1. The single-copy domain of the N-terminal region of the vlhA gene of Mycoplasma synoviae was sequenced, analysed and verified and used to type Iranian field isolates of M. synoviae and the MS-H live vaccine strain. In addition, a restriction fragment length polymorphism (RFLP) method was developed to differentiate between field isolates of Iranian and MS-H vaccine strains. 2. All sequences were analysed and aligned; the percentage similarity of the DNA was calculated and dendrograms were constructed. Based on single nucleotide polymorphism (SNP) that existed in all field isolates in Iran, the PCR-RFLP method allowed the differentiation of all M. synoviae field isolates from the vaccine strain. 3. Using phylogenetic analysis, the isolates were assigned to 8 unique genotypes and, within each group, DNA had a high level of similarity. 4. DNA sequence analysis and PCR-RFLP of the amplicon based on percent similarity and evolutionary relationship appeared to be useful tools for strain differentiation whether M. synoviae clinical isolates from infected chickens were derived from the vaccine strain or wild-type strains. 5. This study confirms the potential value of strain typing for epidemiological purposes and suggests that phylogenetic studies are essential to understand the true relationships between strains.

No abstract

No abstract

No abstract

No abstract

Background and Aims: Newcastle disease (ND) is one of the most serious illnesses of chickens. Live vaccines are widely used to prevent chicken from the disease all over the world. Materials and Methods: To access the effective and potentiate ND vaccine, a homogenous subpopulation from LaSota strain was selected following cultivation of the virus on primary chicken embryofibroblast (CEF) cells. Pathogenicity indices and molecular characterization of a several plaques at 3rd passage were analyzed and then the selected clone was candidate for vaccine development. ND vaccine was prepared according to the standard protocols. Results: The immunogenicity of the live vaccine was examined in specific pathogen free (SPF) and commercial chickens. The geometric mean hemagglutination-inhibition (HI) titers induced in chickens vaccinated with the cloned vaccine were not significantly differ than those induced in chickens vaccinated with the similar ND clone vaccine. Conclusion: Efficacy of the ND vaccine was estimated against the virus challenge. The results indicate that the cloned vaccine could confer a complete protection against NDV.

Background Due to the more stability and a better homogenecity in immune response, the use of thermoresistant vaccines in different chicken types has been increased. Objective This study aimed to evaluate the efficacy of a newly developed Newcastle disease vaccine (ND.TR.IR) originating from I‐2 strain in specific pathogen‐free (SPF) and native and broiler chickens. Methods Following determination of pathogenicity indices on the candidate seed, three efficacy examinations were conducted. In the first experiment, 120 1‐day‐old SPF chickens were randomly allocated to six groups and either vaccinated with ND.TR.IR via eye drop at 1, 7, and 21 days of age (V1, V7, and V21), or considered as non‐vaccinated control groups (C1, C7, and C21). At 20th post‐vaccination day, sera hemagglutination inhibition (HI) antibody titres against ND virus (NDV) were measured and then the chickens were challenged by virulent NDV (vNDV). In the second and third experiments, the efficacy of ND.TR.IR vaccine was compared to routine vaccination program (B1 and LaSota) in native and broiler chickens that were vaccinated at 10 and 20 days of age, respectively. The HI antibody titres were measured on 10, 20, 30, and 40 days of age, and also challenge efficacy test with vNDV was conducted on 30 days of age. Results The studied virus, as a vaccinal seed, complied with the pathogenicity indices of avirulent NDV and molecular identity of I‐2 strain. In the efficacy evaluation trials, the vaccinated chickens had higher HI antibody titres against NDV compared with their corresponding control chickens (p < 0.05). Results of the challenge tests indicated 95% and 100% protection against vNDV in native, SPF, and broiler‐vaccinated chickens, respectively. Conclusions The present findings indicated that administration of ND.TR.IR induced appropriate HI antibody titres against NDV in SPF, native, and broiler chickens associated with good protection in efficacy test.

No abstract