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Clinical and Diagnostic Laboratory Immunology, December 2005, p. 1401-1409, Vol. 12, No. 12
1071-412X/05/$08.00+0     doi:10.1128/CDLI.12.12.1401-1409.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Immunoglobulin G1 Enzyme-Linked Immunosorbent Assay for Diagnosis of Johne's Disease in Red Deer (Cervus elaphus)

Disease Research Laboratory, Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand,¹ Laboratory for Mycobacterial Infections and Brucellosis, Central Institute for Animal Disease Control (CIDC-Lelystad), The Netherlands,² U.S. Department of Agriculture, Agricultural Research Service, National Animal Disease Center, Bacterial Diseases of Livestock Research Unit, Ames, Iowa³

Received 19 July 2005/ Returned for modification 16 September 2005/ Accepted 23 September 2005

This study was designed to develop a customized enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of Johne's disease (JD) in farmed deer. Two antigens were selected on the basis of their superior diagnostic readouts: denatured purified protein derivative (PPDj) and undenatured protoplasmic antigen (PpAg). ELISA development was based on the antigen reactivity of the immunoglobulin G1 (IgG1) isotype, which is a highly specific marker for mycobacterial disease seroreactivity in deer. Sensitivity estimates and test parameters were established using 102 Mycobacterium paratuberculosis-infected animals from more than 10 deer herds, and specificity estimates were determined using 508 uninfected animals from 5 known disease-free herds. A receiver-operated characteristic analysis determined that at a cut point of 50 ELISA units, there was a specificity of 99.5% and sensitivities of 84.0% with PPDj antigen, 88.0% with PpAg, and 91.0% when the antigens were used serially in a composite test. Estimated sensitivity was further improved using recombinant protein antigens unique for M. paratuberculosis, which identified infected animals that were unreactive to PPDj or PpAg. While 80% of animals that were seropositive in the IgG1 ELISA had detectable histopathology, the assay could also detect animals with subclinical disease. The test was significantly less sensitive (75%) for animals that were culture positive for M. paratuberculosis but with no detectable pathology than for those with pathological evidence of JD (>90%). When the IgG1 ELISA was used annually over a 4-year period in a deer herd with high levels of clinical JD, it eliminated clinical disease, increased production levels, and reduced JD-related mortality.