Human exposures to Brucella canis from a pregnant dog during an international flight: Public health risks, diagnostic challenges and future considerations

AIMS

This report documents the exposure of passengers and crew of a commercial international flight to the zoonotic pathogen Brucella canis after an infected dog aborted in the passenger cabin of the aircraft. This case demonstrates the challenges associated with brucellosis screening and the risks that airline personnel, airport employees and travellers face when animals with unrecognized zoonotic infections are transported.

METHODS/RESULTS

The public health investigation of this case was conducted by the Centers for Disease Control, the Illinois Department of Health and the Illinois Department of Agriculture, in collaboration with a local veterinary clinic and several academic and federal diagnostic laboratories. It included an extensive diagnostic evaluation of the dam and aborted foetuses to confirm a diagnosis of canine brucellosis. Passengers, airline personnel and staff from the veterinary clinic where the dogs were treated underwent risk assessments, and clinic staff also received detailed guidance regarding infection prevention practices.

CONCLUSIONS

Animal shelters and breeding programs are recommended to screen dogs routinely for brucellosis, but it is not unusual for domestic or imported animals to have unknown health histories, including the dog's brucellosis status, at the time of purchase, adoption, or re-homing. Testing recommendations and requirements vary by state, making it challenging for state public health and animal health agencies to monitor and respond appropriately. This case highlights the importance of Brucella spp. screening in sexually intact dogs prior to breeding, purchase, or domestic or international transportation of the dogs. The transportation of pregnant dogs may present a previously unrecognized public health threat in addition to contributing to unnecessary stress and health risks for pregnant animals.

Global Estimate of Human Brucellosis Incidence

Brucellosis is a major public health concern worldwide, especially for persons living in resource-limited settings. Historically, an evidence-based estimate of the global annual incidence of human cases has been elusive. We used international public health data to fill this information gap through application of risk metrics to worldwide and regional at-risk populations. We performed estimations using 3 statistical models (weighted average interpolation, bootstrap resampling, and Bayesian inference) and considered missing information. An evidence-based conservative estimate of the annual global incidence is 2.1 million, significantly higher than was previously assumed. Our models indicate Africa and Asia sustain most of the global risk and cases, although areas within the Americas and Europe remain of concern. This study reveals that disease risk and incidence are higher than previously suggested and lie mainly within resource-limited settings. Clarification of both misdiagnosis and underdiagnosis is required because those factors will amplify case estimates.

Intratracheal inoculation results in Brucella-associated reproductive disease in male mouse and guinea pig models of infection

Brucella species are considered a significant cause of reproductive pathology in male and female animals. Importantly, Brucella melitensis can induce reproductive disease in humans. Reproductive pathogenesis and evaluation of newly developed countermeasures against brucellosis studies have traditionally utilized female animal models. However, any potential, new intervention for use in humans would need to be evaluated in both sexes. Therefore, animal models for male reproductive brucellosis are desperately needed to understand disease progression. Accordingly, we evaluated guinea pigs and mice using B. melitensis 16 M in an intratracheal model of inoculation at different stages of infection (peracute, acute, and chronic) with an emphasis on determining the effect to the male reproductive organs. Aerosol inoculation resulted in colonization of the reproductive organs (testicle, epididymis, prostate) in both species. Infection peaked during the peracute (1-week post-infection [p.i.]) and acute (2-weeks p.i.) stages of infection in the mouse in spleen, epididymis, prostate, and testicle, but colonization was poorly associated with inflammation. In the guinea pig, peak infection was during the acute stage (4-weeks p.i.) and resulted in inflammation that disrupted spermatogenesis chronically. To determine if vaccine efficacy could be evaluated using these models, males were vaccinated using subcutaneous injection with vaccine candidate 16 MΔvjbR at 109 CFU/100 μl followed by intratracheal challenge with 16 M at 107. Interestingly, vaccination efficacy varied between species and reproductive organs demonstrating the value of evaluating vaccine candidates in multiple models and sexes. Vaccination resulted in a significant reduction in colonization in the mouse, but this could not be correlated with a decrease in inflammation. Due to the ability to evaluate for both colonization and inflammation, guinea pigs seemed the better model not only for assessing host-pathogen interactions but also for future vaccine development efforts.

Primary and memory immune responses against rough Brucella canis are less robust compared to smooth B. abortus and B. melitensis following intratracheal infection in mice

Brucella canis is the cause of canine brucellosis, a globally distributed, zoonotic pathogen which primarily causes disease in dogs. B. canis is unique amongst the zoonotic Brucella spp. with its rough lipopolysaccharide, a trait typically associated with attenuation in gram-negative bacteria. Unfortunately, no vaccine is available against B. canis, and vaccine development is hampered by a limited understanding of the immune response required to combat it and the course of infection following a physiologically relevant, mucosal route of inoculation. To address these concerns and analyze the impact of the rough phenotype on the immune response, we infected mice intratracheally with rough B. canis or smooth B. melitensis or B. abortus. Bacterial colonization and histologic lesions were assessed in systemic target organs as well as locally in the lungs and draining mediastinal lymph node. Mice were also reinfected with Brucella following antibiotic treatment and cytokine production by T lymphocytes in the lung and spleen was assessed by flow cytometry to investigate the memory immune response. Despite its rough phenotype, B. canis established a persistent infection at the same level of colonization as the smooth strains. However, B. canis induced significantly less granulomatous inflammation in the spleen as well as a lack of bronchial-associated lymphoid tissue (BALT) hyperplasia in the lungs. These differences coincided with increased IL-10 and decreased IFN-γ in the spleen of B. canis-infected mice. Previous exposure to all Brucella strains provided protection against colonization following secondary challenge, although induction of IFN-γ by T lymphocytes was seen only in the lungs during B. canis infection while the smooth strains induced this cytokine in the spleen as well. Neither Brucella strain induced significant polyfunctional T lymphocytes, a potential immunomodulatory mechanism that appears to be independent of lipopolysaccharide phenotype.

