Investigation of the molecular epizootiological characteristics and tracking of the geographical origins of Brucella canis strains in China

First Isolation and Multilocus Sequence Typing of Brucella canis from a Subclinically Infected Pet Dog in China

Canine brucellosis, a worldwide zoonotic disease, is mainly caused by Brucella canis. In the present study, we isolated a Brucella strain (CD3) from a subclinically infected pet dog in Sichuan Province, Southwestern China. Classical biotyping methods and molecular biological tests (BCSP31 and BcSS PCR) proved that the strain belonged to B. canis. Furthermore, B. canis CD3 and another two B. canis strains (WJ5 and YA4), which were all isolated from pet dogs in Sichuan, were genotyped using multilocus sequence typing (MLST). Our results showed that the three B. canis strains were identified as the same sequence type (ST21). The present study is the first to report B. canis strain from a subclinically infected pet dog in China, indicating a potential threat to public health posed by subclinical infections in pet dogs. We suggest that screening for B. canis should be incorporated into routine medical examination of pet dogs and other companion animals in areas with a history of animal or human brucellosis.

Emerging diversity and ongoing expansion of the genus Brucella

Remarkable genetic diversity and breadth of host species has been uncovered in the Brucella genus over the past decade, fundamentally changing our concept of what it means to be a Brucella. From ocean fishes and marine mammals, to pond dwelling amphibians, forest foxes, desert rodents, and cave-dwelling bats, Brucella have revealed a variety of previously unknown niches. Classical microbiological techniques have been able to help us classify many of these new strains but at times have limited our ability to see the true relationships among or within species. The closest relatives of Brucella are soil bacteria and the adaptations of Brucella spp. to live intracellularly suggest that the genus has evolved to live in vertebrate hosts. Several recently discovered species appear to have phenotypes that are intermediate between soil bacteria and core Brucella, suggesting that they may represent ancestral traits that were subsequently lost in the traditional species. Remarkably, the broad relationships among Brucella species using a variety of sequence and fragment-based approaches have been upheld when using comparative genomics with whole genomes. Nonetheless, genomes are required for fine-scale resolution of many of the relationships and for understanding the evolutionary history of the genus. We expect that the coming decades will reveal many more hosts and previously unknown diversity in a wide range of environments.

Canine brucellosis in Costa Rica reveals widespread Brucella canis infection and the recent introduction of foreign strains

Brucellosis is a prevalent disease in Costa Rica (CR), with an increasing number of human infections. Close to half of homes in CR have one or more dogs, corresponding to ∼1.4 million canines, most of them in the Central Valley within or near the cities of San José, Heredia, and Alajuela. From 302 dog sera collected from this region, 19 were positive for Brucella canis antigens, and five had antibodies against smooth lipopolysaccharide, suggesting infections by both B. canis and other Brucella species. B. canis strains were isolated in the Central Valley from 26 kennel dogs and three pet dogs, all displaying clinical signs of canine brucellosis. We detected three recent introductions of different B. canis strains in kennels: two traced from Mexico and one from Panama. Multiple locus-variable number tandem repeats (MLVA-16) and whole-genome sequencing (WGSA) analyses showed that B. canis CR strains comprise three main lineages. The tree topologies obtained by WGSA and MLVA-16 just partially agreed, indicating that the latter analysis is not suitable for phylogenetic studies. The fatty acid methyl ester analysis resolved five different B. canis groups, showing less resolution power than the MLVA-16 and WGSA. Lactobacillic acid was absent in linages I and II but present in linage III, supporting the recent introductions of B. canis strains from Mexico. B. canis displaying putative functional cyclopropane synthase for the synthesis of lactobacillic acid are phylogenetically intertwined with B. canis with non-functional protein, indicating that mutations have occurred independently in the various lineages.

Molecular investigation of infection sources and transmission chains of brucellosis in Zhejiang, China

In the present study, a total of 7793 samples from 5 different types of hosts were collected and tested, with a seroprevalence of 2.4% (184/7793). Although the seroprevalence of human and animal brucellosis is relatively low, numbers of human brucellosis cases reported have increased continuously from 2004 to 2018. A total of 118 Brucella strains containing 4 biotypes were obtained, including Brucella melitensis bv.1 (n = 8) and bv.3 (n = 106), Brucella abortus bv.3 (n = 3) and bv.7 (n = 1). Twenty-one shared MLVA-16 genotypes, each composed of 2 to 19 strains obtained from different hosts, suggest the occurrence of a brucellosis outbreak epidemic with multiple source points and laboratory infection events. Moreover, 30 shared MLVA-16 genotypes were observed among 59.6% (68/114) B. melitensis isolates from Zhejiang and strains from other 21 different provinces, especially northern provinces, China. The analysis highlighted the imported nature of the strains from all over the northern provinces with a dominant part from the developed areas of animal husbandry. These data revealed a potential transmission pattern of brucellosis in this region, due to introduced infected sheep leading to a brucellosis outbreak epidemic, and eventually causing multiple laboratory infection events. It is urgent to strengthen the inspection and quarantine of the introduced animals.

