Strategies for describing myxozoan pathogens, dreadful fish diseases in aquaculture.

Myxozoans are obligate endoparasites, cosmopolitan in distribution with both vertebrate and invertebrate hosts. Their myxospores consist of shell valves, polar capsules with coiled polar tubules that are extrudible, and infective amoeboid germs. Myxozoan parasites are most abundant, and due to their increasing number in recent years, they can pose an emerging threat to the fish industry worldwide. Hence, the immediate need is to devise a strategy to understand and detect parasites and parasitism. They may proliferate to different organs with the advancement of infection. This all warrants the development/devising of strategies and results of integrative studies in order to identify these dreadful parasites and resolve taxonomic issues. Different methods whether classical methods including gross morphology or advanced methods such as electron microscopy (SEM, TEM, STEM), Confocal laser scanning microscopy (CLSM), histopathological studies, site preference, host and tissue specificity, a molecular approach using new markers can be clubbed for identification because these parasites are hidden and are difficult to recognize. This group was earlier classified only on the basis of myxospores morphology, but due to the high structural variability of this group advanced methods and approaches have to be implied which can minimize the problems in assigning new species.

New molecular evidence on the members of the genus Ortholinea (Cnidaria, Myxozoa) and the description of Ortholinea hamsiensis n. sp. infecting the urinary bladder of European anchovy Engraulis engrasicolus in the Black Sea.

Members of the genus Ortholinea are among the worldwide distributed myxozoan parasites that mainly infect marine fish. In this study, a new myxosporean species, Ortholinea hamsiensis n. sp., was isolated from the urinary bladder of European anchovy Engraulis engrasicolus collected from the Sinop coasts of the Black Sea. The prevalence and density values of infection were 1.4% and 1­5 individuals in the field of view (1 + ), respectively. Mature myxospores are subspherical with slight tapering down to the less pronounced tip in the frontal view and subspherical in the sutural view. Myxospores measured 9.1 ± 0.25 (8.8­9.9) µm in length, 9.2 ± 0.11 (8.9­9.4) µm in thickness, and 8.4 ± 0.33 (8.2-9.1) µm in width. Two polar capsules equal in size measured 3.1 ± 0.11 (3.0­3.3) µm in length and 2.7 ± 0.11 (2.6­2.9) µm in width. The polar tubule had 3­4 coils. Along with morphological peculiarities, the results of the 18S rDNA also revealed it to be a new species for science compared to the other species of the genus. In this study, another myxosporean species O. gobiusi was also detected in round goby Neogobius melanostomus with a prevalence of infection value of 4.8% and a density of 1­5 individuals in the field of view (1 + ). The present study also provided the first data of 18S rDNA of O. gobiusi from N. melanostomus and type species of the genus O. divergens from Gobius niger and the phylogenetic relationships of these species with other Ortholinea species have been revealed.

Clinical, histopathological and phylogenetic analysis of Myxobolus lentisturalis (Myxozoa: Myxobolidae) infecting the musculature of farmed population of goldfish (Carassius auratus) in Iran: 2021-2022.

There is a claimed increase in the global prevalence and incidence of emerging diseases observed in many organisms. Myxozoa represents an essential group of metazoan parasites that hold both economic and ecological significance. In the current study, 1% of the fish population at two commercial goldfish (Carassius auratus) farms in Tehran and Ghom province, Iran, developed cavitating muscular lesions resembling humps in February 2021 and January 2022. Fish displaying pathological abnormalities were transported to the Ornamental Fish Clinic and subjected to clinical examination. Light microscopy was subsequently used to examine wet smears of skin and gills, as well as whitish exudate. In addition, tissue homogenates were collected for more precise identification and molecular confirmation. The study discovered that individuals from the goldfish farms were infected with the pathogenic myxozoan Myxobolus lentisuturalis, which caused significant damage to the epaxial muscles. The spores collected from the humps had a lack of uniformity and were primarily ellipsoidal in shape. Histopathological analysis also revealed parasites in various stages of development, such as plasmodia and spores, as well as inflammatory cell infiltration (macrophage, giant cell and lymphoplasmacytic infiltration) between skeletal muscle fibers. Phylogenetic analysis of M. lentisuturalis was performed by using MEGA 11 and the maximum likelihood method. M. lentisuturalis is a myxozoan parasite that has been sparsely recorded and lacks widespread recognition. The current study is the first clinical, histopathological, and molecular characterization of M. lentisuturalis isolated from the skeletal musculature of goldfish (C. auratus) in Iran.

