Detection of Brucella canis from inguinal lymph nodes of naturally infected dogs by PCR

Prevalence of Brucella species in stray cattle, dogs and cats: A systematic review

Stray animals are unowned free roaming, homeless, abandoned, street or sheltered animals, particularly dogs, cats and cattle. They could act as carrier of several zoonotic pathogens such as rabies virus, Mycobacterium and Brucella species. However, comprehensive information on the prevalence of zoonotic pathogens in stray animals is very limited. We conducted a systematic review as per Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) 2020 guidelines to estimate the prevalence of brucellosis in stray dogs, cats and cattle. Eligibility criteria for the study were determined using the PECOS classification (population, exposure, comparison, outcome, study design) as a tool to guide the research and adjust the search strategy. Major bibliographic databases [Web of Science, Medline, Scopus, ScienceDirect, Google Scholar and PubMed] were searched using predefined keywords for published epidemiological studies on brucellosis in stray animals (dogs, cats and cattle). Systematic assessments of all the studies since 1990-2022 were conducted and those reporting the prevalence of brucellosis in stray dogs, cats and cattle using appropriate diagnostic tests (culture, molecular, serological) were included. Studies reporting prevalence of brucellosis (Brucella infection or exposure) in kennel dogs, dairy herds, livestock farms, humans or marine species were excluded. The apparent individual test- wise prevalence along with 95% confidence intervals (CI) was estimated using Epitools. Out of 2689 studies, 37 met the inclusion criteria and were included in the systematic review. Of 37 studies, 28 (75.7%) were conducted in stray dogs, 7 (18.9%) in cattle and 2 (5.4%) in cats. Furthermore, only 21.62% studies (8/37) used probabilistic random sampling approaches and 13.51% studies (5/37) explained and justified the study sample size using appropriate methods for estimation of disease prevalence in the study populations. Higher sero-prevalence in stray dogs has been reported in studies conducted in Jordan (38.0% (95% CI: 24.0-54.0) and Pakistan (38.0% (95% CI: 31.0-45.0) whereas no sero-positivity was recorded in the studies conducted in Brazil, North Colombia, Cyprus, South Korea and USA. All studies on brucellosis (n = 7) in stray cattle were from India; conducted in stray cattle reared in cow-shelters. Sero-prevalence in the range of 4.3%- 64.3% was reported in stray cattle. Differences in diagnostic tests and host species, as well as limited number and non-randomized studies and high statistical heterogeneity did not allow us to determine combined meta-analysed prevalence estimates. Stray animals are likely to pose a zoonotic and disease spillover risk to human and livestock populations.

Comparison of BP26, Omp25 and Omp31 and a Multiepitope-Based Fusion Protein in the Serological Detection of Canine Brucellosis

Background

Brucellosis is one of the most important zoonotic diseases in the world. Canine brucellosis, caused mainly by Brucella canis, is seriously neglected, and there is a lack of accurate diagnostic tools.

Methods

In this study, to compare BP26, Omp25, Omp31 and a multiepitope-based fusion protein in the serological detection of canine brucellosis, using 34 brucellosis-positive dog sera and 62 negative control sera, the Brucella outer membrane proteins Omp31, BP26, Omp25 and a multiepitope-based fusion protein were evaluated by iELISA for their potential use as antigens in the serological diagnosis of canine brucellosis.

Results

The results showed that the multiepitope-based fusion protein performed best in distinguishing brucellosis-positive and brucellosis-negative dog sera, with a positive predictive value (PPV) of 100% and a negative predictive value (NPV) of 98.41%. BP26 and Omp31 showed excellent sensitivity in detecting brucellosis-positive dog sera, but their cross reaction to sera infected with Vibrio parahaemolyticus and Listeria monocytogenes may hinder their application as diagnostic reagents. Omp25 lacked sufficient sensitivity and showed limited ability in distinguishing positive and negative dog sera.

Conclusion

The multiepitope-based fusion protein can be used as an ideal antigen for serologically diagnosing canine brucellosis currently prevalent worldwide.

Seroprevalence of Brucella canis in canines from a dog shelter in Bogotá, Colombia

Introduction: The risk of Brucella canis infection in humans and dogs has increased due to the permanent exposure to asymptomatic carrier dogs. In Colombia, there is evidence of B. canis infection in humans living with dogs. In the case of Bogotá, an additional concern is the lack of updated information related to the prevalence of the infection in dogs. Objective: To determine the seroprevalence of infection by B. canis in dogs intended for adoption programs in Bogotá. Materials and methods: By means of a descriptive cross-sectional study carried out in a dog shelter in Bogotá, anti-B. canis IgG antibodies were detected in the serum from 51 dogs 28 females and 23 males) using a lateral-flow immunochromatographic test. Additionally, seropositive animals were analyzed with PCR to detect Brucella spp DNA. Results: Brucella canis seroprevalence was 1.96% (1/51). The seropositive dog was an asymptomatic three-year-old she-dog in which no bacteria DNA was detected in the blood through PCR. Conclusions: The seroprevalence determined in this study represented by a single dog with anti-B. canis IgG can be considered a potential risk both for canine and human populations since this single dog could have a persistent infection capable of spreading the bacteria.