AgSecure Africa ProgrammeTM: A Blended Training Approach for Africa

An innovative training program entitled "AgSecure Africa Programme^TM" was developed in partnership with the South African Agricultural Research Council-Onderstepoort Veterinary Research (ARC-OVR) to train veterinarians, animal health technicians, researchers and laboratory personnel. Three blended courses consisting of both virtual and in-person delivery were provided with the intent of contributing to the better prevention, detection and control of infectious diseases of livestock and poultry of significant importance for the region with a strong emphasis on transboundary animal diseases. A "train the trainer" model of instruction was employed to equip participants with the ability to train and share knowledge with colleagues and small-holder farmers in their various communities and regions. The design of this program was to increase the capacity of veterinarians and veterinary diagnosticians to safely and accurately diagnose infectious livestock diseases and to also empower small-holder farmers with the knowledge needed to safely and securely manage their livestock and be a first line defense in the prevention and control of infectious livestock diseases. Quantitative and qualitative evaluations were used to measure the impact of the trainings which revealed significant increases in knowledge gains. Course materials were submitted and approved for accreditation by the South African Veterinary Council (SAVC) becoming the first international training program to achieve this. Approval of these courses led to licensed veterinarians and animal health technicians being awarded continuing professional development credits upon their successful completion of courses. A larger goal was to build training capacity, not only for South Africa, but also for the region.

When the Going Gets Rough: The Significance of Brucella Lipopolysaccharide Phenotype in Host-Pathogen Interactions

Brucella is a facultatively intracellular bacterial pathogen and the cause of worldwide zoonotic infections, infamous for its ability to evade the immune system and persist chronically within host cells. Despite the frequent association with attenuation in other Gram-negative bacteria, a rough lipopolysaccharide phenotype is retained by Brucella canis and Brucella ovis, which remain fully virulent in their natural canine and ovine hosts, respectively. While these natural rough strains lack the O-polysaccharide they, like their smooth counterparts, are able to evade and manipulate the host immune system by exhibiting low endotoxic activity, resisting destruction by complement and antimicrobial peptides, entering and trafficking within host cells along a similar pathway, and interfering with MHC-II antigen presentation. B. canis and B. ovis appear to have compensated for their roughness by alterations to their outer membrane, especially in regards to outer membrane proteins. B. canis, in particular, also shows evidence of being less proinflammatory in vivo, suggesting that the rough phenotype may be associated with an enhanced level of stealth that could allow these pathogens to persist for longer periods of time undetected. Nevertheless, much additional work is required to understand the correlates of immune protection against the natural rough Brucella spp., a critical step toward development of much-needed vaccines. This review will highlight the significance of rough lipopolysaccharide in the context of both natural disease and host–pathogen interactions with an emphasis on natural rough Brucella spp. and the implications for vaccine development.

Bench to Shop™: An Interdisciplinary Training Program for Transitioning of Transboundary Animal Disease Research to Commercialization

Transboundary animal diseases (TADs) are livestock diseases characterized as highly contagious, fast-spreading, and capable of producing high morbidity and mortality. Accidental or intentional introduction of these diseases into the United States could devastate the economy, food security, and public health. Training of researchers, scientists and animal health workers is often limited to prevention and diagnosis with little emphasis on the importance of translating knowledge to the development of new products for the prevention, detection and control of outbreaks. The Bench to Shop™ training program was developed to fill this gap and applied an innovative blended-learning method through the use of an online platform, a 3-week experiential training, and a 1-month follow-up project. The program specifically targeted next-generation researchers, including PhD students, post-doctoral researchers, and early-career faculty. A total of 17 trainees, in two cohorts, were selected through a national and international recruitment process. Program evaluation consisted of focus groups, follow-up interviews, and pre- and post-tests of didactic material, revealing statistically significant gains in knowledge. Participants expanded their professional networks with leaders in industry and regulatory agencies related to production and/or commercialization of TAD products and deepened their commitment toward keeping our country safe from TADs. Post-program impacts on trainees included advancing products toward commercialization, partnering with connections made through the program, and demonstrating dedication to homeland security by pursuing product development related educational and career opportunities. Overall, results suggest this program provides an added value and should be readily available to the current and future workforce.

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.

