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This paper provides first information about possible occurrence of the myxosporean genus Kudoa in fish of the World Ocean and, in some cases, in associated freshwater bodies at different depths. An analysis of the theoretically assumed site preference by Kudoa of different habitat depths of their fish hosts in the World Fauna is made for the first time. It is revealed that all species of the myxosporean genus Kudoa can be found in coastal shelf zones, of which 90 species (70.8% of the total) occur exclusively in the shelf zone, and the hosts of 50 Kudoa species (39.4%) live in its shallowest part (down to 50 m). 16 species (12.6%) and 14 species (11%) of this genus can be found at depths from the shelf to 500 meters and 1000 meters, respectively. From 1 to 3 species of Kudoa can be encountered theoretically at 1500 m to 3000 m, which is from 0.8 to 2.4% of all known representatives of these parasites. [ABSTRACT FROM AUTHOR]

The spotted seatrout, Cynoscion nebulosus, is a popular game fish in the southeastern USA. It is estimated that nearly 90% of the adult population in South Carolina estuaries are infected in their skeletal muscle by the myxosporean, Kudoa inornata. However, little is known about this parasite’s biology, including the distribution and densities of myxospores within tissues of infected fish, which we expect affect the physiology of their hosts. In order to correlate densities with physiological parameters in future studies, we quantified the myxospores density in muscle and characterized the variation among individual fish. Naïve juvenile seatrout was experimentally infected via presumed K. inornata actinospores exposure to raw seawater. A plug of muscle was extracted from two bilaterally symmetrical regions in the epaxial fillet from fresh and frozen carcasses. Variation in density data was calculated both within and among individuals. Within individuals, density counts were compared between left- and right-side biopsies. There was no significant difference between fresh and frozen plugs, and variation among individuals accounted for the greatest proportion of variation at 68.8%, while variation within individuals was substantial at 25.6%. Simulation and correlation tests confirmed that bilaterally symmetrical replicates varied significantly within individuals. When sampled from areas surrounding the initial biopsies, myxospore density estimates were more similar than between sides. Our findings have important implications for sampling design, particularly for studies investigating physiological parameters at the cellular or molecular level in association with parasite infection. [ABSTRACT FROM AUTHOR]

The North Atlantic and North Pacific commercial fisheries report problematic occurrences of ‘jellied’ or ‘mushy’ fish. These fish exhibit an abnormally soft and jelly-like musculature that attains a mushy consistency when cooked. The condition affects several economically important species, and is commonly termed ‘jellied condition’ or, specifically for halibut, ‘mushy halibut syndrome’. The inferior quality of ‘jellied’ or 'mushy' products reduces the market value considerably, leading to wastage and losses in the fisheries. The syndrome is associated with an abnormally high moisture content and lowered protein of the white skeletal musculature, particularly the fillets. Alterations in lipid content varies depending on species investigated. In some fish species, myxozoan infections can induce similar fillet alterations, but studies on ‘jellied’ or ‘mushy’ meat indicate a non-infectious myopathy. Several hypotheses have been launched to explain the jelly-like syndrome, including dietary deficiencies, spawning exhaustion, environmental circumstances, genetics and adaptive physiology. This review provides a comprehensive overview of the characteristics of the ‘jellied’ or ‘mushy’ syndrome including a discussion of plausible etiologies and applicable mitigation strategies. The main conclusion is that the syndrome may involve two different etiologies dependent on species and location, but new studies are needed to verify past findings and rule out alternative explanations. A growing human population and an increasing demand for food requires efficient utilization of all harvested fish products. Expanded and updated knowledge is vital to reduce food waste and losses related to ’jellied’ or ‘mushy’ fish in catches, and promote sustainable quota usage. We advocate for further research into the syndrome, including prevalence in commercial fish stocks and correlational studies with focus on association with biological parameters, chemical composition, infectious agents, geographic distribution and seasonal variation.

The purpose of the research is to study the localization of myxosporeans of the genus Kudoa Meglitsch, 1947 in body fish and possible ways for them to master organs and tissues in the process of evolution, the form of spores associated with localization, as well as the ways of their release into the environment and getting into new hosts.Materials and methods. The work is based on our own materials on fish myxosporeans from the Black, Azov and Mediterranean seas, as well as the Atlantic, Indian and Pacific oceans, collected in 1987–2021. In total, we have studied more than 12,000 sp. more than 100 species of fish. We also analyzed descriptions of 126 species of myxosporeans of the genus Kudoa, known in the world scientific literature until 2021 inclusive. For this, 450 domestic and foreign works have been worked out. The material was collected by the method of incomplete parasitological dissections. Smears made from tissues were processed according to the generally accepted method with the manufacture of permanent preparations. All measurements were made according to the standard method. To assess the number of parasites, standard indicators were used: the extensiveness and intensity of infection.Results and discussion. In total, we studied 19 species of myxosporeans of the genus Kudoa and 8 species of Kudoa spp. Six species (K. stellula, K. niluferi, K. anatolica from the Black Sea, K. unicapsula from the Mediterranean Sea, K. borimiri and K. igori from the South China (or East) Sea) were new to science. We have established 24 places of parasitism of myxosporeans of this genus in the body of fish. 83 species (66%, or 2/3 species) are found in muscles, sometimes affecting (8 species) other tissues and organs of the host. 43 species (34%, or 1/3 species) of representatives of the genus Kudoa are never found in muscle tissue. The primary sites of parasitism of myxosporeans of the genus Kudoa were probably the intestinal wall and gallbladder, then the parasites mastered other internal organs of fish and, ultimately, brain and muscle. The hypothetical ways of getting spores into the external environment and into new hosts are indicated. It is assumed that the most ancient forms are bivalve Kudoa, parasitizing in the gallbladder, four-valve Kudoa of an unusual shape, resembling representatives of other genera and parasitizing mainly in internal organs, as well as four-valve Kudoa with a classical square spore shape, rounded valve tops, with four equal polar capsules and the smallest sizes. Spores with a pointed stellate shape (only muscular forms) and spores with five or more valves and polar capsules (occurring in muscle and brain and having a larger size) should be considered to have arisen at a later time. The ways of getting spores into the environment and into new hosts are highlighted.