Exotic myxozoan parasites establish complex life cycles in farm pond aquaculture.

Myxozoans are obligate parasites with complex life cycles, typically infecting fish and annelids. Here, we examined annelids from fish farm pond sediments in the Beit Shean Valley, in the Syrian-African Rift Valley, Israel, for myxozoan infections. We examined 1486 oligochaetes, and found 74 (5 %) were infected with actinospore stages. We used mitochondrial 16S sequencing to infer identity of 25 infected annelids as species of Potamothrix, Psammoryctides, Tubifex and Dero. We identified 7 myxozoan types from collective groups Neoactinomyxum and Sphaeractinomyxon, and characterized them by small subunit ribosomal DNA sequencing. The Neoactinomyxum type was genetically most similar (∼93 %) to cyprinid fish-infecting Myxobolus spp. The six Sphaeractinomyxon types were genetically similar (93-100 %) to Mugilid-infecting Myxobolus spp.; with one being the previously unknown actinospore stage of a myxospore that infects mullet from aquaculture from the Israeli coast of the Mediterranean Sea. As the farm pond system is artificial and geographically isolated from the Mediterranean, the presence of at least seven myxozoans in their annelid hosts demonstrates introduction and establishment of these parasites in a novel, brackish environment.

Myxospore density of Kudoa inornata varies significantly within symmetrical white muscle tissue replicates of its fish host, the spotted seatrout, Cynoscion nebulosus.

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.

First record of metazoan parasites of hybrids between the genera Colossoma and Piaractus in natural environments.

The practice of hybridization is carried out globally in fish farms. Here, we present the first record of the parasitic fauna of hybrids among genus Colossoma and Piaractus in natural environments. We identified a total of 48 hybrids, nine F1 hybrids (nuclear DNA from both species present in the cross) and 38 advanced hybrids (nuclear DNA from one species), both from crosses between Piaractus brachypomus and Piaractus mesopotamicus, and one F1 "tambacu" corresponding to cross between Colossoma macropomum and Piaractus mesopotamicus. This is the first record of Anacanthorus penilabiatus, Anacanthorus toledoensis, Mymarothecium viatorum, Mymarothecium ianwhittington, Haementeria sp., Dadaytrema oxycephala, Rondonia rondoni, and Echinorhynchus gomesi parasitizing hybrids collected in a natural environment. With this, we expand knowledge about the diversity of fish and parasites in the upper Paraná River and warn about the risk that fish escapes can cause in the basin.

Prevalence data on chicken diseases in low-resource settings.

The presence of transmissible disease in livestock has a major impact on welfare and economics in animal and public health. A lack of data enables the spread of diseases due to misinformed decision-making on prevention and control. Low-resource settings face challenges in providing data, turning data availability into a development issue. For this study, a large dataset (n = 997) was collected on prevalence and seroprevalence estimates on viral (n = 224), bacterial (n = 83) and parasitic (n = 690) diseases in backyard chickens in low- and middle-income countries (LMICs). These estimates originate from 306 studies identified during the screening phase of a systematic literature review. An attempt was made to classify the studies according to the Food and Agriculture Organization of the United Nations'classification system for family poultry production systems. Of the studies, 98.7% (302/306) focused on a single poultry production system, while 1.3% (4/306) targeted two different production systems. Within the group of studies that covered one production system, 85.4% (258/302) were classified as â€Ëœsmall extensive scavenging or extensive scavenging,'â€Ëœsmall extensive scavenging'and/or â€Ëœextensive scavenging'. In addition, 52% (159/306) of the studies did not report information on chicken breed type. No data were found on any relevant disease for 56.9% (78/137) of LMICs, signifying a potential data gap. Of the estimates on viral and bacterial diseases, 71.0% (218/307) corresponded to diseases notifiable to the World Organisation for Animal Health, highlighting a tendency to measure disease occurrence for diseases relevant to trade. The latter might not necessarily be priority diseases for the producers, however. Furthermore, 72.3% (222/307) of the estimates originate from random samples and could be used to estimate prevalence in backyard chickens using imputation methods, thus bridging the data gap.