Prevalence and Genomic Characterization of Brucella canis Strains Isolated from Kennels, Household, and Stray Dogs in Chile

Canine brucellosis caused by Brucella canis is a zoonotic disease that causes reproductive alterations in dogs, such as infertility, abortion, and epididymitis. This pathogen is especially prevalent in South America, and due to the lack of official control programs and the growing trend of adopting dogs it constitutes a public health risk that must be addressed. The aim of this study was to determine the prevalence of B. canis infection in kennel, shelter, and household dogs and to characterize the genomic properties of circulating strains, including ure and virB operons and omp25/31 genes. Samples from 771 dogs were obtained, and the infection was detected by blood culture and/or serology in 7.0% of the animals. The complete ure and virB operons and the omp25/31 genes were detected. Interestingly, we found different single-nucleotide polymorphisms (SNPs) in some of the analyzed genes, which could mean a change in the fitness or virulence of these strains. This study provides further evidence about dogs as a source of B. canis strains that can infect people. This also highlights the need to implement official control programs, including the mandatory testing of dogs, especially stray dogs, before adoption.

Molecular Characteristics of Brucella Isolates Collected From Humans in Hainan Province, China

Brucellosis has been reported in several regions of Hainan Province, but the extent of the disease has not been fully elucidated. Conventional biotyping methods, multiple locus variable number tandem repeats analysis (MLVA), and single-nucleotide polymorphisms (SNPs) from draft genome sequencing were employed to characterize the strains. There were four biovars (Brucella melitensis bv. 1, 2, and 3 and Brucella suis bv. 3) detected, which showed that the biovar diversity of Brucella in Hainan is higher than in other areas of China. Both B. melitensis bv. 3 and B. suis bv. 3 were dominant species and showed epidemiology patterns that were compatible with both southern and northern China. Eight of MLVA-11 genotypes were known (31, 111, 116, 120, 136, 291, 297, and 345), and the remaining seven were novel (HN11-1 to HN11-7); these data showed that Brucella strains in this study had multiple geographic origins and exhibited characteristics of origin and evolution of co-existing imported and Hainan specific lineage. A total of 41 strains were found, belonging to 37 unique genotypes that each represented a single strain, which suggests that these strains were not directly related epidemiologically and indicates that the epidemic characteristics of human brucellosis in Hainan was dominated by sporadic strains. The high HGDI values were observed in MLVA-8, MLVA-11, and MLVA-16 among two species, suggesting considerable genetic diversity among these species. MST is characterized based on MLVA-16 that was found both throughout China and on a global level and showed that strains of this study had significant genetic differences with strains from many parts of the globe and seemingly represent a unique genetic lineage. Whole-genome SNP analysis showed that four B. melitensis were closely related to strains from China's northern provinces, and the source of infection was partly of human brucellosis in this province that may have been from these regions. The B. suis were closely related to strains from the United States, and further investigation of the transportation of animals, such as pigs, is needed to elucidate the origins of these strains.

Seroprevalence of human brucellosis and molecular characteristics of Brucella strains in Inner Mongolia Autonomous region of China, from 2012 to 2016

In the present study, a total of 1102304 serum samples were collected to detected human brucellosis between the years 2012 and 2016 in Inner Mongolia. Overall, an average of 3.79% anti-Brucella positive in Inner Mongolia was presented but the range of positive rates were among 0.90 to 7.07% in 12 regions. Seroprevalence of human brucellosis increased gradually from 2012 to 2016. However, the incidence rate of human brucellosis showed a declining trend. One hundred and seven Brucella strains were isolated and identified as B. melitensis species, and B. melitensis biovar 3 was the predominant biovar. MLVA-11 genotypes 116 was predominant and had crucial epidemiology to the human population. All 107 strains tested were sorted into 75 MLVA-16 genotypes, with 54 single genotypes representing unique isolates. This result revealed that these Brucellosis cases had epidemiologically unrelated and sporadic characteristics. The remaining 21 shared genotypes among two to four strains, confirming the occurrence of cross-infection and multiple outbreaks. Extensive genotype-events were observed between strains from this study and Kazakhstan, Mongolia, and Turkey, these countries were key members of the grassland silk road. Long-time trade in small ruminants (sheep) in these countries has possibly promoted the spread of Brucella spp. in these regions.