Salmincola markewitschi or S. carpionis (Copepoda: Lernaeopodidae)? A requirement for taxonomic revision due to their high morphological variations.

Salmincola markewitschi Shedko et Shedko, 2002 (Copepoda: Lernaeopodidae) is an ectoparasitic copepod mainly infecting the buccal cavities of white-spotted charr Salvelinus leucomaenis (Pallas) (Salmonidae). This species has only been recorded from Northeast Asia, where a morphologically similar congener Salmincola carpionis (Krøyer, 1837) is also distributed, using the same host species. These copepods are hard to distinguish from each other because of their similarities. We thus examined the newly collected specimens morphologically and genetically from five populations of white-spotted charr in Japan. Most of the specimens were morphologically consistent with S. markewitschi but showed great variations in the numbers of spines on the exopods of the antennae, shape of the maxilliped myxal palps, and the bulla diameter. Consequently, some specimens shared characteristics with S. carpionis. In addition to the mophological continuities, genetic analyses of 28S rDNA and COI mitochondrial DNA confirmed that all specimens belong to a single species. Further taxonomic revisions are required to draw conclusions of whether S. markewitschi is a valid species different from S. carpionis, by collecting samples from across their wide distributional ranges, such as Europe, North America, and Northeast Asia. A key to identification of species of Salmincola Wilson, 1915 occurring in Japan is also provided.

Somatosensory evoked potentials of the tibial nerve during the surgical decompression of thoracolumbar intervertebral disk herniation in dogs.

This study aimed to identify the impact on spinal cord integrity and determine the electrophysiological safety level during surgery for thoracolumbar intervertebral disk herniation in dogs. A total of 52 dogs diagnosed with thoracolumbar intervertebral disk herniation were enrolled. The tibial nerve somatosensory evoked potential elicited on the scalp by stimulation of the tibial nerve was recorded before and during hemilaminectomy. Both the amplitude and latency of the somatosensory evoked potential were periodically registered, and the percentage changes from the pre-operative control values (amplitude rate and latency rate) were calculated. When the multifidus muscles were retracted after removal from the spinous processes and vertebrae, the somatosensory evoked potential amplitude rate decreased in all dogs, while the latency rate increased in 33 dogs examined. The amplitude rate remained unchanged during the halting procedure, loosening retraction, and hemilaminectomy. After removing the disc material from the spinal canal, the amplitude rate was increased. The somatosensory evoked potential latency increased when the multifidus muscles were retracted and shortened after multifidus muscles closure in four cases. The outcome of all cases showed improvement in clinical signs 7 days after operation. Spinal cord conduction is impaired by retraction of the multifidus muscles and improved by removal of disk materials. Maintaining intraoperative SEP amplitudes above 50% of control may help avoid additional spinal cord injury during surgery. Since we have no case that worsened after the surgery, however, further studies are necessary to confirm this proposal.

Spillover and spillback risks of ectoparasites by an invasive squirrel Callosciurus erythraeus in Kanto region of Japan.

Invasive organisms can alter host-parasite relationships in a given ecosystem by spreading exotic parasites and/or becoming a new reservoir for native ones. Since these problems affect management programs of the invasive host organisms, it is necessary to monitor them individually. The Pallas's squirrel Callosciurus erythraeus is an invasive arboreal mammal introduced into Japan that threatens to exacerbate ecological and public health problems by spreading native and exotic parasites. However, only limited surveys have been available especially for ectoparasites, using the traditional combing method in which the possibility of oversight is inherent. Here, we evaluated the ectoparasite occurrences in Kanto region of Japan, using the whole-shaving method as an alternative approach. As a result of examining 52 hosts from two invaded districts (Yokohama and Yokosuka), chigger mites (Leptotrombidium spp.) and fleas (Ceratophyllus anisus and Ceratophyllus indages indages) were newly recovered in addition to the previously reported tick (Haemaphysalis flava) and exotic lice (Enderleinellus kumadai and Neophaematoponis callosciuri). The parasite burdens were higher in Yokosuka and in male host individuals, affecting infracommunity richness and composition. Our findings on the variety of native and exotic ectoparasites, at higher abundances in some cases than previously known, may suggest that both the spillover and spillback risks need to be adjusted upwards.

