G. Bennejean

The polymerase chain reaction for Mycoplasma gallisepticum detection

On the basis of the aligned 16S rRNA sequences of Mollicutes, a pair of primers was chosen for the detection of Mycoplasma gallisepticum. When used in the polymerase chain reaction (PCR), the primers detected a specific amplification of all Mg strains tested, yielding an expected 330 bp product. Amplification was not detected when other Mollicutes or E. coli were used as PCR templates. SPF chickens were experimentally inoculated with two strains of M. gallisepticum or Mycoplasma iowae. Tracheal swabs were collected 8, 15, 20 and 28 days after inoculation, and cultured for mycoplasma or tested by PCR. PCR products were detected by hybridization with a digoxigenin-labeled probe and by chemiluminescence. The results showed that culture was positive for 49/73 swabs while PCR detected 70/72 positive samples. Thus, PCR can provide the basis of a sensitive, specific, rapid and non-radio-active method for detecting M. gallisepticum.

Vccination of one‐day‐old chicks against newcastle disease using inactivated oil adjuvant vaccine and/or live vaccine

One-day-old chicks, with or without maternal antibodies against Newcastle disease, were vaccinated by different methods: one group received a live vaccine (Hitchner B1 strain), the second group an oil-adjuvant vaccine, and the third group both vaccines simultaneously. The serological response and the protection of the chicks against challenge were evaluated regularly up to 80 days of age. The best results were obtained when using both vaccines, which induced a good level of protection against the challenge virus strain.

Isolation, characterisation and preliminary cross-protection studies with a new pathogenic avian infectious bronchitis virus (strain PL-84084).

Virological 1 examination of a severe infectious bronchitis (IB)-like field case in laying hens, led to the isolation of a coronavirus antigenically different from Massachusetts, Connecticut and four Dutch IB variant strains. The virulence of the isolate for the fowl, and its dual tropism for the respiratory and genital tracts were demonstrated. In preliminary cross-protection studies Commercial vaccines did not protect against challenge with this isolate. These points and the possible economic significance of the virus are discussed.

Characterization of french avian paramyxovirus type 1 pmv 1 isolates with a panel of monoclonal antibodies to the ploufragan strain of newcastle disease virus

SummaryEight monoclonal antibodies against the Ploufragan strain of New-castle disease virus were used to characterize 58 virus strains including 29 French isolates. By combining ELISA and haemagglutination inhibition tests, PMV 1 strains were differentiated from other avian PMV 1 and grouped into 7 classes.

Evaluation of two commercial enzyme‐linked immunosorbent assay kits for the detection of Mycoplasma gallisepticum antibodies

Sensitivity and specificity of two commercial Mycoplasma gallisepticum (MG) enzyme-linked immunosorbent assay (ELISA) kits, rapid slide agglutination (SA) and haemagglutination inhibition (HI) tests were compared using sera from specific pathogen free chickens, turkeys or ducks which had been inoculated with various avian mycoplasmas, bacteria or with a reovirus. Results show that sensitivity of SA was superior to ELISA and HI tests in the ability to detect antibodies formed in early response to MG infection. However, both ELISA kits and HI tests had a higher degree of specificity.

An ELISA blocking test using a peroxidase-labelled anti-HN monoclonal antibody for the specific titration of antibodies to avian paramyxovirus type 1 (PMV1)

SummaryThis report describes an ELISA blocking test using a peroxidase-labelled monoclonal antibody which binds to the HN protein of Newcastle disease (NDV).This test allows specific detection of type 1 avian paramyxovirus (PMV1) antibodies but does not detect other avian paramyxovirus (PMV2-9) antibodies recognized by the usual serological NDV tests (HI, Orgenics, and Agritech ELISA tests). Furthermore, swollen head syndrome and influenza antibodies were also not detected. ELISA blocking and HI titers of sera collected from SPF chickens immunized with 18 different PMV1 strains (including pigeon isolates) were the same; the correlation between ELISA blocking and HI titers was highly significant (P<0.001).In comparison with ELISA tests available commercially at the present time, the ELISA blocking test can be performed more quickly and is applicable without modification to sera from different species of fowls. For this reason, the test appears to be useful for determining the immunity and sanitary status of fowls. When recombinant or deleted vaccines become available, the test should make it possible to demonstrate with confidence any infection of fowls by wild type PMV1.

Mycoplasma Iowae: Field and laboratory studies to evaluate egg transmission in Turkeys

In order to study the egg transmission of Mycoplasma iowae in turkeys, two experiments are undertaken. Experiment 1 was a field trial designed to investigate egg transmission in naturally infected turkeys: commercial hens were inseminated with semen from naturally infected toms. Mycoplasma iowae was regularly cultured from dead-in-shell embryos, pips and culls but not from healthy poults. Egg transmission occurred from the second up to the tenth week of production. Experiment 2 was a laboratory study conducted to observe persistence and egg transmission of M. iowae in experimentally infected turkeys. Specific pathogen free (SPF) hens were inoculated either intracheally or intravaginally. They were then artificially inseminated with semen from SPF toms. Very little egg transmission was observed. The cultures from tracheal or vaginal swabs of the inoculated hens showed a limited invasive ability of M. iowae in the adult bird. The humoral immune response as detected by the metabolism inhibition test, was very poor. The observations made in these two experiments show the importance of venereal spread of M. iowae, especially under artificial insemination. Consequently, the need for monitoring toms is obvious.

A New Pathogenic Avian Infectious Bronchitis Virus Isolated in France

A coronavirus was isolated in an infectious bronchitis (IB) vaccinated (Massachusetts strain) layer flock showing severe IB-like clinical signs. The isolate is antigenically different from the Massachusetts and the Connecticut serotypes and from the four “variant” serotypes isolated by the Doom Institute in Holland. The disease was reproduced in chickens and layers. Respiratory signs were severe in both groups. In layers, egg drop was intense and long-lasting. The eventual development of a suitable medical prophylaxy is discussed.