The role of migration barriers for dispersion of Proliferative Kidney Disease-Balance between disease emergence and habitat connectivity.

Natural and uninterrupted water courses are important for biodiversity and fish population stability. Nowadays, many streams and rivers are obstructed by artificial migration barriers, often preventing the migration of fish. On the other hand, distribution of pathogens by migrating fishes is still a point of concern. Pathogen transport and transmission is a driving force in the dynamics of many infectious diseases. The aim of the study was to investigate the possible consequences of the removal of an artificial migration barrier for the upstream transport of Tetracapsuloides bryosalmonae, the causative agent of Proliferative Kidney Disease (PKD) in brown trout, by migrating fish. To test this question, a river system was selected with a migration barrier separating a PKD positive river from a PKD negative tributary. After removal of the barrier, PKD prevalence and pathology was examined during five years after elimination of the barrier. In the tributary, no PKD was recorded at any time of the survey. By means of unidirectional PIT (passive integrated transponder)-tagging, we confirmed upstream migration of adult brown trout into the tributary during the cold season, presumably for spawning. By eDNA, we confirmed presence of T. bryoalmonae and Fredericella sp., the definitive host, DNA in water from the PKD positive river stretch, but not in the PKD negative tributary. Our study illustrates the importance of the connectivity of streams for habitat maintenance. Although migration of brown trout from a PKD-positive river into a PKD-negative tributary, mainly for spawning, was confirmed, upstream spreading of PKD was not observed.

First report of Kudoa sp. in the palate and pharyngeal musculature of Gobioides grahamae Palmer and Wheeler, 1955 (Perciformes, Gobiidae) from Marajó Island, Brazil / Primeiro registro de Kudoa sp. na musculatura do palato e faringeal de Gobioides grahamae Palmer e Wheeler, 1955 (Perciformes, Gobiidae) da Ilha do Marajó, Brasil

The aim of this study was to describe the first occurrence ofKudoasp. inGobioides grahamae, contributing to the understanding of this group of parasites in the Amazonian ichthyofauna. Forty specimens ofG. grahamaecollected from the natural environment were analyzed. Cysts ofKudoasp. were diffusely distributed through the striated skeletal muscle fibers with severe edema and inflammatory infiltrate composed of lymphocytes were observed in 30% of the specimens. Edema and marked coagulation necrosis of the muscle fibers was associated with infection byKudoasp. spores, which had accumulated inside the skeletal muscle fibers. Although there are no records of foodborne outbreaks caused by Kudoa spp. in Brazil, it is of paramount importance that we evaluate its occurrence, since the consumption of fish, especially raw fish, has increased because of the adoption of Japanese cuisine. To minimize the economic impacts on the fisheries market and the risk of this parasite to public health, it is necessary to initiate a program to monitor the presence of this likely underdiagnosed, emerging parasite.(AU)

O objetivo deste estudo foi descrever a primeira ocorrência de Kudoa sp. em Gobioides grahamae, contribuindo, assim, para a compreensão desse grupo de parasitas na ictiofauna amazônica. Foram analisados 40 espécimes de G. grahamae coletados de ambiente natural. Cistos de Kudoa sp. foram distribuídos difusamente através das fibras musculares esqueléticas estriadas com presença de edema grave e infiltrado inflamatório composto de linfócitos, que foram observados em 30% dos espécimes. Edema e necrose de coagulação acentuada das fibras musculares foram associados com a infecção por esporos de Kudoa sp., acumulados no interior das fibras musculares da faringe. Apesar de não haver registros de surtos de origem alimentar causada por Kudoa spp. no Brasil, é de suma importância a avaliação de sua ocorrência, uma vez que o consumo de peixe, especialmente peixe cru, aumentou por causa da adoção da culinária japonesa. Para minimizar os impactos econômicos no mercado da pesca e o risco desse parasita para a saúde pública, é necessário iniciar um programa para monitorar a presença desse parasita emergente, possivelmente subdiagnosticada.(AU)

Amazonian waters harbour an ancient freshwater Ceratomyxa lineage (Cnidaria: Myxosporea).

A new species of Ceratomyxa parasitizing the gall bladder of Cichla monoculus, an endemic cichlid fish from the Amazon basin in Brazil, is described using morphological and molecular data. In the bile, both immature and mature myxospores were found floating freely or inside elongated plasmodia: length 304 (196-402) µm and width 35.7 (18.3-55.1) µm. Mature spores were elongated and only slightly crescent-shaped in frontal view with a prominent sutural line between two valve cells, which had rounded ends. Measurements of formalin-fixed myxospores: length 6.3±0.6 (5.1-7.5) µm, thickness 41.2±2.9 (37.1-47.6) µm, posterior angle 147°. Lateral projections slightly asymmetric, with lengths 19.3±1.4µm and 20.5±1.3µm. Two ovoid, equal size polar capsules, length 2.6±0.3 (2-3.3) µm, width 2.5±0.4 (1.8-3.7) µm, located adjacent to the suture and containing polar filaments with 3-4 turns. The small subunit ribosomal DNA sequence of 1605 nt was no more than 97% similar to any other sequence in GenBank, and together with the host, locality and morphometric data, supports diagnosis of the parasite as a new species, Ceratomyxa brasiliensis n. sp. Maximum parsimony and maximum likelihood analyses showed that C. brasiliensis n. sp. clustered within the marine Ceratomyxa clade, but was in a basally divergent lineage with two other freshwater species from the Amazon basin. Our results are consistent with previous studies that show Ceratomyxa species can cluster according to both geography and host ecotype, and that the few known freshwater species diverged from marine cousins relatively early in evolution of the genus, possibly driven by marine incursions into riverine environments.

Ultrastructural description of Myxobolus cuneus (Myxosporea) in the skeletal muscle and kidney of tropical farmed fish Piaractus mesopotamicus (Characiformes: Characidae).

This study characterizes by transmission electron microscopy (TEM) and morphometric features the myxozoan Myxobolus cuneus (Myxosporea) in Piaractus mesopotamicus and reports the skeletal muscle and kidney as site of infection. The register was based in 21 young fish from intensive fish farming in Southeast Brazil and the spores were analyzed in fresh-mounted slides of the infected organs stained with Toluidine blue and processed as usual for TEM. It differs from Myxobolus cunhai from the fish host and different polar capsule size, and from Myxobolus serrasalmi on the pyriform spore shape and an oval macrospore, differently to that reported in this study. Morphometric characteristics and TEM study confirmed the present material as M. cuneus.