One in five cheeses sampled in Germany were found to be positive for Brucella, according to a study.

Brucella was detected in 41 of 200 samples from endemic countries sold at weekly markets, in supermarkets, and by delis in Berlin, as well as 15 prepacked cheese samples bought online via eBay.

Cheese made from pasteurized sheep’s milk and sold unlabeled or loose by market vendors was the most frequent type associated with the presence of Brucella DNA. Cheese samples included loose, non-labelled and pre-packed; labelled samples of brine, cream, soft, semi-hard and hard cheeses; and cheese made from bovine, ovine and caprine milk.

Researchers determines nine vendors sold more than 50 percent of the Brucella positive cheese samples, including seven at weekly markets and two supermarkets.

“We suppose that these clusters of positive cheeses can be explained by close trade links of the vendors to dairy farmers and production sites in endemic countries in combination with large-scale illegal import and a prosperous black market. Clustered positive samples at certain vendors suggest organized trade of illegal imports from endemic regions,” said researchers in a study published recently in the Food Control journal.

Most samples, 78 percent, were sold as raw milk cheeses according to product labels or information provided by vendors. To allow for comparison, 44 pasteurized milk cheeses were included in the study.

Brucella was detected in cheese made from pasteurized milk from Belgium, France, Greece and Spain. Six French brine cheeses made from sheep’s milk contained Brucella DNA and seven from Greece were positive. All 12 Turkish cheese samples containing Brucella DNA were pasteurized.

In total, 37 of the 41 positive samples were sold as raw milk cheese, but only three proved to contain raw milk. Brucella detected in three raw milk cheeses came from France, Greece and Spain.

A few cheeses investigated were produced from raw milk and had a short ripening period, according to researchers WiebkeJansen, CatherineLinard, MatthiasNoll, Karsten Nöckler and Sascha Al Dahouk.

“Therefore, the survival of Brucella in the cheese matrix seems to be possible, although no viable bacteria could have been isolated. Nonetheless, our findings may help to explain autochthonous Brucella infections in Germany affecting patients without travel history to endemic countries,” according to the research report.

Cheese for the study were purchased in May, June, August and September 2011. Modeling indicated that Brucella was significantly more often detected in late summer purchases as well as in cheese from Bulgaria, France, Greece and Turkey.

The number of reported human brucellosis cases in Germany was constant in 2012, 2013 and 2014 with 28 cases per year. Almost half of the patients in 2014 had not traveled to countries wher brucellosis is considered endemic. The others could be traced back to endemic countries, most frequently Turkey.

In the European unio brucellosis has been successfully eradicated from livestock in most member states including Germany. The main burden of human disease is due to Brucella melitensis and Brucella abortus transmitted from sheep, goats and cattle. It is a severe disease with most of the patients reported in the EU needing to be hospitalized.

Almost half of the cheese samples, 48 percent, tested by the researchers were made predominantly with sheep’s milk. Goat’s milk was used for 22.5 percent and cow’s milk for 6.5 percent, with 46 samples having been made with a mixture of the three different types of milk.

Researchers mainly investigated short ripened cheeses such as feta and brine cheese, soft and cream cheese, as well as short ripened semi-hard cheese. They also tested 20 hard cheeses, such as Pecorino and Manchego. Countries of origin were Turkey, France, Bulgaria, Greece, Spain, Italy, Belgium, Croatia, Cyprus, Lebanon, Czech Republic, Germany and The Netherlands.