Microhabitat use of Pseudocharopinus markewitschi (Gusev, 1951) (Copepoda: Lernaeopodidae) on the mottled skate, Beringraja pulchra (Liu, 1932): Does biased occurrence on the dorsal side of the pelvic fin imply a safety zone?

The mottled skate Beringraja pulchra is a coastal fish caught by gillnet and bottom trawl fisheries in Hokkaido, Japan. We recently found a parasitic copepod identical to Pseudocharopinus markewitschi (Gusev, 1951) on this commercially important fish. A total of 109 host individuals caught off the coast of northern Hokkaido, Japan, were examined for adult females of this copepod, and 67 cases (61.5%) of infection comprised with 31 cases (67.4%) of 46 males and 36 cases (57.1%) of 63 females were found. The parasite specimens (n = 229) were recovered mainly from the dorsal side of the pelvic fin (n = 168, 73.4%), followed by the claspers (n = 32, 14.0%). The mottled skate is thought to spend most of its lifetime lying in sand or crawling on the seafloor. Therefore, the biased infection to the dorsal side of the pelvic fin may imply that site selection favors less susceptible for disturbances resulting from such host-specific behavior.

Potential negative effects and heterogeneous distribution of a parasitic copepod Salmincola edwardsii (Copepoda: Lernaeopodidae) on Southern Asian Dolly Varden Salvelinus curilus in Hokkaido, Japan.

The genus Salmincola is an ectoparasitic copepod group commonly infesting the branchial and buccal cavities of salmonids. While negative impacts on hatchery fishes have been reported, their impacts on wild fish populations and distribution patterns are critically understudied. In the Shiretoko Peninsula, Hokkaido, Japan, we found parasites belonging to this genus on the branchial cavity of a stream salmonid, Southern Asian Dolly Varden Salvelinus curilus. All parasites recovered were identified as Salmincola edwardsii based on morphological characteristics and partial 28S rDNA sequences. Prevalence was highly heterogeneous even among neighboring streams (0-54.8%, < 10 km) with the mean intensity among streams being generally low (2.19 parasites/infeted fish). Despite the low intensity, quantile regression analysis showed negative trends between parasite intensity and host condition, suggesting that the infestation of S. edwardsii has a potential negative impact on the host salmonid. In addition, a single copepod was found from an anadromous fish, which could indicate some salinity tolerance of the copepods. It is important to evaluate the effects of Salmincola spp. on host species and determine the limiting factors on the parasite's distribution for proper management.

Diphyllobothrium stemmacephalum (Cestoda: Diphyllobothriidae) found from a harbor porpoise in northern Japan, with comments on a geographical gap with human infection cases in southern Japan.

Even though the cetacean tapeworm Diphyllobothrium stemmacephalum occurs in both cold and warm waters, human infections and final host occurrences have been confined to temperate areas in and near Japan. We recently obtained a strobila of this cestode that was excreted from a harbor porpoise accidentally caught offshore of Hokkaido of northern Japan. Genetic analysis of 28S rDNA and cox1 genes confirmed that the cestode was D. stemmacephalum. Our finding sets the northernmost record of D. stemmacephalum in the western Pacific, suggesting that the risk of human infections by this parasite in northern Japan deserves further attention.

Relationship between salmon egg subsidy and the distribution of an avian predator.

As a spatial subsidy, which is the phenomenon of transferring resources from a donor system to a recipient system, anadromous salmonids contribute to the supply of marine-derived nutrients to freshwater and terrestrial systems. Live salmon and salmon carcasses and eggs are utilized by various organisms and affect their abundance and distribution. However, the evaluation of the effect of salmon subsidies on the abundance and distribution of terrestrial animals is biased toward predators or scavengers that utilize spawning adults and carcasses, and few studies have focused on the effect of salmon eggs as a subsidy. To avoid underestimating the function of salmon subsidies, the response to the availability of salmon eggs in various systems should be investigated. Here, we investigated the abundance and feeding behavior of the brown dipper Cinclus pallasii, as a consumer of salmon eggs, based on the hypothesis that the availability of salmon eggs affects the diet composition and stream distribution of this small predator. In addition, to test whether changes in the abundance of brown dippers are determined by salmon spawning, their abundance was compared upstream and downstream of the check dams in three streams during the peak spawning period. Brown dippers used salmon eggs during the spawning season (53.7% of diet composition), and their abundance increased as the number of spawning redds increased. In contrast, this pattern was not observed upstream of the check dam. These results suggested that the abundance and stream distribution of brown dippers vary according to the variation in the spatiotemporal availability of salmon eggs.