In March and April 2018, we carried out a survey of myxosporean parasites in coastal fishes collected from Nha Trang Bay in Vietnam's East Sea. Of the 159 fish specimens, 18 fish species were represented, belonging to 10 families. In 8 host species, 7 myxosporean species were found, representing the genera Kudoa and Unicapsula. Two of these species were new to science: Kudoa igori n. sp. from the gallbladder of Longarm mullet Osteomugil cunnesius (Valenciennes, 1836) (prevalence 10%) and Kudoa borimiri n. sp. from skeletal muscles of Longarm mullet and Longfinned mullet Osteomugil perusii (Valenciennes, 1836) (prevalence 30% and 60%, respectively). Vegetative stages were not found. Spores of K. igori n. sp. were small, orbicular to quadrate in apical view, and with four equal valves. In lateral view, spores were shallowly ovoid with a slightly protruding anterior pole. The 4 polar capsules were slightly unequal sizes and were oriented toward the apex of the spore. Dimensions were as follows: spore length 4.56 ± 0.22 (4.18–4.56), thickness 4.42 ± 0.39 (3.55–5.13), width 5.74 ± 0.46 (4.66–6.50), length of biggest polar capsule 1.38 ± 0.14 (1.1–1.65), middle 1.28 ± 0.12 (1.03–1.53), smallest 1.13 ± 0.11 (0.94–1.30), width of biggest polar capsule 1.03 ± 0.14 (0.83–1.4), middle 0.92 ± 0.12 (0.76–1.08), smallest 0.74 ± 0.12 (0.55–0.94). Spores of K. borimiri n. sp. had four equal valves with slightly rounded ends and were quadrate in apical view. In lateral view, spores were broadly deltoid. Four equal-sized polar capsules opened at the apex of the spore. In O. cunnesius, spore dimensions were as follows: length 3.51 ± 0.15 (3.34–3.92), thickness 3.65 ± 0.38 (2.79–4.21), width 4.97 ± 0.37 (4.13–5.97), length of the polar capsules 1.23 ± 0.18 (0.99–1.57), width 0.88 ± 0.07 (0.70–1.00). Overlapping dimensions for K. borimiri n. sp. spores were also found in O. perusii. Other known myxozoan species we encountered were Kudoa thyrsites and Kudoa whippsi, which had not previously been reported from the East Sea and Vietnam. We also encountered Kudoa monodactyli, which had not previously been reported from Nha Trang Bay. In addition, we report 2 additional species, a Kudoa sp. and a Unicapsula sp., that were not attributable to previously described myxozoans and need further investigation to completely characterize. [ABSTRACT FROM AUTHOR]

The European anchovy represents the main fisheries for countries in the Mediterranean and Black Sea basins. The skeletal muscle of 13 of 48 (27.1%) Engraulis encrasicolus (L.) specimens from North East Atlantic waters (FAO 27.8.c) was found infected with interfibrillar elongated plasmodia (130-980 µm in length) containing mature myxospores belonging to the genus Kudoa Meglitsch, 1947. No flesh softening was found associated with infection. Fresh myxospores were 10.8 ± 0.7 (9.1-12.3) µm in width 1, 11.3 ± 0.9 (9.5-13.4) µm in width 2, 6.7 ± 0.4 (5.8-7.4) µm in thickness, and 6.9 ± 0.5 (5.8-7.5) µm in length. They were almost stellate in apical view having three pointed-edged shell valves bearing three small polar capsules equal in size 5.0 ± 0.3 (4.4-5.4) μm long and 2.4 ± 0.2 (2.0-3.0) μm wide, and one rounded- to rarely bluntly pointed-edged shell valve bearing a large and particularly wide polar capsule 6.8 ± 0.4 (5.9-7.6) μm long and 4.1 ± 0.2 (3.6-4.4) μm wide. Morphological and morphometrical comparisons between these myxospores and those of Kudoa thyrsites (Gilchrist, 1923) from the clupeid Sardina pilchardus (Walbaum) (North East Atlantic waters, FAO 27.9.a), with which exhibited a similarity of 98.9% and 96.2% using SSU and LSU rDNA sequences, respectively, support the creation of Kudoa encrasicolin. sp. Morphometrical analysis of the polar capsules of flattened myxospores is suggested as a useful approach to differentiate phylogenetically related kudoids with stellate or almost stellate myxospores bearing four polar capsules. [ABSTRACT FROM AUTHOR]

Purpose: Members of the genus Kudoa Meglitsch, 1947 are known to infect the muscles of commercially important fishes worldwide, including those in the order Siluriformes. This paper describes the occurrence of a new species of Kudoa in the catfish Brachyplatystoma rousseauxii based on morphological study and molecular analysis of the ribosomal RNA gene (SSU rDNA). Methods: Fifteen specimens of Brachyplatystoma rousseauxii were purchased from fishing zones near Mosqueiro Island, Belém, Pará, Brazil. After necropsy, tissue samples and cysts were analyzed using a stereomicroscope, and fresh slides were viewed under a light microscope to confirm parasitic infection. The tissue fragments were removed and processed for molecular and histological analyses. Results: Microscopic pseudocysts were found in the epaxial region of skeletal muscle fibers in 80% of the analyzed specimens. The myxospores were quadrangular with four shell valves (SV), pyriform polar capsules (PC), and internal symmetry. Phylogenetic analyses indicated that the new species formed a cluster with the species previously described in the Amazon, being close to two freshwater species. Conclusions: Morphological differences and molecular data of SSU rDNA support that Kudoa rousseauxii n. sp. is a new species that infects B. rousseauxii, a freshwater fish with intense migratory cycles that is widely captured and consumed in the Amazon. [ABSTRACT FROM AUTHOR]

Multiple Kudoa spp. (Myxozoa: Myxosporea: Multivalvulida) have been recorded in Japanese parrotfish (Calotomus japonicus) from the Philippine Sea (Northwest Pacific Ocean), off southwestern Japan; Kudoa yasunagai in the brain, and K. igami, K. lateolabracis, and K. thalassomi in the muscles. This study examined eight Philippine Sea Japanese parrotfish samples collected in January and February 2019 and found K. prunusi in the brain (3–57 plasmodia/fish; average 17.9) and K. lateolabracis plasmodia in the trunk muscle of all fish individuals examined. The K. prunusi in this study was characterized by myxospores predominatetly with six shell valves (SVs) and a corresponding number of polar capsules (PCs), contrasting with the original description of the species from farmed Pacific bluefin tuna (Thunnus orientalis) brain that characterized the species as having predominately five SVs/PCs. Molecular-genetic characterization of 18S and 28S ribosomal RNA genes and mitochondrial DNA genes (cytochrome c oxidase subunit 1 and small and large ribosomal RNA subunits) clearly differentiated the K. prunusi isolate from K. yasunagai, commonly characterized by six or seven, but rarely five, SVs/PCs myxospores. The Japanese parrotfish is a new host record for K. prunusi and speculated to be an important reservoir host in its natural waters. Kudoa lateolabracis myxospores isolated from pseudocysts in the myofiber were morphologically and phylogenetically close to a clade of the Kudoa spp. that exhibit cruciform myxospores similar to K. thyrsites. This study is the first to sequence a mitochondrial DNA of small and large subunit ribosomal RNA of K. lateolabracis. [ABSTRACT FROM AUTHOR]