Les maladies transmissibles affectant les animaux d'élevage ont un impact majeur sur la santé animale et la santé publique, avec des effets sur le bien-être et sur l'économie. L'absence de données favorise la propagation des maladies puisque les mesures de prévention et de contrôle reposent sur des décisions mal informées. Les contextes faiblement dotés en ressources se heurtent à la difficulté de produire des données, ce qui fait de la disponibilité des données un enjeu de développement. Pour les besoins de la présente étude, un vaste jeu de données (n = 997) a été constitué, regroupant les taux de prévalence et de séroprévalence estimés d'un certain nombre de maladies virales (n = 224), bactériennes (n = 83) et parasitaires (n = 690) affectant les poulets de basse-cour dans les pays à revenu faible et intermédiaire. Ces estimations sont extraites des 306 études retenues lors de la phase de sélection initiale d'un examen systématique de la littérature. Une tentative de classement de ces études a été réalisée en se basant sur la classification des systèmes d'aviculture familiale élaborée par l'Organisation des Nations Unies pour l'alimentation et l'agriculture. Au total, 98,7 % (302/306) des études portaient sur un système unique de production de volailles, les 1,3 % restantes (4/306) portant sur deux systèmes de production différents. Dans le groupe des études couvrant un seul système de production, 85,4 % des élevages étudiés (258/302) relevaient des catégories " petits systèmes extensifs en liberté ou systèmes extensifs en liberté ", " petits systèmes extensifs en liberté " et/ou " systèmes extensifs en liberté ". En outre, dans 52 % des études (159/306), la race des poulets n'était pas précisée. Aucune donnée n'a pu être trouvée concernant les maladies importantes des volailles dans 56,9 % (78/137) des pays à revenu faible ou intermédiaire, ce qui indique un déficit potentiel de données. S'agissant des maladies virales et bactériennes, 71,0 % des estimations (218/307) correspondaient à des maladies à déclaration obligatoire à l'Organisation mondiale de la santé animale, ce qui souligne la tendance à signaler la survenue des maladies ayant une incidence sur les échanges internationaux. Toutefois, ce ne sont pas nécessairement ces maladies qui sont prioritaires pour les éleveurs. D'autre part, 72,3 % (222/307) des estimations provenaient d'échantillons aléatoires et pourraient donc servir à estimer la prévalence chez les poulets de basse-cour en appliquant des méthodes d'imputation, ce qui permettrait de combler les écarts.

La presencia de enfermedades transmisibles en los animales de granja tiene importantes repercusiones en el bienestar y la economía tanto en el ámbito de la sanidad animal como en el de la salud pública. La falta de datos favorece la propagación de enfermedades debido a la toma de decisiones en materia de prevención y control basada en información mal fundada. En los entornos de bajos recursos existen dificultades para el suministro de información, lo que convierte la disponibilidad de datos en un problema de desarrollo. Para este estudio, se recopiló un amplio conjunto de datos (n = 997) sobre estimaciones de prevalencia y seroprevalencia de enfermedades víricas (n = 224), bacterianas (n = 83) y parasitarias (n = 690) en pollos de traspatio en países de ingresos medios y bajos (PIMB). Estas estimaciones provienen de 306 estudios encontrados durante la fase de selección de una revisión bibliográfica sistemática. Se intentó clasificar los estudios según la clasificación de sistemas de producción avícola familiar de la Organización de las Naciones Unidas para la Alimentación y la Agricultura. El 98,7 % de los estudios (302/306) se centraron en un único sistema de producción avícola, mientras que el 1,3 % (4/306) se centraron en dos sistemas de producción diferentes. Dentro del grupo de estudios que abarcaban un solo sistema de producción, el 85,4 % (258/302) se clasificaron como sistema "extensivo de escarbado pequeño o extensivo de escarbado", "extensivo de escarbado pequeño" o "extensivo de escarbado". Además, en el 52 % (159/306) de los estudios no se proporcionó información sobre el tipo de raza de los pollos. No se encontraron datos sobre ninguna enfermedad pertinente para el 56,9 % (78/137) de los PIMB, lo que indica una posible carencia de datos. De las estimaciones sobre enfermedades víricas y bacterianas, el 71,0 % (218/307) correspondían a enfermedades de declaración obligatoria a la Organización Mundial de Sanidad Animal, lo que evidencia una tendencia a medir la aparición de enfermedades pertinentes para el comercio. Sin embargo, estas podrían no ser necesariamente enfermedades prioritarias para los productores. Por otro lado, el 72,3 % (222/307) de las estimaciones proceden de muestras aleatorias y podrían utilizarse para estimar la prevalencia en los pollos de traspatio utilizando métodos de imputación, lo que permitiría subsanar la carencia de datos.

