Marine Parasites and Disease in the Era of Global Climate Change

Climate change affects ecological processes and interactions, including parasitism. Because parasites are natural components of ecological systems, as well as agents of outbreak and disease-induced mortality, it is important to summarize current knowledge of the sensitivity of parasites to climate and identify how to better predict their responses to it. This need is particularly great in marine systems, where the responses of parasites to climate variables are less well studied than those in other biomes. As examples of climate's influence on parasitism increase, they enable generalizations of expected responses as well as insight into useful study approaches, such as thermal performance curves that compare the vital rates of hosts and parasites when exposed to several temperatures across a gradient. For parasites not killed by rising temperatures, some simple physiological rules, including the tendency of temperature to increase the metabolism of ectotherms and increase oxygen stress on hosts, suggest that parasites' intensity and pathologies might increase. In addition to temperature, climate-induced changes in dissolved oxygen, ocean acidity, salinity, and host and parasite distributions also affect parasitism and disease, but these factors are much less studied. Finally, because parasites are constituents of ecological communities, we must consider indirect and secondary effects stemming from climate-induced changes in host-parasite interactions, which may not be evident if these interactions are studied in isolation.

It is marine: distinguishing a new species of Catatropis (Digenea: Notocotylidae) from its freshwater twin

The morphology of sexual adults is the cornerstone of digenean systematics. In addition, life cycle data have always been significant. The integration of these approaches, supplemented with molecular data, has allowed us to detect a new species that many researchers may have previously seen, but not recognized. Sexual adults from common eiders that we found in northern European seas were extremely similar to other notocotylids, but the discovery of their intermediate host, a marine snail, revealed the true nature of this material. Here we describe sexual adults, rediae and cercariae of Catatropis onobae sp. nov. We discuss how 'Catatropis verrucosa' should be regarded, justify designation of the new species C. onobae for our material and explain why it can be considered a cryptic species. The phylogenetic position of C. onobae within Notocotylidae, along with other evidence, highlights the challenges for the taxonomy of the family, for which two major genera appear to be polyphyletic and life cycle data likely undervalued.

Modeling Pathogen Dispersal in Marine Fish and Shellfish

In marine ecosystems, oceanographic processes often govern host contacts with infectious agents. Consequently, many approaches developed to quantify pathogen dispersal in terrestrial ecosystems have limited use in the marine context. Recent applications in marine disease modeling demonstrate that physical oceanographic models coupled with biological models of infectious agents can characterize dispersal networks of pathogens in marine ecosystems. Biophysical modeling has been used over the past two decades to model larval dispersion but has only recently been utilized in marine epidemiology. In this review, we describe how biophysical models function and how they can be used to measure connectivity of infectious agents between sites, test hypotheses regarding pathogen dispersal, and quantify patterns of pathogen spread, focusing on fish and shellfish pathogens.

A search for tiny dragons (Dracunculus medinensis third-stage larvae) in aquatic animals in Chad, Africa

Dracunculus medinensis, or human Guinea worm (GW), causes a painful and debilitating infection. The global Guinea Worm Eradication Program (GWEP) has successfully reduced human GW cases from 3.5 million in 21 countries in 1986 to only 30 cases in three remaining countries in 2017. Since 2012, an increase in GW infections in domestic dogs, cats and baboons has been reported. Because these infections have not followed classical GW epidemiological patterns resulting from water-borne transmission, it has been hypothesized that transmission occurs via a paratenic host. Thus, we investigated the potential of aquatic animals to serve as paratenic hosts for D. medinensis in Chad, Africa. During three rainy and two dry season trips we detected no GW larvae in 234 fish, two reptiles and two turtles; however, seven GW larvae were recovered from 4 (1.4%) of 276 adult frogs. These data suggest GW infections may occur from ingestion of frogs but the importance of this route is unknown. Additional studies are needed, especially for other possible routes (e.g., ingestion of fish intestines that were recently shown to be a risk). Significantly, 150 years after the life cycle of D. medinensis was described, our data highlights important gaps in the knowledge of GW ecology.

