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Sturgeon farming is rapidly expanding in Europe, where Italy ranks first in farmed caviar production. A major threat to sturgeon health in captivity is infection with Acipenser European Iridovirus (AcIV-E), a viral disease definitively identified in 2016. Here we present data on the occurrence of AcIV-E in 482 sturgeons (age ≤ 12 months, species of the genus Acipenser and the species Huso huso ) collected from sturgeon farms in northern Italy between January 2021 and December 2023. The health status of each specimen was determined by necroscopy and virological assay. Virological analysis was performed on gill samples and real-time PCR specific to the MCP gene of the iridovirus viral capsid. Molecular analysis revealed positivity to the virus in 204 samples (42.68% of the total), while anatomopathological examination of nearly all fish with positive real-time PCR disclosed swollen abdomen, hepatic steatosis, splenomegaly, and increased gill volume. Two challenges to timely diagnosis are the absence of pathognomonic symptoms and the inability to isolate the virus on cell monolayers. Continuous and widespread health monitoring is therefore crucial for disease management and to effectively control spread of the virus.

The swimbladder functions as a hydrostatic organ in most bony fishes, including the European eel, Anguilla anguilla. Infection by the nematode Anguillicoloides crassus impairs swimbladder function, significantly compromising the success of the eel spawning migration. Swimbladders from 32 yellow eels taken from Lake Trasimeno (Central Italy) were analysed by histopathology- and electron microscopy-based techniques. Sixteen eels (50%) harboured A. crassus in their swimbladders and intensity of infection ranged from 2 to 17 adult nematodes per organ (6.9 ± 1.6, mean ± s.e.). Gross observations of heavily infected swimbladders showed opacity and histological analysis found a papillose aspect to the mucosa and hyperplasia of the lamina propria, muscularis mucosae and submucosa. Inflammation, haemorrhages, dilation of blood vessels and epithelial erosion were common in infected swimbladders. In the epithelium of parasitized swimbladders, many empty spaces and lack of apical junctional complexes were frequent among the gas gland cells. In heavily infected swimbladders, we observed hyperplasia, cellular swelling and abundant vacuolization in the apical portion of the gas gland cells. Numerous mast cells and several macrophage aggregates were noticed in the mucosal layer of infected swimbladders. We found more nervous and endocrine elements immunoreactive to a panel of six rabbit polyclonal antibodies in infected swimbladders compared to uninfected.

The greater amberjack Seriola dumerili is a new aquaculture fish that may display reproductive dysfunctions. During extensive follicular atresia, which is a common reproductive dysfunction in females during vitellogenesis, part of the reabsorbed yolk returns to the liver to be metabolized and recycled. Melanomacrophage centres (MMCs) are aggregates of macrophage-like cells that play a role in the destruction, detoxification and recycling of endogenous and exogenous materials, and have been associated with systemic stress. Wild and captive-reared greater amberjack were sampled in the Mediterranean Sea during two different phases of the reproductive cycle. The liver of reproductively dysfunctional captive-reared females sampled during the spawning season showed a high density of both MMCs and apoptotic cells. A weak liver anti-cytochrome P450 monooxygenase 1A immunoreactivity was observed, suggesting that the examined fish were not exposed to environmental pollutants. We propose that the observed increase in MMCs and apoptosis in captive-reared fish was related to the hepatic overload associated to the metabolism of yolk proteins reabsorbed during extensive follicular atresia. Since follicular atresia is a frequent physiological and pathological event in teleosts, we suggest that the reproductive state should be always assessed when MMCs are used as markers of exposure to stress or pollutants., (© 2020 John Wiley & Sons Ltd.)

