Brucellosis in a dog caused by Brucella melitensis Rev 1

The Reasons Behind Long-Term Endemicity of Brucellosis in Low and Middle-Income Countries: Challenges and Future Perspectives

Brucellosis is a neglected worldwide zoonotic disease with more than 500,000 new human cases each year. Direct contact with infected animals and consumption of undercooked animal origin foods are the main routes of brucellosis transmission to humans. Although long endeavor has been applied to control and eliminate brucellosis from animal and human populations in developing countries especially in low- and middle-income countries (LMICs), the disease is still endemic in these regions. Many common or unique factors including raw milk consumption, unhygienic slaughter of livestock, extensive husbandry, budgetary limitations, misdiagnosis, and other conditions play a role in long-term endemicity of brucellosis in these locations. It has been shown that One Health is the only practical approach to control brucellosis; however, applying such methods is challenging in low-resource areas. In such conditions, brucellosis is continuously maintained in animals and repeatedly spread to human populations. In this article, factors playing a critical role in brucellosis endemicity, and the real conditions challenging the application of One Health approach in control of brucellosis are highlighted.

Molecular Investigations of Two First Brucella suis Biovar 2 Infections Cases in French Dogs

Despite Brucella suis biovar 2's (BSB2) active circulation in wildlife, no canine infections have been reported. The present paper is the first to describe two cases of BSB2 infections in French dogs. The first case occurred in 2020 and concerned a 13-year-old male neutered Border Collie with clinical signs of prostatitis. The urine culture revealed the excretion of significant levels of Brucella in the sample. The second case concerned a German Shepherd with bilateral orchitis, in which it was possible to detect Brucella colonies following neutering. HRM-PCR and classical biotyping methods classified both isolated strains as BSB2, in contrast to expected B. canis, which is usually the etiological agent of canine brucellosis in Europe. The wgSNP and MLVA analyses highlighted the genetic proximity of two isolates to BSB2 strains originating from wildlife. No pig farms were present in the proximity of either dog's residence, ruling out potential spill over from infected pigs. Nevertheless, the dogs used to take walks in the surrounding forests, where contact with wildlife (i.e., wild boars or hares, or their excrements) was possible. These cases highlight the importance of adopting a One Health approach to control the presence of zoonotic bacteria in wild animals and avoid spillovers into domestic animals and, potentially, humans.

Presumptive Identification of Smooth Brucella Strain Antibodies in Canines

Brucellosis is a zoonotic disease caused by a Gram-negative coccobacillus. There are four Brucella strains of zoonotic importance in our domestic species, subdivided by their culture phenotypes: Brucella abortus (B. abortus), B. melitensis, B. suis (smooth strains) and B. canis (rough strain). Dogs can serve as hosts for all four of the zoonotic strains; however, routine serologic testing in dogs has been limited to the identification of B. canis antibodies. The aim of our study was to identify smooth Brucella strain antibodies in canines. We hypothesize that the Brucella abortus Fluorescence Polarization Assay would be successful in identifying smooth Brucella strain antibodies in canines. Ninety-five dogs, including forty-five hog hunting dogs were screened for circulating antibodies to any of the four zoonotic strains of the bacteria utilizing a combination of Canine Brucella Slide Agglutination Test (CBSA), Brucella canis Agar Gel Immunodiffusion II test (AGIDII), Brucella abortus Card Agglutination Test (BCA), and the Brucella abortus Fluorescence Polarization Assay (FPA). Test interpretation results yielded a 0% (0/95) smooth Brucella strain seropositivity rate, with 2% (2/95) of dogs yielding inconclusive rough Brucella strain serology results (0–2% rough strain seropositivity rate). Additionally, a retrospective portion of the study was performed to identify sera containing circulating antibodies to any of the smooth strains of Brucella by testing previously banked canine serum samples stored at Cornell's Veterinary Diagnostic Laboratory from 2018 to 2019 via Brucella abortus FPA. Of the 769 serum samples tested, 13/769 (1.7%) yielded an inconclusive result, 725/769 (94.2%) were negative, 30/769 (4%) yielded a positive FPA test result, and 1/769 (0.1%) had to be excluded due to insufficient sample remaining to perform the diagnostic test. Of the 30 FPA positive canine serum samples, 97% (29/30) also tested positive on the CBSA test. Additionally, there was a statistically significant (p < 0.0001) likelihood of altered (spayed/neutered) and mixed breed dogs to be FPA positive when compared to intact, purebred dogs, respectively.

