Validation and field assessment of a rapid lateral flow assay for detection of bovine antibody to Anaplasma marginale.
The lateral flow assay (LFA) is a rapid diagnostic test which may be performed under most conditions and is especially useful for field applications. This type of assay was applied to the detection of antibody to bovine Anaplasma marginale using sera from endemic areas and from areas which have been free from infection for more than 25 years. Briefly, the test uses recombinant A. marginale major surface protein 5 peptide (Msp5), immobilized on a cellulose acetate membrane. A serum sample is added to a pad containing a monoclonal antibody specific for bovine IgG(1), conjugated with colloidal gold, located at one end of the strip. The sample and gold conjugate are wicked along the membrane and if antibody is present in the serum, a visible line will form between the Msp5-antibody-conjugate immune complex in minutes. An additional band of recombinant protein A/G was added to the membrane as a positive control reaction of the monoclonal antibody conjugate. For comparison, direct examination of blood smears and a nested polymerase chain reaction (PCR) were performed on some of the samples. Using samples from herds in one endemic area, the PCR gave a sensitivity value of 9.2% while a commercial competitive enzyme immunoassay (CELISA) gave a sensitivity value of 17.2% and the LFA values of 20.5%. In a second endemic area, selected samples, all positive by direct examination gave a 71.7% sensitivity values with the PCR, 94.5% with the CELISA and 95.5% with the LFA. Using sera from a disease-free area, the specificity values were 100% for the PCR (testing a proportion of randomly selected samples), 99.5% for the CELISA and 98.0% for the LFA. It is envisaged that the validated LFA will be a useful tool for screening cattle moving from an area with infection to a disease-free area.
Nielsen
K
K
Canadian Food Inspection Agency, Ottawa Laboratory (Fallowfield), Ottawa, Ontario, Canada. nielsenk@inspection.gc.ca
Yu
W L
WL
Kelly
L
L
Williams
J
J
Dajer
A
A
Gutierrez
E
E
Ramirez Cruz
G
G
Renteria
T
T
Bermudez
R
R
Algire
J
J
D042322:Anaplasma marginale / Q000276:immunology*; D000712:Anaplasmosis / Q000175:diagnosis*; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood* / Q000276:immunology; D002417:Cattle; D002418:Cattle Diseases / Q000175:diagnosis; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods* / Q000662:veterinary*; D016133:Polymerase Chain Reaction; D011933:Reagent Kits, Diagnostic / Q000662:veterinary*
D000907:Antibodies, Bacterial; D011933:Reagent Kits, Diagnostic