A Case-Control study of a Human Brucellosis Outbreak - Douz, Tunisia, 2018.

  • Water or foodborne
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Background:
Human brucellosis is a mandatory notifiable disease in Tunisia and despite control measures the overall incidence in 2017 was 9.8 per 100,000 population. In Douz (southwestern Tunisia) no cases were notified in 2017. Two cases were reported on March 19, 2018. Therefore, the aim of this study was to identify the source of contamination and set up control interventions.

Methods:
We conducted a case-control study based on case index finding. A case was defined as a resident of Douz who presented clinical brucellosis between January and March 2018 with a positive Wright test ≥ 160. A control was a neighbor of the case who had a negative Rose Bengal test and who showed no signs of brucellosis. Information about consumption of dairy products and contact with animals were collected using a questionnaire. Univariate and Multivariate analysis were performed to estimate odds ratios of risk factors. Active screening for animal brucellosis was carried out in goats.

Results:
A total of 25 cases and 52 controls were enrolled in the study. Of the cases 56% were female and the median age was 41 years. All cases consumed goat’s milk; out of which 92% had bought it from the same breeder. Consumption of goat’s milk from this breeder (aOR=30.78, 95% CI [6.47-235.91]) and consumption of unboiled goat’s milk (aOR=14.84, 95% CI [2.04-310.44]) were independent risk factors for the occurrence of brucellosis in cases. The breeder had 18 goats, five of which were smuggled from a neighboring country. Three of them were diagnosed with brucellosis.

Conclusion:
Consumption of unboiled milk from smuggled sick goats was the main risk factor of human brucellosis in this outbreak. The sick goats were identified and slaughtered. The other goats were put under surveillance. In addition, an education campaign was conducted. Vaccination and control of animal movements across borders need to be strengthened in order to control the disease in animals.

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