The Tilapia Cyst Tissue Enclosing the Proliferating Myxobolus bejeranoi Parasite Exhibits Cornified Structure and Immune Barrier Function.

Myxozoa, a unique group of obligate endoparasites within the phylum Cnidaria, can cause emerging diseases in wild and cultured fish populations. Recently, the myxozoan Myxobolus bejeranoi has been identified as a prevalent pathogen infecting the gills of cultured hybrid tilapia, leading to systemic immune suppression and considerable mortality. Here, we employed a proteomic approach to examine the impact of M. bejeranoi infection on fish gills, focusing on the structure of the granulomata, or cyst, formed around the proliferating parasite to prevent its spread to surrounding tissue. Enrichment analysis showed increased immune response and oxidative stress in infected gill tissue, most markedly in the cyst's wall. The intense immune reaction included a consortium of endopeptidase inhibitors, potentially combating the myxozoan arsenal of secreted proteases. Analysis of the cyst's proteome and histology staining indicated that keratin intermediate filaments contribute to its structural rigidity. Moreover, we uncovered skin-specific proteins, including a grainyhead-like transcription factor and a teleost-specific S100 calcium-binding protein that may play a role in epithelial morphogenesis and cysts formation. These findings deepen our understanding of the proteomic elements that grant the cyst its distinctive nature at the critical interface between the fish host and myxozoan parasite.

Metazoan endoparasites of snakes from Argentina: Review and checklist with distributional notes and remarks.

This article presents a checklist of metazoan parasites of snakes from Argentina, along with a comprehensive review of the relevant literature published between 1922 and June 2023, covering various aspects of interest. We compiled 34 species of metazoan endoparasites from 28 studies. The subclass Digenea showed the highest number of species (n = 22 species), followed by the phylum Nematoda (n = 8 species), and the subclass Pentastomida (n = 3 species and 1 taxa inquirenda). Dipsadidae was the family of snakes with the most species examined for metazoan endoparasites (n = 20 species). In contrast, Viperidae had the largest number of specimens surveyed (n = 343). Of 23 provinces, 15 (65.2%) presented at least one report of metazoan endoparasites in snakes. The northeastern provinces showed the highest richness of metazoan endoparasites and host diversity. Many articles focused on taxonomy, but studies on parasite ecology were not found. Although taxonomic accuracy was high in most reports, some records were correctly deposited in zoological collections or geo-referenced. This is the first attempt to include all groups of metazoan endoparasites of snakes from Argentina in a single checklist in the last century.

First report of Myxobolus neurofontinalis (Bivalvulida: Myxobolidae) infecting anadromous Brook Trout from Prince Edward Island, Canada.

