Genotypic variation of Coxiella burnetii in South West dairy farms.

Over the last 10 years research into the zoonotic disease Q Fever, and the causative bacteria Coxiella burnetii, has increased considerably. This increase is mainly as a result of the large-scale outbreak in The Netherlands from 2007 to 2009 (1). Human infections are primarily due to exposure to infected ruminants, particularly around parturition. This poses a threat to farm workers and veterinarians. Whilst infected goats have been attributed as the primary cause of the Dutch outbreak, dairy cattle are still considered a potential reservoir for the spread of this disease.

Through bulk tank analysis, using qPCR, C. burnetii has been found in South West dairy farms at a herd prevalence of 69.7% (108/155) (2). MLVA (Multiple Locus Variable number tandem repeat (VNTR) Analysis) has been shown to be a viable genotyping assay for C. burnetii, as devised by Arricau-Bouvery et. al (3). We aimed to utilise this assay for the positive BTM samples, which required modification of the methods as the initial assay was developed for individual samples, in addition to the selection of primers which are able to differentiate UK strains of the bacterium.
After validation of the new methods, the positive samples were analysed for their viability by testing them for PCR targets from the MLVA. These extracted DNA samples had been in storage since 2010, resulting in many of the samples being partially degraded. A subset of the samples which had not been degraded (36/107, 34%) were investigated further to determine their genotype.

Initial analysis has led to the possibility of multiple genotypes being identified in single BTM samples. These genotypes are being compared to those found in the rest of Europe, in both dairy cattle and small ruminants .

To our knowledge, this only the 2nd time C. burnetii has been genotyped in the UK and the first time in dairy cattle.