The genus Eustrongylides includes nematodes known as the etiological agent of the "big red worm disease." The aim of this work was to identify Eustrongylides spp. larvae from fish and adults from great cormorant ( Phalacrocorax carbo ) sampled at Lake Trasimeno, Italy, by morphological and molecular analysis. Histopathological description of the lesions in birds was also provided. We described adults of Eustrongylides excisus for the first time in Italy, and we also linked larval stages 3 and 4 to adults. The use of molecular tools combined with the traditional taxonomy will help the identification of the species, including species inquirendae. Moreover, molecular analysis can also help to investigate the role of intermediate and paratenic hosts, to deepen the knowledge about geographical distribution of the different Eustrongylides spp. and to define the zoonotic potential of E. excisus , which has not yet been identified as causal agent of human cases.

Background: The European perch, Perca fluviatilis L. is a common paratenic host of dioctophymatid nematodes belonging to the genus Eustrongylides. In this host, once infected oligochaetes, which serve as the first intermediate host, are ingested, Eustrongylides migrates through the intestine and is frequently encountered within the musculature, free within the body cavity, or encapsulated on the viscera. The current study details the first Italian record of Eustrongylides sp. with larvae reported in the muscle of P. fluviatilis., Methods: Uninfected and nematode-infected muscle tissues of perch were fixed and prepared for histological evaluation and electron microscopy. Some sections were subjected to an indirect immunohistochemical method using anti-PCNA, anti-piscidin 3 and anti-piscidin 4 antibodies., Results: A total of 510 P. fluviatilis (TL range 15-25 cm) from Lake Trasimeno, Perugia were post-mortemed; 31 individuals had encysted nematode larvae within their musculature (1-2 worms fish(-1)). Histologically, larvae were surrounded by a capsule with an evident acute inflammatory reaction. Muscle degeneration and necrosis extending throughout the sarcoplasm, sarcolemmal basal lamina, endomysial connective tissue cells and capillaries was frequently observed. Within the encapsulating reaction, macrophage aggregates (MAs) were seen. Immunohistochemical staining with the proliferating cell nuclear antigen (PCNA) revealed numerous PCNA-positive cells within the thickness of the capsule and in the immediate vicinity surrounding Eustrongylides sp. larvae (i.e. fibroblasts and satellite cells), suggesting a host response had been initiated to repair the nematode-damaged muscle. Mast cells (MCs) staining positively for piscidin 3, were demonstrated for the first time in response to a muscle-infecting nematode. The piscidin 3 positive MC's were seen principally in the periphery of the capsule surrounding the Eustrongylides sp. larva., Conclusions: A host tissue response to Eustrongylides sp. larvae infecting the musculature of P. fluviatilis was observed. Numerous fibroblasts, MAs and MCs were seen throughout the thick fibroconnectival layer of the capsule enclosing larvae. PCNA positive cells within the capsule suggest that host repair of nematode damaged muscle does occur, while the presence of the antimicrobial peptide piscidin 3 is shown for the first time. This is first report of Eustrongylides sp. in an Italian population of P. fluviatilis.

Mycobacterium spp. and Photobacterium damselae subsp. piscicida are recognized as the most frequent causative agents of granulomatous lesions in fish. Although frequent episodes of mycobacterial infections have been reported in wild fish worldwide, only sporadic cases have been documented to date in Italy. To investigate for the presence of lesions referable to mycobacteriosis and to identify the mycobacterial species involved, a total of 159 wild mullets were fished from the eastern coast of the Ligurian Sea, killed and necropsied. Liver and spleen samples were collected from all fish for histopathological and microbiological analyses. Molecular investigations for identification of Photobacterium damselae subsp. piscicida were performed. Gross examination revealed granulomatous lesions in one animal; microscopically, 42.14% of fish displayed granulomas with various histological features, 19.50% resulted positive at Ziehl-Neelsen staining, and were confirmed as mycobacterial lesions by culture. The identified colonies were characterized as M. fortuitum, M. abscessus, M. flavescens, M. chelonae, M. septicum and M. nonchromogenicum. In all, 35% of animals resulted positive for Photobacterium damselae subsp. piscicida. These data suggest widespread mycobacterial infection also by Photobacterium damselae subsp. piscicida infections in wild fish. Moreover, the pathogenicity of some mycobacterial species, previously considered as saprophytic, was demonstrated., (© 2013 John Wiley & Sons Ltd.)

