Brucellosis in the world today

Summary

Brucellosis is the most common bacterial zoonosis world-wide, with more than half a million estimated new cases each year. The traditional epidemiology of the disease has changed dramatically over the last two decades, related to major political and socio-economic events. Thus while the incidence remains high in the Near and Middle East and North African countries, it has been greatly reduced in Latin America (excluding Mexico and parts of Peru) and south European countries (although with slower progress recorded in Greece and Sicily). Simultaneously, two new hyperendemic foci have emerged: the former Soviet republics of Asia, and the Balkans (with the disease incidence increasing dramatically in Bosnia-Herzegovina and being increasingly recognized in Albania). The absence of data from endemic areas such as India, China and subSaharan Africa, and also the possibility of rapid and diverse introduction of the disease in the non-endemic developed world, further highlights the increased need for proper epidemiological surveillance at a global level.

Introduction

Brucellosis is the most common bacterial zoonosis world-wide; in addition to the hundreds of thousands of new infections reported annually, the disease is characterized by progression, in a significant percentage of patients, to residual pathology and chronicity.
The typical global epidemiology of the disease, as described in most textbooks and reproduced in a few current scientific publications, is a disease endemic in the Mediterranean, Middle East and Latin America. But during the last two decades, the epidemiology of brucellosis has changed significantly, with the emergence of new global outbreaks in association with major political/historical events, successful control of the disease in many parts of the Mediterranean, and the referral of epidemiological data from countries where brucellosis was endemic but in an unknown proportion [1,2]. The global map of the disease incidence is depicted in Table 1 and Figure 1.

 

The old endemic foci today

Brucellosis remains a major problem in the Near and Middle East, the existing evidence from Syria making this country the highest in the global endemicity map. Turkey consistently reports more than 15,000 new cases per year (largely the result of systematic surveillance and recording) and is still, as shown by molecular typing techniques, the main input source of brucellosis in certain western European countries such as Germany [3]. Iran displays a similarly high annual number of new cases and has an increasing presence in the scientific literature. Disease endemicity in Iraq and Afghanistan is important and underappreciated by official figures: the presence of Western troops in these two countries and the outbreaks reported in military personnel [4] maintain the association of chronic brucellosis with chronic fatigue syndromes, including the Gulf War Syndrome, although this relationship has had limited investigation at a pathophysiological level. In the Mediterranean, growing reports indicate major endemicity issues in North African countries, including Egypt [5]. In contrast, in European Mediterranean countries the incidence has been reduced significantly through extensive programs of systematic animal vector vaccination. Thus France has achieved the eradication of brucellosis; annual numbers in Spain and Portugal have been dropping significantly according to the latest reports from the European Center for Disease Prevention and Control (ECDC) [6]; in Italy the disease is confined exclusively to Sicily; and Greece and Sicily (because of unique geographical parameters, mentioned below) are showing a slow decrease in annual cases. In Latin America, the incidence is now generally low, with the exception of  Mexico, showing steady annual cases, but it is also the main source of about 80-100 new cases diagnosed annually in the USA. Besides Mexico, only Peru can be considered as a country of moderate endemicity in the region.

Emerging hyperendemic foci I The dissolution of the Soviet Union and the collapse of communist regimes has led to major social and economic changes in the new countries that have been created, with a breakdown in public health infrastructures and prevention, surveillance and veterinary services, in conjunction with the opening of borders hitherto strictly controlled. This has led to soaring rates of brucellosis in all former Soviet republics in Asia. The maintenance of this hyperendemicity, often despite scientific assistance from the developed world, is partly because of the internal displacement of people as a result of civil conflict, climate and economic parameters.

Emerging hyperendemic foci II In the Balkans, after the collapse of communist regimes, recent history has been marked by the violent formation of new government structures, war and incessant involuntary population movements. The current situation, with the presence of multiple minorities and lax border formations (literally and in terms of monitoring the traffic of people, animals and products), has enabled the rapid spread of disease even in areas previously free of brucellosis, such as Bulgaria, where the disease has been introduced from Greece (by employees working with infected herds) and from Turkey (with localization in Muslim areas of southern Bulgaria) [7]. The main focus of endemicity remains Albania, where the extent of the disease is still largely underestimated by official figures. However, the dynamics of this endemicity are obvious and largely responsible for the constant high incidence observed in the Former Yugoslav Republic of Macedonia (FYROM) (despite systematic attempts at disease control), the existing, albeit to an unknown extent, endemicity of the disease (and multiple other zoonoses) in Kosovo, and the introduction and subsequent explosive, exponentially increasing, annual incidence of brucellosis in Bosnia-Herzegovina, which is currently the most endemic part of Europe. The epidemiological context inevitably adversely affects the attempted eradication of disease in Greece.

Table 1

Countries with an annual incidence of above 100 cases/105 population
Syria
Countries with an annual incidence of 50-100 cases/105 population
Albania
Afghanistan
Bosnia-Herzegovina
Kyrgyzstan
Mongolia
Countries with an annual incidence of 8-50 cases/105 population
Algeria
FYROM
Iraq
Iran
Kazakhstan
Saudi Arabia
Tajikistan
Turkey
Countries with an annual incidence of 2-8 cases/105 population
Azerbaijan
Armenia
United Arab Emirates
Jordan
Kuwait
Lebanon
Mexico
Oman
Peru
Turkmenistan
Tunisia
Countries with an unknown annual incidence, estimated as above 2 cases/105 population
Egypt
India
China
Pakistan

Data are derived from references [1] and [2] updated chronologically from the annual epidemiological official data from each country, where available.


The uncharted areas

There are increasing reports from various countries such as Uganda, Tanzania and Kenya that emphasize that brucellosis is hyperendemic in subSaharan Africa. The difficulties in brucellosis diagnosis, and the presence of other infections with more significant mortality and morbidity burden, limits the ability to characterize the prevalence in these countries analytically. Brucellosis is endemic almost throughout India, but adequate epidemiological data are lacking. The situation is similar in China, where the abundant literature is available only in Chinese. As for Russia, endemicity is recognized in Caucasian regions bordering endemic former Soviet republics in the region, including Armenia and Azerbaijan.

References:

Pappas G, Papadimitriou P, Akritidis N, et al. The new global map of human brucellosis. Lancet Infect Dis 2006;6:91-99.

Pappas G. The changing Brucella ecology: novel reservoirs, new threats. Int J Antimicrob Agents 2010;36(Suppl 1):S8-11

Gwida M, Neubauer H, Ilhan Z, et al. Cross-border molecular tracing of brucellosis in Europe. Comp Immunol Microbiol Infect Dis. 2012; 35:181-185

Bechtol D, Carpenter LR, Mosites E, et al. Brucella melitensis infection following military duty in Iraq. Zoonoses Public Health 2011;58:489-492.

El-Metwally MT, Elwan MA, El-Bahnasawy MM, et al. Zoonotic brucellosis: an underestimated or misdiagnosed disease in Egypt. J Egypt Soc Parasitol 2011;41:35-46.

European Center for Disease Prevention and Control. Annual Epidemiological Report on Communicable Diseases in Europe. ECDPC, 2010.

Russo G, Pasquali P, Nenova R, et al. Reemergence of human and animal brucellosis, Bulgaria. Emerg Infect Dis 2009;15:314-316.

Georgios Pappas, Institute of Continuing Medical Education of Ioannina, Head, Zoonoses Working Group, International Society of Chemotherapy, Editor, Clinical Microbiology and Infection