Gastric ulceration caused by genetically identified Anisakis simplex sensu stricto in a harbor porpoise from the Western Pacific stock.

The genus Anisakis is a well-known group of nematodes that parasitize cetaceans as the final host and cause mucosal damage to their stomach. However, little has been done to precisely identify the nematodes recovered from the final hosts, especially in the Western Pacific, because of taxonomic confusion about the discrimination of sibling species and the difficulties of obtaining specimens from cetaceans. We describe the results of genetic identification and histopathological observations of specimens recovered from an ulcerated lesion and stomach contents in the forestomach of a female harbor porpoise accidentally caught by a set net fishery in Usujiri, southern Hokkaido, Japan. All the specimens arbitrarily collected from the lesion and stomach contents were identified as Anisakis simplex sensu stricto according to their ITS rDNA sequences. The size of the ulcer was approximately 6.3 mm in diameter and it was infected with 119 individual nematodes, mostly consisting of L3 and L4 stage larvae (95.0%). Histological sections were characterized by a locally extensive ulcer with the parasites penetrating into the muscularis externa that caused a thickening of the surrounding mucosa.

Interspecific variation of prevalence by Scaphanocephalus (Platyhelminthes: Trematoda: Heterophyidae) metacercariae in parrotfishes (Labridae: Scarini) from an Okinawan coral reef.

Metacercarial cysts of the parasite Scaphanocephalus (Platyhelminthes: Trematoda: Heterophyidae) are frequently found on the pectoral fins and skin of parrotfishes (Labridae: Scarini) inhabiting Okinawan coral reefs in southern Japan. The prevalence of metacercarial cysts in 30 parrotfish species was investigated and compared through a market survey. Although parasite prevalence differed between parrotfishes, all species examined are considered to be suitable hosts. Prevalence was high in Scarus chameleon (38.5%, n = 13), S. rubroviolaceus (33.4%, 2797), S. ghobban (26.6%, 6441), and several other species that share, in part, common feeding habits. Conversely, prevalence was low in S. prasiognathos (0.4%, 1842), Bolbometopon muricatum (0.4%, 270), and Hipposcarus longiceps (0.1%, 8512) which have different feeding habits. Despite a few exceptions, feeding ecology and other indirect behaviors are considered to affect the prevalence of metacercarial cysts in parrotfishes. Taxonomic affiliation and nocturnal mucous cocoon usage are not considered to affect parasite prevalence.

One-sided infections by intestinal parasites in two sympatric porpoises bycaught from the Nemuro Strait of Hokkaido, Japan.

Due to the difficulties and limitations associated with field sampling of marine mammals, quantitative surveys on their parasites are still scarce in Japan. We here report the infection statuses of intestinal parasites in harbor porpoises (n = 34) and Dall's porpoises (n = 10), bycaught between 2014 and 2018 by a bottom set-net fishery in the northern part of the Nemuro Strait, Japan. Necropsies of the harbor porpoises recovered one digenean, Synthesium nipponicum, and two acanthocephalans, Corynosoma sp. and Bolbosoma sp.; no infection was observed in the Dall's porpoises. The dominant parasites were Corynosoma sp. and S. nipponicum, with a prevalence of 73.53 and 64.71% and a mean abundance of 43.88 and 7.38 individuals, respectively. Although the two porpoise-species have a sympatric distribution in this narrow strait, the findings support the existence of trophic-link dependences, which can differentially affect vulnerability to these parasites.

Infection status of commercial fish with cystacanth larvae of the genus Corynosoma (Acanthocephala: Polymorphidae) in Hokkaido, Japan.

