Abstract
The objectives of the study were determination of seroprevalence of M. gallisepticum of chickens in selected areas of Bangladesh, isolation of M. gallisepticum and characterization of field isolates and preparation of antigen (Ag) followed by evaluation of its efficiency.
The serum plate agglutination (SPA) test conducted on 2432 sera sample revealed a prevalence of 57.15% of M. gallisepticum. Seasonal variation of such infection was found to be highest in winter (42.44%) followed by monsoon (33.38%) and lowest in summer (24.17%). As regards, occurrences in geographical regions, it was observed 57.93% in Dhaka, 63.14% in Rajshahi, 52.63% in Khulna, 81.63% in Chittagong, 52.36% in Barisal and 35% in Sylthet division. The adult layers had the highest rate (66.95%) of infection than pullets (54.66%) and cockerels (53.50%). The highest prevalence of 67.34% was found in public sector while it was 50% in the commercial and 29.75% in breeder's farms.
For isolation of M. gallisepticum, a total of 360 cloacal and oropharynx swabs and respiratory tissue homogenate samples of chickens suspected to be suffering from respiratory diseases were cultured in Mycoplasma broth medium. From these, 240 positive samples were randomly selected and cultured on Mycoplasma solid media. Out of these, a total of 67 samples were taken to Victorian Institute of Animal Science (VIAS), Australia. These samples were subjected to growth inhibition (GI) test, immunofluorescent antibody (IFA) test and polymerase chain reaction (PCR) test and 5 isolates were finally characterised and selected for further use as M. gallisepticum.
M. gallisepticum antigen was prepared from a selected isolate and evaluated for its sensitivity and specificity on 200 M. gallisepticum free chicken received from a Japanese aided Farm. The birds were reared and maintained under standard feeding and strict hygienic condition and without use of any vaccine. At 8 weeks of age, when the birds were found negative for Mycoplasma antibody, half of these were vaccinated with a killed M. gallisepticum vaccine (Intervet, Netherlands), and the rest equal number was kept as unvaccinated control. These were bled at 4, 8 and 12 weeks post vaccination. The sera sample were tested with two commercial antigens (Ag) obtained from Intervet, Netherlands and Japan, and also with the experimental test antigen; the sensitivity was found to be 98.8%, 99.6% and 98.4%, respectively. On the other hand, the specificity was 98.5% and 100% in case of commercial antigens from Intervet and Japan, respectively, while with experimental antigen it was 98.66%. The sensitivity and specificity of the commercial and experimental antigen were not significantly different (p>0.05).