Abstract
Sixteen chickens' flocks and six ducks᾿ flocks were surveyed for presence of fowl cholera (FC) during the period from July 2013 to November 2016. A total of 81 freshly dead birds (51 chickens of average age 50 to 180 days and 30 ducks of average age 30-100 days) were received from different farms and house breeding in Dakahlia Governorate at Mansoura Laboratory of Animal Health Research Institute for further laboratory examination. FC was diagnosed based on case history, postmortem lesions, bacteriological isolation, polymerase chain reaction (PCR), capsular typing, virulence factor detection (Tox A gene), and immunohistochemistry (IHC). In this study, Pasteurella multocida (P. multocida) were bacteriologically isolated from 22 chickens and 16 ducks. The infection occurred in 4 layer chickens flocks, 2 breeder flocks and 3 broiler flocks. Meanwhile, all affected flocks of ducks were broiler. Age susceptibility in chickens varied as the age ranged from 30-54 days in broiler flocks, 45-150 days in layer flocks during the rearing period and before start egg production, 70-150 days in breeder flocks during the rearing period. In ducks the susceptible age ranged from 30-100 days. The most affected cases of chickens were from farm housing and the most affected cases of ducks were from back yard housing. Mortality rate in chickens was 0.03 to 0.36 and in ducks was 33.3 to 46.6%. Main gross findings in affected chickens and ducks were corn meal liver, fibrinous perihepatitis and fibrinous pericarditis. Swollen hock joint and thickened foot pad were grossly detected in ducks only. The histopathological lesions in the infected ducks were more severe than those detected in the infected chickens that characterized by multiple granulomata in most examined organs. Therefore, the IHC positive reaction against antigen of P. multocida serotype A were more intensely stained and widely distributed in all examined organs of infected ducks than in chickens.
Highlights
Fowl cholera (FC) is one of the most important highly contagious bacterial diseases caused by Pasturella multocida (P. multocida)
The most affected cases of chickens were from farm housing and the most affected cases of ducks were from back yard housing
Age susceptibility in chickens varied as the age ranged from 30-54 days in broiler flocks, 45-150 days in layer flocks during the rearing period and before start egg production, 70-150 days in breeder flocks during the rearing period
Summary
Fowl cholera (FC) is one of the most important highly contagious bacterial diseases caused by Pasturella multocida (P. multocida). FC causes high economic losses in poultry production It produced 1.8-21% mortalities and 15-20% decreases in egg production, in addition to the costs of vaccination and treatment of diseased birds and culling of the infected flock (Kapetanov et al, 2000; Charitha Devi et al, 2012 and Wilkie et al, 2012). There were many predisposing factors caused stress on birds increasing the risk of the disease despite of vaccination (Jonas et al, 2001). Improper environmental factors like cold temperature increased host susceptibility to avian cholera (Samuel et al, 2007). Overcrowding of susceptible birds was considered as one of the most important stress factors that enable the disease to affect large number of birds of different species (Blanchong et al, 2006). The virulence of the microorganism was greatly variable between different P. multocida strains (Wilkie et al, 2000; Petersen et al, 2001 and Samuel et al, 2003)
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