Comparison of four diagnostic tests for the identification of serum antibodies in small ruminants infected with Mycoplasma agalactiae.
OBJECTIVE
To determine the diagnostic capability of a newly developed Western blot (WB) assay for the detection of serum antibodies against Mycoplasma agalactiae compared with conventional serological tests, and to identify the best test for routine diagnostic use.


METHODS
The serological test methods used were: two commercial indirect enzyme-linked immunosorbent assays (ELISA), viz ELISA-1, using a bacterial antigen preparation, and ELISA-2, using a recombinant protein (lipoprotein p48) antigen; the complement fixation test (CFT); and a newly developed WB assay, the latter both using a bacterial antigen preparation. Thirty sera from goats infected with M. agalactiae and 97 sera from non-infected sheep were tested using all four methods.


RESULTS
Staining patterns in the WB were quite variable. An immuno-dominant band of 41 kDa was detected in 63% of sera from infected animals. The same band also appeared, although mostly very weakly, in 10% of sera from non-infected animals. When suspicious or very weak reactors were omitted, the diagnostic sensitivity (DSE) and diagnostic specificity (DSP), respectively, for the four assays were: WB=56.7%, 97.9%; ELISA-1=76.7%, 99.0%; ELISA-2=56.7%, 100%; and CFT=40.0%, 94.8%.


CONCLUSIONS
ELISA-1 performed best in this comparison. While the WB can be used, it did not have a technical advantage over the ELISA. The CFT should be discouraged as the primary screening method for contagious agalactia and should be replaced by ELISA-1. Results from this study confirm that serological test methods for contagious agalactia are useful for the detection of infected flocks but will not detect every individual infected animal.
Kittelberger
R
R
Investigation and Diagnostic Centre Wallaceville, Ministry of Agriculture and Forestry, PO Box 40742, Upper Hutt, New Zealand. Reinhold.Kittelberger@maf.govt.nz
O'Keefe
J S
JS
Meynell
R
R
Sewell
M
M
Rosati
S
S
Lambert
M
M
Dufour
P
P
Pépin
M
M
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D015153:Blotting, Western / Q000379:methods / Q000662:veterinary; D003168:Complement Fixation Tests / Q000379:methods / Q000662:veterinary; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000662:veterinary; D005260:Female; D015511:Goat Diseases / Q000175:diagnosis*; D006041:Goats; D045644:Mycoplasma agalactiae / Q000276:immunology*; D011002:Pleuropneumonia, Contagious / Q000175:diagnosis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012698:Serologic Tests / Q000379:methods / Q000662:veterinary*; D012756:Sheep
D000907:Antibodies, Bacterial