OBJECTIVE: During routine histological examination of tissues from mortality events of anadromous Brook Trout Salvelinus fontinalis from Prince Edward Island (PEI), Canada, myxospores consistent with Myxobolus were observed infecting the central nervous system. The objective of this study was to identify the species of Myxobolus infecting the nervous system of anadromous Brook Trout from PEI, Canada. METHODS: Myxospore morphology, small subunit (SSU) ribosomal DNA (rDNA) sequence data, and histology were used to identify myxospores isolated from infected Brook Trout. RESULT: Myxospore measurements from the PEI samples matched those reported in the description of Myxobolus neurofontinalis from North Carolina. A 1057-bp fragment of the SSU rDNA from myxospores collected from Brook Trout in PEI was identical to an isolate of M. neurofontinalis (MN191598) collected previously from the type locality, New River basin, North Carolina. Histological sections confirmed infections were intercellular in the central nervous system. Minimal host response was observed, with only sparse mononuclear inflammatory infiltrates present at the periphery of and within dispersed myxospores, suggesting that infections are not pathogenic to Brook Trout. CONCLUSION: Myxospores were identified as M. neurofontinalis, which was previously described from the central nervous system of Brook Trout from the New River basin, North Carolina, USA. This constitutes the first time M. neurofontinalis has been documented outside of the New River basin in North Carolina.

First report of a Kudoa lutjanus outbreak in farmed Chicken Grunts Parapristipoma trilineatum.

OBJECTIVE: As part of the National Disease Surveillance Program for Taiwanese Aquaculture, we investigated the causative agent of disease outbreaks in farmed Chicken Grunts Parapristipoma trilineatum. METHODS: In this study, outbreak cases on two separate farms were noticed in coastal Pingtung County, Taiwan. In total, 50 juvenile fish showing clinical signs (such as emaciation and erratic swimming behavior) and broodstock (two females and two males) from both farms were collected to perform gross lesion assessment, histopathological examination, and molecular identification of the pathogen. RESULT: Clinical symptoms were infected fish exhibited erratic swimming behavior, such as whirling and floating on the surface of the water. In the following months, cumulative mortality had reached 19% and 24%, respectively. The gross lesions in the infected fish included white oval cysts in the muscle, serosa of the internal organs, sclera of the eyes, and cerebral meninges. After conducting a wet mount examination of cysts using a light microscope, we observed a significant quantity of spores with morphological characteristics, suggesting their affiliation with the Myxosporea group. The spores were semiquadrate, with four tiny suture notches at the periphery; the mean spore length was 7.3 µm (SD = 0.5), and the mean spore width was 8.2 µm (SD = 0.6). The mean length and width of the pyriform polar capsules (nematocysts) were 3.6 µm (SD = 0.5) and 2.2 µm (SD = 0.5), respectively. The 18S and 28S ribosomal RNA sequences of these specimens were identical to those of Kudoa lutjanus. CONCLUSION: As this was the first time an outbreak of K. lutjanus in Chicken Grunts was confirmed, its reappearance with substantial mortality should serve as a warning to the aquaculture industry.

Histopathological evaluation of the infection elicited by three species of Myxobolus (Cnidaria: Myxosporea), with identification of Myxobolusxiaoganensis n. sp. isolated from the silver carp Hypophthalmichthys molitrix.

Several parasites infecting the Asian carp species have been broadly spread along with the global fish trade. However, the diversity of specific parasite groups and their pattern of parasitism remain insufficiently elucidated even in their native regions. Here, we conducted a holistic identification and histological analysis of three Myxobolus species. The oblate myxospores of the first isolates were found infecting the spleen of silver carp Hypophthalmichthys molitrix, measuring 6.4 ± 0.4 (5.4-7.1) µm in length, 8.2 ± 0.4 (7.5-9.0) in width, and 5.9 ± 0.3 (5.2-6.2) in thickness. They were morphologically distinct from other congeners and regarded as a novel species, Myxobolus xiaoganensis n. sp. For the second isolates, we associated the formation of round plasmodia on the gill raker of silver carp with Myxobolus allotypica Chen, 1998. The third isolates, encapsulated in the intestinal serosa membrane of the grass carp Ctenopharyngodon idella, was proved to be conspecific to Myxobolus huasaensis Chen, 1998. While M. xiaoganensis n. sp. and M. huasaensis exhibited distinct origins, with genetic differences exceeding 4% from other congeners, M. allotypica displayed complete genetic congruence with an item available in Genbank. Histologically, myxospores of M. xiaoganensis n. sp. were scattered in the spleen, and the branchial and intestinal infections of M. allotypica and M. huasaensis were determined, respectively. Phylogenetic analysis demonstrated a non-monophyletic origin of both the Thelohanellus and Myxobolus genera, with a remarkable association of host affinity with myxosporean clustering.

