Eighteen years of vaccination against viral haemorrhagic septicaemia in France.

Viral haemorrhagic septicaemia (VHS) has been considered for many years to be a major cause of loss in the French trout industry. The high prevalence of VHS in certain geographic areas made a control strategy based on control policy unfeasible. This provided the impetus for immunoprophylaxis development that resulted in 3 successive types of vaccines: inactivated, live attenuated and recombinant vaccines. When delivered by intraperitoneal injection, the 2 propiolactone-inactivated VHS virus was immunogenic and/or protective for trout all of sizes, but it was not suitable for the practical immunization of alevin, the trout life stage that is the most sensitive to VHS. A carp cell-passed, attenuated variant of the VHS virus was effective after both immersion or injection delivery and met the practical requirements of juvenile vaccination. However, this vaccine was discarded because it retained some virulence that discouraged the launching of its commercialization. Then came the era of genetically engineered vaccines. The recombinant glycoprotein of VHSV produced in Escherichia coli or in Saccharomyces cerevisiae failed to protect fish whatever the route of delivery. A recombinant baculovirus vaccine was found to be immunogenic and protective against VHS, but only when delivered by injection. Due to its cost and route of delivery, the latter vaccine was not licensed. Simultaneously, the sudden occurrence of another rhabdovirosis, infectious haematopoietic necrosis (IHN), in France, rendered vaccination against VHS questionable. Indeed, no cross-protection between these 2 rhabdoviroses exists. If vaccination is still believed to be an effective control method for VHS, it should be based in the future upon an autoreplicative vaccine.(ABSTRACT TRUNCATED AT 250 WORDS)

[Avian mycoplasmosis: Comparative study of the plate agglutination test, haemagglutination inhibition test and metabolic inhibition test for detection of antibody against Mycoplasma gallisepticum]. / Depistage serologique des mycoplasmoses aviaires: Agglutination rapide sur lame, inhibition de l'hemagglutination, inhibition metabolique, techniques appliquees au serodiagnostic des infections a Mycoplasma gallisepticum.

This study was performed with the use of the MG/S6 strain of Mycoplasma gallisepticum, reference sera, sera from vaccinated chickens (given at inactivated vaccine) and sera from infected turkeys in the field. Titres of antibody detected were well correlated for the three tests. However, the plate agglutination test (PAT) allowed the earliest detection, and metabolic inhibition test (MIT) was as sensitive and specific as the haemagglutination inhibition test (HIT). MIT allowed a good repeatability of results, and discriminated very well between positive and negative sera. Serological studies with MIT using a constant dilution of sera gave results comparable with titration by MIT, with a valuable saving of time and material. PAT was found to be one of the best techniques for mass serological screening. Results with MIT and HIT confirmed the PAT results, but MIT was more easily interpreted, particularly with sera taken during the late phase of antibody decrease.

[Enzootic bovine leukosis application of E.L.I.S.A. technique for the detection of antibodies]. / Leucose bovine enzootique application de la technique E.L.I.S.A. à la détection des anticorps.

A simple microplate method of enzyme-linked immunosorbent assay (E.L.I.S.A.) for detecting antibodies to bovine leukosis virus (B.L.V.) is described. The antigen consisted of a solution containing the two major antigens of the B.L.V. (gp 51 and p 24) obtained by a technique of purification using CN-Br activated Sepharose 4B. This E.L.I.S.A. was compared with the agar gel immunodiffusion test (A.G.I.D.T.) in a study of 545 bovine sera. The total discrepancy rate between the two tests was 11% with a better sensitivity for E.L.I.S.A.

Enzootic bovine leukosis: an epidemiological survey among cattle in the west of France by precipitating antibody detection.

In order to inform the sanitary veterinaty authorities, an epidemiological survey was carried out in the West of France to appreciate the level of infection by BLV in cattle. More than 10,000 sera from 763 herds were tested by agar gel immuno-diffusion. The animals were more than one-year-old dairy cattle. 23 sera (0.22%) from 11 herds (1.44%) were found positive. In the 11 herds the levels of serologically positive animals ranged from 1.6 to 40% with a 9% average. These levels are comparatively low and are almost in correspondence with the number of leukotic tumours recorded in the slaughter houses and knackeries.