• Journal of Fisheries and Marine Sciences Education
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• v.28 no.6
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• pp.1822-1827
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• 2016

Consumption of Paralichthys olivaceus in raw fish have been reported as the cause of outbreaks of food-born illness, and Kudoa septempunctata in muscle of Paralichtys olivaceus was suggested with the causative agent. For this reason, distinguish of vital and dead spore is important to study survivability of Kudoa septempunctata in human intestinal condition and in vitro inactivation of Kudoa septempunctata. In this reports, we suggest NR & MB (Neutral red and Methylene blue) staining method that is easier and simpler than the previously described HO & PI (Hoechst33342 and Propidium iodide) method according to a experimental condition.

• Parasites, Hosts and Diseases
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• v.61 no.1
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• pp.15-23
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• 2023

Concerns about foodborne illnesses caused by Kudoa septempunctata are steadily growing, but reports of K. septempunctata in clinical and food specimens related to food poisoning in Korea are limited. This study aimed to genetically identify K. septempunctata in patients with acute diarrhea and in clinical and food samples related to food poisoning caused by sashimi consumption. Both real-time and nested polymerase chain reaction assays were performed to detect K. septempunctata 18S and 28S rDNA genes in the stools of 348 patients with acute diarrhea, 11 samples (6 stool and 5 rectal swab samples) from patients with food poisoning, and 2 raw Paralichthys olivaceus samples collected from a restaurant where a food poisoning incident occurred. K. septempunctata was identified in 5 clinical specimens (4 stools and 1 rectal swab) and 1 P. olivaceus sashimi sample. All detected K. septempunctata were of genotype ST3. This is the first study to identify K. septempunctata in both patients and food samples with epidemiological relevance in Korea, providing evidence that it is a pathogen that causes food poisoning. Also, this is the first study to confirm the presence of K. septempunctata genes in rectal swabs. Despite continuing suspected occurrences of Kudoa foodborne outbreaks, the rate of identification of K. septempunctata is very low. One reason for this is the limitation in obtaining stool and vomit samples for the diagnosis of Kudoa infection. We strongly suggest the inclusion of rectal swabs among the diagnostic specimens for Kudoa food poisoning.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.1
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• pp.23-30
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• 2018

Kudoa septempunctata, a myxosporean parasite that infects olive flounder Paralichthys olivaceus is known to cause Kudoa food poisoning. Entire trunk muscle (ETM) is used for diagnosis of the parasite in fish and this method demands sacrifice of the host, causing a loss of commercial value. We developed a non-destructive method that uses a plastic syringe-style implanter to draw the sample, called the part-point muscle (PPM) sampling technique. We validated the PPM method in fish infected with K. septempunctata at the level detectable by the ETM method. We confirmed that the PPM method is equally sensitive in comparison to the ETM method for diagnosing K. septempunctata spores in olive flounder muscle. Our study also confirmed that the parasite is uniformly distributed in the dorsal muscle of infected fish. Over a period of 1 month, we observed no mortality of the host fish used for sampling by the PPM method. Thus, our studies demonstrate that the PPM sampling technique is an efficient, non-destructive method for diagnosing K. septempunctata in olive flounder.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.5
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• pp.611-621
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• 2014

A nationwide survey was conducted to study the rate of Kudoa septempunctata parasitization in cultured olive flounder, Paralichthys olivaceus, in Korea in 2013. Of 1107 olive flounder sampled randomly from 89 culture farms in five different regions in Korea, K. septempunctata was detected only in Jeju, where 10 of 318 fish (3.14%) were PCR positive, with genomic concentrations of $4.67{\times}10^5$ to $1.48{\times}10^{11}$ rDNA copies/g by real-time PCR. Of the ten Kudoapositive fish, K. septempunctata spores with 5-7 polar capsules were detected only in four fish. No samples of K. septempunctata were detected in olive flounder from the other regions surveyed. Furthermore, K. septempunctata was not detected in 326 samples of olive flounder seeds sampled from 39 hatcheries in seven different regions in Korea. Therefore, the parasite infection is restricted to Jeju and K. septempunctata infection is not spread from hatcheries.

• Journal of fish pathology
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• v.28 no.2
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• pp.109-112
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• 2015

A survey was conducted to investigate the infection of Kudoa septempunctata in 660 olive flounder (Paralichthys olivaceus) (132 pooling samples) cultured in 11 hatcheries in 6 different regions of Korea between 2014 and 2015. Polymerase chain reaction (PCR) results were negative for K. septempunctata for all samples. Based on the kudoa diagnostic manual, K. septempunctata was not detected in olive flounder hatcheries.

• Parasites, Hosts and Diseases
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• v.58 no.5
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• pp.593-597
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• 2020

Kudoa septempunctata have been reported as a causative agent for acute transient gastrointestinal troubles after eating raw olive flounder (Paralichthys olivaceus). It raised public health concerns and quarantine control in several countries. Quantitative evaluation on viability of K. septempunctata is crucial to develop effective chemotherapeutics against it. A cytometry using fluorescent stains was employed to assess effect of three compounds on viability of K. septempunctata. Epigallocatechin gallate reduced markedly viability of K. septempunctata at 0.5 mM or more, and damaged K. septempunctata spores by producing cracks.

