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Bacterio-pathological Studies on Salmonellosis, Colibacillosis and Pasteurellosis in Natural and Experimental Infections in Chickens

M. A. Rahman
Department of Medicine and Surgery, Barisal Government Veterinary College, Khanpura, Babugonj, Barisal, Bangladesh.

M. A. Samad
Department of Medicine, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

M. B. Rahman
Department of Microbiology and Hygiene, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

S. M. L. Kabir
Department of Microbiology and Hygiene, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

Bacterio-pathological investigation on 1751 dead chickens during one year period from January to December 2002 at the BRAC Poultry Disease Diagnostic Centre, Gazipur showed that 39.81% (n = 697) cases with seven types of different bacteriological diseases of which salmonellosis ( n = 385 ), colibacillosis ( n = 147 ) and fowl cholera ( n = 114 ) were found significantly higher rate of prevalence then staphylococcosis (n = 6), gangrenous dermatitis (n = 17), necrotic enteritis (n = 24) and infectious coryza (n = 4). Accordingly, avian salmonellosis, colibacillosis and pasteurellosis were selected for detailed investigation. Age wise prevalence of avian salmonellosis showed highest infection rate4n adult layers (53.25%) in comparison to brooding (14.55%), growing (16.10%) and pullet (16.10%) chickens. The avian colibacillosis was found widely prevalent in all age groups of chickens ( 9.52 to 36.73%) with specially high prevalence rate in adult layer birds (36.73%). Fowl cholera was recorded in chickens more than two weeks of age with significantly ( p < 0.01 ) highest occurrence in adult chickens. Seasonal influence showed significantly (p < 0.01) highest proportionate prevalence of salmonellosis during summer (48.05%) in comparison to rainy ( 28.31% ) and winter (23.66%) seasons. Colibacillosis was recorded more or less uniformly in all the three seasons of the year with significantly (p < 0.01) higher rate during summer (40.82%) season. Similarly, the prevalence of fowl cholera was also found significantly (p < 0.01) highest during summer (49.12%) in comparison to rainy (26.32%) and winter (24.56%) seasons. The isolated causative agents of avian salmonellosis (Salmonella pullorum), avian colibacillosis (Escherichia coli) and avian pasteurellosis (Pasteurella multocida) were characterized by bacteriological methods which were also subjected to pathogenicity study in 52-day old broiler chickens. Pathogenicity study showed that the incubation period of these three bacterial diseases were recorded as 96 hours and clinical signs appeared on 46' day of inoculation and observed that S. pullorum, E. coli and P. multocida resulted 100% morbidity in chickens.

Keywords: Characterization, Pathogenicity, Salmonellosis, Colibacillosis, Pasteurellosis, Chickens

Location: Department of Microbiology and Hygiene, Bangladesh Agricultural University (BAU), Mymensingh, Bangladesh

Start Date: 00-01-2002

End Date: 00-12-2002

Program Area: Animal Health and Management

Commodity: Chicken, Diseases

Objectives:

To determine the characterization of the isolated causative organisms of these diseases and their pathogenicity in experimentally infected broiler chickens.

Methodology:

Moribund and dead birds presented at the Bangladesh Rural Advancement Committee (BRAC), Poultry Disease Diagnostic Centre ( PDDC ), Nagapara, Gazipur for diagnosis of the diseases during one year period from January to December 2002 formed the material for this study. Specimens were collected from heart, liver, intestine and other organs of the dead birds had characteristic signs and gross lesions (Calnek et al., 1997) belonging to different age groups of broiler, layer and parent stock chickens. These bacterial diseases were routinely diagnosed at the PDDC primarily on necropsy and finally by the isolation and identification of the causative organisms as described by Cowan (1985). Bacteriological specimens suspected for colibacillosis (n = 147), salmonellosis (n = 385) and pasteurellosis (n = 114) were collected at necropsy examination in sterilized cotton swabs which were kept into the sterilized test tube containing nutrient broth. These test tubes were then transported via thermo-flask containing ice to the bacteriological laboratory of the Department of Microbiology and Hygiene, Bangladesh Agricultural University (BAU), Mymensingh. Then the swab containing test tubes were incubated for growth of the causative organisms at 37°C for overnight. Blood agar, Nutrient agar, EMB agar, MacConkey agar, SS agar, Nutrient broth and five basic sugars (dextrose, maltose, lactose, sucrose and mannitol) were used for isolation and identification of these causative agents as described by Cheesbrough (1985) Parker and Collier (1990) and Swayne et al. (1998). Day-old broiler chicks (Vencobb broiler strain) purchased locally from Goalundo Hatchery, Faridpur, and maintained in the poultry sheds of the Department of Veterinary Medicine in deep litter system by using rice husk as litter. The birds were supplied with commercial feed ( Quality Feed Ltd., Dhaka ) and water ad libitum, supported with vitamin-mineral premix ( Magavit WS, Navartis ). Twelve healthy broiler birds at the age of 52 days, were divided into three groups (A, B and C), each consisting of four birds. For colony forming unit (CFU) count, the organisms were grown in nutrient broth with yeast extract for overnight. Then 10 fold dilution was made and 0.5 nil of each 10 fold dilution was transferred aseptically to the nutrient agar plate using a fresh pipette for each dilution. The diluted samples were spread on the plate with sterile L-shaped glass spreader. One sterile glass spreader was used for each plate. The plates ,were then incubated at 37°C for 24 to 48 hours. Following incubation only those plates exhibiting 30 to 300 colonies were counted. For each dilution three plates were used and the mean of the three plates were calculated. The number of bacteria per ml of original sample was obtained by multiplying the number of colonies by diluting factor. CFU was calculated according to ISO (1995). The results of CFU were expressed as the number of organism per ml of sample. Each bird of group A, B and C was injected with 1.0 ml suspension of Salmonella pullorum (5.75 x 106 CFU), Escherichia coli (4.5 x 107 CFU) and Pasteurella multocida (6.25 x 106 CFU) orally. All the birds were allowed to rear on same feed and environmental condition and were observed for clinical signs at every six hours interval. The findings were recorded as normal, sick or dead and any signs of sickness or death of the birds during the period was considered as their susceptibility. Faecal samples from each of infected birds were collected directly from the cloaca by using sterilized cotton swabs which were kept in nutrient broth for further growth and multiplication at 37°C for overnight in the laboratory. Each faecal sample was divided and inoculated separately in Nutrient agar (NA) and Blood agar (BA) to promote growth of bacteria. Each group of these media was incubated at 37°C for overnight. The colonies on primary cultures were repeatedly subcultured by streak plate method ( Cheesbrough, 1985 ) until the pure culture with homogenous colonies were obtained. Media such as blood agar, Nutrient agar, Eosine Methylene blue (EMB) agar, Salmonella-Shigella ( SS ) agar etc. were used for sub-cultures and were incubated at 37°C for 24 hours for growth. Cultures revealing typical reactions of organisms were further screened on the basis of morphological, cultural and biochemical character as described by Cowan (1985).

Source of Information: Bang!. J. Vet. Med. ( 2004 ). 2 ( 1 ) : 01-08

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Achievement/Findings:

Necropsy and bacteriological methods were mainly used to determine the bacterial diseases in commercial chickens. During the one year period of the 1751 dead cases examined, of which 697 (39.81%) cases diagnosed as bacterial infection. Of the 697 bacterial cases, of which salmonellosis (n = 385), colibacillosis (n = 147), fowl cholera (n=114), staphylococcosis (n = 6), gangrenous dermatitis (n = 17), necrotic enteritis (n = 24) and infectious coryza (n = 04) were diagnosed. Thus, the prevalence of salmonellosis, colibacillosis and pasteurellosis were found significantly high in comparison to other bacterial diseases. Accordingly, the characterization and pathogenicity of the isolated causative agents of these most important bacterial diseases were studied. Necropsy examination of salmonellosis affected dead bird showed enlarged and necrotic foci on liver and spleen, congested liver and lungs, mucus and haemorrhages in intestine, petechial haemorrhages in heart base, greenish to bronze colour liver. In chronic cases resulted in deformed and under developed ova attached with stalk, discoloured and cystic ovarian follicles in the laying hens. There was catarrhal enteritis, peritonitis and pericarditis. Salmonella organisms were isolated from liver and /or spleen of dead birds on bacteriological media. On nutrient agar small round translucent smooth colony, on blood agar no haemolysis, on EMB agar no growth, on SS agar pinkish colour colony were observed. Microscopic examination of Gram's stained smears prepared from colony showed Gram negative, very short rods, arranged as single or paired organisms. Salmonella organisms were identified on biochemical tests with five basic sugars, in which showed fermentation of dextrose and mannitol but it did not ferment lactose, sucrose and maltose.

Knowledge Management: Journal