Investigation of small ruminant brucellosis among smallholder farms: The missing link in control programmes of endemic areas

Brucellosis is a neglected zoonotic infection with a worldwide distribution and high levels of endemism in some regions, including the Middle East. In Iran, sheep and goats constitute a major part of the livestock population, often kept by small-scale farmers for their own consumption and economic purposes. This investigation aimed at characterizing the Brucella spp. and biovars circulating in sheep and goats under smallholder farming and their potential spillover across farms. For this purpose, from two randomly selected pastoral districts of Alborz and Fars provinces in Iran, a total of 54 aborted foetuses (38 from sheep and 16 from goats) and 528 blood samples were collected from sheep (n = 435), goats (n = 77), farmers (n = 11) and dogs (n = 5). Then, serological, bacteriological and molecular characterization of Brucella isolates was performed using standard methods. Our results showed the high seroprevalence of brucellosis in pastoral districts of Fars and Alborz provinces reaching 16.3%, 11.7% and 12.7% by using the Rose Bengal plate test (RBPT), serum agglutination test (SAT) and indirect enzyme-linked immunosorbent assay (iELISA) test, respectively. Furthermore, the results of bacterial culture, conventional biotyping and PCR analyses showed the presence of Brucella melitensis biovar 1 and 2 infections among goat, farmers and dog of the Alborz farms and B. melitensis biovars 1, 2 and 3 among sheep of the Fars farms. Among nine seropositive farmer and dog blood samples (four farmers and five dogs), only three (two farmers and one dog) were positive in both culture and PCR tests. These results stress the need to strengthen screening and control measures in small flocks of small ruminants in Iran that could be the starting point of new outbreaks at the livestock/human interface. The present study also suggests that infected dogs may further maintain the risk of exposure to Brucella pathogens in small farms and beyond.

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.

Brucella melitensis infection in dog: a critical issue in the control of brucellosis in ruminant farms

Canine brucellosis is a contagious disease associated with health implications for humans as well as for a wide range of wild and domesticated animals. In this study, 173 dog blood specimens were sampled from herding dogs in three different provinces including Tehran (n = 127), Qom (n = 40) and Alborz (n = 6) provinces. The presence of Brucella antibodies was determined using Rose Bengal plate test (RBPT), slow agglutination test (SAT) and 2-mercaptoethanol (2-ME), respectively. The seropositive samples were further screened using blood culture and PCR tests to identify and differentiate the implicated Brucella species. According to our results, 24.3% (42/173), 13.8% (24/173) and 6.3% (11/173) of blood samples were tested positive using RBPT, SAT and 2-ME, respectively. However, among 42 seropositive samples, only 38.1% (16/42) and 14.2% (6/42) were positive by PCR and culture, respectively. Brucella melitensis biovar 1 and biovar 2 was isolated from the bacterial cultures of 6 blood samples and confirmed by biotyping, AMOS PCR and Bruce-ladder PCR assays. These findings highlight the potential risk of Brucella transmission from dog to humans along with other livestock and reflect the critical role of infected dogs in the persistence of Brucella infections among ruminant farms. This study stresses the need for further epidemiological investigations on canine brucellosis among herding dogs and suggests the systematic screening of the disease among companion animals such as dogs in order to improve brucellosis surveillance and control programs.

Brucella ovis mutant in ABC transporter protects against Brucella canis infection in mice and it is safe for dogs

BACKGROUND/OBJECTIVES

Vaccination is the most important tool for controlling brucellosis, but currently there is no vaccine available for canine brucellosis, which is a zoonotic disease of worldwide distribution caused by Brucella canis. This study aimed to evaluate protection and immune response induced by Brucella ovis ΔabcBA (BoΔabcBA) encapsulated with alginate against the challenge with Brucella canis in mice and to assess the safety of this strain for dogs.

