Mode of infection and spread of <i>Vibrio anguillarum</i> in turbot <i>Scophthalmus maximus</i> larvae after oral challenge through life feed

The infection route of the marine fish pathogen Vibrio anguillarum was studied after oral challenge of the juvenile turbot Scophthalmus maximus L. through a life feed. Artemia nauplii were incubated in a suspension of V. anguillarum cells, and subsequently fed twice to the fish. All challenged fish died within 4d after the first challenge, while no mortality occurred in the non-challenged controls. The results of an immunohistochemical examination of the sectioned fish samples clearly demonstrated that V. anguillarum cells were ingested by the Artemia and that the latter were ingested by the fish. Bacteria were released from the Artemia mainly in the anterior part of the intestine. Most challenged fish started to show disease signs 24h after the second challenge and died 2d later. A histopathological analysis of moribund fish showed the development of septicaemia. Moreover, the sequential sampling, allowed the reconstruction of the infection route after oral challenge. Our results show that V. anguillarum was transported through the intestinal epithelium by endocytosis, after which the bacterium was released in the lamina propria. From there the bacterium was transported by the blood to the different organs, eventually leading the septicaemia and mortality

Phenotypic characterization of the marine pathogen <i>Photobacterium damselae</i> subsp. <i>piscicida</i>

The taxonomic position of Photobacterium damselae subsp. piscicida, the causative agent of fish pasteurellosis, is controversial as this organism has also been described as 'Pasteurella piscicida'. To clarify the taxonomic position of the pathogen, a total of 113 P. damselae subsp. piscicida strains and 20 P. damselae subsp. damselae strains, isolated from different geographical areas and from the main affected fish species, were analysed using 129 morphological and biochemical tests, including the commercial API 20E and API CH50 test systems. For comparison, the type strains of other Photobacterium species (i.e. Photobacterium leiognathi and Photobacterium angustum) were included in the analyses. The results were statistically analysed by unweighted pair group average clustering and the distance between the different clusters was expressed as the percentage disagreement. The analyses showed that, based on morphological and biochemical identification tests, P. damselae subsp. piscicida is related to other Photobacterium species. However, it is clearly distinguishable from P. damselae subsp. damselae and no phenotypic evidence was found to include P. damselae subsp. piscicida as a subspecies in the species P. damselae

Experimentally induced infections of European eel <i>Anguilla anguilla</i> with <i>Anguillicola crassus</i> (Nematoda, Dracunculoidea) and subsequent migration of larvae

Migration patterns 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 (1g) were fed infected Paracyclops fimbriatus (Copepoda). Eel samples were collected and examined histologically at varying intervals during 6 mo post-infection period. Third-stage larvae (L-III) migrated directly through the intestinal wall and body cavity to the swimbladder within 17h post-infection. 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

First report of eprinomectin-resistant isolates of Haemonchus contortus in 5 dairy sheep farms from the Pyrénées Atlantiques département in France

Infection of sheep by gastrointestinal nematodes (GIN) in pastoral systems such as those found in the South Western area of France, the Pyrénées Atlantiques, is one of the main reasons for economic loss and degradation of their welfare. In the present study, the efficacy of eprinomectin (EPN) was monitored on farms from this area following suspicion of lack of anthelmintic efficacy. Suspicions were raised by veterinarians, based on clinical signs ranging from milk and body condition loss, to anaemia, and mortality. Resistance was evaluated according to the World Association for the Advancement for Veterinary Parasitology (WAAVP) guidelines using fecal egg count reduction tests reinforced by individual analysis of drug concentration in the serum of all treated ewes by high-performance liquid chromatography (HPLC). EPN was administered by subcutaneous (SC) and topical (T) route according to manufacturer's requirements, as well as by the oral route (O) with the topical solution according to off-labelled practices in the field. For the first time in France, the presence of resistant isolates of Haemonchus contortus to EPN was observed in 5 dairy sheep farms. The HPLC dosages showed exposure of worms to concentrations compatible with anthelmintic activity for animals treated by the SC and O routes. By contrast, they showed under exposure to the drug of most individuals treated by the T route. EPN is the only null milk withdrawal anthelmintic molecule currently available. The presence of resistant isolates of the pathogenic H. contortus to EPN in this important dairy region requires an urgent change in grazing, and sometimes production, systems

Comparative serology of the marine fish pathogen <i>Vibrio anguillarum</i>

The different serotyping systems, based on thermostable O antigens, reported for Vibrio anguillarum and V. ordalii were compared by quantitative agglutination, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and subsequent silver staining or Western blotting (immunoblotting) of purified lipopolysaccharide (LPS), using polyclonal rabbit antisera. The results demonstrate that 16 different serotypes within V. anguillarum (designated 01 to 016) can be distinguished. Each of these serotypes is characterized by a distinct polysaccharide banding pattern, as revealed by silver-stained gels of purified LPS. The comparative analysis allowed a complete alignment of the different stereotypes for the first three serovars: 01, 02 and 03. Moreover, immunoblotting showed that strains belonging to each of these serotypes had the same LPS banding pattern independent of the origin of the strain. Stereotype 02 contains different subtypes, 02a and 02b. While no differences were apparent between these subgroups in silver-stained gels, they could be separated by quantitative agglutination (titer determination) or immunoblotting. V. ordalii, the former biotype II of V. anguillarum, strongly reacts with anti-V. anguillarum 02a antiserum. Strains of the two species can be separated in the basis of different LPS profiles in the high-molecular-weight region of silver-stained gels of purified LPS. The silver-stained LPS profiles of the different serotypes of V. anguillarum that have been established are provided for further comparison in the future

The use of API 20E for the identification of <i>Vibrio anguillarum</i> and <i>V. ordalii</i>

Sixty-eight strains of Vibrio anguillarum, five of V. ordalii and the type strains of V. alginolyticus, V. carchariae, V. damsela and V. parahaemolyticus were compared using the API 20E gallery. Within the V. anguillarum strains, distinct groups could be separated mainly on the basis of their reaction on indole production and the fermentation of amygdalin and arabinose. Vibrio ordalii, the former V. anguillarum biotope 2, could easily be separated from V. anguillarum and from the other fish pathogenic Vibrio spp