Porcine Babesiosis Caused by Babesia sp. Suis in a Pot-Bellied Pig in South Africa

Babesiosis is a worldwide, tick-borne disease of economic importance in livestock caused by Babesia spp., which are hemoparasitic piroplasms that target the host erythrocytes. Cattle, dogs, small ruminants, and wild ruminants are the species most commonly affected, while in cats, horses, and pigs, it is less frequently reported. Although babesiosis has been observed worldwide, porcine babesiosis remains an uncommon disease with a very limited number of cases reported. Here, we describe a case in a 12-year old pot-bellied pig from South Africa that died after a history of anorexia and reluctance to rise for 2 days. A complete necropsy, blood smear cytology, reverse line blot (RLB) hybridization and 18S rRNA sequencing were performed. Numerous Babesia spp. hemoparasites and a moderate regenerative anemia were identified on blood smear, and a urine dipstick test yielded 4+ heme. Diffuse icterus and splenomegaly were observed upon gross examination. Histopathology revealed hemoglobin casts within renal tubules and collecting ducts, pulmonary edema, splenic congestion, and intrahepatic cholestasis. BLASTN homology of the 18SrRNA sequence revealed a 100% identity to the published sequence of Babesia sp. Suis isolated from pigs in Italy. This case of babesiosis in a pig highlights the clinical manifestations and gross and pathological findings of porcine babesiosis.

Brucella abortus and Pregnancy in Mice: Impact of Chronic Infection on Fertility and the Role of Regulatory T Cells in Tissue Colonization

Stealthy intracellular bacterial pathogens are known to establish persistent and sometimes lifelong infections. Some of these pathogens also have a tropism for the reproductive system, thereby increasing the risk of reproductive disease and infertility. To date, the pathogenic mechanism involved remains poorly understood. Here, we demonstrate that Brucella abortus, a notorious reproductive pathogen, has the ability to infect the nonpregnant uterus, sustain infection, and induce inflammatory changes during both acute and chronic stages of infection. In addition, we demonstrated that chronically infected mice had a significantly reduced number of pregnancies compared to naive controls. To investigate the immunologic mechanism responsible for uterine tropism, we explored the role of regulatory T cells (Tregs) in the pathogenesis of Brucella abortus infection. We show that highly suppressive CD4+FOXP3+TNFR2+ Tregs contribute to the persistence of Brucella abortus infection and that inactivation of Tregs with tumor necrosis factor receptor II (TNFR2) antagonistic antibody protected mice by significantly reducing bacterial burden both systemically and within reproductive tissues. These findings support a critical role of Tregs in the pathogenesis of persistence induced by intracellular bacterial pathogens, including B. abortus Results from this study indicate that adverse reproductive outcomes can occur as sequelae of chronic infection in nonpregnant animals and that fine-tuning Treg activity may provide novel immunotherapeutic and prevention strategies against intracellular bacterial infections such as brucellosis.

Intratracheal Inoculation with Brucella melitensis in the Pregnant Guinea Pig Is an Improved Model for Reproductive Pathogenesis and Vaccine Studies

Reproductive failure is the hallmark of brucellosis in animals. An uncommon but important complication in pregnant women who become acutely infected with Brucella melitensis is spontaneous pregnancy loss or vertical transmission to the fetus. Unfortunately, the mechanism behind reproductive failure is still obscure, partially due to the lack of a proper study model. Recently, it was demonstrated that intratracheal (IT) inoculation of nonpregnant guinea pigs would replicate features of clinical disease in humans. To determine if IT inoculation would induce reproductive disease, guinea pigs were infected at mid-gestation and monitored daily for fever and abortions. Fever developed between day 14 to 18 postinoculation, and by 3 weeks postinoculation, 75% of pregnant guinea pigs experienced stillbirths or spontaneous abortions mimicking natural disease. Next, to investigate the guinea pig as a model for evaluating vaccine efficacy during pregnancy, nonpregnant guinea pigs were vaccinated with S19, 16MΔvjbR + Quil-A, or 100 μl PBS + Quil-A (as control). Guinea pigs were bred and vaccinated guinea pigs were challenged at mid-gestation with B. melitensis IT inoculation and monitored for fever and abortions. Vaccination with both vaccines prevented fever and protected against abortion. Together, this study indicates that pregnant guinea pigs are an appropriate animal model to study reproductive disease and offer an improved model to evaluate the ability of vaccine candidates to protect against a serious manifestation of disease.

Brucellosis in the Middle East: Current situation and a pathway forward

Brucellosis is a bacterial endemic zoonotic disease of global significance with detrimental impacts on public health and food animal production. It is caused by Brucella spp., an expanding group of pathogens able to infect various host species. Bovines and small ruminants, which excrete the bacteria in milk and in reproductive discharges, are major sources of infection for humans and other animals. Contact with contaminated animals and consumption of unpasteurized dairy products are the main routes for human infection. In spite of the considerable progress of knowledge gained and success achieved in brucellosis control in the developed world, this disease continues to be an important burden in the Middle East (ME). Common risk factors implicated in the difficulty and complexity of brucellosis control within the region include (1) social and political instabilities; (2) insufficient resources and infrastructure for appropriate diagnosis, reporting, and implementation of control measures; (3) variation of livestock husbandry systems and their commingling with other livestock and wildlife; and (4) traditional cultural practices, including consumption of unpasteurized dairy products. Development of core interdisciplinary competencies is required for a true One Health–based endeavor against the disease. National awareness and educational programs addressing all population sectors from consumers to decision-makers seem to be the next logical, sustainable, and economically viable approach toward improving disease status in this region. In the present review, we describe the current situation of brucellosis in the ME, focusing on the major limitations and shortcomings regarding disease control. We propose a regional approach toward public awareness of brucellosis as the first step in mitigating the disease and discuss the potential benefits, and components of such a strategy, which can further be used as a model for other endemic zoonotic diseases.

