Serological Investigation On Chicken Salmonellosis In Parts Of China And Identification Of Specific Nucleic Acid Sequences In Salmonella Pullorum By Suppression Suppression Subtractive Hybridization

Salmonellosis in chickens can be classified into three diseases: pullorum disease caused by Salmonella pullorum, fowl typhoid caused by Salmonella gallinarum and paratyphoid infections due to a diverse group of serovars related to foodborne illness in humans. Salmonella pullorum and Salmonella gallinarum are economically important pathogens of chickens, and the threat of paratyphoid to public health is present. There is no effective vaccines in protecting against infections with salmonellae in chickens, especially for pullorum disease and fowl typhoid. The most valid means of control of pullorum disease and fowl typhoid is a combination of stringent management procedures and eradication. For many years, the slide agglutination test has been used to monitor the specific antibody caused by Salmonella pullorum and Salmonella gallinarum, however the sensitivity of this methods is limited. Slide agglutination test can yield erratic results, which can be dependent on antigen quality.Results of field and experimental investigations have confirm that vertical transmission is also a very important route of infection for these paratyphoid salmonellae, making identification and elimination of infected parent flocks particularly important. Poultry is one of the most important reservoirs of paratyphoid salmonellae that can be transmitted to humans through the food-chain. Effective measures must betaken to prevent food-borne transmission of disease to humans. Bacteriological methods may not be sufficiently sensitive to identify salmonella-infected flocks showing intermittent or no excretion of the bacteria. Enzyme-linked immunosorbent assay (ELISA) methods have been developed for the detection of specific serum antibodies to paratyphoid salmonellae. Up to now, there is not an ELISA method which could detect the antibodies to all sorts of paratyphoid salmonellae owing to the variety of their antigens. So, it is difficult to realize exactly the prevalence status of paratyphoid Salmonellae in chicken flocks. Salmonella pullorum and Salmonella gallinarum are responsible for distinctly different diseases in chickens, and the differentiation between them is critical from both epidemiological and preventive aspects. The two biotypes are generally differentiated on the basis of biochemical characteristics, however intermediate strains which are dulcitol and ornithine decarboxylase positive have been reported, which brings difficulty to typing these strains.1. Development of blocking ELISA for the diagnosis of pullorum disease and fowl typhoid by using peroxidase-labelled monoclonal antibody and Salmonella pullorum lipopolysaccharideA peroxidase-labelled monoclonal antibody blocking ELISA was developed for diagnosing pullorum disease and fowl typhoid. The test measured the inhibition of binding between a peroxidase-labeled, monoclonal antibody 3-47-0 and Salmonella pullorum lipopolysaccharide(LPS). Good discrimination was observed between 72 proven pullorum disease sera (98.5+4.0% inhibition) and nonpullorum disease sera. The latter consisted of 54 sera negative for pullorum disease (15.3 ±8.0% inhibition) and 42 sera of SPF chicken (10.8 ±7.2% inhibition). Chickens infected with S. pullorum was monitored serologically by this assay from one through eight weeks. From the second week after infection, 100% of the chickens were serologically positive by blocking ELISA, which was one week earlier than PAT. The high specificity and sensitivity of blocking ELISA was further verified by detection of 344 clinical sera with parallelly conducted PAT. Meanwhile, the assay potentially detects those systemic infections caused by salmonellae that possess common antigen to Salmonella pullorum and Salmonella gallinarum .2. Development of blocking ELISA for the diagnosis of fowl paratyphoid by using peroxidase-labelled monoclonal antibody and salmonella flagellinsA peroxidase-labelled monoclonal antibody blocking ELISA was developed for diagnosing fowl paratyphoid. The test measured the inhibition of binding between a labeled, monoclonal ant...