Sixteen specimens of female crucian carp, Carassius carassius (L.), during the breeding season, were investigated for post-mortem and full diagnostic examination during a mortality outbreak in a tributary stream of the Arno River in Tuscany in 2011. Necropsy highlighted the presence of a swollen anus and widespread haemorrhages in the body, fins, gills and eyes. Haemorrhages in internal organs and spleen granulomas were also observed. Bacteria isolated from the brain, kidney and spleen of affected fish were identified as A. sobria. Microscopic lesions observed in gills were characterized by necrosis of the secondary lamellae, congestion and multifocal lamellar fusion. The kidney showed necrosis, oedema, fibrin exudation and areas of haemorrhages, while in the spleen the main lesions were by multifocal necrosis of the lymphoid tissue. In the gills, transmission electron microscopy revealed herpesvirus-like particles, subsequently identified as Cyprinid herpesvirus-2 (CyHV-2) with a nested PCR protocol. Although it was not possible to attribute a pathogenic role to CyHV-2 in this mortality event, the identification of this herpesvirus in crucian carp increases the concern about its potential role in this species., (© 2013 John Wiley & Sons Ltd.)

Background: Changes in the production of proliferating cell nuclear antigen (PCNA), a 36 kd protein involved in protein synthesis, within intestinal epithelia can provide an early indication of deviations to normal functioning. Inhibition or stimulation of cell proliferation and PCNA can be determined through immunohistochemical staining of intestinal tissue. Changes in the expression of PCNA act as an early warning system of changes to the gut and this application has not been applied to the fields of aquatic parasitology and fish health. The current study set out to determine whether a population of wild brown trout, Salmo trutta trutta (L.) harbouring an infection of the acanthocephalan Dentitruncus truttae Sinzar, 1955 collected from Lake Piediluco in Central Italy also effected changes in the expression of PCNA., Methods: A total of 29 brown trout were investigated, 19 of which (i.e. 65.5%) were found to harbour acanthocephalans (5-320 worms fish-1). Histological sections of both uninfected and infected intestinal material were immunostained for PCNA., Results: The expression of PCNA was observed in the epithelial cells in the intestinal crypts and within the mast cells and fibroblasts in the submucosa layer which is consistent with its role in cell proliferation and DNA synthesis. The number of PCNA-positive cells in both the intestinal epithelium and the submucosa layer in regions close to the point of parasite attachment were significantly higher than the number observed in uninfected individuals and in infected individuals in zones at least 0.7 cm from the point of parasite attachment (ANOVA, p < 0.05)., Conclusions: An infection of the acanthocephalan D. truttae within the intestinal tract of S. t. trutta effected a significant increase in the number of PCNA positive cells (mast cells and fibroblasts) at the site of parasite attachment when compared to the number of positive cells found in uninfected conspecifics and in tissue zones away from the point of parasite attachment.

Background: Among the European cyprinids, tench, Tinca tinca (L.), and the pathological effects their cestodes may effect, have received very little or no attention. Most literature relating to Monobothrium wageneri Nybelin, 1922, a common intestinal cestode of tench, for example, has focused on aspects of its morphology rather than on aspects of the host-parasite interaction., Results: Immunopathological and ultrastructural studies were conducted on the intestines of 28 tench, collected from Lake Piediluco, of which 16 specimens harboured tight clusters of numerous M. wageneri attached to the intestinal wall. The infection was associated with the degeneration of the mucosal layer and the formation of raised inflammatory swelling surrounding the worms. At the site of infection, the number of granulocytes in the intestine of T. tinca was significantly higher than the number determined 1 cm away from the site of infection or the number found in uninfected fish. Using transmission electron microscopy, mast cells and neutrophils were frequently observed in close proximity to, and inside, the intestinal capillaries; often these cells were in contact with the cestode tegument. At the host-parasite interface, no secretion from the parasite's tegument was observed. Intense degranulation of the mast cells was seen within the submucosa and lamina muscularis, most noticeably at sites close to the tegument of the scolex. In some instances, rodlet cells were encountered in the submucosa. In histological sections, hyperplasia of the mucous cells, notably those giving an alcian blue positive reaction, were evident in the intestinal tissues close to the swelling surrounding the worms. Enhanced mucus secretion was recorded in the intestines of infected tench., Conclusions: The pathological changes and the inflammatory cellular response induced by the caryophyllidean monozoic tapeworm M. wageneri within the intestinal tract of an Italian population of wild tench is reported for the first time.

