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

Abstract

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.

Figure 1

Map of the Netherlands showing locations of farms sampled during the Q fever outbreak, 2007–2010. Farms are indicated by letter and ruminant species (black squares, goats; black triangles, sheep; black star, cattle); genotypes of Coxiella burnetii found per farm are indicated by bars at each farm’s location. The height of the bar indicates numbers of isolates per genotype.

Figure 2

Phylogenetic tree with genotypes of Coxiella burnetii of all samples in the study, the Netherlands, on the basis of 10 multilocus variable-number tandem-repeat analyses (MLVA). Repeats per locus are shown; open spots indicate missing values. NM, Nine Mile reference strain.

Figure 3

Phylogenetic tree with genotypes of Coxiella burnetii that are most closely related to the Dutch genotypes on the basis of 4 multilocus variable-number tandem-repeat analyses (MLVA). Genotypes are derived from the Multiple Loci VNTR Analysis databases for genotyping (http://minisatellites.u-psud.fr/MLVAnet/querypub1.php: Coxiella2009_Netherlands [accessed 2011 Jan 11]). Repeats per locus are shown; open spots indicate missing values. NL, the Netherlands.

Figure 4

Phylogenetic tree with genotypes of Coxiella burnetii that are most closely related to the Dutch genotypes on the basis of 9 multilocus variable-number tandem-repeat analyses (MLVA). Genotypes are derived from the Multiple Loci VNTR Analysis databases for genotyping (http://minisatellites.u-psud.fr/MLVAnet/querypub1.php: Coxiella2007 [accessed 2011 Jan 11]). Repeats per locus are shown; open spots indicate missing values. NL, the Netherlands; Slovak Rep, Slovak Republic.