Anadromous river herring have declined in many parts of their range, leading to fisheries management efforts to help repopulate this species by improving connectivity of rivers and restoring populations by fish transfers. With data lacking on parasites in these species, this study sought to better understand myxozoans across various life stages and habitats in river herring populations in New Jersey, USA. We compared fish from riverine habitats during early-life growth and adults returning to spawn, marine-phase fish, and landlocked Alewife populations. Three myxozoan species were identified in young-of-the-year (YOY) anadromous river herring, including Kudoa clupeidae in the skeletal musculature, Myxobolus mauriensis in the rib cartilage, and an uncharacterized coelozoic myxozoan within the lumen of mesonephric tubules. In YOY river herring, Blueback Herring were 2 times more likely to be infected by K. clupeidae than Alewife (p = 0.019) and in the Maurice River, fish were 4 times more likely to be infected with M. mauriensis than fish from Great Egg Harbor River (p = 0.000) and 11 times more likely than the Delaware River (p = 0.001). Spawning adult river herring were infected with a previously undescribed myxozoan parasite infecting the kidney. Sequencing the 18S rDNA indicated this species is closely related to Ortholinea species. Myxobolus mauriensis and the Ortholinea-like species were absent from marine-phase river herring indicating that infections were linked to river environments occurring during early-life growth and spawning, respectively. No myxozoans were present in landlocked Alewife, showing that similar infections occurring in rivers were absent in lake environments in the region. [ABSTRACT FROM AUTHOR]

The North Atlantic and North Pacific commercial fisheries report problematic occurrences of 'jellied' or 'mushy' fish. These fish exhibit an abnormally soft and jelly-like musculature that attains a mushy consistency when cooked. The condition affects several economically important species, and is commonly termed 'jellied condition' or, specifically for halibut, 'mushy halibut syndrome'. The inferior quality of 'jellied' or 'mushy' products reduces the market value considerably, leading to wastage and losses in the fisheries. The syndrome is associated with an abnormally high moisture content and lowered protein of the white skeletal musculature, particularly the fillets. Alterations in lipid content varies depending on species investigated. In some fish species, myxozoan infections can induce similar fillet alterations, but studies on 'jellied' or 'mushy' meat indicate a non-infectious myopathy. Several hypotheses have been launched to explain the jelly-like syndrome, including dietary deficiencies, spawning exhaustion, environmental circumstances, genetics and adaptive physiology. This review provides a comprehensive overview of the characteristics of the 'jellied' or 'mushy' syndrome including a discussion of plausible etiologies and applicable mitigation strategies. The main conclusion is that the syndrome may involve two different etiologies dependent on species and location, but new studies are needed to verify past findings and rule out alternative explanations. A growing human population and an increasing demand for food requires efficient utilization of all harvested fish products. Expanded and updated knowledge is vital to reduce food waste and losses related to 'jellied' or 'mushy' fish in catches, and promote sustainable quota usage. We advocate for further research into the syndrome, including prevalence in commercial fish stocks and correlational studies with focus on association with biological parameters, chemical composition, infectious agents, geographic distribution and seasonal variation., Competing Interests: The authors declare no competing interests., (© 2024 The Authors.)

Members of the myxosporean genus Kudoa are defined as having a myxospore with four or more shell valves (SVs) and a corresponding number of polar capsules (PCs). Here, we employed integrated taxonomic approaches to four kudoid isolates from Acentrogobius chlorostigmatoides and Konosirus punctatus from the South China Sea, off Guangdong, Pentanemus quinquarius from the Southeast Atlantic Ocean, off West African coast, and Atheresthes stomias from the Bering Sea, off Alaska, and concluded that all these kudoids were novel species, named Kudoa acentrogobia n. sp., Kudoa guangdongensis n. sp., Kudoa iidae n. sp., and Kudoa aburakarei n. sp., respectively. Kudoa guangdongensis n. sp., forming pseudocysts in the trunk muscle myofibers of K. punctatus, had large-sized tripod myxospores with three wing-like SV extensions and three PCs (one prominent PC and two rudimentary PCs). Phylogenetic analyses based on the 18S and 28S ribosomal RNA gene (rDNA) demonstrated its affinity to the genus Kudoa, not to Unicapsula characterized by a myxospore with one prominent PC and two rudimentary PCs, suggesting the atypical nature of this new species in the context of myxospore morphology. Three other kudoid isolates had four SVs and PCs in a semi-quadrated, ray-like, or cruciform myxospore, respectively, forming pseudocysts in the trunk muscle myofibers. Kudoa iidae n. sp. forming pseudocysts in the muscles of P. quinquarius from Southeast Atlantic Ocean had unique myxospores with ray-like form, showing close morphological resemblance to Kudoa rayformis, which were recorded from the muscle of Scomberomorus sierra from the Pacific Ocean off Panama. These two species had a phylogenetic relationship of morphological convergence, evolving separately in different sea areas. It is fairly difficult to differentiate K. acentrogobia n. sp. and K. aburakarei n. sp., prevalent in their host fishes, from kudoid species with similar myxospore morphology (e.g., Kudoa nova and Kudoa thyrsites, respectively), but distinct in phylogeny from known Kudoa spp. Combined taxonomic identification of multivalvulid myxosporeans based on both morphological criteria of isolated myxozoans and their molecular characterization could disclose their real biodiversity and phylogeny. [ABSTRACT FROM AUTHOR]

