Evaluation of two commercial enzyme‐linked immunosorbent assay kits for the detection ofMycoplasma gallisepticumantibodies

Clinical expression, epidemiology and monitoring of Mycoplasma gallisepticum and Mycoplasma synoviae: an update

Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) are of clinical and economic importance for the global poultry industry. Many countries and integrations are involved in monitoring programs to control both mycoplasma species. This review provides an extensive historic overview of the last seven decades on the development of the knowledge regarding the factors that influence the clinical expression of the disease, the epidemiology and monitoring of both MG and MS. This includes the detection of new virulent strains, studies unravelling the transmission routes, survival characteristics and the role of other avian hosts. Also the role of molecular typing tests in unravelling epidemiology, and factors that complicate the interpretation of test results such as heterologous mycoplasma infections, use of heterologous oil-emulsion vaccines, use of antibiotic treatments, occurrence of MG and MS strains with low virulence, and last but not least the use of live and/or inactivated MG and MS vaccines are discussed.

Rate of false positive reactions in 11 M. gallisepticum and M. synoviae serological tests in samples obtained from SPF birds inoculated with heterologous mycoplasma species

No recent information is available on the specificity of current M. synoviae (Ms) and M. gallisepticum (Mg) serological tests. In this study the performance of a currently available Mg and Ms Rapid Plate Agglutination (RPA) test, and three Mg, three Ms and three Mg/Ms combination ELISAs were evaluated on SPF sera that were obtained from days (D) 0-28 after M. gallinarum, M. imitans or M. gallinaceum inoculation, after sham inoculation and without inoculation. Tracheal swabs for mycoplasma culture were obtained before inoculation (D0), 7 and 28 days post inoculation (d.p.i.) in all groups except the sham inoculated group. The different mycoplasma species colonized well. In the early stage after inoculation (7-14 d.p.i.) with heterologous mycoplasma species, the specificity varied from 85% to 100% in the Mg RPA test and from 70% to 85% in the Ms RPA test. The specificity of both Mg and Ms RPA test was 100% in the sham inoculated samples and ruled out the effect of sham medium. In the late stage (21-28 d.p.i.) specificity was 100% for both RPA tests. The test specificity was 100% for seven ELISAs except for two combination ELISAs where a specificity of 95% was found in the late stage after inoculation. However, this was not significantly different from the specificity of all other tests in the late stage of these groups. These results show that it is not advisable to establish Mg and Ms seromonitoring programmes on the Mg and Ms RPA test alone as other mycoplasma species frequently occur in poultry.

High seroprevalence of respiratory pathogens in hobby poultry

Seroprevalence studies on respiratory pathogens have been done extensively in commercial laying hens, broilers, and, to a lesser extent, backyard poultry. In Europe, seroprevalence studies in backyard and fancy breed poultry flocks are scarce and limited to a few pathogens, such as Mycoplasma gallisepticum (MG); others, such as Ornithobacterium rhinotracheale (ORT), are missing. A commercial ELISA for detection of antibodies against six selected pathogens was performed on 460 serum samples from chickens across Flanders. Anti-ORT antibodies were, by far, the most prevalent, with a prevalence of 95.4%. Infectious bronchitis virus, Mycoplasma synoviae, and avian metapneumovirus antibodies were found in 75.6%, 76.3%, and 63.5% of the animals, respectively. Antibodies against MG and infectious laryngotracheitis virus were found in 36.7% and 30% of the animals, respectively. These data demonstrate the high seroprevalence of respiratory pathogens among hobby poultry; therefore, it is possible that this group could act as a reservoir for commercially kept poultry.

Comparison of Culture, PCR, and Different Serologic Tests for Detection of Mycoplasma gallisepticum and Mycoplasma synoviae Infections

In this study, the technical performance of culture, two commercially available polymerase chain reaction (PCR) tests, rapid plate agglutination (RPA) test, hemagglutination inhibition (HI) test, and eight commercially available enzyme-linked immunosorbent assays (ELISAs) were compared for the detection of avian mycoplasma infections from 3 days postinfection (d.p.i.) through 35 d.p.i. The tests were carried out on samples from specified pathogen-free layers that were infected at 66 wk of age with recent Mycoplasma synoviae (MS) and Mycoplasma gallisepticum (MG) field strains, MS and MG ATCC strains, and Mycoplasma imitans (MIM), respectively. Results showed a high percentage of positive samples in the homologous infected groups and a high percentage of negative samples (100%) in the uninfected and heterologous infected groups during 35 d.p.i. of both culture and PCR tests. For the group infected with the MG 15302 ATCC strain, serology was more sensitive than bacteriology. All MG and MS tests, with the exception of MG ELISA kit D showed a lower percentage of positive samples during 35 d.p.i. for the detection of the MG and MS ATCC strain infection compared with that of the field strains. Also, the number of cross-reactions (false positives) in the serologic tests was lower after infection with an ATCC strain than after an infection with the MG or MS field strain. Contradictory to other studies, the ELISAs and the RPA test using undiluted serum showed a relatively high number of false-positive results. The MG ELISAs (except ELISA kit D) showed more false-positive results (up to 37%) in the MIM-infected group than in the MS-infected groups. This was not unexpected, as MIM and MG have a close antigenic relationship. The results of the serologic tests in this study showed that a certain level of false-positive results can be expected in about any serologic test. Although the level of false-positive results varied between several serologic tests, this study showed that it is not advisable to rely completely on one test (system) only.

