Abstract
Brucellosis is a major zoonotic infection in Kazakhstan. However, there is limited data on its incidence in humans and animals, and the genetic diversity of prevalent strains is virtually unstudied. Additionally, there is no detailed overview of Kazakhstan brucellosis control and eradication programs. Here, we analyzed brucellosis epidemiological data, and assessed the effectiveness of eradication strategies employed over the past 70 years to counteract this infection. We also conducted multiple loci variable-number tandem repeat analysis (MLVA) of Brucella abortus strains found in Kazakhstan. We analyzed official data on the incidence of animal brucellosis in Kazakhstan. The records span more than 70 years of anti-brucellosis campaigns, and contain a brief description of the applied control strategies, their effectiveness, and their impact on the incidence in humans. The MLVA-16 method was used to type 94 strains of B. abortus and serial passages of B. abortus 82, a strain used in vaccines. MLVA-8 and MLVA-11 analyses clustered strains into a total of four and seven genotypes, respectively; it is the first time that four of these genotypes have been described. MLVA-16 analysis divided strains into 28 distinct genotypes having genetic similarity coefficient that varies from 60 to100% and a Hunter & Gaston diversity index of 0.871. MST analysis reconstruction revealed clustering into "Kazakhstani-Chinese (Central Asian)", "European" and "American" lines. Detection of multiple genotypes in a single outbreak confirms that poorly controlled trade of livestock plays a crucial role in the spread of infection. Notably, the MLVA-16 profile of the B. abortus 82 strain was unique and did not change during 33 serial passages. MLVA genotyping may thus be useful for epidemiological monitoring of brucellosis, and for tracking the source(s) of infection. We suggest that countrywide application of MLVA genotyping would improve the control of brucellosis in Kazakhstan.
Highlights
The incidence of brucellosis reaches as much as 200 cases per 100,000 of the population in some regions of the world; besides, the infection has become endemic in many countries [1]
Brucellosis was reported in central Kazakhstan
Medical expedition to remote areas with semi-nomadic pastoralism that took place in 1937 revealed a high incidence of brucellosis among the local population, which indicates that there was a continuous circulation of Brucella in Kazakhstan by this time [35]
Summary
The incidence of brucellosis reaches as much as 200 cases per 100,000 of the population in some regions of the world; besides, the infection has become endemic in many countries [1]. Control in animals is critical for prevention of spread to humans; the majority of human cases in brucellosis-free regions are due to import by people who have traveled to endemic regions, as they may have had contact with wild animals or with imported products [7,8,9,10]. Continued surveillance of brucellosis in disease-free area is important to prevent re-emergence of the zoonosis [14]
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