic pharyngitis or laryngitis . human laryngitis caused by c. complanatum is a rare disease ; however , in japan , korea , and other asian countries where eating raw fish is a tradition , it is possible for individuals to become infected by this intestinal parasite . in this study , we describe a patient with laryngitis caused by c. complanatum that occurred after the patient ate freshwater fish sashimi . a 64-year - old japanese man visited the outpatient s department of otolaryngology , yamaguchi university hospital , ube , japan . his symptoms occurred two days after he had eaten raw carp sashimi for dinner at a japanese - inn situated at a hot spring . furthermore , a blood test showed no increase in white blood cell count or c - reactive protein level , and a differential white blood cell count showed no eosinophilia . a fiberoptic examination of the larynx revealed no clear signs of inflammation , such as redness or swelling of the pharynx or larynx . however , there was a foreign object attached to the surface of the right aryepiglottic fold that moved slowly during observation ( figure 1 ) . considering that the patient had consumed raw carp and that the shape of the object resembled a fluke when more closely observed , the probable diagnosis was infection by a parasitic fluke . after explaining the procedure to the patient and obtaining his consent , an endoscopic removal of the fluke was performed under local anesthesia because he did not have a strong gag reflex . to stop the parasite moving and to make the removal easier , 1 ml of 4% lidocaine via inhalation was administered to the patient ; with the patient in the right lateral decubitus position , a parasite of approximately 6-mm length was removed using biopsy forceps with a laryngeal endoscopy . the parasite was almost completely motionless during removal because of the effects of the lidocaine . removal was easy because the parasite was not strongly attached to the mucosa , too . the patient s throat discomfort disappeared almost immediately after the parasite was removed . the patient was consulted and visited the gastroenterology department of our hospital for an upper gastrointestinal endoscopy to confirm that there were no residual parasites in the esophagus or stomach , and his treatment was completed . microscopic findings showed that the frontal end consisted of an oral sucker with a ventral sucker slightly caudal to it . there were black ovaries on both sides of the body , which was identified as the digenetic trematode c. complanatum . endoscopic findings of clinostomum complanatum infection 
  a slow - moving worm attached to the surface of the larynx ( arrow ) . gross image of clinostomum complanatum ( 6.0 mm in length ) the frequency of parasitic infections in humans is decreasing because of changes in lifestyle and environments where food is cultivated . for example , roundworm infections spread because of the agricultural use of human waste , but their incidence has been greatly reduced with the widespread use of chemical fertilizers . similarly , in japan , improvements in sanitation have decreased the incidence of parasitic diseases , such as tapeworms and pinworms . sometimes overseas travelers carry parasitic diseases such as malaria .   however , infections from parasites in food are still observed in areas where people consume raw meat or fish . people in japan , korea , and other asian countries have consumed raw fish for long . one traditional dish is sashimi and slices of raw fish that are now consumed all over the world as typical japanese food such as sushi . sashimi prepared from fresh marine fish can be safely consumed , but not completely safe , because parasite such as anisakis can infect human , and other bacteria or virus also can cause gastroenteritis . however , wild fish that live in brackish water or fresh water may be infected with parasites ; thus , they are inappropriate to be consumed as sashimi . sashimi made from carp , a freshwater fish , is a traditional dinner item that is sometimes served at japanese - style hot spring inns near lakes or streams . currently , only carp farmed in spring water that can not be infected by parasites are used to make sashimi because cooking wild carp is an issue . to consume the wild fresh - water fish without heating it , it would normally have to be frozen for 24 h at 20c ( 4f ) in order to kill the parasites . as far as we searched previous reports extensively , this case constitutes the 19th documented case of clinostomum infection in japan ( table 1 ) . there are many reports from western japan , and the infection is prevalent in areas along the sea of japan . interestingly , there have also been two recent reports from korea . sites of parasitic infection include the pharynx , arytenoid region , posterior oropharyngeal wall , and lateral lymphatic band . however , some case reports also mention a sore throat or swallowing pain , while others report bloody phlegm and fever . if the patient has consumed raw freshwater fish , the physician can search for a parasite while carefully inspecting the symptomatic area . reported methods of removal include endoscopic removal under local anesthesia and removal using a direct laryngoscope under general anesthesia . the alleged reason for choosing to remove the parasite under general anesthesia is to ensure a proper grip on the fluke , but the fluke can almost be completely removed under local anesthesia . in our case , the patient s gag reflex was not strong ; therefore , we had performed the endoscopic removal of the fluke under local anesthesia . if a direct laryngoscope was required to remove the fluke , the position of the laryngoscope should be changed in case the fluke moved , which would probably make the procedure more complicated . in contrast , with an endoscope , even if the fluke moves the endoscope can easily bend and follow it . kitagawa et al . 
  reported that when they were removing c. complanatum , the fluke was quickly moving ; therefore , they had to apply directly spraying it with 8% lidocaine solution to decrease its movements . in our case , the patient inhaled 1 ml of 4% lidocaine to stop the parasite s movements before safely removing the parasite using biopsy forceps . in the report described above , a minimal amount of lidocaine was used to effectively stop the parasite s movements , and we found that inhaled only 1 ml of 4% lidocaine was also effective . in the life cycle of c. complanatum , the metacercariae enter a patient s body , excyst in the stomach , migrate through the esophagus , and then attach to the throat and mature , causing parasitic laryngitis . therefore , there may be a delay of several days between oral ingestion and emergence of symptoms . even when a fluke is removed from the throat , the metacercariae may remain in the digestive tract or there may be more than one parasite , making it necessary to not only examine the throat but also perform an upper gastrointestinal endoscopy . we also performed an upper gastrointestinal endoscopy in this case the day after removing the parasite and confirmed that there were no residual parasites . we described a rare case of laryngitis caused by c. complanatum . in cases where patients develop throat discomfort after consuming raw freshwater fish , this disease should be considered as a possible diagnosis , and a fiberoptic examination of the laryngopharynx should be performed .