Members of the myxozoan genus Kudoa (Myxosporea: Multivalvulida: Kudoidae) are characterized as having four or more shell valves in a myxospore, with a corresponding number of polar capsules. Certain Kudoa spp. are critical pathogens in fish, causing postmortem myoliquefaction, unmarketable fish musculature due to unsightly macroscopic cysts, and reduced aquaculture production due to the outbreaks of neurological symptoms or cardiac diseases. Molecular genetic techniques have enabled the differentiation of Kudoa spp. with morphologically similar myxospores. In the present study, we employed integrated taxonomic approaches on five Kudoa spp. forming cysts between the trunk muscle myofibers (K. bora from Osteomugil perusii and K. lutjanus from Acanthopagrus latus), or cysts in the gallbladder wall (K. petala from Sillago sihama), and pseudocysts in the trunk muscle myofibers (K. uncinata from Nuchequula nuchalis and K. fujitai n. sp. from O. perusii). These four host fishes, which originated in the South China Sea, were purchased in the wet markets in Zhanjiang City, Guangdong Province, China, between August 2016 and April 2018. We have redescribed the four Kudoa spp. (K. bora, K. lutjanus, K. petala, and K. uncinata) on which little data are available after their original descriptions. Particularly, genetic characterization of K. bora and K. lutjanus, which are known to have myxospores morphologically similar to those of K. iwatai, was performed based on the nuclear ribosomal RNA gene and partial mitochondrial DNA genes such as cytochrome c oxidase subunit I and small and large ribosomal genes, demonstrating the validity and independence of these three kudoid species. We also provide description of a new species—K. fujitai n. sp.—in the present study. Application of integrated taxonomic approaches to known species characterized solely based on morphological criteria, as well as unknown species (e.g., K. fujitai n. sp. in the present study), contributes to better understanding of the biodiversity of Kudoa and multivalvulid myxosporeans. [ABSTRACT FROM AUTHOR]

Ultrastructural and phylogenetic description of a fish-infecting myxosporean found infecting the gallbladder wall of the teleostean Eugerres brasilianus Cuvier, 1830, collected from the Atlantic coast near the city of Maceió (Alagoas State), Brazil. Groups of mature pseudo-conical myxospores, agglutinated forming pseudocyst structures, occurring in the mucosa of gallbladder were 5.2 ± 0.8 μm (4.5–6.0) (n = 30) long, 4.3 ± 0.6 μm (3.8–4.7) (n = 25) thick, and 2.9 ± 0.2 μm (2.7–3.2) (n = 25) wide. The two ellipsoidal polar capsules, 1.8 ± 0.4 × 1.2 ± 0.4 μm (n = 25), opened close to the sutural line, each containing an isofilar polar tubule. The latter consisted of a single coil with five to six turns, arranged obliquely to the axis of the polar capsule. This myxosporean parasite, while being morphologically similar to Sphaerospora spp., displays tissue tropism and phylogenetic relationships distinct from the latter. Bayesian inference (BI) and maximum likelihood (ML) analyses showed the parasite and two other related species clustering within the marine clade, more specifically within a subclade of the larger Kudoa (Multivalvulida) clade. Consequently, this atypical new myxozoan species was classified as Kudoa eugerres n. sp. and two other histozoic Sphaerospora spp. sensu lato were transferred to the genus Kudoa. [ABSTRACT FROM AUTHOR]

To date, 26 Kudoa spp. (Myxozoa: Myxosporea: Multivalvulida) have been recorded in edible marine fishes in Japan. In the future, it is likely that even more marine fish multivalvulid myxosporeans will be characterized morphologically and genetically, which will aid the precise understanding of their biodiversity and biology. We examined 60 individuals of six fish species collected from the Philippine Sea off Kochi or from the border between the Philippine Sea and East China Sea around Miyako Island, Okinawa, i.e., the southern part of Japan. Newly collected parasite species included Kudoa yasunagai from the brain of Japanese meagre (Argyrosomus japonicus) and Japanese parrotfish (Calotomus japonicus), Kudoa miyakoensis n. sp. and Kudoa thalassomi from the brain and trunk muscle, respectively, of bluespine unicornfish (Naso unicornis), and Kudoa igami from the trunk muscle of Carolines parrotfish (Calotomus carolinus), African coris (Coris gaimard), and Pastel ringwrasse (Hologymnosus doliatus). With the exception of Japanese parrotfish for K. yasunagai, all these fish are new host records for each kudoid species. Notable variation in the number of shell valves (SV) and polar capsules (PC) was observed for all four kudoid species. In particular, spores with seven or eight SV/PC were prominent in K. igami isolates, despite the original Japanese parrotfish-derived description characterizing it as having spores with six, or less commonly five, SV/PC. However, molecular genetic characterization based on the ribosomal RNA gene (rDNA) and mitochondrial DNA (cytochrome c oxidase subunit 1 and ribosomal RNA small and large subunits) found no significant differences in the nucleotide sequences of isolates with different phenotypical features as far as examined in the present study. A newly erected species, K. miyakoensis n. sp., was determined to be phylogenetically closest to brain-parasitizing species, such as K. chaetodoni, K. lemniscati, and K. yasunagai based on rDNA nucleotide sequences, but differed from them morphologically. [ABSTRACT FROM AUTHOR]

We screened 360 chemicals and discovered that 71 chemicals had anti-Kudoa septempunctata effect. Especially 19 and seven of 71 chemicals were antibiotics and antibacterial agents/disinfectants, respectively. The other 45 chemicals were pesticides, natural toxins, industrial chemicals and medicines for non-infectious diseases. Nineteen antibiotics that possessed anti-Kudoa effect contained four tetracyclines, one steroid, two macrolides, one aminoglycoside, three 々-lactams, one quinolone, two rifamycines, one polyene, one novobiocine, one sulfonamide and two nitroimidazoles. To use these drugs for prevention of Kudoa infection, the further study is need for the determination of effective dose. [ABSTRACT FROM AUTHOR]

The Japanese Spanish mackerel (Scomberomorus niphonius; Perciformes: Scombridae) is widely distributed in the continental shelves of the northwestern Pacific Ocean around Japan, Sea of Japan, and East China Sea. In the present study, small, spindle-shaped myxosporean plasmodia (0.15–0.53 mm by 0.04–0.13 mm) were frequently encountered in the myofiber of trunk muscles of two Japanese Spanish mackerels; one fished in the Sea of Japan off western Japan and the other in the northwestern Pacific Ocean off southern Japan in the autumn of 2016. Isolated myxospores of Kudoa konishiae n. sp. (Myxosporea: Multivalvulida) from these two fish were stellate with six equal shell valves and polar capsules, 8.1–9.7 μm in width, 7.1–8.8 μm in thickness, and 7.1–8.8 μm in length. The polar capsules were teardrop-shaped, 2.7–4.7 μm by 1.2–2.5 μm. The lateral view of spores revealed a drawstring-pouch shape. The nucleotide sequences of the 18S and 28S ribosomal RNA gene (rDNA) were distinct from any recorded species. Phylogenetic trees demonstrated a close relationship of the present new species with Kudoa spp. with stellate spores with five or more shell valves/polar capsules, recorded in scombrid fishes. To clarify the phylogenetic relationships between three closely related species, i.e., Kudoa konishiae n. sp., Kudoa hexapunctata, and Kudoa neothunni, three mitochondrial DNA genes (cytochrome c oxidase subunit 1 gene (cox-1) and the small and large subunits of the ribosomal RNA gene (rns-rnl)) of two isolates of the new species, six isolates of K. hexapunctata, and 13 isolates of K. neothunni were sequenced. The interspecific and intraspecific variations of the newly obtained cox-1 and rns-rnl nucleotide sequences of K. hexapunctata, K. neothunni, and K. konishiae n. sp. were clarified for the first time. [ABSTRACT FROM AUTHOR]

