Use of a dot enzyme-linked immunosorbent assay on absorbed sera for the diagnosis of bovine paratuberculosis.
This study describes the response of cattle to a dot enzyme-linked immunosorbent assay (ELISA) using sera absorbed with Mycobacterium phlei. Results obtained by visual observation are compared with those obtained using a densitometer. Infection status of cattle was determined by faecal culture. Cattle of different levels of exposure and disease manifestation were examined. A significantly higher dot ELISA response was observed (using both absorbed and non-absorbed sera) in animals with heavy shedding of M. paratuberculosis than in animals which tested negative by faecal culture or shed M. paratuberculosis at lower levels (P < 0.05). Paratuberculosis was diagnosed by visual determination of dot ELISA results using non-absorbed sera in 29 of 44 (65.9%) clinically-suspect animals giving positive results by faecal culture, and 85 of 93 (91.4%) cattle testing negative by faecal culture. With absorbed sera, the sensitivity of visual determination decreased to 15 of 44 (34.1%), while specificity increased to 91 of 93 (97.8%). Approximately 75% of cattle yielding positive results by dot ELISA were heavy bacterial shedders (> 1,500 colonies/g of faeces) at the time of serological testing. Comparison of the dot ELISA results determined visually with results obtained by objective densitometric measurement showed compatible specificity. Sensitivity of the dot ELISA was 65.9% for non-absorbed sera using visual evaluation and 87.5% using densitometric evaluation at a cut-off optical density value of 0.2. For absorbed sera, the values were 34.1% and 82.5%, respectively.
Bech-Nielsen
S
S
Department of Veterinary Preventive Medicine, College of Veterinary Medicine, Ohio State University, Columbus 43210.
Shulaw
W P
WP
Frandsen
P L
PL
Jorgensen
J B
JB
Ahrens
P
P
Feld
N C
NC
D000042:Absorption; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D002417:Cattle; D002418:Cattle Diseases / Q000175:diagnosis*; D003720:Densitometry; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary*; D005243:Feces / Q000382:microbiology; D009168:Mycobacterium phlei / Q000502:physiology; D009169:Mycobacterium tuberculosis / Q000276:immunology / Q000302:isolation & purification*; D010283:Paratuberculosis / Q000175:diagnosis*; D012680:Sensitivity and Specificity
D000907:Antibodies, Bacterial