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A serological survey of the prevalence of antibodies to Salmonella gallinarum among chickens under two different management systems around Jos, Plateau State, Nigeria was carried out using the standard plate agglutination test. The objective of this study was to determine serologically the prevalence of antibodies against Salmonella gallinarum among apparently healthy chickens around Jos. A total of 700 serum samples made up of 450 exotic and 250 local breed of chickens were used for this study with 37.9% seropositvity. In the free range system (19.3%) of the flocks sampled were seropositive for Salmonella gallinarium antibodies while in the semi intensive, 18.6% of the flock tested positive. The serum agglutination test (SAT) was adapted to the microtitre format used to determine somatic and flagella titres. The antigen used for this study was specific for S. gallinarum, hence differentiation between species infection was assessed in this study. Perhaps the most feasible way to eradicate the disease is to encourage farmers (both small and large scale) to break the disease cycle at their levels by embarking on prompt and regular vaccination programmes. It is thus concluded that Salmonella gallinarum (fowl typhoid) is present in the area investigated. Fowl typhoid may continue to have a negative effect on the economy of poultry production in Nigeria if not controlled. A statistical analysis was precluded due to inadequate data sets. Key Words: Fowl typhoid, Antibodies, Chickens, Jos, Nigeria Introduction Fowl typhoid is caused by the bacterium Salmonella gallinarum, a member of the family Enterobacteriaceae widely distributed throughout the world, but have been eradicated from commercial poultry in many developed countries of western Europe, the United States of America (USA), Canada, Australia and Japan with an intensive poultry industry.(1) The disease (Fowl typhoid) is of particular economic importance in those countries which are beginning to intensify their industry, eg countries in Latin America, south America, the Middle East, the Indian subcontinent and parts of Africa.(2) In Africa for example, fowl typhoid has been ed in many countries including Nigeria (3), Tanzania (4), Uganda (5), Zambia (6), Libya (7), Senegal (8) and Morocco.(9) Salmonella has been of great concern to the poultry industry ever since man began raising poultry in a concentrated fashion. Salmonella gallinarum is highly host adapted and seldom causes significant problems in host other than chickens, turkeys and pheasants.(10) It was formerly known as Shigella gallinarum when first isolated in 1989 by Klein in England.(2) Fowl typhoid infection usually follows the ingestion of food or water contaminated by the excreta of clinically infected birds or carriers and can also be transmitted by attendants through hands, feet and clothes.(11) Fowl typhoid seriously threatened the poultry industry in the early 1900s due to widespread outbreaks accompanied by high mortality.(2) The majority of the strains of S. gallinarum is very similar at the chromosomal level.(12) A definitive diagnoses of fowl typhoid requires the isolation and identification of S. gallinarum. However, a tentative diagnoses can be made based on the flock history, clinical signs mortality and lesions. Positive serological findings are of great value in detecting infection.(13) In Nigeria, various serotypes of Salmonella species have been isolated from apparently healthy chickens with a carrier rate of 1.3% in 300 broilers as ed by Falade and Elizokhale.(14) The aim of this study was to determine the prevalence of Salmonella gallinarum antibodies in vaccinated and non vaccinated birds and to advice farmers where asymptomatic infection in unvaccinated birds are identified. Preparation And Standardization Of Stained Antigen Lyophilized reference strains of S. gallinarum was obtained from the Fowl Typhoid Vaccine Department, National Veterinary Research Institute, Vom. The strains were inoculated into trytose broth, incubated at 370 C and subsequently subcultured onto nutrient agar containing 1 /800 phenol. This inactivates the Vi antigen (if present) which could mask O antigen and to obtain much growth. The cultures were incubated at 37o C for 24 hours. Bacteria growth on the surfaces of the plates were harvested into 10ml of nutrient broth, emulsified thoroughly and 20 times the volume of absolute alcohol was added. Heated for 30minutes at 56o C, centrifuged hard, and re-suspended deposit in 0.2% formol saline solution. Tinged with crystal violet. Standardized by an opacity method to 750 x 106 organisms/ml using 0.2% formal saline and controlled using fowl typhoid vaccine as the standard reference antigen. Serological Test The standard plate agglutination test was used (15). Reagents used were the prepared S. gallinarum stained antigen. The reagent was allowed to warm up to room temperature prior to use. Using a sterile Pasteur pipette, 0.02ml of the sera was dispensed on a tile and 0.02ml of the antigen was added using separate sterile pipette. Antigen and sera were properly mixed with wooden applicator sticks, the tile plate was gently rocked for a few seconds and reaction read within 2 minutes. Known positive and negative sera were tested simultaneously on each day of testing. Test serum samples giving visible agglutination were considered positive. While those that does not give visible agglutination were considered negative. Itroduction These results are comparable with other surveys in Africa, although knowledge on the prevalence of disease in Africa poultry seems to be rather limited.(23) Chryosostome et al, (24) in a similar study documented the presence of antibodies to S. gallinarum among chickens in Benin City, Nigeria. The overall prevalence of 9.4% found in all chickens sampled in Vom and Bukuru appears very high when compared with other s from different parts of Nigeria. Onunkwo and Onoviran (25) ed S. gallinarum antibody prevalence in Plateaus State to be 3.2%. This variation could be due to differences in environmental contamination and management systems. Long term cohort studies examining the causes of poultry mortality have not been carried out in the free range production systems. Unlike the findings of Oliveira et al, (26) which assessed the ability of an immunoenzymatic assay performed with either peroxidase or alkaline phosphatase conjugates to investigate serological response to a soluble protein antigen from S. gallinarum, the present study has addressed the simple antibody detection as the antigen was capable of promoting reliable serological reaction as suggested by Barrow et al, (13) and Iba et al.(27) This study is further buttressed by the findings of Bauzoubaa et al, (9) who in Morocco revealed that up to 58% of the village chickens had antibodies against S. gallinarum and S. pollorum. Similar findings were ed in Nigeria by Adesiyun et al.(28) There is no doubt that the disease play an important role in village poultry and semi-intensive poultry in Nigeria. In conclusion regular blood testing and depopulation of infected flocks have enormously reduced the prevalence of S. gallinarum in other countries, but this approach is seldom practicable in Nigeria.()，英语论文网站，英语论文 |
