Review
Imported brucellosis: A case series and literature review

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Summary

Background

Brucellosis is one of the main neglected zoonotic diseases. Several factors may contribute to the epidemiology of brucellosis. Imported cases, mainly in travellers but also in recently arrived immigrants, and cases associated with imported products, appear to be infrequently reported.

Methods

Cases of brucellosis diagnosed at a referral unit for imported diseases in Europe were described and a review of the literature on imported cases and cases associated with contaminated imported products was performed.

Results

Most imported cases were associated with traditional risk factors such as travel/consumption of unpasteurized dairy products in endemic countries. Cases associated with importation of food products or infected animals also occurred. Although a lower disease incidence of brucellosis has been reported in developed countries, a higher incidence may still occur in specific populations, as illustrated by cases in Hispanic patients in the USA and in Turkish immigrants in Germany. Imported brucellosis appears to present with similar protean manifestations and both classical and infrequent modes of acquisition are described, leading on occasions to mis-diagnoses and diagnostic delays.

Conclusions

Importation of Brucella spp. especially into non-endemic areas, or areas which have achieved recent control of both animal and human brucellosis, may have public health repercussions and timely recognition is essential.

Introduction

Brucellosis, caused by several species of the cocobacillus Brucella spp., is a zoonosis with a worldwide distribution. Brucellosis affects cattle, sheep, goats, pigs and other animals and is considered the most common zoonosis globally with over 0.5 million new cases reported annually [1], [2]. The majority of human cases are caused by Brucella melitensis, although Brucella abortus, Brucella suis, Brucella canis. and more recently Brucella pinnipedialis and Brucella ceti have also been associated with human disease. Humans acquire the infection mainly by ingesting unpasteurized milk or cheese from infected goats or sheep, but may also become infected through direct contact with infected animals, by eating contaminated animal products, by inhaling airborne agents and rarely through human to human transmission (sexual transmission, through organ transplantation and blood transfusions from an infected donor, vertically from mother to child, or through breast-feeding) [3], [4], [5], [6]. Brucellosis may develop after a prolonged incubation period of up to several months, and manifestations are protean often making diagnosis of this infection challenging. Brucellosis is under-reported, often mis-diagnosed even in higher income countries and is considered one of the main neglected zoonoses [1], [7].

The epidemiology of human brucellosis has changed significantly over the last few decades. Areas traditionally considered to be endemic included the Mediterranean basin countries, the Indian subcontinent and parts of Central and South America but countries in Europe and many areas of Latin America appear to have achieved control of the disease in recent years [8]. However, other foci of brucellosis have emerged recently and the highest recorded incidence of human brucellosis occurs in some Mediterranean countries, in the Middle East and in Central Asia [8], [9]. Spain has been classically recognised as an endemic region of animal and human brucellosis. However, official epidemiological surveillance data for communicable diseases in Spain have revealed a steady decrease in the incidence of brucellosis since the 1990s with a reported rate of 0.22 cases per 100.000 in 2013 [10]. The incidence of human cases has decreased in great part due to animal control programs and outbreaks in humans have occurred sporadically in abattoir workers in contact with culled animals from these programs and in individuals who consume non-controlled dairy products. In Spain, many regions have been declared free of brucellosis [10].

Several factors may contribute to the epidemiology of imported brucellosis. Globalization, mainly the increase in travel, immigration and commercial transactions with possible importation of contaminated food or animals may contribute to re-emergence of the disease. Outbreaks related to consumption of non-controlled imported food or contact with illegally imported animals or their products have been well documented [11], [12] and may still occur. Imported cases, mainly in travellers, but possible also in recently arrived immigrants, have been recognised, but appear to be infrequently reported in large series of ill-returned travellers and recent publications consist mainly of isolated cases or small series.

The objective of this study was to describe the cases of brucellosis diagnosed at a national referral centre for imported diseases in a European country and to review the available literature on imported cases and cases associated with contaminated imported products.

Section snippets

Methods

A literature search was performed in PubMed for all published articles until August 2015 using the terms “Brucella” or “brucellosis” or “Malta fever” AND “travel” or “traveler” or “imported” or “importation” or “immigrant(s)” or “immigration”. A secondary search reviewed the references for the main articles. Articles in English were considered as well as abstracts in English from non-English language articles when available.

Patients diagnosed with brucellosis at a Tropical Medicine Reference

Case reports

The main epidemiological and clinical features for the patients in the study are summarized in Table 1. Five patients were diagnosed with brucellosis at the unit during the period 1990–2015 (3 males and 2 females, average age 39.2 years). Three patients were long-term immigrants (9 months-20 years) and two patients were travellers. One traveller to Mexico (#4) recalled consumption of untreated cheese at a hotel during the trip. The other traveller, a long-term Dutch resident in Spain, (#3) had

Discussion

Imported brucellosis (either associated with travel/immigration or with importation of contaminated foods/infected animals) appears to be rare, with under 1000 cases identified in the literature. Most imported cases were associated with traditional risk factors such as travel and/or consumption of unpasteurized dairy products in/from endemic countries. Less frequent modes of transmission such as sexual contact (even in the absence of overt genitourinary involvement [24]), congenital

Conflict of interest

None.

Acknowledgements

This work was supported by the Spanish Ministry of Science and Innovation and the Instituto de Salud Carlos III within the Network of Tropical Diseases Research RICET [RD06/0021/0020]. The authors would like to thank E. Axelrod for providing data from the GeoSentinel database and acknowledge their colleagues from other centres currently contributing data to this network.

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