Serological monitoring of 40 Swiss fancy breed poultry flocks

Rapid serum agglutination, haemagglutination inhibition and enzyme-linked immunosorbent assays were used to screen Swiss fancy breed chicken flocks for antibodies against 12 avian infectious agents. For this purpose, 1,002 blood samples from 40 flocks were collected and tested. Ten percent of the samples were positive for Salmonella gallinarum-pullorum and 62.5% of the flocks were affected. More than 75% of the flocks had antibodies against Mycoplasma gallisepticum/Mycoplasma synoviae, infectious bronchitis, infectious bursal disease, avian encephalomyelitis, infectious chicken anaemia and reoviral arthritis. Low prevalence of antibodies was recorded for Salmonella enteritidis, avian influenza, avian leukosis and Newcastle disease (2.0 to 4.0%).

Development of a blocking enzyme-linked immunosorbent assay for detection of turkey antibodies to Mycoplasma meleagridis

A blocking enzyme-linked immunosorbent assay (B-ELISA) was developed to detect antibodies to Mycoplasma meleagridis (MM) in turkey sera. This assay was based on two mouse monoclonal antibodies recognising all MM strains tested but none of seven avian mycoplasmal species tested. Furthermore, their binding to the Tween 20 antigen was inhibited by serum from MM-infected birds. The B-ELISA test format was optimized. The cut-off was determined using a set of sera from MM-free turkeys. This B-ELISA was then compared with a commercial indirect ELISA (I-ELISA). Specificities of the two ELISA tests were not significantly different (100 or 99%, respectively). The sensitivity of B-ELISA was significantly higher than the I-ELISA when I-ELISA suspicious results were considered as negative. Testing sera from experimentally MM-infected animals showed that serum plate agglutination (SPA) test detected positive birds before both ELISA methods. Samples were collected in MM-infected commercial flocks and analyzed by SPA, ELISAs, MM-PCR or culture. Results showed that the sensitivity of the B-ELISA appeared superior to the I-ELISA. Moreover, the ability to detect maternal antibodies makes it a useful tool for eradication or control of MM infections.

Experimental infection of chickens with an atypical Mycoplasma gallisepticum strain: comparison of diagnostic methods

Fifteen chickens were inoculated with the atypical Mycoplasma gallisepticum (MG) K703 strain. On different dates post inoculation, tracheal swab samples were collected for mycoplasma culture and blood samples were analysed by slide agglutination test (SA) with commercial or homologous antigen and enzyme-linked immunosorbent assay (ELISA) with three different kits. Results showed that MG isolation rate was low on several sampling dates. The SA with commercial antigen did not yield positive results, although birds were positive when tested with homologous antigen. With commercial ELISA kits, the numbers of positive samples remained low. These results illustrate the difficulty of diagnosis of infections with such MG variant strains.

Immunoblot examination of humoral response of chickens infected with Mycoplasma gallisepticum at various ages

Mycoplasma gallisepticum- and Mycoplasma synoviae-free chickens were infected with 0.2 ml broth culture of M. gallisepticum strain 1226 intra air sac at 3, 14, 18, 28, 42, 49 and 65 days of age. Blood samples were taken 0-5 weeks before infection and 1-6 weeks after infection (depending on age of infection). The antibody response was examined by Western blot. As a control of infection, serum plate agglutination test (SPA), pathological lesions, and presence of Mycoplasma in air sacs were used. Antibodies to p64-67 kDa appeared in all groups of birds on the first week post-infection. Antibodies to p56 were detected from the second week post-challenge if infection was performed at 3 or 14 days of age, while on first week if challenge was done at 18, 28, 42, 49 or 65 days of age. Antibodies to p200, p120, p98, p80, p75, p72, p60, p50, p45, p40, p35, p33, p31, p28, p26, p24 and p22 were also detected.