Kudoa septempunctata, a myxosporean parasite, is the causative agent of a foodborne illness associated with consumption of raw Paralichthys olivaceus (olive flounder). Because the lag phase of this illness is short (from 1 to 12 h), it is possible that an allergic response is relevant to this illness. To test whether a K. septempunctata antigen is the possible allergen, we injected a myxospore extract into BALB/c mice and measured IgE levels in serum. When the mice were injected with the myxospore extract, the total serum IgE concentration increased significantly after the second immunization as compared to the negative control. After the third immunization, total IgE concentration in the immunized mice reached 26.5 ng/ml and was almost equivalent to that of egg albumin-injected mice. Western blot analysis revealed that IgE antibodies-in serum samples that were collected from myxospore extract-injected mice-bound to at least two Kudoa proteins with molecular weight between 28 and 36 kDa. These results suggested that a K. septempunctata antigen is the allergen. Further studies are needed to clarify the contribution of allergy to the foodborne illness caused by K. septempunctata. [ABSTRACT FROM AUTHOR]

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Kudoa septempunctata , a myxosporean parasite of the olive flounder ( Paralichthys olivaceus ), causes foodborne gastroenteritis after ingestion of contaminated raw flounder. Available methods to detect K . septempunctata require expensive equipment, well-trained personnel, and lengthy procedures. Here we generated a novel monoclonal antibody (MAb 15G11) against K. septempunctata and used it to produce a prototype immunochromatographic assay (prototype Kudoa-ICA). Within 15 min, the prototype Kudoa-ICA detected ≥ 1.0 × 10 5 spores/mL in a spore suspension and ≥ 2.0 × 10 4 spores/g of P. olivaceus muscle. The prototype Kudoa-ICA weakly cross-reacted with spores of K. lateolabracis and K. iwatai . cDNA sequence, expression, and western blot analyses revealed that MAb 15G11 detected an approximately 24-kDa protein encoded by a 573 bp mRNA. The cDNA nucleotide and predicted amino acid sequences were not significantly similar to any sequence in the GeneBank database. Immunoelectron microscopy revealed that MAb 15G11 reacted with the sporoplasmic cells and mainly with the capsulogenic cells of the K. septempunctata spore. Although the Kudoa-ICA was weakly cross-reactive with two other Kudoa species, it detected > 1.0 × 10 6 spores/g of K. septempunctata in P. olivaceus muscle, which is the criterion used to indicate a violation of the Food Hygiene Law of Japan. We conclude that MAb 15G11 may be suitable for use in an immunochromatographic assay for screening P. olivaceus muscle contaminated with K. septempunctata at food distribution sites such as food wholesalers, grocery stores, and restaurants. [ABSTRACT FROM AUTHOR]

A variety of tunas of the genus Thunnus are consumed daily in Japan as sliced raw fish (sashimi and sushi). The consumption of fresh sliced raw fish, i.e., unfrozen or uncooked, can sometimes cause food poisoning that is manifested by transient diarrhea and vomiting for a single day. One of the causes of this type of food poisoning has been identified as live Kudoa septempunctata (Myxosporea: Multivalvulida) in the olive flounder ( Paralichthys olivaceus). Furthermore, raw slices of fresh tunas are highly suspected to be a possible causative fish of similar food poisoning in Japan. In the present study, we conducted a survey of kudoid infections in tunas (the yellowfin tuna Thunnus albacares, the Pacific bluefin tuna Thunnus orientalis, and the longtail tuna Thunnus tonggol) fished in the western Pacific Ocean off Japan and several East Asian countries and characterized morphologically and genetically the kudoid myxospores in pseudocysts or cysts dispersed in the trunk muscles. Pseudocysts of solely Kudoa hexapunctata were identified in the Pacific bluefin tuna (four isolates), whereas in the yellowfin tuna (21 isolates) pseudocysts of Kudoa neothunni and K. hexapunctata were detected at a ratio of 15:6, respectively, in addition to cyst-forming Kudoa thunni in five yellowfin tunas. In the trunk muscles of six longtail tunas examined, pseudocysts of K. neothunni (all six fish) and K. hexapunctata (two fish) were densely dispersed. The myxospores of K. neothunni found in these longtail tunas had seven shell valves and polar capsules (SV/PC) instead of the more common six SV/PC arranged symmetrically. Nucleotide sequences of the 18S and 28S ribosomal RNA gene (rDNA), some with the internal transcribed spacer regions as well, of K. hexapunctata and K. neothunni from the three Thunnus spp., including the seven-SV/PC morphotype, were very similar to previously characterized nucleotide sequences of each species, whereas the 18S and 28S rDNA of four isolates of K. thunni from yellowfin tunas showed a range of nucleotide variations of 99.0-99.9% identity over 1752-1763-bp long partial 18S rDNA and 97.4-99.9% identity over 797-802-bp long partial 28S rDNA. Therefore, this rather high variation of the rDNA nucleotide sequences of K. thunni proved to be contrary to the few variations of K. neothunni and K. hexapunctata rDNA nucleotide sequences. The present study provides a new host record of the longtail tuna for K. neothunni and K. hexapunctata and reveals a high prevalence of the seven-SV/PC myxospore morphotype of K. neothunni in this tuna host. [ABSTRACT FROM AUTHOR]