Evaluation of the Efficacy of the Brucella canis RM6/66 ΔvjbR Vaccine Candidate for Protection against B. canis Infection in Mice

Brucella canis is a Gram-negative, facultative intracellular bacterium and the causative agent of canine brucellosis, a highly contagious disease of dogs that can be transmitted to humans. Unfortunately, no vaccine is available to prevent infection. We recently characterized the kinetics of B. canis infection in the mouse model, establishing the required dose necessary to achieve systemic infection. The objective of this study was to investigate the utility of the mouse model in assessing canine brucellosis vaccine candidates and to subsequently investigate the safety and efficacy of a live attenuated vaccine, the B. canis RM6/66 ΔvjbR strain. Mice vaccinated with a dose of 109 CFU of the vaccine strain by both intraperitoneal and subcutaneous routes were afforded significant protection against organ colonization and development of histopathologic lesions following intraperitoneal challenge. Addition of an adjuvant or a booster dose 2 weeks following initial vaccination did not alter protection levels. Vaccination also resulted in a robust humoral immune response in mice, and B. canis RM6/66 ΔvjbR was capable of activating canine dendritic cells in vitro These data demonstrate that the B. canis RM6/66 ΔvjbR strain shows promise as a vaccine for canine brucellosis and validates the mouse model for future vaccine efficacy studies.IMPORTANCE Canine brucellosis, caused by Brucella canis, is the primary cause of reproductive failure in dogs and represents a public health concern due to its zoonotic nature. Cases in dogs in the United States have been increasing due to the persistent nature of the bacterium, deficiencies in current diagnostic testing, and, most importantly, the lack of a protective vaccine. Current estimates place the seroprevalence of B. canis in the southern United States at 7% to 8%, but with the unprecedented rates of animals moving across state and international borders and the lack of federal regulations in regard to testing, the true seroprevalence of B. canis in the United States may very well be higher. Vaccination represents the most effective method of brucellosis control and, in response to the demand for a vaccine against B. canis, we have developed the live attenuated B. canis RM6/66 ΔvjbR vaccine strain capable of protecting mice against challenge.

Building the Evidence Base for the Prevention of Raw Milk-Acquired Brucellosis: A Systematic Review

Background: The scientific evidence of the health risks associated with the consumption of raw milk has been known for a long time. However, less clear is the impact of acquiring infectious diseases from raw milk consumption in the United States (US) due to incomplete reporting of cases and the complex factors associated with the sale and consumption of raw milk. Investigations of this current study focused on human brucellosis, one of the infectious diseases commonly acquired through the consumption of raw milk and milk products, and which continues to be a public health threat worldwide.

Methodology: A qualitative systematic review of the sources of opinions that contribute to the increased trend of raw milk sales and consumption in the US was conducted.

Results: Interestingly, opinions about the sale of raw milk and/or the benefits arising from its consumption varied by US region, with the proportion of messages supporting raw milk consumption being highest in the Northeast compared to other US regions. Several evidence gaps and factors that possibly contribute to the increased prevalence of raw milk-acquired brucellosis were identified including inadequate monitoring of the raw milk sales process and lack of approved diagnostic methods for validating the safety of raw milk for human consumption.

Conclusions: The unavailability of data specifying brucellosis cases acquired from raw milk consumption have precluded the direct association between raw milk and increased brucellosis prevalence in the United States. Nevertheless, the evidence gaps identified in this study demonstrate the need for intensified surveillance of raw-milk acquired infectious diseases including human brucellosis; establishment of safety and quality control measures for the process of selling raw milk; and design of an effective strategy for the prevention of raw milk-acquired infectious diseases including brucellosis. Overall, for the first time, this study has not only shown the gaps in evidence that require future investigations, but also, variations in the perception of raw milk consumption that may impact disease acquisition in different US regions.

Immersion Foot Syndrome in 6 Equids Exposed to Hurricane Floodwaters

Prolonged exposure to water, known as immersion foot syndrome in humans, is a phenomenon first described in soldiers during World War I and characterized by dermal ischemic necrosis. In this report, we describe the pathologic findings of a condition resembling immersion foot syndrome in 5 horses and 1 donkey with prolonged floodwater exposure during Hurricane Harvey. At necropsy, all animals had dermal defects ventral to a sharply demarcated "water line" along the lateral trunk. In 5 animals, histologic examination revealed moderate to severe perivascular dermatitis with vasculitis and coagulative necrosis consistent with ischemia. The severity of the lesions progressed from ventral trunk to distal limbs and became more pronounced in the chronic cases. The pathophysiology of immersion foot syndrome is multifactorial and results from changes in the dermal microvasculature leading to thrombosis and ischemia. Prompt recognition of this disease may lead to appropriate patient management and decreased morbidity.