Phylogenetic and host-parasite relationship analyses of Henneguya caquetaia sp. nov (Myxosporea: Myxobolidae) infecting an Amazonian cichlid fish.

The present study describes a new species of Henneguya infecting the ornamental fish Caquetaia spectabilis from the Brazilian Amazon. Fish specimens were collected where the Tapajós and Amazon rivers merge, municipality of Santarém in the State of Pará, Brazil. Infections were intense, with several plasmodia spread on the opercula, fins and eye. Phylogenetic characterization and host-parasite relationship studies of the new Henneguya species used a combination of small subunit ribosomal DNA (ssrDNA) and morphological (photonic and transmission electron microscopy) analyses. Plasmodia were white round to ellipsoidal measuring up to 1.8 mm. The myxospores body measured 20.5 ± 3.9 (15-27) in length, 7.9 µm (6.2-10.8) in width, 6.7 µm (6.0-7.6) in thickness, 20.5 µm (14.4-32.3) in caudal appendages length, and 40.6 µm (34.2-54.6) in total length. The two polar capsules were elongated and equal in size, measuring 4.3 µm (3.3-5.4) in length and 2.1 µm (1.3-2.8) in width. Histological analysis revealed the parasite development in connective tissues of the fins, eyes and opercula. The skin of the fins and opercula presented detachment of the epidermis, however, no inflamatory infiltrate was observed. In the eye were observed inflammatory infiltratate in the epithelium and stroma of the cornea. Ultrastructure analysis showed the connective tissue capsule composed by an inner cellular layer with fibroblasts and outer layer where collagen fibers arranged transversely yet interspersed by layers of fibers arranged longitudinally. Numerous invaginations and extensive pinocytotic channels were observed in the plasmodial membrane. A layer of microfilament-like microfilament-like material was observed in the ectoplasm area and along to the internal surface of the plasmodial membrane. Generative cells and early stages of sporogenesis were seen more internally. The ssrDNA based phylogeny showed the South American species grouped in two lineages and the new species arises in a well-sustained subclade as sister branch of the clade composed by Henneguya spp. parasites of cichlids fish.

Myxobolus nekrasovae n. sp. (Cnidaria, Myxozoa) is a new species parasitizing the gills of the gibel carp, Carassius auratus gibelio.

A new Myxobolus species, Myxobolus nekrasovi n. sp., was found in the gill arch of the gibel carp Carassius auratus gibelio during investigation of fish myxosporean fauna of ponds of Lake Baikal basin. The parasites were studied on the basis of spore morphology, as well as with histological and molecular methods. Mature spores of M. nekrasovi n. sp. are ellipsoidal in frontal view and lemon-shaped in lateral view, measuring 13.84 ± 0.4 (12.2-15) µm in length, 9.73 ± 0.2 (8.5-10.7) µm in width, 6,75 ± 0.1 (6.0-7.6) µm in thickness. Polar capsules are unequal and pyriform, measuring: length 6.31 ± 0.1 (5.4-7.4), width 3.49 ± 0.04 (3.12-4) µm and length 2.88 ± 0.1 (2.1-3.5), width 1.4 ± 0.03 (1-1.6) µm. Phylogenetic analysis with the SSU rDNA gene shows Myxobolus nekrasovae n. sp. as a sister species of the subclade formed by Thellohanellus sinensis, Myxobolus acutus, M. zhaltsanovae that infect gibel carp Carassius auratus gibelio.

Morphological, histopathological, ultrastructural and phylogenetic analysis of Henneguya archosargus n. sp. (Cnidaria, Myxosporea) infecting the sparid fish Archosargus probatocephalus in Brazilian waters.