• Journal of fish pathology
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• v.26 no.3
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• pp.129-137
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• 2013

The study surveyed infection rate of Kudoa septempunctata parasitized in the trunk muscle of olive flounder, Paralichthys olivaceus, cultured in Jeju Island and wild fish species caught in the coastal area around Jeju Island during 2012. Among 143 olive flounder that were randomly sampled from 26 different culture farms, K. septempunctata was detected in 7 fish samples (4.9%) from 4 different culture farms, showing no typical Kudoa infestation. However, K. septempunctata was not detected in olive flounder fry sampled from hatcheries and 8 species of wild fish. In addition, we compared 3 different sampling sites on trunk muscle of 7 Kudoa positive fish that included head part, tail part and entire muscle. Among 7 fish, K. septempunctata was detected in 3 fish that were sampled from head part; while 4 fish from tail part of trunk muscle. However, all 7 fish were positive when sampled from entire muscle. Thus, we suggest that it will be more efficient to use entire muscle sample than sampling partial muscle parts for detection of K. septempunctata.

• Korean Journal of Veterinary Research
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• v.55 no.3
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• pp.175-179
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• 2015

Proteases play important roles in parasite development and host parasite interactions. The protease of Kudoa spp. has been recognized as a key factor of severe proteolysis of fish muscle post-mortem; however, there is little information available regarding the protease of Kudoa (K.) septempunctata, which was recently identified as a cause of food poisoning in humans. The present study was conducted to isolate and characterize proteases to elucidate the type of protease contained in the parasite and determine the optimal pH for protease activity. We confirmed the cysteine protease and metalloprotease produced by K. septempunctata. While the cysteine protease showed optimal activity at pH 5 that decreased rapidly with increasing pH, the optimal activity of metalloprotease was pH 7, and it remained stable from pH 6 to pH 8. These results indicate that the pH of cysteine protease is not proper for fish muscle postmortem, and that metalloprotease can act in human intestines. Overall, the present study provides important information that improves our understanding of the role of protease physiology and the subsequent food poisoning caused by K. septempunctata.

• Fisheries and Aquatic Sciences
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• v.24 no.8
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• pp.277-283
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• 2021

Kudoa septempunctata has been reported as a new parasite in aquacultured olive flounder Paralichthys olivaceus, and also as a causative agent of food poisoning in humans. This paper investigated the infection of K. septempunctata in 216 sashimi and 20 sushi made of olive flounders in Busan, Korea. Among 236 samples, K. septempunctata was detected in eleven sashimi with 6-7 polar capsules by the microscopy. Among eleven sashimi, five sashimi were positive in Polymerase Chain Reaction (PCR) assay with the targets of 18S rDNA and 28S rDNA. The genotype of all the five PCR results is identified as the genotype ST3 which is common in Korea. K. septempunctata was found in olive flounders sashimi from Samcheonpo and Wando outside of Jeju Island. These findings would contribute to establish the standard of K. septempunctata for preventing food-borne outbreaks in advance and providing further preventive management for the seafood safety.

• Fisheries and Aquatic Sciences
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• v.20 no.8
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• pp.16.1-16.8
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• 2017

The exportation of cultured olive flounder (Paralichthys olivaceus) in Korea has been recently decreasing due to the infections with a myxozoan parasite Kudoa septempunctata, and there is a strong demand for strict food safety management because the food poisoning associated with consumption of raw olive flounder harbouring K. septempunctata has been frequently reported in Japan. The life cycle and infection dynamics of K. septempunctata in aquatic environment are currently unknown, which hamper establishment of effective control methods. We investigated sea water and marine invertebrates collected from olive flounder farms for detecting K. septempunctata by DNA-based analysis, to elucidate infection dynamics of K. septempunctata in aquaculture farms. In addition, live marine polychaetes were collected and maintained in well plates to find any possible actinosporean state of K. septempunctata. The level of K. septempunctata DNA in rearing water fluctuated during the sampling period but the DNA was not detected in summer (June-July in farm A and August in farm B). K. septempunctata DNA was also detected in the polychaetes Naineris laevigata intestinal samples, showing decreased pattern of 40 to 0%. No actinosporean stage of K. septempunctata was observed in the polychaetes by microscopy. The absence of K. septempunctata DNA in rearing water of fish farm and the polychaetes N. laevigata intestinal samples during late spring and early summer indicate that the infection may not occur during this period. N. laevigata was suspected as the possible alternate invertebrate host of K. septempunctata, but the actinosporean stage was not found by well plate method and further studies will be necessary. This research provides important baseline information for understanding the infection dynamics of K. septempunctata in olive flounder farms and further establishment of control strategies.