Vaccine safety studies of Brucella abortus S19 and S19ΔvjbR in pregnant swine

Brucellosis in swine is caused by Brucella suis, a bacterial infection of nearly worldwide distribution. Brucella suis is also transmissible to humans, dogs and cattle and is considered a reemerging disease of public health concern. To date, there is no effective vaccine for swine. This prompted us to investigate the potential use of the commercially available vaccine for cattle or the live attenuated vaccine candidate S19ΔvjbR. As the first step, we sought to study the safety of the vaccine candidates when administered in pregnant sows, since one of the major drawbacks associated with vaccination using Live Attenuated Vaccines (LAV) is the induction of abortions when administered in pregnant animals. Fifteen pregnant gilts at mid-gestation were divided into four groups and subsequently vaccinated subcutaneously using different formulations containing 2.0 ± 0.508 × 109 CFU of either S19 or S19ΔvjbR. Vaccination in pregnant animals with the vaccine candidates did not induce abortion, stillbirths or a reduction in litter size. Multiple tissues in the gilts and piglets were examined at the time of delivery to assess bacterial colonization and histopathological changes. There was no evidence of vaccine persistence in the gilts or bacterial colonization in the fetuses. Altogether, these data suggest that both vaccine candidates are safe for use in pregnant swine. Analysis of the humoral responses, specifically anti-Brucella IgG levels measured in serum, demonstrated a robust response induced by either vaccine, but of shorter duration (4-6 weeks post-inoculation) compared to that observed in cattle or experimentally infected mice. Such a transient humoral response may prove to be beneficial in cases where the vaccine is used in eradication campaigns and in the differentiation of vaccinated from infected animals. This study provides evidence to support future efficacy studies of both vaccine candidates in swine.

Brucellosis in Colombia: Current Status and Challenges in the Control of an Endemic Disease

Brucellosis is a zoonosis of nearly worldwide distribution. The disease is considered to be endemic in most of the developing countries with a substantial impact on both human and animal health as well as on the economy. The aim of this scoping review is to provide an overview of the brucellosis status in Colombia and the factors associated with its persistence, to highlight the strengths and gaps of the adopted countermeasures and to supply evidence to policy-makers on the best approaches to mitigate the disease burden. Due to the presence of brucellosis in several susceptible production livestock systems scattered throughout the country, a plan for its control, prevention and eradication was established almost 20 years ago. However, despite extensive efforts, brucellosis prevalence has fluctuated over the years without any trend of decreasing. The restricted budget allocated for brucellosis control is a limiting factor for the success of the program. For instance, the absence of indemnities for farmers results in infected animals remaining on farms which potentially increases the risk of disease spread. Likewise, disease surveillance is restricted to Brucella abortus and excludes other Brucella species of importance, such as B. melitensis and B. suis. The countermeasures are mostly focused on cattle and only a few actions are in place for the management of brucellosis in other livestock species. In humans, cases of brucellosis are annually diagnosed, although the disease remains highly underreported. High impact educational and training programs are required to address the disease in a comprehensive manner, including vulnerable groups, such as traditional smallholders and low-productivity regions, as well as other stakeholders, such as healthcare and veterinary authorities. Important financial investments based on sustained cooperation between governmental institutions, industry, and farmers are important for developing affordable and effective strategies to control the disease.

Characterization of Brucella canis infection in mice

Canine brucellosis, caused by Brucella canis, is a disease of dogs and represents a public health concern as it can be transmitted to humans. Canine brucellosis is on the rise in the United States and there is currently no vaccine for use in dogs. Mice have been extensively utilized to investigate host-pathogen interactions and vaccine candidates for smooth Brucella species and could serve a similar role for studying B. canis. However, comparatively little is known about B. canis infection in mice. The objective of this study was to characterize the kinetics of colonization and pathogenicity of B. canis in mice in order to evaluate the mouse as a model for studying this pathogen. C57BL/6 mice were inoculated intraperitoneally with 105, 107, or 109 CFU of Brucella canis RM6/66 and euthanized 1-, 2-, 4-, 6-, 9-, and 12-weeks post-inoculation. B. canis induced splenomegaly in mice infected with 109 CFU at 1- and 2 weeks post-inoculation while no gross lesions were observed in other dose groups. Infection at the two higher doses resulted in dose-dependent granulomatous hepatitis and histiocytic infiltration of the spleen and mesenteric lymph nodes by 1-2 weeks. B. canis was cultured from the liver, spleen, uterus, bone marrow, lung, and kidney in all groups with colonization declining at a slow but steady rate throughout the experiment. Clearance was achieved by 9 weeks 105 CFU group and by 12 weeks in the 107 CFU group, while B. canis persisted in the spleen until 12 weeks in the highest dose group. Although B. canis does not demonstrate significant replication in C57BL/6 mice, it has the ability to establish an infection, induce splenomegaly, and persist for several weeks in multiple organs. Moreover, 1 x 107 CFU appears to be a suitable challenge dose for investigating vaccine safety.

Correction: Characterization of an intratracheal aerosol challenge model of Brucella melitensis in guinea pigs

[This corrects the article DOI: 10.1371/journal.pone.0212457.].

Brucellosis in Dogs and Public Health Risk

Brucella canis infects dogs and humans. In dogs, it can cause reproductive failure; in humans, it can cause fever, chills, malaise, peripheral lymphadenomegaly, and splenomegaly. B. canis infection in dogs is underrecognized. After evaluating serologic data, transmission patterns, and regulations in the context of brucellosis in dogs as an underrecognized zoonosis, we concluded that brucellosis in dogs remains endemic to many parts of the world and will probably remain a threat to human health and animal welfare unless stronger intervention measures are implemented. A first step for limiting disease spread would be implementation of mandatory testing of dogs before interstate or international movement.

