Evaluation of Indirect and Absorbed ELISA For Serodiagnosis of Bovine Farcy

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Hussein Ahmed El Hussein Babiker, Babiker
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Bovine farcy was surveyed at selected areas in Kordofan States. Sera, biopsy and purulent materials were collected from infected cattle and subjected to histopathological and bacteriological examination. Two serological methods, Indirect and absorbed ELISA were evaluated for diagnosis of bovine farcy. Whole cell suspension of Mycobacterium farcinogenes, the causal agent of bovine farcy was used as antigen. Cells of M. smegmatis and M. phlei were used for the absorbed ELISA. A total of 171 serum samples were analysed with antibody detecting ELISA (Indirect ELISA) and absorbed ELISA with M. smegmatis and M. phlei against whole cell antigen of M. farcinogenes. Of the 171 samples, 134 serum samples were collected from Kordofan States, 36 from Khartoum State and one sample from Geziera State. Thin layer chromatography of cell wall glycolipids and mycolic acids was conducted to confirm identification of the isolates in comparison with the reference strains of M. farcinogenes and M. senegalense. The results showed that the field isolates from cases of bovine farcy were typical of M. farcinogenese. Using indirect ELISA, out of 134 serum samples from Kordofan areas, 125 (92.7%) serum samples were positive for bovine farcy antibodies with average optical density value 2.4 (filter 405 nm). Nine serum samples (7.3%) were negative with average optical density value less than 1.8. Out of the serum samples from Khartoum and one from Geziera, 36 (97%) were negative to antibodies titre of bovine farcy indicating specificity of 97% and one animal was found positive for bovine farcy antibody. The results using absorbed ELISA with M. smegmatis as adsorptive agent were similar to the results obtained by the indirect ELISA in both sensitivity and specificity, no significant changes (P > 0.5) were observed. The absorbed ELISA using M. phlei showed similar specificity but a very low sensitivity in comparison to the one obtained by the indirect ELISA. These results indicated that the absorbed ELISA is not the perfect method for the serodiagnosis of bovine farcy The cut-off value for serodiagnosis of bovine farcy was determined in this study as 1.8 optical density (OD) value using filer 405 nm after one hour of incubation at 37°C. OD of 1.8 was obtained with all known farcy infected cattle. Infections such as M. avium, M. avium subsp paratuberculosis and cattle free of mycobacteriosis gave optical density below the above mentioned cut-off value. The mean per cent positively (PP) of 32.3±4.2% and OD value 0.8±0.07 were obtained from calves of disease-free area (Khartoum North). From the result, a sero-positive test with 99% confidence limit was taken at PP and OD equal or more than 36.5% and 0.87, respectively
Evaluation of Indirect and Absorbed ELISA For Serodiagnosis of Bovine Farcy