Acanthocephalans of the genus Corynosoma are known as intestinal parasites, mainly of pinnipeds. Human corynosomiasis has been reported as an infrequent foodborne disease in Hokkaido, the northernmost island of Japan. Potential sources of the human infection are marine fish, because they are paratenic hosts of these parasites. In this study, the prevalence and intensity of larval Corynosoma in commercial fish from 17 fishing ports of Hokkaido were examined from April 2016 to January 2019. Out of a total of 1217 fish examined, 122 (10.0%) were infected with cystacanth larvae. The infected fish assemblage was composed of 7 families and 13 species from all the coastal seas of Hokkaido (the Pacific Ocean, Okhotsk Sea, and Japan Sea), showing that commercial fish can be source of human infection when eaten raw. Flatfish of the family Pleuronectidae showed the highest intensity of cystacanths, ranging from 1 to 56. A DNA barcoding system was developed in this study, based on the standard mitochondrial cox1 sequences of morphologically identified adults of Corynosoma spp. from pinnipeds in Hokkaido. By using the DNA barcoding, most of the fish-derived cystacanths were identified as either C. strumosum or C. villosum, and furthermore, a clinical isolate from human as C. villosum. Both of the species were commonly detected from various fish of Hokkaido, irrespective of the coastal seas. Flatfish frequently harbored C. villosum. Considering the wide range of commercial fish in Hokkaido and the advanced transportation system of fresh fish, there is a possibility that human corynosomiasis will occur everywhere in Japan.

Brachylaima asakawai sp. nov. (Trematoda: Brachylaimidae), a rodent intestinal fluke in Hokkaido, Japan, with a finding of the first and second intermediate hosts.

In the 1970's and 1980's, an unknown species of the genus Brachylaima (Trematoda: Brachylaimidae) had been recorded from the intestines of Rattus norvegicus and Apodemus speciosus in Hokkaido, Japan. The rodent fluke was characteristic in extending a bilateral vitellarium till the level of posterior margin of anterior testis and in keeping almost the same-sized spherical ovary and testes. In this study, the rodent fluke was rediscovered from A. speciosus, Apodemus argenteus, and Myodes rufocanus in Hokkaido. The resultant parasite collection enabled us to make a mitochondrial DNA (mtDNA) barcode for tracking its intermediate hosts. The metacercaria of the rodent fluke was detected frequently from the kidney of three species of land snails (Discus pauper, Succinea lauta, and Ainohelix editha). However, its sporocyst with cercariae was found only from the hepatopancreas of D. pauper, a fairly small snail. The wide-spectrum of the second intermediate host seems to increase the chance of transmitting the parasite to various mammals and birds. The use of indigenous land snails as the first and second intermediate hosts, the distinctiveness of the mtDNA sequence, and the characteristic morphology of all the developmental stages prompted us to propose Brachylaima asakawai sp. nov. for the rodent intestinal fluke in Hokkaido. The present field survey suggests that the life cycle of the new species is primarily dependent on a predator-prey relationship between rodents and D. pauper.

Prevalence, risk factors, and genetic diversity of veterinary important tick-borne pathogens in cattle from Rhipicephalus microplus-invaded and non-invaded areas of Benin.

Babesiosis, theileriosis, anaplasmosis, and heartwater are tick-borne diseases (TBD) that threaten livestock production in sub-Saharan Africa including Benin. This country has been faced with an invasion of Rhipicephalus microplus, a major vector for babesiosis, theileriosis, and anaplasmosis over the last decade. Yet, data on TBD and the impact of the invasive ticks are lacking, making risk level evaluation and disease control arduous. In this study, epidemiological features of Babesia bovis, B. bigemina, Theileria spp., Anaplasma marginale and Ehrlichia ruminantium infections in Benin cattle were investigated in R. microplus-invaded and non-invaded areas. Detection of pathogens was based on species-specific PCR assays and resulting data were used to identify risk factors. Genetic diversity and phylogenies were then evaluated using several markers. Out of 207 samples examined, 170 (82.1%), 109 (52.7%), 42 (20.3%) 24 (11.6%) and 1 (0.5%) were positive for T. mutans, A. marginale, B. bigemina, B. bovis and E. ruminantium, respectively. Animal gender (for B. bovis), exposure to R. microplus (for B. bigemina and A. marginale), animal age (for B. bigemina and A. marginale) and cattle breed and/or antiprotozoal treatment (for T. mutants) significantly modulated pathogen occurrence. In addition, R. microplus exposure was significantly related to co-infection patterns and cases of clinical theileriosis and/or anaplasmosis were recorded among cattle highly exposed to the tick. In the genetic characterization, Theileria spp. and E. ruminantium sequences were conserved. Babesia spp. and A. marginale, however, showed high sequence polymorphisms that indicate the presence of several strains and may be linked to R. microplus invasion. Taken together, these results ascertain the endemicity of tick-borne infections in Benin and suggest that the characteristics of Babesia spp. and A. marginale infections in R. microplus-invaded and non-invaded areas are different.