Characterization of an intratracheal aerosol challenge model of Brucella melitensis in guinea pigs

B. melitensis is considered the most virulent of the Brucella species, and a need exists for an improved laboratory animal model of infection that mimics natural transmission and disease. Guinea pigs are highly susceptible to infection with Brucella spp. and develop a disease syndrome that mimics natural disease after aerosol inoculation. Intratracheal inoculation is a targeted means of generating aerosols that offer advantages over aerosol chamber delivery. To establish this delivery method, female, Hartley guinea pigs were infected via intratracheal inoculation with PBS or 16M B. melitensis at low dose (101 to 103) or high dose (106 to 108) and monitored for 30 days for signs of disease. Guinea pigs in the high dose groups developed fever between 12-17 days post-inoculation. Bacteria were recovered from the spleen, liver, lymph nodes, lung, and uterus at 30-days post-inoculation and demonstrated dose dependent mean increases in colonization and pathologic changes consistent with human brucellosis. To study the kinetics of extrapulmonary dissemination, guinea pigs were inoculated with 107 CFU and euthanized at 2-hours post inoculation and at weekly intervals for 3 weeks. 5.8x105 to 4.2x106 CFU were recovered from the lung 2 hours post-inoculation indicating intratracheal inoculation is an efficient means of infecting guinea pigs. Starting at 1-week post inoculation bacteria were recovered from the aforementioned organs with time dependent mean increases in colonization. This data demonstrates that guinea pigs develop a disease syndrome that models the human manifestation of brucellosis, which makes the guinea pig a valuable model for pathogenesis studies.

A systematic review and meta-analysis of the prevalence of osteoarticular brucellosis

BACKGROUND

Infection of bones and joints remains one of the most commonly described complications of brucellosis in humans and is predominantly reported in all ages and sexes in high-risk regions, such as the Middle East, Asia, South and Central America, and Africa. We aimed to systematically review the literature and perform a meta-analysis to estimate the global prevalence of osteoarticular brucellosis (OAB).

METHODOLOGY

Major bibliographic databases were searched using keywords and suitable combinations. All studies reporting the incidence and clinical manifestations of osteoarticular brucellosis in humans, and demonstrated by two or more diagnostic methods (bacteriological, molecular, serological, and/or radiographic) were included. Random model was used, and statistical significance was set at 0.05.

PRINCIPAL FINDINGS

A total of 56 studies met the inclusion criteria and were included in the systematic review and meta-analysis. There was an evidence of geographical variation in the prevalence of osteoarticular disease with estimates ranging from 27% in low-risk regions to 36% in high-risk regions. However, the difference was not significant. Thus, brucellosis patients have at least a 27% chance of developing osteoarticular disease.

CONCLUSIONS

The prevalence of OAB is not dependent on the endemicity of brucellosis in a particular region. Hence, further research should investigate the potential mechanisms of OAB, as well as the influence of age, gender, and other socioeconomic factor variations in its global prevalence, as this may provide insight into associated exposure risks and management of the disease.

A Neglected Animal Model for a Neglected Disease: Guinea Pigs and the Search for an Improved Animal Model for Human Brucellosis

Brucellosis is a bacterial disease caused by species of the Brucella genus and affects a wide variety of domestic and wildlife species and is also an important zoonosis. The global burden of disease is difficult to assess but Brucella spp. have a worldwide distribution and are endemic in the Middle East, Africa, South America, and Asia. The clinical signs of fever and malaise are non-specific, and the available serological diagnostic tests lack a high degree specificity in endemic regions compared to other important public health diseases such as malaria. A better understanding of the pathogenesis of brucellosis through discoveries in animal models could lead to improved diagnostics and potentially a vaccine for human use. Mouse models have played an important role in elucidating the pathogenesis but do not replicate key features of the disease such as fever. Guinea pigs were instrumental in exploring the pathogenesis of brucellosis in the early nineteenth century and could offer an improvement on the mouse model as a model for human brucellosis.

Brucellosis remains a neglected disease in the developing world: a call for interdisciplinary action

BACKGROUND

Brucellosis is an endemic zoonotic disease in most of the developing world that causes devastating losses to the livestock industry and small-scale livestock holders. Infected animals exhibit clinical signs that are of economic significance to stakeholders and include reduced fertility, abortion, poor weight gain, lost draught power, and a substantial decline in milk production. In humans, brucellosis typically manifests as a variety of non-specific clinical signs. Chronicity and recurring febrile conditions, as well as devastating complications in pregnant women are common sequelae.

DISCUSSION

In regions where the disease is endemic, brucellosis has far-reaching and deleterious effects on humans and animals alike. Deeply entrenched social misconceptions and fear of government intervention contribute to this disease continuing to smolder unchecked in most of the developing world, thereby limiting economic growth and inhibiting access to international markets. The losses in livestock productivity compromise food security and lead to shifts in the cognitive competency of the working generation, influence the propagation of gender inequality, and cause profound emotional suffering in farmers whose herds are affected. The acute and chronic symptoms of the disease in humans can result in a significant loss of workdays and a decline in the socioeconomic status of infected persons and their families from the associated loss of income. The burden of the disease to society includes significant human healthcare costs for diagnosis and treatment, and non-healthcare costs such as public education efforts to reduce disease transmission.