The blue mussel Mytilus edulis is vulnerable to the toxic dinoflagellate Karlodinium armiger-Adult filtration is inhibited and several life stages killed

Blooms of the toxic dinoflagellates Karlodinium armiger and K. veneficum are frequently observed in Alfacs Bay, Spain, causing mass mortality to wild and farmed mussels. An isolate of K. armiger from Alfacs Bay was grown in the laboratory and exposed to adults, embryos and trochophore larvae of the blue mussel, Mytilus edulis. Adult mussels rejected to filter K. armiger at cell concentrations >1.5·103 cells ml-1. Exposure of adult mussels (23-33 mm shell length) to a range of K. armiger cell concentrations led to mussel mortality with LC50 values of 9.4·103 and 6.1·103 cells ml-1 after 24 and 48 h exposure to ~3.6·104 K. armiger cells ml-1, respectively. Karlodinium armiger also affected mussel embryos and trochophore larvae and feeding by K. armiger on both embryos and larvae was observed under the microscope. Embryos exposed to low K. armiger cell concentrations suffered no measurable mortality. However, at higher K. armiger cell concentrations the mortality of the embryos increased significantly with cell concentration and reached 97% at 1.8·103 K. armiger cells ml-1 after 29 h of exposure. Natural K. armiger blooms may not only have serious direct effects on benthic communities, but may also affect the recruitment of mussels in affected areas.

PCR survey for Paramoeba perurans in fauna, environmental samples and fish associated with marine farming sites for Atlantic salmon (Salmo salar L.)

Amoebic gill disease (AGD) caused by the amoeba Paramoeba perurans is an increasing problem in Atlantic salmon aquaculture. In the present PCR survey, the focus was to identify reservoir species or environmental samples where P. perurans could be present throughout the year, regardless of the infection status in farmed Atlantic salmon. A total of 1200 samples were collected at or in the proximity to farming sites with AGD, or with history of AGD, and analysed for the presence of P. perurans. No results supported biofouling organisms, salmon lice, biofilm or sediment to maintain P. perurans. However, during clinical AGD in Atlantic salmon, the amoeba were detected in several samples, including water, biofilm, plankton, several filter feeders and wild fish. It is likely that some of these samples were positive as a result of the continuous exposure through water. Positive wild fish may contribute to the spread of P. perurans. Cleaner fish tested positive for P. perurans when salmon tested negative, indicating that they may withhold the amoeba longer than salmon. The results demonstrate the high infection pressure produced from an AGD-afflicted Atlantic salmon population and thus the importance of early intervention to reduce infection pressure and horizontal spread of P. perurans within farms.

Redescription of Paraleptus chiloscyllii Yin et Zhang, 1983 (Nematoda: Physalopteridae) from the Arabian carpetshark Chiloscyllium arabicum (Chondrichthyes: Hemiscylliidae) off Iraq

The nematode Paraleptus chiloscyllii Yin et Zhang, 1983 (Physalopteridae) is redescribed on the basis of new material collected from the stomach of the Arabian carpetshark Chiloscyllium arabicum Gubanov (Hemiscylliidae) from marine waters off Iraq. Originally, P. chiloscyllii was found in C. plagiosum (Anonymous [Bennett]) from Fujian, China, but its description was rather poor and some important morphological features, such as deirids, shape and number of structures surrounding mouth, ventral unpaired papilla on the anterior cloacal lip, among others, were overlooked. It differs from its congeners in the shape of spicules and body length, although is very similar to the type species, P. scyllii Wu, 1927, only differing in the inequality of spicules. The generic diagnosis of Paraleptus was amended. Paraleptus minnanensis (Damin et Heqing, 2001) is considered a junior synonym of P. chiloscyllii and some morphological details of the posterior end of a male of P. australis Johnston et Mawson, 1943 are provided. The present finding of P. chiloscyllii in C. arabicum from off Iraq represents new host and geographical records.

Vector ecology of human schistosomiasis in south India and description of a new species of the genus Ferrissia (Mollusca: Gastropoda: Planorbidae)

BACKGROUND & OBJECTIVES

Vector ecology and taxonomy of snails is a prerequisite for controlling schistosomiasis in the tropics. The ecology of the freshwater limpet genus Ferrissia was investigated for detection of cercariae larvae in them, and taxonomic description of a new species of the genus Ferrissia.

METHODS

This study was conducted in 15 perennial streams from five different hills of south India. To study the seasonal patterns, a stream from each hill was selected and sampled in three seasons. In each study site, triplicate sampling was done and specimens were collected from stream substrates as well as waste material submerged in stream. Microscopic examination was carried out for detecting cercariae larvae in limpets.

