Date Published: September 26, 2008
Publisher: BioMed Central
Author(s): Ann-Charlotte Godin, Camilla Björkman, Stina Englund, Karl-Erik Johansson, Rauni Niskanen, Stefan Alenius.
Reports worldwide indicate high prevalence of Chlamydophila spp. infection in cattle. To assess the prevalence in Sweden, 525 cows in 70 dairy herds with reproductive disorders was investigated.
To detect antibodies two commercially available kits were used. Moreover, 107 specimens, including vaginal swabs, organ tissues and milk were analysed by Polymerase Chain Reaction (PCR).
Two (0.4%) cows were seropositive in the Pourquier Cp. abortus ELISA. The seroprevalence with the Chekit ELISA was 28% with no difference between cases and controls. Five specimens were positive in real-time PCR and further analysed by nested PCR. Cp. pecorum was confirmed by partial omp1 DNA sequencing of the nested PCR product of vaginal swabs from control cows.
The results suggest that Cp. abortus infection is absent or rare in Swedish cows whereas Cp. pecorum is probably more spread. They also suggest that Chlamydophila spp. are not related to reproduction disorders in Swedish cattle.
Chlamydia are obligate, intracellular, gram-negative bacteria that cause a wide range of diseases in humans, other mammals and birds. The two species Chlamydophila (Cp.) abortus (formerly Chlamydia (C.) psittaci serotype 1) and Cp. pecorum (formerly C. pecorum) are known to infect ruminants . It has also been reported that Cp. psittaci may infect cattle [2-4]. In many sheep-producing countries Cp. abortus is known to cause Ovine Enzootic Abortion (OEA) . The zoonotic potential of Cp. abortus is well known and poses a threat to mainly pregnant women, handling sheep and goats . Chlamydial infection in cattle has been associated with reproductive disorders including abortion, endometritis, repeat breeding, vaginitis, seminal vesiculitis, weak calves and perinatal mortality [7-11]. Moreover, symptoms such as pneumonia, conjunctivitis, enteritis, polyarthritis and encephalitis have been reported [12-14]. It has been suggested that both Cp. abortus and Cp. pecorum are ubiquitous in cattle [10,15,16].
The results of this first investigation of Chlamydophila spp. infection in Swedish dairy cows suggest that Cp. abortus infection is absent or rare in Sweden. Only two samples were positive in the Pourquier ELISA. These might well be false positive results because both samples were negative in the Chekit assay, which is based on an antigen containing lipopolysaccharide shared by several Chlamydiaceae, including Cp. abortus. Even if we had applied the lower cut-off value used for sheep sera, only six samples would have been positive in the Pourquier ELISA, of which all except one, were negative in the Chekit ELISA. The specificity of the Pourquier ELISA has been reported to be 100% when analysed Scottish sheep documented free of OEA  and 90% when sera from New Zealand, a country free from Cp. abortus, were analysed .
This investigation suggests that infections with Cp. abortus are absent or rare in Swedish cows whereas Cp. pecorum are probably more spread. It also suggests that Chlamydophila spp. is not related to reproduction disorders in Swedish cattle.
The authors declare that they have no competing interests.
ACG drafted and rewrote the manuscript, carried out the PCR and serology analysis, interpreted the results and performed the statistical analysis. CB and SA conceived and designed the study, and participated in its coordination. SE implemented the PCR systems and carried out the sequencing analysis. KEJ participated in the sequencing analysis. All authors participated in the design of the study and have been involved in revising the manuscript.