Effects of experimental infections with different doses of Anguillicola crassus (Nematoda, Dracunculoidea) on European eel (Anguilla anguilla) (original) (raw)
Related papers
Histopathological Examination of Wild American Eels Infected with Anguillicola crassus
Journal of Aquatic Animal Health, 2006
We describe for the first time the histopathology caused in wild American eels Anguilla rostrata by the introduced nematode Anguillicola crassus. All of the American eels examined showed signs of previous or ongoing infections with A. crassus. Gross observations included opacity of the normally translucent swim bladder and dilation of blood vessels. The swim bladders of infected American eels showed focal, multifocal, and diffuse histological changes. Consistently observed pathologies included abnormal papillose appearance of the mucosa; hyperplasia of the lamina propria, muscularis mucosa, and submucosa; edema of the mucosa and muscularis mucosa; dilation of the blood vessels; and damage in the submucosa caused by migrating A. crassus L3 and L4 larvae. Less-common pathologies included fibrosis and lymphocytic aggregates around L3 and L4 larvae in the submucosa; destruction of the mucosa, which in some cases completely exposed the mucosal blood vessels; L2 larval penetration of the tissues of the swim bladder; bacterial infections in the submucosa and muscularis mucosa; and migration of an L4 larva through the rete mirabile.
Diseases of Aquatic Organisms, 1989
Migration pattern of third-stage Anguillicola crassus larvae, and pathogenesis of the lesions induced by third-stage larvae, was investigated in European eel Anguilla anguilla L. Young elvers (l g) were fed infected Paracyclops fimbriatus (Copepoda). Eel samples were collected and examined histologically at varying intervals during the 6 mo post-infection period. Third-stage larvae (L-111) migrated directly through the intestinal wall and body cavity to the swimbladder within 17 h postinfection. L-IV larvae were detected 3 mo post-infection, and immature adults were detected within 4 mo post-infection. The parasites occasionally showed aberrant migration paths. Pathological effects caused by the parasite were less severe after experimentally induced infections than those detected in some natural infections.
Acquired resistance of the eel, Anguilla anguilla L., to challenge infections with gill monogeneans
Journal of Fish Diseases, 1993
The European eel, Anguilla anguilla L., is able to respond to infections with ectoparasitie gill monogeneans of the genus P.seudoduct\logvrus Gussev, 1965. A primary infection offers the host a relative resistance to ehallenge infeetions. The relative proteetion was detected at hoth 14 and 33 days after mebcndazolc termination of the primary infection by a significantly greater parasite reduction in previously infeeted eels eompared to nonprimed eels. No complete immunity was obtained.
Diseases of Aquatic Organisms, 2005
Swimbladder changes resulting from Anguillicola crassus infection of the European eel Anguilla anguilla have been the subject of several studies reported in the literature. These investigations, however, studied exclusively the status of infection at a given point in time and did not deal with changes in swimbladder infection in eels suffering from anguillicolosis over a period of time. In this study, A. crassus-induced pathological changes were monitored in 78 eels naturally infected in Lake Balaton and subsequently kept in the laboratory, thus excluding the possibility of further infection. During the 3 mo study, the status of the swimbladder was checked by radiographic examination on 4 occasions. At the end of the study the eels were dissected and the gross pathological changes in the swimbladders were compared with the radiographic findings. As compared to their starting condition, by the end of the study the pathological status of the swimbladder had deteriorated in 55% and remained the same in 37% of the cases. Tendency to improvement (1%) and variable findings (7%) were recorded in a low percentage of cases only. With the help of the radiographs presented, the dynamics of A. crassus infection and of changes in the swimbladder of individual eel specimens can be monitored easily.
Central European Journal of Immunology, 2015
Parasitic invasions are recognized as one of the primary factors responsible for decreasing populations of European eel. The aim of the present study was to determine the influence of infestation with the nematode Anguillicoloides crassus on the innate immunity in European eel (Anguilla anguilla). Anguillicoloides crassus parasitizes the swim bladder of this fish. Levels of the following immunological parameters were measured: spleen phagocyte respiratory burst activity, spleen phagocyte potential killing activity, pronephros lymphocyte proliferation stimulated by concanavaline A or lipopolisaccharide, plasma lysozyme and ceruloplasmin activity, total protein and immunoglobulin (Ig) serum levels. The analyses of the results of humoral and cellular immunity indicate that all studied parameters were statistically significant higher (p < 0.05) in non-infested fish compared to the ones with anguillicolosis except for ceruloplasmin level. These data suggest that the A. crassus infestation in European eel is responsible for a decreased immune response what could result in higher susceptibility to other pathogenic conditions.
Infection by Anguillicoloides crassus in a riverine stock of European eel, Anguilla anguilla
Fisheries Management and Ecology, 2010
Infection by the parasitic nematode Anguillicoloides crassus Kuwahara, Niimi & Itagaki, in a wild riverine stock of European eel, Anguilla anguilla (L.), in a near pristine river was investigated. Samples were collected on a seasonal basis in distinct habitats along the river gradient. This study highlighted the presence of the parasite and completion of the whole life cycle in eels from the Rı´o Esva. Infection levels by A. crassus were high at three sites between the mid river to the estuary and also varied among seasons. Condition of eels was lower at upstream sites compared with downstream locations. Although high-quality, environmental conditions in the Rı´o Esva may buffer the effects of A. crassus on eels, potential impacts and limiting factors for the parasite are discussed.
Parasitology, 2008
SUMMARYThe original host of the swimbladder nematodeAnguillicola crassus, the Japanese eel (Anguilla japonica) and the recently colonized European eel (Anguilla anguilla) were immunized with 40 irradiated (500 Gy) 3rd-stage larvae (L3) of this parasite and challenged with an infection of 40 normal L3. The immunization induced a significant reduction of the number of adult worms developing from the challenge infection inA. japonica, but not inA. anguilla. The induced resistance (calculated using the relation of the number of adult worms in immunized eels and in non-immunized control eels) inA. japonicawas 87·3%±30·4%. Following a single infection, the percentage of adult worms found inA. japonicawas lower as compared toA. anguilla, and the few adult worms were much smaller, revealing a lower susceptibility ofA. japonicatoA. crassusin comparison toA. anguilla. Both eel species developed an antibody response againstA. crassus, but the level of antibody responses was not positively corr...
Journal of Fish Diseases, 2011
This study compares two alternative indices for quantifying the gross pathology of the swimbladder of eels, Anguilla anguilla (L.), infected with the nematode Anguillicoloides crassus. Two observers recorded twice the scores obtained by the two indices on the same set of 71 wild caught eels (from elver to silver eels, French Mediterranean lagoons). The Length Ratio Index (LRI), performed better than the Swimbladder Degenerative Index (SDI), in three of four predefined criteria of decision. First, the LRI better correlated with an estimate of the swimbladder volume reduction, a functional consequence of the infection (representativeness). Also, the LRI was less prone to subjectivity (inter-observer variability) and more precise (intra-observer variability), although less easy to generate (time needed for measurement/ assessment). Using a sub-sample of 32 unaffected eels (showing minor if any swimbladder damage and no living worms at autopsy), we ascertained a linear relationship between the swimbladder length and the total body length, a prerequisite of isometric growth, to definitively accept the new ratio index as a valid alternative to the SDI. Also, because the LRI can be recorded on live specimens with radio-imagery (non-invasive method), we recommend its use, and provide a graph of correspondence between the SDI scores, the LRI scores and the estimated proportion of gas loss in the swimbladder.