The introduction of new fish species to the aquaculture industry is essential to halt the progressive decline of natural fish stocks. The sheepshead Archosargus probatocephalus is a commercially valuable sparid fish with potential for breeding in captivity, but with limited information regarding parasitic infections that could pose a significant threat for its sustainable production. Thus, the present study aimed to study the myxozoan diversity infecting A. probatocephalus. A novel Henneguya sp. was detected forming plasmodia in the gill lamellae of specimens inhabiting the Brazilian coast, and is characterized based on morphological, histopathological, ultrastructural, molecular, and phylogenetic data. Myxospore total length was 21.3 ± 0.8 µm, with myxospore body 10.0 ± 0.5 µm long, 6.2 ± 0.3 µm wide, and 4.8 ± 0.5 µm thick. Caudal appendages were 10.3 ± 0.5 µm long and did not present any type of coating. Two pyriform polar capsules, 3.4 ± 0.3 µm long and 1.5 ± 0.2 µm wide, each containing an isofilar polar tubule with 4-5 coils. Histopathological analyses showed large intralamellar polysporic plasmodia associated with vascular congestion of the gill filament and gill lamellae, as well as epithelial hyperplasia causing partial or total fusion of gill lamellae. Maximum likelihood and Baysesian inference SSU rDNA-based phylogenetic analyses showed the novel sequence grouped within the marine clade of Henneguya spp. that mostly parasitize fishes belonging to Eupercaria incertae sedis.

Understanding how temperature shifts could impact infectious disease.

Climate change is expected to have complex effects on infectious diseases, causing some to increase, others to decrease, and many to shift their distributions. There have been several important advances in understanding the role of climate and climate change on wildlife and human infectious disease dynamics over the past several years. This essay examines 3 major areas of advancement, which include improvements to mechanistic disease models, investigations into the importance of climate variability to disease dynamics, and understanding the consequences of thermal mismatches between host and parasites. Applying the new information derived from these advances to climate-disease models and addressing the pressing knowledge gaps that we identify should improve the capacity to predict how climate change will affect disease risk for both wildlife and humans.

Morphological and genetic analysis of Ceratomyxa saurida Zhao et al. 2015 and Ceratomyxa mai sp. nov. (Myxozoa: Ceratomyxidae) from the East China Sea.

We describe Ceratomyxa saurida Zhao et al. 2015 and Ceratomyxa mai sp. nov. (Myxozoa: Ceratomyxidae) from the East China Sea. C. saurida was found in the gallbladders of 3/13 specimens of its type host, Saurida elongata Temminck and Schlegel 1846 (Aulopiformes). Myxospore characters were consistent with the original description to which we have added small subunit (SSU) rRNA gene data. C. mai sp. nov. was found in gallbladders of 3/13 specimens of S. elongata and 5/13 specimens of Neobythites sivicola Jordan and Snyder 1901 (Ophidiiformes). Mature myxospores of C. mai sp. nov. were crescentic in sutural view, with a deeply concave posterior angle 142.2±8.2° (125.8‒158.2°) and an arched anterior side. Shell valves were smooth and equal, 20.9±1.9 (17.3‒24.7) µm thick and 9.2±0.5 (8.1‒9.9) µm long, and joined at a straight, thin sutural plane passing between two nematocysts (polar capsules). The nematocysts were equal-sized, pyriform, 2.6±0.2 (2.4‒2.9) µm long and 2.7±0.2 (2.4‒3.3) µm wide, with their tapered ends pointed toward each other, located in the anterior third of the spore. Sequences of the SSU rRNA gene and internal transcribed spacer 1 showed that the isolates of C. mai sp. nov. obtained from S. elongata and N. sivicola were identical. The SSU rRNA gene sequence of C. mai sp. nov. was distinct from all known myxosporeans and clustered with C. saurida, and then with Ceratomyxa filamentosi Kalatzis, Kokkari and Katharios 2013, both of which also infect Aulopiformes fishes.