METHODS

Intracellular growth of the vaccine strain BoΔabcBA was assessed in canine and ovine macrophages. Protection induced by BoΔabcBA against virulent Brucella canis was evaluated in the mouse model. Safety of the vaccine strain BoΔabcBA was assessed in experimentally inoculated dogs.

RESULTS

Wild type B. ovis and B. canis had similar internalization and intracellular multiplication profiles in both canine and ovine macrophages. The BoΔabcBA strain had an attenuated phenotype in both canine and ovine macrophages. Immunization of BALB/c mice with alginate-encapsulated BoΔabcBA (108 CFU) induced lymphocyte proliferation, production of IL-10 and IFN-γ, and protected against experimental challenge with B. canis. Dogs immunized with alginate-encapsulated BoΔabcBA (109 CFU) seroconverted, and had no hematologic, biochemical or clinical changes. Furthermore, BoΔabcBA was not detected by isolation or PCR performed using blood, semen, urine samples or vaginal swabs at any time point over the course of this study. BoΔabcBA was isolated from lymph nodes near to the site of inoculation in two dogs at 22 weeks post immunization.

CONCLUSION

Encapsulated BoΔabcBA protected mice against experimental B. canis infection, and it is safe for dogs. Therefore, B. ovis ΔabcBA has potential as a vaccine candidate for canine brucellosis prevention.

Serological and Molecular Investigation of Brucella Species in Dogs in Pakistan

Brucellosis is an important bacterial zoonosis caused by B. abortus and B. melitensis in Pakistan. The status of canine brucellosis caused by B. canis remains obscure. In total, 181 serum samples were collected from stray and working dogs in two different prefectures viz. Faisalabad (n = 87) and Bahawalpur (n = 94). Presence of antibodies against B. canis and B. abortus/B. melitensis was determined using the slow agglutination test (SAT) and ELISA, respectively. Real-time PCR was performed to detect and differentiate Brucella DNA at the species level. In Faisalabad, the serological prevalence was found to be 9.2% (8/87) and 10.3% (9/87) by SAT and ELISA, respectively. Only one of the ELISA positive samples (1.15%) yielded amplification for B. abortus DNA. In Bahawalpur, 63.8% (60/94) samples were found positive by SAT; however, none of the samples was positive by ELISA or by real-time PCR. Location, age (≥1 year) and body condition (weak) were found to be associated with B. canis infection, whereas presence of wounds was found to be associated with B. abortus infection only. These findings point towards a risk of transmission from dog to livestock and humans and vice versa. The study expects to draw the attention of concerned authorities towards infection prevention and animal welfare. This study warrants further epidemiological investigation on brucellosis in pet dogs and their owners. To the best of our knowledge, this is first ever report on B. canis and B. abortus in dogs in Pakistan.

Detection of Brucella spp. in dogs at Pantanal wetlands

Canine brucellosis is an infectious disease that produces reproductive disease in both males and females. Although Brucella canis is more common, the infection by Brucella abortus is more frequent in dogs sharing habitats with livestock and wild animals. We decided to investigate the role of dogs in the maintenance of Brucella spp. in the Pantanal wetland. Serum and whole blood samples were collected from 167 dogs. To detect antibodies against B. abortus and B. canis, buffered acidified plate antigen (BAPA) and agar gel immunodiffusion (AGID) tests were performed. To detect Brucella spp., B. abortus and B. canis DNA, PCR was performed using the bcsp31, BruAb2_0168, and BR00953 genes, respectively. To confirm the PCR results, three bcsp31 PCR products were sequenced and compared with sequences deposited in GenBank. The seropositivity rates of 7.8% and 9% were observed for the AGID and BAPA tests, respectively. Positivity rates of 45.5% and 10.8% were observed when testing bcsp31 and BruAb2_0168, respectively, while there was no positivity for BR00953. The sequenced products had 110 base pairs that aligned with 100% identity to B. abortus, B. canis, and B. suis. Considering our results, dogs may be acting as maintenance hosts of Brucella spp. in the Pantanal region.

