Influence of flumequine and oxytetracycline on the resistance of the European eel against the parasitic swimbladder nematode Anguillicola crassus.

The effect of the antibacterial drugs flumequine (FQ) and oxytetracycline (OTC) on the defence system of the European eel (Anguilla anguilla L., 1758) was investigated using an experimentally induced infection with the parasitic swimbladder nematode Anguillicola crassus. Eight weeks after oral administration of infective larvae, the mean recovery of the parasites in FQ-treated eels was lower than in non-medicated control animals, and significantly lower than in OTC-treated eels. Mean numbers of peripheral blood granulocytes and B-lymphocytes, as well as the total number of circulating lymphoid cells, showed a significant increase as a result of the infection, while drug treatment merely affected the quantity of the lymphoid cells. The difference in protection against the parasite after FQ or OTC administration points to a modulation of the fish resistance as a result of the drug treatment. The results favour a modulation of the cellular rather than the humoral response, as no specific antibodies were found.

[A study of the cause of massive mortality among marine-cultured rainbow trout (Oncorrhynchus mykiss, Walbaum) in a fish farm in the southwestern Netherlands]. / Een onderzoek naar de oorzaak van massale sterfte van marien gekweekte regenboogforellen (Oncorhynchus mykiss, Walbaum) op een aquacultuurbedrijf in zuidwest Nederland.

The present study investigated the mass mortality of marine cultured young rainbow trout (Oncorhynchus mykiss, Walbaum) in the Netherlands. The course of the disease, the clinical symptoms, and bacteriological and virological investigations lead to the diagnosis: 'primary infectious pancreatic necrosis virus (IPNV) infection followed by secondary vibriosis'. Treatment with flumequine seemed to be effective. The trout were possible infected with IPNV at the trout hatchery and nursery from which they originated.

Influence of flumequine on in vivo mitogen responses of European eel (Anguilla anguilla L., 1758) lymphoid cells.

The influence of flumequine on mitogen induced lymphoid cell proliferation in European eels (Anguilla anguilla L., 1758) was studied. For this purpose an in vivo test, using peroral drug administration followed by successive intraperitoneal injections with concanavalin A (ConA) or bacterial lipopolysaccharides (LPS) and 5-bromo-2'-deoxyuridine, was applied. Direct counting of proliferated cells in blood smears revealed that flumequine possesses mitogenic properties. A synergistic and an antagonistic effect of the drug was observed after LPS and ConA stimulation, respectively. Flow cytometric analysis of peripheral blood lymphoid cells showed a significant reduction of the mean proportion surface immunoglobulin positive cells in the flumequine-treated animals. It is concluded that flumequine enhances proliferation of lymphoid cells (probably surface immunoglobulin negative cells) in eel under the present experimental conditions.

Production, characterisation and applicability of monoclonal antibodies to European eel (Anguilla anguilla L., 1758) immunoglobulin.

Monoclonal antibodies (mAbs) to European eel (Anguilla anguilla L., 1758) immunoglobulin (Ig) were produced, characterised and tested for applicability in a number of immuno(cyto)chemical assays. The selected mAbs, WEI 1 and WEI 2, were specifically reactive with Ig heavy and light chain, respectively. WEI 1 appeared to react with all or nearly all Ig molecules, B cells and plasma cells. WEI 2 was reactive with a subpopulation of those cells, indicating that European eel possesses at least two antigenically different light chain types. Both mAbs could be used for detection of antigen-specific antibodies in plasma by means of an enzyme-linked immunosorbent assay (ELISA).

Numbers of myosatellite cells in white axial muscle of growing fish: Cyprinus carpio L. (Teleostei).

By means of transmission electron microscopy (TEM), the percentage of myosatellite cells was shown to decrease from about 6% in carp of 5 cm standard length (SL) to less than 1% in carp larger than 18 cm SL. The ratio between muscle nuclei and non muscle nuclei remained constant. These TEM data, combined with data on the amount of DNA per gram of muscle tissue and per nucleus, were used to calculate the numbers of myosatellite cells per gram of tissue (TEM-DNA method). Total numbers of myosatellite cells could be calculated from the TEM-DNA data and the calculated amounts of muscle tissue per fish. After a slight initial increase, the total number of myosatellite cells in the white axial muscle of a carp appears to be rather constant during the growth phase of the fish. But the myosatellite cells become more and more diluted over an increasing number of myonuclei with age. In addition, the reliability of two new light microscopic methods for the determination of numbers of myosatellite cells was examined. The percentages of myosatellite cells were determined by counting the numbers of total nuclei and of heterochromatic nuclei situated inside the muscle fibers' basal laminae which were stained using an antibody against laminin. These percentages were not significantly different from those determined with TEM. The yield of myosatellite cells per gram of muscle tissue, isolated with a previously developed dissociation method, showed a direct relation to the number of myosatellite cells calculated to be present in the tissue (TEM-DNA method), but at a 1% level. Both methods are alternative ways to determine numbers of myosatellite cells when it is impossible or difficult to use TEM (e.g., large sample sizes, combination with immunohistochemical methods).

Relationship between cytologic changes in bronchoalveolar lavage fluid and weight gain in calves with gastrointestinal nematodes and lungworms.

Two of three groups of 10 calves each were infected with either 100,000 infective larvae (L3) of Ostertagia spp. and 100,000 L3 of Cooperia spp. or with 4000 L3 of Dictyocaulus viviparus, respectively, at the age of 14 weeks. The third group was not infected. After treatment with an anthelminthic five calves from each group were challenged with either 100,000 L3 of Ostertagia spp. and 100,000 L3 of Cooperia spp. or 4000 L3 of Dictyocaulus at the age of 20 weeks. The calves were 25 weeks old when slaughtered. Total and differential cell counts were determined in bronchoalveolar lavage fluid and showed that neutrophils were the most frequent and eosinophils the least frequent cell present. There was a significant negative relationship between eosinophil levels and weight gain of the calves.