Host characteristics and infection level of an intestinal parasite Corynosoma strumosum (Acanthocephala) in the Kuril harbor seal of Erimo Cape, Hokkaido, Japan.

The Kuril harbor seal around Hokkaido is presently recovering from a resource crisis while conflicts with local fisheries have become a concern. However, its feeding habits, which are fundamental information for taking proper preventive measures, are still poorly understood. We thus examined the infection status of a trophically-transmitted parasite, Corynosoma strumosum in the seals of Erimo Cape, to assess the host's feeding habits with a practical view of the parasite as a biological indicator. A total of 2802 worms were found from 20 male and 20 female by-caught animals in salmon set nets within local fisheries during August to November 2014. The parasite abundance was explained mainly by the host's developmental stage and intestinal length while weakly affected by gender and body size, through an estimation of generalized linear models combined with hierarchical partitioning. Considering the past records that demersal fishes are the probable main sources of infection, the infection level may owe to individual host differences regarding these sources and/or feeding grounds with relating the host characteristics. This supports that the resource management of Kuril harbor seals requires careful consideration of the individual differences in feeding behavior.

Potential risk of a liver fluke Opisthorchis viverrini infection brought by immigrants from prevalent areas: A case study in the lower Northern Thailand.

Considering the long lifespan of the liver fluke Opisthorchis viverrini, human mobility from prevalent regions to other neighboring areas has the possibility to disperse carriers and complicate the opisthorchiasis problem. To evaluate this, mass screening of the fluke infection was conducted in nine communities of lower Northern Thailand, combined with a questionnaire survey to distinguish the participant's origin. The liver fluke infection was found in 70 individuals (7.2%) of the examined 971 stool samples from seven communities, with light intensity providing small numbers of eggs in the examined stool. Prevalence in the positive communities varied from 2.1% to 28.7%. As a result of generalized linear mixed models fitting, regional origin and raw-fish eating habits were stably selected as variables affecting the parasite infection while occupation and educational background were secondary ones. Majority of the infected cases (64.3%) were found from the immigrants of northeastern Thailand (the fluke prevalent region), providing 2.28-2.42 times higher infectious risk on average against the local residents. Daily consumption of raw fish averaged a 3.12-3.60 times higher risk compared to those with no raw-fish eating habit. Our findings suggest that people's origin and moving history deserve further attentions in health promotion programs including education for safe eating.

Human infection by acanthocephalan parasites belonging to the genus Corynosoma found from small bowel endoscopy.

A 73-year-old man with a suspected ileus in January 2013 and subsequently suffered melena in February 2014 was endoscopically examined. As a result of the examinations, unidentified species of Corynosoma sp. and Corynosoma villosum were recovered from the small intestine, further endoscopic diagnosis suggested relevance between abdominal pain and the present infections in the small intestine. The recovered worms were composed of gravid females with developed eggs, suggesting that these parasites can survive for a long time in the intestine after infection. In this case, the short interval between infections appears to be due to the individual's eating habits which consist of regularly consuming uncooked seafood.

Euryphorus brachypterus (Copepoda: Caligidae) on wild pacific bluefin tuna from the Tsugaru Strait, northern Japan.

Parasitic copepods infecting large scombrid fishes have been known for a long time because their hosts are economically important. Most studies, however, have focused on their morphology or their infection status in aquaculture from pathological viewpoints, and very few quantitative surveys have been conducted under conditions in the wild. This study therefore investigated the prevalence of Euryphorus brachypterus (Caligidae) in wild Pacific bluefin tuna (PBF). Results of sampling from August to September 2014 at the western area of the Tsugaru Strait, Japan showed that 13.2% of the PBF individuals (n = 1978) were infected with this copepod. The prevalence of infections was highest in larger fish but varied among landing dates, which were classified into three clusters and in all smaller fish, the prevalence of infections was zero. This suggests that E. brachypterus mainly uses the larger PBF, which becomes sources of further infections in other seas, and that at least two host populations with different infection statuses at the strait.