Canine Brucellosis: An Update

Canine brucellosis is an infectious and zoonotic disease caused by Brucella canis, which has been reported worldwide, and is a major public health concern due to close contact between dogs and humans. In dogs, canine brucellosis manifests with abortion outbreaks, reproductive failure, enlargement of lymph nodes, and occasionally affects the osteoarticular system, although the occurrence of asymptomatic infections in dogs are not uncommon. In humans, the disease is associated with a febrile syndrome, commonly with non-specific symptoms including splenomegaly, fatigue, and weakness. Infection of dogs occurs mostly by the oronasal route when in contact with contaminated tissues such as aborted fetuses, semen, urine, and vaginal secretions. In humans, contact with contaminated fluids from infected dogs is an important source of infection, and it is an occupational risk for veterinarians, breeders, laboratory workers, among other professionals who deal with infected animals or biological samples. The diagnosis in dogs is largely based on serologic methods. However, serologic diagnosis of canine brucellosis remains very challenging due to the low accuracy of available tests. Molecular diagnostic methods have been increasingly used in the past few years. Treatment of infected dogs is associated with a high frequency of relapse, and should be employed only in selected cases. Currently there are no commercially available vaccines for prevention of canine brucellosis. Therefore, development of novel and improved diagnostic methods as well as the development of efficacious and safe vaccination protocols are needed for an effective control of canine brucellosis and its associated zoonotic risk.

Characterization of epididymal and testicular histologic lesions and use of immunohistochemistry and PCR on formalin-fixed tissues to detect Brucella canis in male dogs

In male dogs, Brucella canis frequently causes epididymitis, ultimately resulting in testicular atrophy and infertility. Although B. canis predominantly affects the epididymis, the misleading term "orchitis" is still commonly used by clinicians. Of additional concern, diagnosis in dogs remains challenging because of variable sensitivity and specificity of serologic assays and fluctuations in bacteremia levels in infected dogs, reducing the sensitivity of blood culture. We describe here the histologic lesions in the scrotal contents of 8 dogs suspected of being infected with B. canis and clinically diagnosed with orchitis. We explored the possibility of using immunohistochemistry (IHC) and real-time PCR (rtPCR) in formalin-fixed, paraffin-embedded (FFPE) tissues to detect the presence of B. canis. Epididymitis of variable chronicity was identified in all 8 dogs, with only 3 also exhibiting orchitis. Using rtPCR, the presence of B. canis was identified in 4 of 8 dogs, with 3 of these 4 dogs also positive by IHC. These results suggest that rtPCR and IHC are promising techniques that can be used in FFPE tissues to detect B. canis when other detection techniques are unavailable. Additionally, accurate recognition of epididymitis rather than orchitis in suspect cases could aid in accurate diagnosis.

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.

Comparison of three methods for recovery of Brucella canis DNA from canine blood samples

Brucella canis, a gram-negative, facultative intracellular and zoonotic bacterium causes canine brucellosis. Direct methods are the most appropriate for the detection of canine brucellosis and bacterial isolation from blood samples has been employed as gold-standard method. However, due to the delay in obtaining results and the biological risk of the bacterial culturing, the polymerase chain reaction (PCR) has been successfully used as an alternative method for the diagnosis of the infection. Sample preparation is a key step for successful PCR and protocols that provide high DNA yield and purity are recommended to ensure high diagnostic sensitivity. The objective of this study was to evaluate the performance of PCR for the diagnosis of B. canis infection in 36 dogs by testing DNA of whole blood obtained through different extraction and purification protocols. Methods 1 and 2 were based on a commercial kit, using protocols recommended for DNA purification of whole blood and tissue samples, respectively. Method 3 was an in-house method based on enzymatic lysis and purification using organic solvents. The results of the PCR on samples obtained through three different DNA extraction protocols were compared to the blood culture. Of the 36 dogs, 13 (36.1%) were positive by blood culturing, while nine (25.0%), 14 (38.8%), and 15 (41.6%) were positive by PCR after DNA extraction using methods 1, 2 and 3, respectively. PCR performed on DNA purified by Method 2 was as efficient as blood culturing and PCR performed on DNA purified with in-house method, but had the advantage of being less laborious and, therefore, a suitable alternative for the direct B. canis detection in dogs.

The first case of Brucella canis in Sweden: background, case report and recommendations from a northern European perspective

Infection with Brucella canis has been diagnosed in Sweden for the first time. It was diagnosed in a three-year-old breeding bitch with reproductive disturbances. Fifteen in-contact dogs were tested repeatedly and all of them were negative for B. canis. The source of infection could not be defined. The present article describes the case and the measures undertaken and gives a short review over B. canis. Recommendations on how to avoid the infection in non-endemic countries are given.