Muhammad Zeeshan (2014-VA-535)

Study On The Pathogenesis Of Field Isolate Of Salmonella Pullorum In Experimentally Infected Broiler Chicken - 2016. - 52p.;

Poultry is one of the well organized sectors in Pakistan and generates employment for up
to 1.5 million people. As use of modern techniques and medicine has reduced a risk lot but it is
still facing threat from many diseases. One of these is Salmonellosis which is and hatchery borne
infection and it also has a zoonotic importance. This organism is gram negative bacterium, non
acid fast, uniform staining and non spore forming bacillus.
Pullorum disease produced by it is also known as bacillary white diarrhea due to whitish
droppings produced by birds. Day old chicks are affected because it can be transmitted vertically.
Infected fomites and utensils also play a role in the transmission of infection. Growth of S.
pullorum rapidly occurs upon beef agar on nutrient media and growth is best at 37 °C. Selective
media such as selenite, tetrathionate broths and differential media such as MacConkey, bismuth
sulfide and brilliant green agar are best for the proper growth of organism.
The organism was isolated from the 30 different infected samples of broiler birds taken
from different farms and was grown upon the selective media. The colonies were picked from
the cultures and were subjected to PCR for the further process. After confirmation with PCR,
inoculums was prepared with a bacterial load of 2 x 107 (CFU) in 0.5 ml of normal saline at the
ph of 7.2.
Chicks were randomly divided in to three groups as group 1, 2 and 3, each group
containing 30 chicks. Group 1 was infected with field strain of S.pullorum, Group 2 with
vaccinal strain and Group 3 was set as control group and no infection was given to it. Samples
were collected from birds at 10th, 15th, 20th and 25th days of age. Observations were made upon,
clinical signs, histopathological lesions, mortality and morbidity rate, FCR and gross
pathological lesions.
Clinical signs included were anorexia, depression, huddling, labored breathing, loss of
feed and water intake, ruffled feathers, reduced mean body weights, low FCR and pasty vent.
Gross and histopathological lesions were much observed and were prominent in the birds
affected with field strain of S. pullorum. One Way-ANOVA was used for statistical analysis in
between the groups. Gross pathological lesions included were liver congestion 55%, cheesy
material in caeca 70% in the birds which were affected with field strain of S. pullorum.
Histopathological findings in the birds affected with field strain were monocytes in spleen,
leukocytes in intestine and heterophils in liver. Low FCR was recorded in infected birds of
Group 1 and was 1.63 at 25th day. Mortality rate in the birds affected with field strain was
maximum 43.33% and morbidity rate was 73.33% at the 10th day of age. Birds of group 2 were
less affected and only showed medium level of lesions. No specific lesions were seen in group 3.
The total prevalence of of S.pullorum after conformation with PCR was 20% out of total 30
infected samples. The organs for histopathology taken were liver, spleen, caeca and intestine and
were preserved in 10% formalin prior to the infection.
The overall pathogenesis of experimental bacteria after given through oral route was that
it first localizes in digestive tract from where it enters into the blood stream and invades in the
different organs and tissues at different time intervals producing lesions and immunological



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