CONCLUSION

Brucellosis places significant burdens on the human healthcare system and limits the economic growth of individuals, communities, and nations where such development is especially important to diminish the prevalence of poverty. The implementation of public policy focused on mitigating the socioeconomic effects of brucellosis in human and animal populations is desperately needed. When developing a plan to mitigate the associated consequences, it is vital to consider both the abstract and quantifiable effects. This requires an interdisciplinary and collaborative, or One Health, approach that consists of public education, the development of an infrastructure for disease surveillance and reporting in both veterinary and medical fields, and campaigns for control in livestock and wildlife species.

Caprine brucellosis: A historically neglected disease with significant impact on public health

Caprine brucellosis is a chronic infectious disease caused by the gram-negative cocci-bacillus Brucella melitensis. Middle- to late-term abortion, stillbirths, and the delivery of weak offspring are the characteristic clinical signs of the disease that is associated with an extensive negative impact in a flock's productivity. B. melitensis is also the most virulent Brucella species for humans, responsible for a severely debilitating and disabling illness that results in high morbidity with intermittent fever, chills, sweats, weakness, myalgia, abortion, osteoarticular complications, endocarditis, depression, anorexia, and low mortality. Historical observations indicate that goats have been the hosts of B. melitensis for centuries; but around 1905, the Greek physician Themistokles Zammit was able to build the epidemiological link between "Malta fever" and the consumption of goat milk. While the disease has been successfully managed in most industrialized countries, it remains a significant burden on goat and human health in the Mediterranean region, the Middle East, Central and Southeast Asia (including India and China), sub-Saharan Africa, and certain areas in Latin America, where approximately 3.5 billion people live at risk. In this review, we describe a historical evolution of the disease, highlight the current worldwide distribution, and estimate (by simple formula) the approximate costs of brucellosis outbreaks to meat- and milk-producing farms and the economic losses associated with the disease in humans. Successful control leading to eradication of caprine brucellosis in the developing world will require a coordinated Global One Health approach involving active involvement of human and animal health efforts to enhance public health and improve livestock productivity.

Identification of Brucella spp. in feral swine (Sus scrofa) at abattoirs in Texas, USA

Various tissues, nasal swabs, urine and blood samples were collected from 376 feral swine at two federally inspected abattoirs in Texas during six separate sampling periods in 2015. Samples were tested for Brucella spp. by culture and serology. Brucella spp. were cultured from 13.0% of feral swine, and antibodies were detected in 9.8%. Only 32.7% of culture-positive feral swine were also antibody positive, and 43.2% of antibody-positive feral swine were culture positive. Approximately, the same number of males (14.0%) and females (12.1%) were culture positive, and slightly more males (10.5%) than females (8.7%) were antibody positive. Our results indicate that serology likely underestimates the prevalence of feral swine infected, and that those who come in contact with feral swine should be aware of the symptoms of infection with Brucella spp. to ensure prompt treatment.

Human Brucellosis and Adverse Pregnancy Outcomes

Purpose of Review

Brucellosis is a neglected, zoonotic disease of nearly worldwide distribution. Despite brucellosis being recognized as a reproductive disease in animals, it has been historically known as a flu-like illness in humans with little or no significant role in maternal or newborn health. This review focuses on what is currently known relative to the epidemiology of brucellosis in human pregnancy as well as new insights of placental immunology.

Recent Findings

New evidence suggests that maternal infection poses a significant risk factor for adverse pregnancy outcomes including increased risk for miscarriage during the first and second trimester of gestation, preterm delivery, and vertical transmission to the fetus. Adverse pregnancy outcomes were not associated with any specific clinical sign. However, prompt diagnosis and treatment significantly decreased the risk of miscarriage or any other adverse effect.

Summary

Brucellosis during pregnancy should be considered a significant risk factor for adverse pregnancy outcomes in humans. The identification of the mechanism behind bacterial tropism should prove powerful for the development of new countermeasures to prevent these detrimental effects. Increased awareness concerning brucellosis in pregnant women, its transmission, and prevention measures should be considered as a pressing need.

Aerosol-induced brucellosis increases TLR-2 expression and increased complexity in the microanatomy of astroglia in rhesus macaques

Brucella melitensis, a bacterial pathogen and agent of epizootic abortion causes multiple pathologies in humans as well as a number of agriculturally important animal species. Clinical human brucellosis manifests as a non-specific, chronic debilitating disease characterized by undulant fever, arthropathies, cardiomyopathies and neurological sequelae. These symptoms can occur acutely for a few weeks or persist for months to years. Within the brain, endothelial and glial cells can be infected leading to downstream activation events including matrix metalloprotease (MMP) and cytokine secretion and Toll-like receptor (TLR) signaling. These events are likely to lead to tissue remodeling, including morphologic changes in neuronal and glial cells, which are linked to neurological complications including depressive behavior, immune activation and memory loss. Our hypothesis was that B. melitensis infection and neurobrucellosis would lead to activation of astrocytes through upregulation of TLR2 and stimulate concurrent changes in the microanatomy. All six animals were infected via inhalation route. TLR2 expression was approximately doubled in white matter astrocytes of infected rhesus macaques. There was also a 50% increase in the number of astrocytes per unit area in subcortical white matter tracts suggesting increased innate immune activation. This coincided with dramatic increases in the length and complexity of the cell arbor of hypertrophic astrocytes in both cortical gray and white matter. Thus, aerosol-induced brucellosis results in dramatically increased innate immune activation of astrocytes in the absence of widespread neuroinflammation.

