Journal of fish diseases最新文献

The minute intestinal trematode Centrocestus formosanus is a major problem that can be found in the gills of various fish species. This parasite can destroy the gill structure of fish, leading to increased fish morbidity and mortality rates. In this study, loop-mediated isothermal amplification (LAMP) based on the internal transcript spacer 1 region combined with a lateral-flow dipstick (LAMP-LFD) assay was used to detect C. formosanus in goldfish, Carassius auratus. The results showed that LAMP-LFD was specific to C. formosanus and had no cross-amplification with other co-infecting parasite species, close related parasite species or their hosts (both intermediate host and definitive host). The limit of detection is as low as one metacercaria per gill. In testing 40 goldfish gill samples, the LAMP-LFD method showed 100% accuracy when compared to traditional morphological identification. This method can be used as a rapid diagnostic tool for C. formosanus detection to obtain epidemiological information for monitoring, controlling, and preventing outbreaks of this parasite.

Unexpected mass mortality of black bullhead Ameiurus melas (Rafinesque, 1820) fingerlings occurred 1 week after their arrival at our animal facility. The specimens of the invasive fish species originated from Lake Balaton, the largest natural freshwater lake in Hungary. The mortality reached 100% within 3 days. Gross pathological examination detected inflammation in the inner organs, renomegaly, and a marble, pale pink liver. Two pathogenic bacteria strains, Vibrio cholerae Pacini, 1854, and Plesiomonas shigelloides (Bader 1954), were detected in the fish liver examined. The molecular virological examination showed the presence of the nucleic acid of two dsDNA viruses. One is the Ictalurid herpesvirus 2 (IcHV-2), which is a well-known pathogen of the black bullhead that has only been reported from Italian fish farms previously. This is the first report of IcHV-2 from a natural freshwater habitat. The other viral DNA detected in fish belongs to an unidentified virus species. Sequence analysis of the partial DNA polymerase gene confirmed that the novel virus is a member of the subfamily Chordopoxvirinae within the family Poxviridae. Although the causative agent of this mass mortality could not be identified with certainty, the clinical signs suggest that the detected viruses are the most suspicious. Furthermore, our results highlight that the health monitoring of invasive species is also important for the timely detection of pathogens that threaten the native fish fauna.

Seafood is an important resource for global nutrition and food security, with both land and marine aquaculture playing pivotal roles. High visual acuity is key for health and survival of farmed, cultured, and wild fish. Cleaner fish technology to control parasite infestation has become important in marine aquaculture and highlights the importance of visual acuity in the efficacy of cleaner fish species. New clinical diagnostic approaches towards understanding and optimising fish visual health could benefit both aquacultured and wild fish populations. Opportunities for developing and using advanced non-invasive clinical assessment and diagnosis of ocular health in wild, cultured, and experimental fish are key to more rapidly realising how threats to eye health in these animals might be better understood and mitigated. Ophthalmoscopy can rapidly and non-invasively image anatomical aspects of retinal and anterior ocular tissues and has been used in mammalian biomedicine since the turn of the 20th century. More now than ever, labour-intensive post-mortem approaches for ocular analysis such as histology are increasingly being replaced or supplemented by application of various forms of optical coherence tomography (OCT) imaging of ocular tissues in mammalian biomedicine. Advances and availability of other methodological approaches such as three-dimensional printing and computer science make instrument customisation affordable and adaptable. This review article will outline how ophthalmoscopy, OCT, and other methodologies are being applied towards understanding ocular health in teleost fish species and will describe some of the future opportunities that technological advances might afford in advancing ocular imaging in fish health and disease in general.

Kudoa thyrsites is a myxosporean parasite that infects the skeletal muscle of various teleost fish species globally. Severe infections lead to 'soft flesh' in fish fillets, resulting in food spoilage and subsequent discard. While K. thyrsites has previously been identified in migratory Atlantic mackerel in the northern Northeast Atlantic Ocean, it has not been observed in resident or farmed fish species in Norwegian waters until now. This study presents the first evidence of K. thyrsites infection and the associated 'soft flesh' condition in resident commercially important gadoid species from Norwegian waters, including Norwegian coastal cod (NCC), Northeast Arctic cod (NEA) and tusk. Molecular analyses confirmed the parasitic infection in 'soft flesh'-affected fish sampled from multiple coastal locations in Norway. The life cycle of Kudoa remains unknown but likely involves an alternating annelid host as in other myxosporeans. These findings in resident hosts suggest that the parasite completes its life cycle also at higher latitudes, in northern Norway. Consequently, there is a risk for the Norwegian fishing industry, as the effect of the parasite on fish fillet texture can occasionally occur and impact both consumer acceptance and industry revenues.