Molecular genetic characterization using the ribosomal RNA (rDNA) gene accrues a wealth of knowledge regarding the true nature of species diversity of Kudoa Meglitsch, 1947 (Myxozoa: Myxosporea: Multivalvulida) and the biogeographical relationships of isolates from different host fish and sea areas. In the present study, we characterized morphologically and genetically three Kudoa spp. with four shell valves and polar capsules (SV/PC), forming pseudocysts in the myofiber of trunk muscles of Cheilodactylus zonatus or Acanthogobius hasta in the natural seawater around Japan. Myxospores from C. zonatus fished in the western Pacific Ocean off Kochi, Japan, were unequal quadrangular pyramids with one large and three smaller SV/PC, morphologically closest to Kudoa whippsi recorded in various pomacentrid and apogonid fish from the Australian Coral Sea. The 18S and 28S rDNA nucleotide sequences of the Japanese isolate were highly similar to some Australian K. whippsi isolates, but also displayed less similarity to other K. whippsi isolates from the same sea mainly due to instability of nucleotides at certain base positions and/or segments of different isolates. All the K. whippsi isolates including the present Japanese isolate, however, were distinct from Kudoa gunterae, K. whippsi's closest kudoid species in morphology, molecular phylogeny, and biogeography. Our detection of K. whippsi from C. zonatus in the natural seawater around Japan is a new host and geographical record. Kudoid myxospores from A. hasta from the Sea of Ariake, a deep bay of the western part of Japan, exhibited two morphotypes, one resembling K. whippsi and the other Kudoa quadricornis with distinct posteriolateral SV projections. However, rDNA nucleotide sequencing revealed that these two Kudoa spp. were distinct from any known congeners; thus, Kudoa akihitoi n. sp. and Kudoa empressmichikoae n. sp. were erected. The morphological differentiation of K. akihitoi n. sp. from multiple Kudoa spp. with scalene stellate myxospores containing one large and three smaller SV/PC was difficult, whereas K. empressmichikoae n. sp. with spherical spore bodies extending small posteriolateral SV projections was distinct from known congeners with similar but elongated spore bodies and PC, i.e., K. quadricornis and Kudoa paraquadricornis, found in the trunk muscle of carangid fish from the Australian Coral Sea. [ABSTRACT FROM AUTHOR]

We developed a PCR assay targeting the 28S rDNA of Kudoa iwatai (Multivalvulida: Myxozoa) and investigated the prevalence of infection in rock bream Oplegnathus fasciatus, which is commercially an important aquaculture species in Korea, with this assay. Detection limit of the PCR assay was 2.5 fg/μl with plasmid DNA and 8.6 × 10 spores/ml with purified spores, respectively. This PCR assay did not amplify DNA of other Kudoa species ( Kudoa septempunctata, Kudoa lateolabracis, Kudoa thyrsites) tested. Sliced muscles of whole body from 318 rock bream (wild and cultured) were examined by this PCR assay and also with the naked eyes. All of the wild fish did not produce amplicons nor did harbor visible Kudoa cysts (0/70). Three of the cultured fish were PCR-positive and also harbored visible Kudoa cysts (3/248, 1.2%). The sequences of amplicons (574 bp) were 100% identical with those of the K. iwatai already registered in Genbank. When the visceral organs of these three fish were examined, visible cysts were not found, but one stomach sample was found to be PCR-positive. There was no difference in the prevalence of infection estimated by PCR assay and the presence of visible Kudoa cysts in our samples. This is thought to be because the development of K. iwatai is already completed and only mature Kudoa cysts existed in our samples. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate the antibacterial and antiadhesive activities of ethanol extracts from five edible plant parts: cinnamon bark ( Cinnamomum zeylanicum), licorice root ( Glycyrrhiza radix), nettle leaves ( Urtica dioica), green tea leaves ( Camellia sinensis), and elderberry flowers ( Sambucus nigra). The chemical constituents of the extracts were identified using high-performance liquid chromatography and liquid chromatography plus mass spectrometry. Six strains of Asaia lannensis and Asaia bogorensis bacteria isolated from spoiled commercial fruit-flavored noncarbonated mineral water were used. Bacterial adhesion to polystyrene as an attachment substrate in culture media supplemented with 10% plant extract was evaluated using luminometric measurement of the ATP extracted from adhered cells. The viability of the adhered and planktonic cells was assessed using the plate count method, and the relative adhesion coefficient was calculated. All tested crude extracts contained flavonols (kaempferol, quercetin, and their derivatives), flavanols (catechin and derivatives), flavanones (glabrol, licorice glycoside A, and liquiritin), and phenolic acids (gallic, quinic, chlorogenic, neochlorogenic, caffeic, coumaric, and ferulic). The culture medium with 10% elderberry extract provided the least favorable environment for all tested bacterial strains. Extracts from green tea, cinnamon, and licorice also had significant inhibitory effects on the adhesion of the tested bacterial strains. This research suggests that the addition of selected edible plant extracts could improve the microbial stability of noncarbonated soft drinks. [ABSTRACT FROM AUTHOR]

Since the identification of Kudoa septempunctata as a causative agent of human food poisoning, Kudoa infections have become a serious concern in the aquaculture of olive flounder ( Paralichthys olivaceus ). In order to ensure the safety of cultured flounder, various methods have been developed to detect K . septempunctata . However, less attention has been paid for inspection and detection of other Kudoa species. To date, six Kudoa spp. have been reported from olive flounder, 3 species each from the trunk muscle, 2 species from the brain, and one species from the heart. During our routine inspection of cultured olive flounder, we isolated several Kudoa species including Kudoa igami and Kudoa ogawai in addition to the list of previously reported species. In the present study, a multiplex PCR (mPCR) was developed to detect all Kudoa spp. known to date from olive flounder in Japan. The mPCR also differentiate K . septempunctata among other Kudoa spp. simultaneously. The developed mPCR successfully detected seven Kudoa spp. and differentiated K. septempunctata with a sensitivity of 10 3 myxospores. Thus, mPCR offers a reliable and relatively simple method to detect Kudoa infection in olive flounder, specifically aiming to identify K . septempunctata infection. Statement of Relevance Olive flounder Paralichthys olivaceus is one of the most important fish species for commercial aquaculture and fishery trading in Japan and Korea. Infections of microscopic myxozoan parasite of genus Kudoa (Myxozoa: Multivalvulida) has become a serious concern in flounder culture since the recent identification of Kudoa septempunctata as a causative agent of human food poisoning. Although various detection methods have been developed for the inspection of K. septempunctata , relatively little attentions are given to other Kudoa spp. We added K. ogawai and K. igami to the list of Kudoa spp. infecting olive flounder and developed multiplex PCR to simultaneously detect Kudoa spp. and distinguish K. septempunctata . This offers relatively simple and method to inspect Kudoa spp. in cultured flounder. [ABSTRACT FROM AUTHOR]