Differentially expressed transcripts of Tetracapsuloides bryosalmonae (Cnidaria) between carrier and dead-end hosts involved in key biological processes: novel insights from a coupled approach of FACS and RNA sequencing.

Tetracapsuloides bryosalmonae is a malacosporean endoparasite that infects a wide range of salmonids and causes proliferative kidney disease (PKD). Brown trout serves as a carrier host whereas rainbow trout represents a dead-end host. We thus asked if the parasite adapts to the different hosts by changing molecular mechanisms. We used fluorescent activated cell sorting (FACS) to isolate parasites from the kidney of brown trout and rainbow trout following experimental infection with T. bryosalmonae. The sorted parasite cells were then subjected to RNA sequencing. By this approach, we identified 1120 parasite transcripts that were expressed differentially in parasites derived from brown trout and rainbow trout. We found elevated levels of transcripts related to cytoskeleton organisation, cell polarity, peptidyl-serine phosphorylation in parasites sorted from brown trout. In contrast, transcripts related to translation, ribonucleoprotein complex biogenesis and subunit organisation, non-membrane bounded organelle assembly, regulation of protein catabolic process and protein refolding were upregulated in rainbow trout-derived parasites. These findings show distinct molecular adaptations of parasites, which may underlie their distinct outcomes in the two hosts. Moreover, the identification of these differentially expressed transcripts may enable the identification of novel drug targets that may be exploited as treatment against T. bryosalmonae. We here also describe for the first time how FACS based isolation of T. bryosalmonae cells from infected kidney of fish fosters research and allows to define differentially expressed parasite transcripts in carrier and dead-end fish hosts.

Myxobolus lentisuturalis infection in a farmed population of goldfish Carassius auratus from the USA.

Myxobolus lentisuturalis is a myxozoan parasite of piscine muscle that has been described in goldfish Carassius auratus and Prussian carp Carassius gibelio. This report documents a naturally occurring infection of M. lentisuturalis in a population of farmed goldfish in the USA. Postmortem examination was performed on 4 affected goldfish. Gross findings included large cystic cavities along the dorsal midline filled with caseous exudate. Histopathology revealed myxozoan plasmodia and spores in the epaxial muscles with varying degrees of granulomatous and necrotizing myositis accompanied by lymphohistiocytic meningoencephalitis. Spore morphology and dimensions were consistent with M. lentisuturalis, as observed by light microscopy. PCR and sequence analysis of the small subunit ribosomal DNA of infected muscle samples from 2 goldfish confirmed the parasite to have 99-100% nucleotide identity to M. lentisuturalis sequences recovered from similar cases of this parasite infecting goldfish in China and Italy and Prussian carp in China. This is the first reported case of M. lentisuturalis in the USA and furthers the understanding of the pathogenicity of this under-described parasite.

A new species of Myxobolus (Cnidaria: Myxosporea: Myxobolidae) from the gibel carp Carassius gibelio (Cypriniformes: Cyprinidae).

Myxobolus zhaltsanovae n. sp., is described from the gills of gibel carp Carassius gibelio found during a survey of myxozoans from the watershed of Lake Baikal, Russia, based on morphological and molecular characterizations. Plasmodia of M. zhaltsanovae n. sp. develop extravascularly and measure 500-1000 µm long, 25-100 µm wide. The myxospore is circular to oval, measuring 13.23 ± 0.09 (11.3-14.8) µm (mean ± SD, range) in length, 10.19 ± 0.07 (9.1-11.4) µm in width, and 6.49 ± 0.12 (5.4-7.2) µm in thickness. Polar capsules are unequal and subspherical; measurements of polar capsules are: length 5.62 ± 0.06 (4.7-6.7), width 3.44 ± 0.04 (2.4-4.4) µm and length 3.42 ± 0.05 (2.5-4.1), width 1.94 ± 0.04 (1.3-3.3) µm. Phylogenetic analysis with the 18S rDNA gene shows M. zhaltsanovae n. sp. as a sister species of the subclade formed by M. musseliusae, M. tsangwuensis, and M. basilamellaris, which infect common carp Cyprinus carpio.