ABSTRACT
From 1995 to 1997, the prevalence of serum antibodies against Mycobacterium avium subspecies paratuberculosis (M. av. ssp. ptbc.)--the causal agent of paratuberculosis (Johne's Disease)--was examined in 11,028 Austrian cattle. Samples from the four oldest cattle on 2757 farms were collected according to a specific sampling schedule for this epidemiological study. District, age and breed of animals were included as variables in this study. For antibody screening against M. avium subspecies paratuberculosis, a modified, commercially available ELISA (ALLIED Monitors, Fayette, USA) was employed. A total of 2253 samples that were found to be positive or questionable were subjected to further testing with a more specific ELISA (Institute of Microbiology and Infectious Animal Diseases). Results of this study were used for statistical analysis. The average prevalence of antibodies to M. avium subspecies paratuberculosis was 1.99% in Austria. The highest prevalence was seen in 6-year-old cattle (2.84%) and Holstein Frisian cattle (3.51%). Sero-positive animals were found on 6.96% of farms tested, and the prevalence was highest in Vorarlberg, followed by Salzburg, the Tyrol, Styria and Carinthia. This study is unique in Europe in the use of an adequate random sampling plan for an investigation of this magnitude.
Subject(s)
Cattle Diseases/epidemiology , Mycobacterium avium subsp. paratuberculosis/immunology , Paratuberculosis/epidemiology , Age Factors , Animals , Antibodies, Bacterial/blood , Austria/epidemiology , Cattle , Cross-Sectional Studies , Enzyme-Linked Immunosorbent Assay/veterinary , Female , Seroepidemiologic StudiesABSTRACT
A local clinical Mycobacterium avium ssp. paratuberculosis (M. paratuberculosis) isolate was cultivated in large-scale culture. A procedure for efficient preparation of a lipoarabinomannan-containing antigen was developed and standardized; 25 mg of purified antigen were obtained per gram of bacterial wet weight. An ELISA based on this antigen was developed. Intra- and interassay variation were determined to be 20% and 27%, respectively. The ELISA was evaluated using the sera of groups of 39 non-randomly selected and 92 randomly selected animals from which ileocaecal lymph nodes were cultured to isolate viable M. paratuberculosis. Combining the results of both groups a positive predictive value of 74% and a negative predictive value of 99% were calculated. The ELISA was licensed by the German regulatory agencies and, in a direct comparison, was found to be superior to both other licensed assays.
