Identification of Coxiella burnetii by touch-down PCR assay in unpasteurized milk and dairy products in North - East of Iran

Coxiella burnetii is the causative agent of the zoonotic disease Q fever, and ruminants being considered as the main source for human infection. Although the main route of infection in human is inhalation of contaminated aerosols, oral transmission by contaminated raw milk or unpasteurized dairy products is also a possible route of infection. Raw milk or dairy products produced from unpasteurized milk may contain virulent C. burnetii. OBJECTIVES: This study aimed to determine the contamination rate of milk and unpasteurized dairy products with C. burnetii. METHODS: Touch-down PCR was used to examine the presence of C. burnetii on 147 dairy product samples collected from local traditional and commercial markets in Mashhad-Khorasan Razavi province- Iran. RESULTS: 2 of 28 (7.14%) cheese samples, 2 of 26 (7.69%) yoghurt samples, 8 of 23 (34.78%) sheep milk samples, and 2 of 60  (3.33%) cow milk samples were found to be positive for C. burnetii DNA. However, 10 goat milk samples were found to be negative. CONCLUSIONS: The results of this study indicate that the clinically healthy dairy livestock and their dairy products are important sources of C. burnetii infection.