Chlamydia spp. in dairy herds have been associated with reduced performance and occasional, but severe, disease manifestations. While chlamydial infections are well described in sheep, very little is known about these infections and the associated risk factors in cattle, including in Australia. This study sought to understand chlamydial infection and on-farm risks in dairy cattle herds from Southeast Queensland (SE Qld) region of Australia.
In total, 228 paired vaginal and rectal swabs were collected from 114 outwardly healthy dairy cows from four farms in SE Qld. Risk factors were rated by observational study and included: hygiene of cows, walkway and parlour, perinatal mortality, external replacements, mode of breeding, calving pen management, heat reduction strategies and feed ration usage. Screening for chlamydial pathogens (Chlamydia pecorum, Chlamydia psittaci and Chlamydia abortus) was done using species-specific quantitative polymerase chain reaction (qPCR) assays. Detected levels of chlamydial infection were evaluated against the on-farm risk factors known to correlate with increased chlamydial infection loads. C. pecorum was found to be present at high levels in all four farms, with an overall prevalence of 56.1% (64/114). C. abortus and C. psittaci were not detected in any animals with C. abortus believed to be exotic to Australia. No statistically significant relationship was found to exist with risk factors and C. pecorum infection levels in these dairy farms.
A retrospective screening of healthy and diseased beef cattle from Central NSW also revealed high prevalence for C. pecorum, but that other chlamydial infections such as C. psittaci are common. In beef cattle, C. pecorum infections could range from sub-clinical shedding through to Sporadic Bovine Encephalomyelitis associated with high mortality.
This study suggests that C. pecorum is the endemic species infecting cattle in Australia, and that these infections are likely to cause economical loses to the producers as well the overall industry.