Comparison of mycoplasma gallisepticum infection in different samples and ages of chicken breeder flocks

Abstract

This study aimed to compare method-based and newly developed sample-based methods for Mycoplasma gallisepticum (MG) detection in different samples of breeder flocks suffering from respiratory disease problems by using culture, real-time PCR (rPCR) and ELISA from chicks and embryonated eggs. Overall, 450 samples of 19-day-old chicken embryo's trachea, 450 samples of 8-day-old chicken tracheal swabs and 900 blood samples of 20-, 27-, 34-, 40- and 46-week-old breeder chickens from 5 flocks were sampled for 26 weeks, and were all tested for MG by culture, MG-rPCR and MG-ELISA. Culturing assays and rPCR were applied to 450 mixture samples from 19-day-old chicken embryo's trachea and 450 tracheal swab samples (each pooled into groups of 3) from 8-day-old chicks from the same flocks. Also, 900 blood samples from the same 5 breeder flocks suffering from respiratory disease problems were tested by MG-ELISA.In individual sample-based analyses, 55 (18.3%) of the 300 pooled swab samples were positive for MG using culture methods, and 106 (35.3%) of the same samples were found positive by rPCR (sensitivity, specificity). The ELISAs indicated that 252 (28%) of the 900 breeding blood samples were MG seropositive. Using age-based analyses, the most positive period was 46 weeks, followed by 40 weeks, 34 weeks, 27 weeks and at least 20 weeks, in order of decreasing seropositivity. When comparing the culture and rPCR results of the two different sampling methods, chicken embryo's trachea yielded more positive results than did tracheal swabs from the same flocks. In conclusion, rPCR is a highly specific, sensitive and reliable method for MG identification.