Molecular epidemiology of Coxiella burnetii from ruminants in Q fever outbreak, the Netherlands

Q fever is a zoonosis caused by the bacterium Coxiella burnetii. One of the largest reported outbreaks of Q fever in humans occurred in the Netherlands starting in 2007; epidemiologic investigations identified small ruminants as the source. To determine the genetic background of C. burnetii in domestic ruminants responsible for the human Q fever outbreak, we genotyped 126 C. burnetii–positive samples from ruminants by using a 10-loci multilocus variable-number tandem-repeat analyses panel and compared them with internationally known genotypes. One unique genotype predominated in dairy goat herds and 1 sheep herd in the human Q fever outbreak area in the south of the Netherlands. On the basis of 4 loci, this genotype is similar to a human genotype from the Netherlands. This finding strengthens the probability that this genotype of C. burnetii is responsible for the human Q fever epidemic in the Netherlands.

Q fever is a zoonosis caused by Coxiella burnetii, an intracellular gram-negative bacterium that is prevalent throughout the world. Domestic ruminants are considered the main reservoir for Q fever in humans. However, other animal species, including pet animals, birds, and several species of arthropods, can be infected by C. burnetii and cause human cases of Q fever. The main clinical manifestations of Q fever in goats and sheep are abortion and stillbirth. In cattle, Q fever has been associated with sporadic abortion, subfertility, and metritis. With an abortion, up to 1 billion C. burnetii per gram of placenta can be excreted. Most animal species that carry C. burnetii show no symptoms. Transmission to humans occurs mainly through inhalation of contaminated aerosols.

Recently, 2 DNA-based methods for typing C. burnetii were reported. Multispacer sequence typing is based on DNA sequence variations in 10 short intergenic regions and can be performed on isolated C. burnetii strains or directly on extracted DNA from clinical samples. Multilocus variable-number tandem-repeat analyses (MLVA) is based on variation in repeat number in tandemly repeated DNA elements on multiple loci in the genome of C. burnetii and might be more discriminatory than multispacer sequence typing. MLVA also can be performed on C. burnetii strains or directly on DNA extracted from clinical samples. A total of 17 different minisatellite and microsatellite repeat markers have been described.

Emerging Infectious Diseases
April 19, 2011

Original web page at Emerging Infectious Diseases