Fecal shedding of thermophilic Campylobacter in a dairy herd producing raw milk for direct human consumption

Factors affecting the thermophilic Campylobacter fecal shedding in Italian dairy farming conditions have been investigated in a 12-month longitudinal study performed in a dairy farm authorized to sell raw milk in Italy. Fifty animals were randomly selected from 140 adult and young animals, and fecal sampling was performed six times at two month intervals; additionally at each sampling, three trough water samples and two trough feed samples were collected for both adult and young animals. Samples were analyzed by real-time PCR and cultural examination. Overall 33 samples (9.7%) were positive for thermophilic Campylobacter by real-time PCR: 26 out of 280 (9.2%) fecal samples, six out of 36 water points (16.6%) and one of the 24 feed samples (4.2%). Campylobacter jejuni was isolated from 6 out of 280 samples; no other Campylobacter sp. was isolated. A higher but not significant positivity was observed in fecal samples of younger animals (11.33%% versus 6.92% of adult animals) and a higher and significant positivity was observed in water samples collected from the water troughs of young animals. A distinct temporal dynamic trend was observed during the study period for both cows and calves, with two prevalence peaks between November/December and between May/July. Several factors such as calving, housing practices, herd size, management practices forcing together a higher number of animals, variations in feeding or water source, which were previously reported as cause of temporal variation in different farming conditions, could be excluded as cause of the two seasonal peaks in this study. The factors affecting the seasonality of Campylobacter shedding in the dairy herds remain unclear and warrant further investigation. The results of the present study indicate that special attention should be paid to farm hygiene management in farms authorized to produce and sell raw milk with increased surveillance by the authorities in certain periods of the year.