Viral encephalopathy and retinopathy (VER), otherwise known as viral nervous necrosis (VNN), is a neuropathological condition affecting > 40 species of fish. Although VER affects mainly marine fish, the disease has also been detected in certain species reared in freshwater environments. There are relatively few reports concerning the disease in freshwater species, and there is not much information on clinical signs. Nevertheless, the most common clinical findings reported from affected freshwater species are consistent with the typical signs observed in marine species. In this paper we describe the main clinical signs and the laboratory results associated with the detection of a betanodavirus in hybrid striped bass x white bass (Morone saxatilis x Morone chrysops) and largemouth bass Micropterus salmoides, reared in a freshwater environment. We also detected the virus by real-time PCR and isolated it in cell culture from a batch of pike-perch Sander lucioperca farmed in the same system.

Immunopathological and ultrastructural studies were carried out on the gut of 30 specimens of powan Coregonus lavaretus (L.) from Lake Piediluco, Italy. The digestive tracts of 10 (33.3%) of the powan were found to harbour an acanthocephalan Dentitruncus truttae (Sinzar 1955). The numerous trunk spines of D. truttae reduced the number of mucosal folds near the parasite site of infection. The acanthocephalan induced hyperplasia and hypertrophy of the intestinal mucous cells and many worms were surrounded with an adherent mucous gel. Near the site of acanthocephalan attachment, the number of mucous cells was significantly higher (P<0.01) in comparison to those found in uninfected intestines. Rodlet cells (RCs) were present in the epithelial layer in both infected and uninfected fish, with no significant difference in the numbers observed (P>0.05). In infected intestine, mast cells were more abundant than in uninfected gut (P<0.01). Migration of the mast cells and their intense degranulation at the site of infection were suggested. Immunohistochemical tests applied to sections of intestinal tissue of both infected and uninfected powan revealed that the parasitized C. lavaretus had a larger number of mast cells positive for met-enkephalin and serotonin antisera.

The occurrence of Mycobacterium spp. in freshwater and marine ornamental fish was studied in Italy from June 2002 to May 2005. Two surveys were carried out, one of aquarium fish sent to the Laboratory for diagnosis, and the other of prevalence of infection by mycobacteria in ornamental fish imported into Italy. Bacterial isolation was carried out from the spleen, kidney and liver, and the isolates were subsequently identified by biochemical tests. In the first survey, 387 fish were examined and Mycobacterium spp. were isolated from 181 (46.8%) fish. In the second survey 127 batches of ornamental fish from different countries were examined. Mycobacterium spp. were isolated from 38 (29.9%) batches. The following species were found: M. fortuitum, M. peregrinum, M. chelonae, M. abscessus, M. marinum, M. gordonae, M. nonchromogenicum and M. interjectum. There was a high prevalence of infection independent of the presence of macroscopic lesions. Mycobacterium fortuitum and M. chelonae were more prevalent than M. marinum in the samples examined.