RESULTS

Three freshwater limpets (F. tenuis, F. verruca and F. fivefallsiensis) were observed. Seasonality influenced the abundance of limpets. The highest abundance was observed during post-monsoon (December and January). The distribution of Ferrissia was observed at riffle in pebbles, leaf litter and wastes (polyethylene bags and snacks cover) submerged in water. No cercariae larvae were found from the body of limpets. In this study, we described a new species of Ferrissia fivefallsiensis.

INTERPRETATION & CONCLUSION

Our results showed the distribution, habitat preference and seasonality of limpets, and recommend the detection of Schistosoma from limpets as well as human samples by use of molecular tools.

First records of parasitic copepods (Crustacea, Siphonostomatoida) from marine fishes in Korea

The knowledge of the biodiversity of parasitic copepods in South Korea is increasing. Interestingly we report here, some parasitic copepods considered as the first record of findings from Korea. Nine species of parasitic copepods (Siphonostomatoida) including six genera of three different families [Caligidae (7), Lernaeopodidae (1), Lernanthropidae (1)] were recovered from eight species of wild fishes in Korea: 1) Caligus hoplognathi Yamaguti & Yamasu, 1959 (♀, ♂) from the body surface of barred knifejaw Oplegnathus fasciatus (Temminck & Schlegel); 2) Caligus lagocephali Pillai, 1961 (♀) from the gills of panther puffer Takifugu pardalis (Temminck & Schlegel); 3) Euryphorus brachypterus (Gerstaecker, 1853) (♀, ♂) from the opercular cavity of Atlantic bluefin tuna Thunnus thynnus (Linnaeus); 4) Euryphorus nordmanni Milne Edwards, 1840 (♀, ♂) from the opercular cavity of common dolphin fish Coryphaena hippurus Linnaeus; 5) Gloiopotes huttoni (Thomson) (♀, ♂) from the body surface of black marlin Istiompax indica (Cuvier); 6) Lepeophtheirus hapalogenyos Yamaguti & Yamasu, 1959 (♀) from the gill filaments of O. fasciatus; 7) Lepeophtheirus sekii Yamaguti, 1936 (♀, ♂) from the body surface of red seabream Pagrus major (Temminck & Schlegel); 8) Brachiella thynni Cuvier, 1830 (♀) from the body surface of longfin tuna or albacore Thunnus alalunga (Bonnaterre); 9) Lernanthropinus sphyraenae (Yamaguti & Yamasu, 1959) (♀) from the gill filaments of moon fish Mene maculata (Bloch & Schneider). Since the female was already reported in Korea, it is a new record for the male of C. hoplognathi. A checklist for the parasitic copepods of the family Caligidae, Lernaeopodidae and Lernanthropidae of Korea is provided.

A new copepod with transformed body plan and unique phylogenetic position parasitic in the acorn worm Ptychodera flava

Symbiotic copepods compose one-third of the known copepod species and are associated with a wide range of animal groups. Two parasitic copepods endoparasitic in acorn worms (Hemichordata), Ive balanoglossi and Ubius hilli, collected in the Mediterranean Sea and Australian waters, respectively, were described a century ago. Here we report a new parasitic copepod species, Ive ptychoderae sp. nov., found in Ptychodera flava, a widespread acorn worm in the Indo-Pacific Ocean and an emerging organism for developmental and evolutionary studies. The female of I. ptychoderae is characterized by having a reduced maxilliped and five pairs of annular swellings along the body that are morphologically similar but distinguishable from those in the two previously described parasitic copepods in acorn worms. Phylogenetic analysis based on the 18S rDNA sequence shows that I. ptychoderae may belong to Poecilostomatoida but represent a new family, which we name Iveidae fam. nov. Ive ptychoderae is commonly found in the acorn worm population with an average prevalence of 42% during the collecting period. The infection of the parasite induces the formation of cysts and causes localized lesions of the host tissues, suggesting that it may have negative effects on its host. Interestingly, most cysts contain a single female with one or multiple male copepods, suggesting that their sex determination may be controlled by environmental conditions. The relationships between the parasitic copepods and acorn worms thus provide a platform for understanding physiological and ecological influences and coevolution between parasites and hosts.