In the present study, 100 samples of different sizes of the common sea bream fish Pagrus pagrus were collected from the Egyptian water along the Gulf of Suez, Red Sea and examined for the prevalence of myxosporidian parasites in general and Kudoa spp. in particular. Fish samples were thoroughly externally examined. After dissection, all the internal organs were removed and examined. A total of 60 out of 100 fish specimens were found to be infected with Kudoa stages. Parasitic infection was restricted to the heart muscles of the examined fish. None of the other organs was found to be infected. Macroscopic cysts (plasmodia) heavily infested the different parts of the heart muscles. Each plasmodium measured 1.2-2.5 (1.53 ± 0.2) mm × 0.63-0.80 (0.65 ± 0.2) mm. Mature spores are quadratic in shape in the apical view showing four equal valves and four symmetrical polar capsules. Fresh spores were 5.0-7.1 (5.7 ± 0.2) μm long × 5.4-8.5 (6.1 ± 0.3) μm wide. On the basis of spore morphology, the present species was identified as Kudoa pagrusi. Morphometric characterization revealed that the relatively small size of this Kudoa species was the distinctive feature that separates it from all previously described species. Molecular analysis based on small subunit ribosomal DNA (SSU rDNA) sequences revealed that the highest percentage of identity was observed with K. scomberomori and followed by K. shiomitsui, K. hypoepicarclialis, K. amamiensis, and K. kenti. The kudoid spores showed morphometric variations to some extents but had essentially identical nucleotide sequences of the SSU rDNA gene sequences closest to those of K. scomberomori and K. shiomitsui recorded from elasmobranchs in the Indo-Pacific Ocean. The present findings support the identification of an ancestral marine origin of the present Kudoa species. [ABSTRACT FROM AUTHOR]

Kudoa septempunctata (Myxosporean: Multivalvulida) is known as a cause of foodborne disease associated with consumption of raw flesh of the olive flounder ( Paralichthys olivaceus). Knowledge of its life cycle, particularly alternate annelid hosts and reservoirs or susceptible fish hosts in natural waters, may facilitate disease control in aquaculture farms. Our recent survey of myxosporean infection in monacanthid fish in natural waters around Japan revealed infection with three kudoid species prevalent in the olive flounder, i.e., K. septempunctata, Kudoa thyrsites, and Kudoa shiomitsui. Of the 51 black scrapers ( Thamnaconus modestus) examined, five fish were infected: two fish with K. septempunctata and three with K. thyrsites. One of the fish infected with K. septempunctata was also infected with a K. thyrsites-like species. One of the 17 threadsail filefish ( Stephanolepis cirrhifer) and two of four unicorn leatherjackets ( Aluterus monoceros) were parasitized with K. shiomitsui. Three modest filefish ( Thamnaconus modestoides) had no kudoid infection. K. septempunctata from a black scraper fished in the Inland Sea of Japan off Yamaguchi had 6-8 (predominantly 7) shell valves/polar capsules, whereas K. septempunctata found in another black scraper from the Sea of Japan off Tottori had 5 or 6 (predominantly 6). However, the two isolates displayed identical 18S and 28S ribosomal RNA gene (rDNA) nucleotide sequences, which were also identical to the isolates from the olive flounder. K. thyrsites from the Inland Sea of Japan off Yamaguchi and Sea of Japan off Tottori and K. shiomitsui from the Sea of Japan off Shimane and western Pacific Ocean off Kochi were also morphologically and genetically characterized. They were found to be coincident with the previous reports from olive flounders. Furthermore, the K. thyrsites-like species found in a black scraper from the Inland Sea of Japan off Yamaguchi was morphologically and genetically characterized; a new species, Kudoa parathyrsites n. sp., is erected for this species. The relationships of the new species with K. thyrsites and related species as well as those of K. shiomitsui with Kudoa pericardialis and related species parasitizing the pericardium are briefly discussed. [ABSTRACT FROM AUTHOR]

To elucidate whether Kudoa septempunctata was able to live in the human intestine, we assessed viability of K. septempunctata sporoplasms under conditions that mimicked human and ragworm digestive tracts. To study the effect of osmotic pressure on viability, sporoplasms were incubated in 0.9 or 3.4 % sodium chloride solutions, which roughly corresponded to the osmotic pressure in human or ragworm tissues, respectively. While viability in 3.4 % sodium chloride did not change after 72 h, it dropped to 21 % in 0.9 % sodium chloride. To study the effect of temperature on viability, sporoplasms were incubated at 37, 15, or 25 °C, which were representative of human, winter ragworm, or summer ragworm temperatures, respectively. Viability decreased sharply to 8.4 % after 48 h at 37 °C, but remained essentially unchanged at 15 and 25 °C. In addition, sporoplasms showed strong susceptibility to bile. These results indicate that K. septempunctata could not live in the human intestine for a long time. [ABSTRACT FROM AUTHOR]

Foodborne disease outbreaks caused by raw olive flounders ( Paralichthys olivaceus) parasitized with Kudoa septempunctata have been reported in Japan. Origins of olive flounders consumed in Japan vary, being either domestic or imported, and aquaculture-raised or natural. Although it is unknown whether different sources are associated with different outcomes, it is desirable to identify whether this is the case by determining whether unique K. septempunctata strains occur and if so, whether some are associated with foodborne illness. We here developed an intraspecific genotyping method, using the sequence variation of mitochondrial genes. We collected olive flounder samples from foodborne disease outbreaks, domestic fish farms or quarantine offices and investigated whether K. septempunctata genotype is associated with pathogenicity or geographic origin. The 104 samples were classified into three genotypes, ST1, ST2 and ST3. Frequency of symptomatic cases differed by genotypes, but the association was not statistically significant. Whereas K. septempunctata detected from aquaculture-raised and natural fish from Japan were either ST1 or ST2, those from fish inspected at quarantine from Korea to Japan were ST3. Our method can be applied to phylogeographic analysis of K. septempunctata and contribute to containing the foodborne disease. The genotype database is hosted in the Pub MLST website (). [ABSTRACT FROM AUTHOR]