The distribution of Sphaerospora dicentrarchi Sitjà-Bobadilla et Alvarez-Pellitero, 1992 and S. testicularis Sitjà-Bobadilla et Alvarez-Pellitero, 1990, myxozoan parasites of European seabass Dicentrarchus labrax (L.), was investigated in different farming systems in Italy. In total, 1406 fish were examined. High S. dicentrarchi prevalence was observed in all the farming systems involved in this survey (extensive farms: 51.5%; intensive farms: inland 59.6%, inshore floating cages 76.2%, offshore floating cages 41.6%) except for submersible cages (7.4%). S. testicularis was detected only in nine male fish from two intensive farms. The epidemiology and pathological effects of the parasites are discussed.

Over a 5 yr period, severe infestations due to Gnathia vorax larvae affecting different teleosts have been registered at the Civic Aquarium of Messina, Italy. Here, the damage caused by these parasites is evaluated from a macroscopical and histopathological point of view. We also attempt to evaluate the amount of blood sucked up by a single parasite and make some observations about the haematophagia. The histopathological changes confirm mucosal electrolytic failure as the main problem, even though the mean value of blood sucked up by a single parasite, about 1.9 mg, suggests that haematophagia may play an important role in the pathogenesis of such infestation. In conclusion, it was found that the G. vorax larvae caused 2-fold damage that was responsible for the death of the fish. Little by little, the parasitic problem was successfully removed by washing the tank, using fresh water rather than costly and dangerous chemotherapeutans.

Nematobothrinae are trematoda digenea that usually live in cysts in fish tissues. They have been reported in different teleost species although the host-parasite relationships remain to be elucidated. This report is aimed at analysing the presence of Unitubulotestis sardae in the Atlantic bonito (Sarda sarda) populations fished in the Straits of Messina. The histopathological change reported in literature in similar cases is an aneurisma verminosa saccata, whereas, in the specimens here described, we show neovascularisation and at the same time, hyperplasia of the gill epithelium, leading to the formation of a bistratified cystic wall. The SEM examination of the parasitic cysts gave us a better understanding of the surface microanatomical details of the cystic walls. The external surface appeared to be constituted by a pluristratified covering epithelium of the gill arch. The internal layer was constituted by a net of blood vessels richly anastomosed with those originating from the gill arch arteries. This could be in agreement with data reported by Grabda (1947) on the localisation of the juvenile stages of the parasite in this blood vessel, but the evolution in cysts formation does not show similarities with the formation of an aneurisma.

Viral encephalopathy and retinopathy, otherwise known as fish encephalitis or viral nervous necrosis (VNN), is an emerging problem in several farmed marine fish species in various geographic areas all over the world. Since summer 1995, heavy losses affecting mainly juvenile and adult sea bass (Dicentrarchus labrax) have been observed in several on-growing facilities in Italy. Dying fish show abnormal swimming behaviour and, at temperatures higher than 20-22 degrees C, mortality rates range between 15 and 50%. Neither significant external nor internal gross pathological signs, except frequent abnormal swim bladder hyperinflation, were detected. Histological investigations reveal vacuolations in the grey matter of the brain and spinal cord and in the granular layers of the retina. Serial tissue sections examined by an immunohistochemical method carried out with antisera against fish nodaviruses showed a positive reaction. Additionally, spherical virus-like particles 22-25 nm in diameter were detected by electron microscopy in negative stained preparations of brain tissues, and the same samples gave a positive reverse transcription-polymerase chain reaction (RT-PCR) for the T4 region of the fish nodavirus gene. These results indicate that both juvenile and adult sea bass subject to mass mortality in Italy since summer 1995 are infected with a fish nodavirus and strongly suggest that the identified virus is the cause of the observed mortality.

During researches on helminth parasites of Salmo trutta L. from the River Tirino (L'Aquila - Italy) histological studies of the intestinal tract of brown trout infected by the following species: Crowcrocaecum testiobliquum (Wisnewski, 1932) Skrjabin e Koval, 1956; Cyathocephalus truncatus (Pallas, 1781);o Truttaedacnitis truttae (Fabricius, 1794) Petter, 1974 and Dentitruncus truttae Sinzar, 1955 have been carried out. The attachment of the single species and the histological changes in the host gut due to parasite species have been described.