During spring 2024, a heat wave induced sustained water temperatures of 34°C during a week in Veracruz, Mexico. Serendipitously, we monitored Gyrodactylus cichlidarum infecting farmed tilapia fry during this pulse warming event and recorded a drastic decline of parasite populations over the following days. We subsequently established that parasites incubated in vitro at ca. 27°C survived up to 24 h, while at ca. 30°C and 34°C, all worms died within 4-7 h. Abnormal haptor structures were observed in parasites that developed and were born at a water temperature of 34°C. Under farming conditions, no unusual fish mortality was recorded, suggesting that pulse heat treatment may be an effective method to control G. cichlidarum, a recognised tilapia pathogen.

The pejerrey (Odontesthes bonariensis) is a key species for recreational and commercial fisheries in Argentina and holds significant aquaculture potential. It has been introduced to various countries worldwide, including Japan, where intensive aquaculture has developed. However, infectious diseases present major challenges to its cultivation, as pejerrey is susceptible to diverse pathogens, including bacteria, fungi and parasites. The primary bacterial pathogens affecting pejerrey include the genera Aeromonas, Pseudomonas and Mycobacterium (M. piscida). Fungal-like pathogens such as Saprolegnia spp., and fungal pathogens such as Achyla racemosa and Fusarium species (F. solani and F. semitectum) are also prevalent. Additionally, pejerrey hosts external and internal parasites, primarily Lernaea cyprinacea and members of the genera Cangatiella, Gyrodactylus, Contracaecum and Diplostomum. This review explores the primary infectious diseases affecting pejerrey, focusing on their symptoms, epidemiology and causative pathogens, based on literature from multiple countries and languages. Although no new diseases have emerged, we have identified persistent challenges that have remained unsolved for decades, highlighting the need for further research. Understanding the biology and epidemiology of these pathogens is crucial for expanding the aquaculture of pejerrey. Moreover, we examine how environmental changes, such as global warming, pollution and alien species, may influence disease dynamics in wild populations, stressing the need for management measures to preserve this valuable resource.

This study presents the first case in Poland of isolation and molecular identification of the Spironucleus vortens parasite from the digestive tract of diseased ornamental fish belonging to the species discus fish (Symphysodon discus Heckel, 1840). Recently, an increasing percentage of fish submitted for testing to the Department of Biology and Fish Diseases, have been observed that show typical symptoms of hole-in-the-head disease, therefore it is important to have accurate information about this disease. In preparation of this work, two fish were studied. The polymerase chain reaction (PCR) used a pair of primers designed specifically for this experiment. The amplification product was sequenced and the partial sequence of small ribosomal subunit (18S rRNA) was deposited in the GenBank database. The obtained nucleotide sequence showed a high percentage of identity with the compared sequence of the S. vortens reference strain (98.52%). Additionally, the presence of potentially dangerous bacteria belonging to four species, namely Citrobacter braakii, Acinetobacter lwoffi, Pseudomonas putida and Comamonas testosteroni was confirmed in the material collected from the tested fish. Bacterial isolates were examined biochemically. An antibiotic susceptibility testing showed that in three of the four isolates there appeared resistance to the drugs used. Trial Registration: Clinical trial registration was not required for this study.

Melanisation can occur in the musculature of fish. A well-known form is the melanised focal changes, or ‘black spots’, in the fillet of farmed Atlantic salmon (Salmo salar). The aetiology of black spots has not been fully determined, though recent research has emphasised the role of fat necrosis in their development. The initial stages of the changes are observed as focal haemorrhages or ‘red spots’, and these can progress into melanised focal changes (MFCs). The focal haemorrhages are acute changes characterised by necrotic myocytes and adipocytes and diffuse haemorrhage in the tissue. These changes evolve into a chronic inflammation dominated by fibrosis, encapsulated lipid droplets or pseudocysts, presence of epithelioid cells, granulomas of varying character, giant cells and melano-macrophages, whose presence accounts for the discolouration. The inflammation ranges from mild to severe, and the severity of the lesion has been associated with localised piscine orthoreovirus 1 (PRV 1) replication in macrophages and melano-macrophages within granulomas. The possibility of a genetic impact on the condition has not been supported by available data. The lipid composition and the antioxidative properties of the feed have been shown to affect the development of the changes. Physiological and environmental factors are also believed to influence the prevalence and severity of the condition. Here, we review the current state of knowledge concerning melanisation in fish skeletal musculature, with a special emphasis on the MFCs in Atlantic salmon.