Comparative Genomics and in vitro Infection of Field Clonal Isolates of Brucella melitensis Biovar 3 Did Not Identify Signature of Host Adaptation

Brucella spp. are responsible for brucellosis, a widespread zoonosis causing reproductive disorders in animals. Species-classification within this monophyletic genus is based on bacteriological and biochemical phenotyping. Traditionally, Brucella species are reported to have a preferential, but not exclusive mammalian host. However, this concept can be challenged since many Brucella species infect a wide range of animal species. Adaptation to a specific host can be a driver of pathogen variation. It is generally thought that Brucella species have highly stable and conserved genomes, however the degree of genomic variation during natural infection has not been documented. Here, we investigated potential genetic diversity and virulence of Brucella melitensis biovar 3 field isolates obtained from a single outbreak but from different host species (human, bovine, small ruminants). A unique MLVA-16 pattern suggested all isolates were clonal. Comparative genomic analyses showed an almost non-existent genetic diversity among isolates (only one SNP; no architectural rearrangements) and did not highlight any signature specific to host adaptation. Similarly, the strains showed identical capacities to enter and replicate in an in vitro model of macrophage infection. In our study, the absence of genomic variability and similar virulence underline that B. melitensis biovar 3 is a broad-host-range pathogen without the need to adapt to different hosts.

A review of Brucella seroprevalence among humans and animals in Bangladesh with special emphasis on epidemiology, risk factors and control opportunities

Brucellosis is a neglected bacterial zoonotic disease in many countries affecting both humans and animals. The aim of this paper is to review published reports of the seroprevalence of brucellosis in humans and animals (cattle, buffalo, sheep, goats and dogs) in Bangladesh. The prevalence studies are based primarily on the following serological tests: rose bengal plate agglutination test (RBT), plate agglutination test (PAT), tube agglutination test (TAT), mercaptoethanol agglutination test (MET), standard tube agglutination test (STAT), slow agglutination test (SAT), milk ring test (MRT), indirect enzyme-linked immunosorbant assay (I-ELISA), competitive ELISA (C-ELISA) and fluorescent polarization assay (FPA). Seroprevalences of brucellosis were found to be affected by the sensitivity and specificity of serological tests employed. Brucellosis prevalence varied based on occupations of people (2.5-18.6%) and species of animals (3.7% in cattle, 4.0% in buffalo, 3.6% in goats and 7.3% in sheep). The prevalence of brucellosis in humans was reported in livestock farmers (2.6-21.6%), milkers (18.6%), butchers (2.5%) and veterinarians (5.3-11.1%) who have direct contact with animal and its products or who consume raw milk. According to published reports brucellosis does affect people and livestock of Bangladesh. There is an immediate need for a concerted effort to control and eradicate brucellosis from domesticated animals in Bangladesh.

Ovine and Caprine Brucellosis (Brucella melitensis) in Aborted Animals in Jordanian Sheep and Goat Flocks

Two hundred and fifty five biological samples were collected from 188 animals (81 sheep and 107 goats) during the lambing season from September 2009 to April 2010 from the Mafraq region of Jordan. Sampled animals belonged to 93 sheep and goat flocks that had abortion cases in the region. One hundred and seven (41.9%) biological samples were positive for the omp2 primers that were able to identify all Brucella species in the collected samples which were obtained from 86 aborted animals (86/188 = 45.7%). Using the B. melitensis insertion sequence 711 (IS711) primers on the 107 omp2 positive samples, only 61 confirmed to be positive for B. melitensis. These positive samples were obtained from 28 sheep and 33 goats. The prevalence rate of B. melitensis was 27.1% (51/188) among aborted animals. For differentiation between vaccine strain and field strain infection, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method using PstI endonuclease enzyme was used. Vaccination with Rev-1 in the last year (OR = 2.92, CI: 1.1–7.7) and grazing at common pasture (OR = 2.78, CI: 1.05–7.36) were statistically significant (P ≤ .05) risk factors positively associated with the occurrence of brucellosis in sheep and goat flocks.