Kudoa rayformis n. sp. (Myxozoa; Multivalvulida) was observed in the trunk muscle of Pacific sierra Scomberomorus sierra caught off the coast of Tonosi, Panama. The species formed pseudocysts in myofibers and infection was subclinical. The myxospores possessed four polar capsules and spore valves, one of which had a distinct filamentous extension. This unique morphological characteristic of the myxospore validated this as a new species of Kudoa . Genetically, K. rayformis n. sp. is closest to K. inornata , with 98% and 91% similarity in 18S and 28S rDNA, respectively, but its spore shape was clearly distinct. The 18S rDNA and concatenated sequences from K. rayformis were used in molecular phylogenetic analyses of kudoids to examine the congruence of phylogeny with infection site tropism, spore morphology and cyst/pseudocyst formation. The results demonstrated that the phenotypic traits were correlated with the phylogeny of Kudoidae, and that the biological features of K. rayformis originated from the ancient Kudoidae as exhibited by the non-specific infection site tropism and the ability to infect muscle and form pseudocysts. [ABSTRACT FROM AUTHOR]

This study describes a co-infection of Kudoa islandica (Myxozoa) and Nucleospora cyclopteri (Microsporida) in farmed lumpfish, Cyclopterus lumpus L. , in Norway. Several other parasites ( Cryptocotyle sp., protozoan ciliates and Gyrodactylus sp.) were also found in gills. In June 2013, the mortality in a farmed lumpfish population increased to 65%. Lumpfish showed erratic swimming behaviour and loss of weight. At necropsy, nodules in the kidney were the only visible lesions. Histologically, all fish showed severe changes with gill inflammation and necrosis in the spleen, kidney and liver. Haemorrhages and necrosis were observed in some hearts. Intracellular microsporidians associated with the lesions were detected in most organs using histological examination and Calcofluor White. Kudoa spores were diagnosed in the skeletal muscle, but no inflammatory response was associated with the presence of the plasmodia. Comparison of 18S ribosomal DNA sequences showed 100% similarity to Kudoa islandica and Nucleospora cyclopteri. Kudoa islandica and N. cyclopteri have previously been described associated with lesions in wild lumpfish in Iceland. In the present case, N. cyclopteri is believed to be the main cause of systemic pathology. This is the first description of K. islandica and N. cyclopteri causing pathology in farmed lumpfish in Norway. [ABSTRACT FROM AUTHOR]

The influence of prior infection with Kudoa thyrsites or host size on the susceptibility of Atlantic salmon post-smolts to infection with the parasite was investigated. Exposure to infective K. thyrsites in raw seawater (RSW) was regulated by the use of ultraviolet irradiation (UVSW). Naïve smolts were exposed to RSW for either 38 days (440 degree-days, DD) or 82 days (950 DD) after which they were maintained in UVSW. Control fish were maintained on UVSW only. Microscopic examination at day 176 (1985 DD) revealed K. thyrsites infection in nearly 90% of exposed fish but not in controls. Prevalence and severity of the infection decreased in later samples. Following a second exposure of all fish at day 415 (4275 DD), prevalence and severity were elevated in the UVSW controls compared to previously exposed fish groups, suggesting the acquisition of protective immunity. In a second experiment, naïve smolts were exposed to RSW at weights of 101 g, 180 g, 210 g or 332 g and the prevalence and severity of K. thyrsites in the smallest fish group were higher than in any other group. However, infection parameters in the 101 g fish were not different from those in control fish (495 g) exposed in the first experiment. Concurrently, RSW was screened for K. thyrsites ribosomal DNA (rDNA) and the number of rDNA copies L − 1 seawater did not agree well with prevalence or severity of infections. Possible reasons for this poor agreement are discussed. Increased resistance to K. thyrsites was evident in Atlantic salmon post-smolts that have recovered from the infection, suggesting strategies for the mitigation of soft-flesh in market-size salmon. Statement of Relevance We showed that Atlantic salmon which had recovered from infection with Kudoa thyrsites were resistant to reinfection with the parasite, suggesting an acquired immunity and the possibility of vaccination as a management strategy. Quantitative detection of parasite DNA in seawater provides a tool for predicting the risk of infection with this economically important parasite. [ABSTRACT FROM AUTHOR]

A new myxosporean species is described from the muscle of the Amazonian freshwater fish Chaetobranchopsis orbicularis (Teleostei, Cichlidae), with basis on morphometric, ultrastructural and molecular data. Numerous myxospores were observed within pseudocysts located on the hosts' dorsal and ventral muscles, near the neural spines and neural canal (spinal cord). Mature myxospores quadrangular with rounded ends in apical view, measuring 4.3 (3.6-5.0) μm in length and 5.1 (4.2-5.8) μm in width. The myxospores wall is formed by four symmetric valves. Within, four pyriform polar capsules, 2.1 (1.7-2.6) μm long and 1.3 (0.9-1.7) μm wide, located two by two in opposite sides of the myxospores longitudinal axis, each containing a polar filament forming 2-3 coils. Molecular analysis of the SSU rRNA gene by maximum likelihood, neighbor-joining and maximum parsimony confirms the parasite as a new member of the genus Kudoa, herein named Kudoa orbicularis n. sp., the second species of its genus reported from the South American freshwater fauna, and the fourth species worldwide known to occur in the freshwater environment. Furthermore, its sequence of the SSU rRNA gene constitutes the first entry of a freshwater Kudoa species in GenBank. [ABSTRACT FROM AUTHOR]

The majority of Kudoa species infect the somatic muscle of fish establishing cysts. As there is no effective method to detect infected fish without destroying them these parasited fish reach the consumer. This work was developed to determine whether this parasite contains antigenic compounds capable of provoking an immune response in laboratory animals, in order to consider the possible immunopathological effects in man by the ingestion of Kudoa infected fish. BALB/c mice were injected by the subcutaneous route with the following extracts suspended in aluminium hydroxide: group 1 (black Kudoa sp. pseudocyst extract), group 2 (white Kudoa sp. pseudocyst extract), and group 3 (non-infected hake meat extract). Specific antibody levels were measured by ELISA against homologous and heterologous antigens. The highest responses were obtained from the black Kudoa sp. pseudocyst extract (group 1).The low optic density levels detected in group 3 proved that the results obtained in groups 1 and 2 were a consequence of the parasitic extract injection. The IgG1 was the predominant subclass. IgE detected in groups 1 and 2 showed the possible allergenic nature of some of the components of the parasitic extract. High IgA levels and medium IgG2a and IgG3 levels were obtained in groups 1 and 2. Low IgG2b responses were shown. No cross-reactions between Kudoa sp. pseudocyst extracts and the non-infected hake meat extract were observed.

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. [ABSTRACT FROM AUTHOR]