| dc.description.abstract | Poultry industry targets the production of animal protein of excellent quality with low costs and
helps in national economy for generating jobs and foreign exchange credits for the balance of
trade. But outbreaks of different infectious diseases are one of the major constraints of poultry
farming. Mycoplasma gallisepticum organism is one of the most infectious organism and
economically significant throughout the world. The present research was performed with the
objective of serological and molecular characterization of Mycoplasma gallisepticum organism
from field samples in order to get pure culture of the etiological agent. The epidemic behavior of
the etiological agents were studied based on age and breed of birds, seasons and location where
the birds were rearing. The incidence rate of infections were recorded as per information
collected from farmers by using a set of questionnaire, symptoms of affected birds and post
mortem lesions. In association with the epidemiological investigation, the overall incidence rate
was 11.54%. For detection of specific antibody of Mycoplasma gallisepticum, 920 sera were
tested from ten selected farms based on location, age groups, seasons, breeds and flock size, by
SPA test and found 526 sera were positive. The overall incidence was 57.17%. The highest
incidence rate (61.96%) was found at Dinajpur and the lowest (51.09%) at Rangpur in
comparison to other districts. The highest incidence (64.78%) was found in above 40 wks
followed by 59.30% in 21-40wks, 56.52% in 9-20wks and 48.26% in 0-8wks respectively. The
prevalence was found 61.96% in winter and 52.39% in summer season, 59.78% in Sonali and
56.52% in Isa brown breed, 61.96% in large and 51.44% in small flock. No significant difference
was observed as their location and breed but significant was in age and season variation.
Furthermore 526 SPA positive sera were tested by iELISA test and 164 (31.18%) sera were
positive. 80 representative sera were tested by HI from iELISA positive sera and found that 15
(18.75%) sera were positive. A total of 156 different organs of trachea, lungs and air sacs were
cultured for isolation of etiological agent of Mycoplasmosis and the positive cases were 5.77%.
The highest rate (13.46%) of organism was found in tracheal swabs followed by 1.92% in air sac
and 1.92% in lung. For molecular characterization of Mycoplasma gallisepticum, 48 different
organs were tested by direct PCR without culture and overall positive was 12.5% (6 bands).
Among them 25%, 6.25% and 6.25% were found from tracheal swabs, air sacs and lungs
respectively and 0.64% (1 band) from culture positive isolates. The DNA sequencing of the
present study showed 99 to 100% per cent similarity with the sequence of the duck isolate from
South Africa, chicken isolate of Spain and USA as demonstrated by blast (NCBI). It is
recommended that the samples from live birds are sufficient enough to identify the organism and
tracheal swab samples gave more isolations than from lung and air sac by molecular technique. It
is justified that PCR is a serviceable tool in the accurate diagnosis of Mycoplasma infections, not
only for its sensitivity but also for its high specificity. This technique overcome culture method as
it depends on the direct detection of the micro organism’s DNA without the need for cultivation.
PCR has allowed the study of microbial genes, directly amplified from samples. It is a sensitive,
easy, rapid and inexpensive technique and the most important advantage is eliminating the need
for isolation of Mycoplasma gallisepticum. | en_US |
