High frequency of chlamydial co-infections in clinically healthy sheep flocks
1 Institut für Molekulare Pathogenese, Friedrich-Loeffler-Institut, Naumburger Straße 96a, 07743 Jena, Germany
2 Tiergesundheitsdienst, Thüringer Tierseuchenkasse, Victor-Goerttler-Straße 4, 07745 Jena, Germany
3 Institut für Epidemiologie, Friedrich-Loeffler-Institut, Seestraße 55, 16868 Wusterhausen, Germany
4 Landesamt für Lebensmittelsicherheit und Verbraucherschutz, Abteilung Veterinäruntersuchung, Tennstedter Straße 8/9, 99947 Bad Langensalza, Germany
5 Institut für Bakterielle Infektionen und Zoonosen, Friedrich-Loeffler-Institut, Naumburger Straße 96a, 07743 Jena, Germany
BMC Veterinary Research 2011, 7:29 doi:10.1186/1746-6148-7-29Published: 16 June 2011
The epidemiological situation of ovine chlamydial infections in continental Europe, especially Germany is poorly characterised. Using the German state of Thuringia as a model example, the chlamydial sero- and antigen prevalence was estimated in thirty-two randomly selected sheep flocks with an average abortion rate lower than 1%. Seven vaccinated flocks were reviewed separately.
A wide range of samples from 32 flocks were examined. Assumption of a seroprevalence of 10% (CI 95%) at flock level, revealed that 94% of the tested flocks were serologically positive with ongoing infection (i.e. animals with seroconversion) in nearly half (47%) of the flocks. On the basis of an estimated 25% antigen prevalence (CI 95%), PCR and DNA microarray testing, together with sequencing revealed the presence of chlamydiae in 78% of the flocks. The species most frequently found was Chlamydophila (C.) abortus (50%) followed by C. pecorum (47%) and C. psittaci genotype A (25%). Mixed infections occurred in 25% of the tested flocks. Samples obtained from the vaccinated flocks revealed the presence of C. abortus field samples in 4/7 flocks. C. pecorum was isolated from 2/7 flocks and the presence of seroconversion was determined in 3/7 flocks.
The results imply that chlamydial infections occur frequently in German sheep flocks, even in the absence of elevated abortion rates. The fact that C. pecorum and the potentially zoonotic C. psittaci were found alongside the classical abortifacient agent C. abortus, raise questions about the significance of this reservoir for animal and human health and underline the necessity for regular monitoring. Further studies are needed to identify the possible role of C. psittaci infections in sheep.