Ovine Enzootic Abortion (OEA): a comparison of antibody responses in vaccinated and naturally-infected swiss sheep over a two year period.
BACKGROUND
Prevention and control of ovine enzootic abortion (OEA) can be achieved by application of a live vaccine. In this study, five sheep flocks with different vaccination and infection status were serologically tested using a competitive enzyme-linked immunosorbent assay (cELISA) specific for Chlamydophila (Cp.) abortus over a two-year time period.


RESULTS
Sheep in Flock A with recent OEA history had high antibody values after vaccination similar to Flock C with natural Cp. abortus infections. In contrast, OEA serology negative sheep (Flock E) showed individual animal-specific immunoreactions after vaccination. Antibody levels of vaccinated ewes in Flock B ranged from negative to positive two and three years after vaccination, respectively. Positive antibody values in the negative control Flock D (without OEA or vaccination) are probably due to asymptomatic intestinal infections with Cp. abortus. Excretion of the attenuated strain of Cp. abortus used in the live vaccine through the eye was not observed in vaccinated animals of Flock E.


CONCLUSIONS
The findings of our study indicate that, using serology, no distinction can be made between vaccinated and naturally infected sheep. As a result, confirmation of a negative OEA status in vaccinated animals by serology cannot be determined.
Gerber
Andrea
A
Institute of Veterinary Pathology, Vetsuisse Faculty, University of Zurich, Switzerland. gerber_andrea@access.unizh.ch
Thoma
Ruedi
R
Vretou
Evangelia
E
Psarrou
Evgenia
E
Kaiser
Carmen
C
Doherr
Marcus G
MG
Zimmermann
Dieter R
DR
Polkinghorne
Adam
A
Pospischil
Andreas
A
Borel
Nicole
N
D000034:Abortion, Veterinary / Q000453:epidemiology / Q000276:immunology / Q000382:microbiology*; D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis* / Q000097:blood; D001428:Bacterial Vaccines / Q000008:administration & dosage / Q000276:immunology*; D023501:Chlamydophila / Q000235:genetics / Q000276:immunology*; D023521:Chlamydophila Infections / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011247:Pregnancy; D012338:RNA, Ribosomal, 23S / Q000737:chemistry / Q000235:genetics; D016036:Seroepidemiologic Studies; D012756:Sheep; D012757:Sheep Diseases / Q000453:epidemiology / Q000276:immunology* / Q000382:microbiology*; D013557:Switzerland / Q000453:epidemiology; D014613:Vaccines, Attenuated / Q000276:immunology
D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines; D004269:DNA, Bacterial; D021903:DNA, Ribosomal Spacer; D012338:RNA, Ribosomal, 23S; D014613:Vaccines, Attenuated