Prevalence and Molecular Characterisation of Campylobacter spp. from Free-Living Animals and Dairy Cattle

Bijay Adhikari1, Joanne H Connolly2, Per Madie, Peter R Davies, Department of Livestock Services, Kathmandu, Nepal;, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand

The reported numbers of human Campylobacter jejuni infections have increased considerably in many countries during the last few years. In New Zealand, the current annual incidence rate (302.5 cases/100 000) of human campylobacteriosis is higher than that of any other notifiable disease, and surpasses the incidence of campylobacteriosis reported by other developed countries. This study investigates the potential role of free-living animals (sparrows, rodents and flies) as potential reservoirs of Campylobacter spp. and was carried out at Massey University No. 4 dairy farm. We isolated Campylobacter from the faeces of cattle and from other samples, and used molecular charecterisation with pulsed-field gel electrophoresis (PFGE) typing of the organisms to determine the similarity between isolates. Campylobacter jejuni was the only Campylobacter species isolated from the 290 samples collected at the dairy farm and from sparrows in the urban area. The highest isolation rate was found in dairy cows (54%), followed by urban sparrows (40%), farm sparrows (38%), rodents (11%) and flies (9%). Other samples from the farm environment such as grass silage, water, worker’s apron and boots were also found to be positive for C. jejuni. Most of the rodents caught during the study period were mice. The high isolation rate in this study of Campylobacter from dairy cows (54%) and sparrows (40%) supports the notation that these species are important reservoirs of infection. Overall the results of the present and previous study show that at least some dairy cows from the same farm can be asymptomatic carriers of Campylobacter jejuni for at least 24 months. Molecular charecterisation of genomic DNA from 61 C. jejuni isolates from farm and urban sources obtained during the study was performed by PFGE after digestion with the enzyme Sma I. Of the 22 restriction patterns, seven were common to more than one source. PFGE analysis of the C. jejuni isolates shows a high degree of diversity of the organisms within a limited geographical area and provides evidence of identical clones infecting cattle, sparrows, flies and rodents probably originated from a common source.