Brucellosis has markedly increased in recent years in Germany, according to a study.

Experts from the Robert Koch Institute found unpasteurized milk products were the top identified source of infection and most cases involved foreign travel.

Researchers analyzed demographic, clinical, laboratory and exposure information of symptomatic lab-confirmed brucellosis cases reported from 2006 to 2018. Findings were published in the International Journal of Infectious Diseases.

Infections associated with travel
In this period, 408 cases were reported in Germany of which 75 percent were travel-associated. Yearly notifications peaked in 2014 at 47 and remained higher compared to 2006 to 2013 when annual reports ranged from 18 to 28.

Asylum seekers arriving in Germany accounted for nine of 44 cases in 2015 and 15 of 36 infections in 2016. Unpasteurized milk products were most frequently reported as the source of infection.

Brucellosis reportable according to the German Protection against Infection Act. It was endemic in Germany until the 1980s but the country was declared officially free of bovine, ovine and caprine brucellosis in 2000.

Brucella melitensis was the most commonly isolated species from 180 of 197 with information, followed by Brucella abortus for 16 people and Breucella suis in one case.

Cases occurred in all age groups and both sexes were equally affected with the highest age-specific incidence in women aged 60 to 69 and the lowest in children under 10 years. Thirteen deaths were attributed to brucellosis, according to information from federal health monitoring in 2006 to 2016.

Fever was the most common symptom, followed by arthralgia and exhaustion, headache, loss of appetite and night sweats. Of 393 cases with information, 272 were hospitalized. The mean time between symptom onset and notification was seven and a half weeks.

Country and source of infection
Comparing incidences among asylum seekers and non-asylum seekers in 2015 and 2016, the former had a 28 times higher risk of reportable brucellosis.

Of 371 cases with information on place of exposure, 75 percent reported foreign travel prior to illness; mainly to the Middle East including 182 to Turkey, followed by 55 to Europe, 21 to Asia excluding the Middle East and 18 to Africa.

Except for a peak in 2014, the proportion of cases exposed in Turkey decreased over time, with a low in 2016 of two but increased again in 2017. In 2015, Middle East countries other than Turkey became the most important region of exposure, mainly due to cases among arriving asylum seekers from Syria and Iraq, but were surpassed again by Turkey in 2018. European countries have been increasingly reported as place of exposure since 2017.

For 136 cases at least one likely source of infection was identified in addition to foreign travel. A total of 104 had unpasteurized milk products. The raw cheese and milk most commonly originated from Turkey. A total of 47 cases had contact with livestock such as sheep and goats and 11 people had consumed or prepared fresh meat such as lamb.

The study found imported milk products seem to play a role in brucellosis in Germany but risk factors in the absence of travel are not well understood and need to be investigated further.

Of 94 cases that reportedly acquired brucellosis in Germany, 29 indicated at least one likely source of infection. For most no source of infection was recorded. Twelve had consumed imported food, mainly unpasteurized cheese from Iraq, Italy and Turkey. Three cases had unpasteurized cheese purchased in Germany and 11 people were occupationally exposed.

Researchers said people travelling to endemic countries should be advised about risk factors for and symptoms of the disease.

“In the study period brucellosis notifications increased and epidemiology in Germany has changed in response to migration from brucellosis endemic countries, change in travel patterns and changing brucellosis epidemiology in countries that are frequently visited by people living in Germany. In patients without foreign travel, physicians and public health officers should inquire about consumption of imported meat and unpasteurized milk products.”