Hydrological modelling of Toxoplasma gondii oocysts transport to investigate contaminated snowmelt runoff as a potential source of infection for marine mammals in the Canadian Arctic

Toxoplasma gondii (T. gondii) is a zoonotic protozoan that sometimes causes serious illness in humans and other animals worldwide, including the Canadian Arctic. Wild and domestic felids, the only hosts able to shed T. gondii oocysts, are practically non-existent in the Canadian Arctic. So here the hypothesis that T. gondii oocysts, shed in the southern areas of the boreal watershed, could contaminate the Arctic coastal marine environment via surface runoff, particularly during the spring snowmelt period, was explored. A watershed model was applied to simulate the hydrological transport of T. gondii oocysts during the snowmelt period and test the possible efficiency of river-to-sea transport as a potential source of marine organisms' exposure to this pathogen. Simulations were run for two pilot watersheds with the ultimate aim of extrapolating the results across the Canadian Arctic watersheds. Results suggest that daily stream flow concentrations of T. gondii oocysts at the river outlet are likely to be very low. However, accumulation of oocysts in the estuarine areas may be large enough to contaminate estuarine/marine filter-feeding molluscs and snails on which seals and other marine mammals may feed. Potential maximum concentrations of T. gondii oocysts in runoff are reached at the beginning of the snowmelt period with maxima varying with discharge rates into rivers and how far upstream oocysts are discharged. Meteorological conditions during the snowmelt period can affect simulated concentrations of oocysts. These findings support the hypothesis that T. gondii oocysts carried in snowmelt runoff could be a source of T. gondii infection for marine mammals in the Canadian Arctic, and for Arctic human populations that hunt and consume raw meat from marine mammals.

Nerocila species (Crustacea, Isopoda, Cymothoidae) from Indian marine fishes

Eleven Nerocila species are recorded from 22 marine fishes belonging to 15 families. Three, Nerocila arres, Nerocila depressa, and Nerocila loveni, are new for the Indian fauna. N. arres and Nerocila sigani, previously synonymized, are redescribed and their individuality is restored. Nerocila exocoeti, until now inadequately identified, is described and distinctly characterized. A neotype is designated. New hosts were identified for N. depressa, N. loveni, Nerocila phaiopleura, Nerocila serra, and Nerocila sundaica. Host-parasite relationships were considered. The parasitologic indexes were calculated. The site of attachment of the parasites on their hosts was also observed. A checklist of the nominal Nerocila species until now reported from Indian marine fishes was compiled.

Protozoa interaction with aquatic invertebrate: interest for watercourses biomonitoring

Toxoplasma gondii, Cryptosporidium parvum, and Giardia duodenalis are human waterborne protozoa. These worldwide parasites had been detected in various watercourses as recreational, surface, drinking, river, and seawater. As of today, water protozoa detection was based on large water filtration and on sample concentration. Another tool like aquatic invertebrate parasitism could be used for sanitary and environmental biomonitoring. In fact, organisms like filter feeders could already filtrate and concentrate protozoa directly in their tissues in proportion to ambient concentration. So molluscan shellfish can be used as a bioindicator of protozoa contamination level in a site since they were sedentary. Nevertheless, only a few researches had focused on nonspecific parasitism like protozoa infection on aquatic invertebrates. Objectives of this review are twofold: Firstly, an overview of protozoa in worldwide water was presented. Secondly, current knowledge of protozoa parasitism on aquatic invertebrates was detailed and the lack of data of their biological impact was pointed out.

Cavearhynchus, a new genus of tapeworm (Cestoda: Trypanorhyncha: Pterobothriidae) from Himantura lobistoma Manjaji-Matsumoto & Last, 2006 (Rajiformes) off Borneo, including redescriptions and new records of species of Pterobothrium Diesing, 1850

