Genotypic Variation of Coxiella Burnetii in South-West Dairy Farms in the Uk

Objectives: 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. 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.

Materials and Methods: Through bulk tank milk analysis, using qPCR, C. burnetii has been found in South West dairy farms at a herd prevalence of 69.7% (108/155). We wanted to investigate the molecular epidemiology of these samples by determining if the genotype was related to C. burnetii found in Europe. Multiple Locus Variable number tandem repeat (VNTR) Analysis (MLVA) has been shown to be a viable genotyping assay for C. burnetii, as devised by Arricau-Bouvery et. al, although some modification was required to detect organisms from Bulk Tank Milk (BTM) samples. We aimed to utilise this assay for the positive BTM samples, by selecting a sub-set of primers which are able to differentiate UK strains of the bacterium. The size of the VNTR alleles is converted to units, with clustering analysis on these units. Clustering analysis is by Unweighted Pair Group Methodusing Arithmatic averages (UPGMA).

Results: Initial analysis has led to the possibility of multiple genotypes being identified in single BTM samples. For a number of samples, more than 1 PCR product was visualised following gel electrophoresis. These additional PCR products were larger than from other samples, indicating that additional tandem repeats were present. Full MLVA analysis utilising capilary gel electrophoresis to determine exact amplicon length is still ongoing. These genotypes are being compared to those found in the rest of Europe, in both dairy cattle and small ruminants from a collaborative MLVA dataset.

Conclusions: As this investigation is still ongoing, it would be premature to draw any confident conclusions. Once completed, knowledge of the MLVA genotypes present in the UK will be of interest to European peers researching this bacteria. To our knowledge, this only the 2nd time C. burnetii has been genotyped in the UK and the first time in UK dairy cattle.