%0 Journal Article
%T Ovine Enzootic Abortion (OEA): a comparison of antibody responses in vaccinated and naturally-infected swiss sheep over a two year period
%A Andrea Gerber
%A Ruedi Thoma
%A Evangelia Vretou
%A Evgenia Psarrou
%A Carmen Kaiser
%A Marcus G Doherr
%A Dieter R Zimmermann
%A Adam Polkinghorne
%A Andreas Pospischil
%A Nicole Borel
%J BMC Veterinary Research
%D 2007
%I BioMed Central
%R 10.1186/1746-6148-3-24
%X 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.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.Chlamydophila abortus (formerly Chlamydia psittaci serotype 1) is the most common infectious bacteria causing abortion in small ruminants in Switzerland with a previous study demonstrating that 39% of the examined abortions in sheep and 23% in goats were caused by this agent [1]. In the Swiss canton of Graub¨¹nden, a mountainous region in the countries' east, the economic losses associated with ovine enzootic abortion (OEA) are significantly higher than in other cantons [2].Cp. abortus is generally introduced into immunologically na£¿ve flocks by a latently infected animal with the agent being subsequently transmitted from aborting ewes via shedding of large amounts of infectious Chlamydia in the foetal membranes and in vaginal discharges [3]. In newly infected flocks, up to 30% of ewes may abort in the last trimester of gestation or give birth to weak or dead lambs. After abortion, ewes in these flocks may develop a protective immunity. Subsequent yearly losses in endemically infected flocks may decrease to a lower level (eg. 5¨C10%) with sheep either bor
%U http://www.biomedcentral.com/1746-6148/3/24