Heliconema anguillae Yamaguti, 1935, a physalopterid nematode found in Japanese eels: taxonomic resurrection with a note on the third-stage larva from intertidal crabs in western Japan.

A parasitic nematode from the stomach of Japanese eel Anguilla japonica Temminck et Schlegel in western Japan, previously identified as Heliconema longissimum (Ortlepp, 1922), was morphologically re-examined and compared with the previous descriptions. In addition, the third-stage larva of this nematode is described, based on the specimens of encapsuled larvae found in musculature of two crabs, Hemigrapsus sp. and Perisesarma bidens (De Haan), caught from the upper-intertidal zone of the same locality. As a result of the morphological observation, seven pairs of postcloacal papillae in adult males are confirmed. This matches with the character of H. longissimum, but the shape of the fifth postcloacal papillae differs between the present material and H. longissimum; the former possesses pedunculate papillae in the fifth pair whereas the latter has sessile papillae. Since the pedunculate papillae can be found in the original description and the syntype specimens of H. anguillae Yamaguti, 1935 that has been synonymised with H. longissimum, we thus here resurrect H. anguillae as an accepted species. For the life-cycle of the present nematode, littoral crabs, including the two infected species, are likely to be the source of infections for Japanese eels, acting as intermediate hosts.

Helminths from the giant mottled eel Anguilla marmorata Quoy & Gaimard in Japan, with a description of Acanthocephalus longiacanthus n. sp. (Acanthocephala: Echinorhynchidae).

Five helminths, including a new echinorhynchid acanthocephalan Acanthocephalus longiacanthus n. sp., are described based on specimens from the giant mottled eel Anguilla marmorata Quoy & Gaimard caught in a small river, western Japan. The new acanthocephalan is distinguished from the other congeners in terms of hook arrangement (8-9 longitudinal rows with 5-6 hooks per row) on proboscis, maximum length of hook blade (81-95 µm in male, 150-190 µm in female), lemnisci being longer than proboscis receptacle, and small-sized eggs (80-83 µm). Two monogeneans, Pseudodactylogyrus anguillae (Yin & Sproston, 1948) and P. bini (Kikuchi, 1929), and two acanthocephalans, Acanthocephalus gotoi Van Cleave, 1925 and Southwellina hispida (Van Cleave, 1925), were also found; this new material is described. The monogeneans are notorious as invasive parasites spreading worldwide via anthropogenic transportations of anguillid eels, but in Japanese waters A. marmorata appears to be an indigenous host for these parasites. Anguilla marmorata is a new host record for the acanthocephalans A. gotoi and S. hispida.

Influence of host habitat on the occurrence of gill monogeneans Pseudodactylogyrus spp. on wild Japanese eels Anguilla japonica.

With technological improvements in otolith microchemical analysis, the flexible use of habitat from coastal marine to fresh waters has been discovered in Japanese eels Anguilla japonica. We examined the occurrence of 3 congeneric gill monogeneans-Pseudodactylogyrus anguillae, P. bini, and P. kamegaii-on wild Japanese eels, in relation to the host's flexibility. From April 2008 to October 2009, 114 eels were collected from a brackish-water cove and 2 rivers flowing into the cove in Ehime Prefecture, western Japan. Based on otolith microchemical analysis, the eels were discriminated according to the following 4 types of habitat use: freshwater residents (Type I), individuals utilizing low-salinity habitats (Type II), downstream habitat-shifters (Type III), and cove residents (Type IV). P. anguillae occurred mainly on Type I and II eels, while P. bini was primarily found on Type I eels. In contrast, P. kamegaii occurred mainly on Type III and IV eels. Thus, we conclude that species composition and infection levels of Pseudodactylogyrus spp. clearly differed with habitat-use patterns of Japanese eels. Also, since P. anguillae was scarcely found on either Type III or IV eels, this study suggests that previous identifications of monogeneans collected from European brackish-water localities as P. anguillae may require verification.