A new genus of trypanorhynch cestode is described from the tubemouth whipray Himantura lobistoma Manjaji-Matsumoto & Last, 2006 in the South China Sea off Malaysian Borneo. Cavearhynchus foveatus n. g., n. sp. possesses four pedicellate bothria in a cruciform arrangement, a heteroacanthous, heteromorphous metabasal tentacular armature with five hooks per principle row and an alternating longitudinal file of intercalary hooks on the bothrial surface of each tentacle, but lacks prebulbar organs and gland-cells within the bulbs. It, thus, closely resembles taxa belonging to the lacistorhynchoid family Pterobothriidae Pintner, 1931. However, the new genus differs from other genera within this family in the possession of bothrial pits. Although a distinguishing characteristic of the superfamily Otobothrioidea Dollfus, 1942, representatives of this group exhibit two bothria and the bothrial pits are lined with spiniform microtriches, whereas the pit-like structures.of C. foveatus n. g., n. sp. entirely lack microtriches. Redescriptions of two species of Pterobothrium, namely P. lesteri Campbell & Beveridge, 1996 and P. platycephalum (Shipley & Hornell, 1906) Dollfus, 1930 are provided from material collected off Borneo and several localities off Australia. Moreover, new host and locality records are added for P. australiense Campbell & Beveridge, 1996 and P. pearsoni (Southwell, 1929) Beveridge & Campbell, 1989.

Adaptive radiation within marine anisakid nematodes: a zoogeographical modeling of cosmopolitan, zoonotic parasites

Parasites of the nematode genus Anisakis are associated with aquatic organisms. They can be found in a variety of marine hosts including whales, crustaceans, fish and cephalopods and are known to be the cause of the zoonotic disease anisakiasis, a painful inflammation of the gastro-intestinal tract caused by the accidental consumptions of infectious larvae raw or semi-raw fishery products. Since the demand on fish as dietary protein source and the export rates of seafood products in general is rapidly increasing worldwide, the knowledge about the distribution of potential foodborne human pathogens in seafood is of major significance for human health. Studies have provided evidence that a few Anisakis species can cause clinical symptoms in humans. The aim of our study was to interpolate the species range for every described Anisakis species on the basis of the existing occurrence data. We used sequence data of 373 Anisakis larvae from 30 different hosts worldwide and previously published molecular data (n = 584) from 53 field-specific publications to model the species range of Anisakis spp., using a interpolation method that combines aspects of the alpha hull interpolation algorithm as well as the conditional interpolation approach. The results of our approach strongly indicate the existence of species-specific distribution patterns of Anisakis spp. within different climate zones and oceans that are in principle congruent with those of their respective final hosts. Our results support preceding studies that propose anisakid nematodes as useful biological indicators for their final host distribution and abundance as they closely follow the trophic relationships among their successive hosts. The modeling might although be helpful for predicting the likelihood of infection in order to reduce the risk of anisakiasis cases in a given area.

[Approaches to developing a procedure for mapping water basin regions, by using the parasitological criteria]

The structure of a parasite system is formed and its functioning takes place in qualitatively different environments. The aquatic environment serves as a source of new elements and modules, energy, and information for parasite systems. And the parasite systems, for their part, affect the physical and biological parameters of the environment. Many intestinal infections caused by pathogenic microorganisms generally characterized by an acute disease course are related to a water factor. Such are typhus, typhoids, dysentery, cholera, salmonellosis, virus hepatitis, and others. Many parasitic diseases caused by pathogenic intestinal protistae (lambliasis, amebiasis, balantidiasis), blood parasite protistae (malaria), helminthes (opisthorchiasis, fascioliasis, diphyllobothriasis, cercariosis, pseudoamphistomosis) are also closely related to a water factor. Ascaridiasis, hymenolepiasis, trichocephalosis, and echinococcosis have a less close but still self-evident relationship to a water factor. The clbse relationships of many parasitic diseases to a water factor are also determined by the fact that the life cycles of many parasites necessarily include various intermediate hosts and parasite vectors, such as fishes, mollusks, crustaceans, and insects, which are aquatic organisms at some stages of their life. The results of continuous exposure of people to parasitic diseases are quite similar to the suppressive effects of the environment in the ecologically troublesome regions. The most prognostically useful information is formed while mapping by medical and ecological regions, by employing a combination of current mathematical and cartographical methods. The former include cluster analysis, quartering method, informational logical analysis, which are all described in this article and others. Regional mapping using the parasitological criteria should achieve at least two goals: 1) a scientific one that aids in finding causative connections and to prognosticate a situation; 2) a practical one that assists in developing regional programs for disease control and prevention. It is necessary to use the recommendations described in detail in the article in order to have the maximum results during medical and ecological mapping by the regions with a future goal of obtaining useful prognostic information.