Sclerosing cholangitis in baboons (Papio spp) resembling primary sclerosing cholangitis of humans

Primary sclerosing cholangitis is a chronic and progressive cholestatic liver disease that has been extensively documented in the human literature. Although it shares many features in common with chronic lymphocytic cholangitis in cats, primary sclerosing cholangitis has never been reported in a nonhuman primate. Primary sclerosing cholangitis is characterized by the presence of intrahepatic and/or extrahepatic inflammation and concentric fibrosis of bile ducts, eventually leading to cirrhosis and hepatic failure. The pathogenesis and cause remain unknown, but the disease likely involves a multifactorial mechanism with genetic- and immune-mediated components. The authors report 2 cases that histologically resemble the condition in humans; they consist of 2 adult male baboons with a clinical history of chronic elevated liver enzymes. In both cases, the liver was histologically characterized by thick bands of fibrosis and mild lymphoplasmacytic periportal cholangiohepatitis with concentric periductal fibrosis, resulting in atrophy and loss of bile ducts. Immunohistochemical analysis revealed positivity of hepatocytes to cytokeratin 7. Masson stain demonstrated marked biliary fibrosis. This is the first report that resembles sclerosing cholangitis in a nonhuman primate, and it suggests that the baboon may provide a useful animal model for this condition in humans.

A fibrous band associated with the non-coronary aortic valve cusp in a dog

A fibrous band connecting the middle of the free edge (nodulus Arantii) of the non-coronary aortic valve cusp to the ascending aorta just above the level of the non-coronary sinus of Valsalva was observed in an asymptomatic, 11-year-old, male Border Collie. The fibrous band was unrelated to the cause of the death in this dog. Such fibrous bands are usually reported in humans with congenital bicuspid aortic valves. To our knowledge, this is the first report of a fibrous band in the aortic valve in a domestic animal.

Epithelioid haemangiosarcoma in the ocular tissue of horses

Haemangiosarcomas (HSAs) are malignant tumours of endothelial cell origin. Epithelioid HSA is a variant of the histologically conventional HSA that has little or no morphological evidence of a vascular origin and has been reported rarely in domestic animals. The following report documents six cases of equine epithelioid HSA occurring in the ocular tissues of horses with a mean age of 19.8 years at the time of diagnosis. Microscopically, all of the lesions consisted of solid sheets or cords of epithelioid cells with rare narrow clefts or small spaces containing erythrocytes that were often the only feature indicating a vascular origin. On immunohistochemistry, the neoplastic cells expressed vimentin, CD31 and factor VIII-related antigen, but not cytokeratin, indicating an endothelial nature.

Brucellosis: the case for live, attenuated vaccines

The successful control of animal brucellosis and associated reduction in human exposure has limited the development of human brucellosis vaccines. However, the potential use of Brucella in bioterrorism or biowarfare suggests that direct intervention strategies are warranted. Although the dominant approach has explored the use of live attenuated vaccines, side effects associated with their use has prevented widespread use in humans. Development of live, attenuated Brucella vaccines that are safe for use in humans has focused on the deletion of important genes required for survival. However, the enhanced safety of deletion mutants is most often associated with reduced efficacy. For this reason recent efforts have sought to combine the optimal features of a attenuated live vaccine that is safe, free of side effects and efficacious in humans with enhanced immune stimulation through microencapsulation. The competitive advantages and innovations of this approach are: (1) use of highly attenuated, safe, gene knockout, live Brucella mutants; (2) manufacturing with unique disposable closed system technologies, and (3) oral/intranasal delivery in a novel microencapsulation-mediated controlled release formula to optimally provide the long term mucosal immunostimulation required for protective immunity. Based upon preliminary data, it is postulated that such vaccine delivery systems can be storage stable, administered orally or intranasally, and generally applicable to a number of agents.

Aerosol infection of BALB/c mice with Brucella melitensis and Brucella abortus and protective efficacy against aerosol challenge

Brucellosis is a zoonotic disease with a worldwide distribution that can be transmitted via intentional or accidental aerosol exposure. In order to engineer superior vaccine strains against Brucella species for use in animals as well as in humans, the possibility of challenge infection via aerosol needs to be considered to properly evaluate vaccine efficacy. In this study, we assessed the use of an aerosol chamber to infect deep lung tissue of mice to elicit systemic infections with either Brucella abortus or B. melitensis at various doses. The results reveal that B. abortus causes a chronic infection of lung tissue in BALB/c mice and peripheral organs at low doses. In contrast, B. melitensis infection diminishes more rapidly, and higher infectious doses are required to obtain infection rates in animals similar to those of B. abortus. Whether this difference translates to severity of human infection remains to be elucidated. Despite these differences, unmarked deletion mutants BADeltaasp24 and BMDeltaasp24 consistently confer superior protection to mice against homologous and heterologous aerosol challenge infection and should be considered viable candidates as vaccine strains against brucellosis.