Global Comprehensive Literature Review and Meta-Analysis of Brucella spp. in Swine Based on Publications From 2000 to 2020

Brucella suis in feral pigs in Australia: what is the risk?

In Australia, feral pigs (Sus scrofa) are the primary host for Brucella suis. The incidence of B. suis brucellosis in dogs in Queensland (QLD) and New South Wales (NSW) has increased, likely due to hunting and consumption of feral pig meat. This study aimed to update estimates of B. suis seroprevalence and spatial distribution in feral pigs and assess the risk of transmission to dogs. Serology results from 686 feral pigs in QLD and NSW were analysed, with seroprevalence correlated to pig population density. Serology results from 3074 dogs in QLD and NSW were mapped to local government areas (LGAs) and compared with pig density. Raw feral pig meat sold for pet consumption was tested for B. suis. Thirty-seven feral pigs were seropositive, with a survey adjusted true seroprevalence of 17% (95% confidence interval [CI] 12% to 22%) in QLD and 11% (95% CI 8% to 14%) in NSW. No positive spatial autocorrelation between positive and negative pigs was identified. Six hundred dogs from 26 QLD LGAs and 37 NSW LGAs were seropositive, showing a positive association with pig density. Brucella suis DNA was detected in commercially sold feral pig meat. This study found an increased prevalence and geographical expansion of infected pig populations potentially increasing the risk for B. suis transmission. The wide distribution and high level of detection in at-risk dogs highlight the links to pig hunting. Investigating human and dog cases could help identify infected pig populations, enabling hunters to reduce contact with infected pigs in those areas.

Exposure to three zoonotic pathogens in the pig population of Southern Italy

Pigs represent a reservoir of infectious diseases that can be transmitted to humans through feeding or close contact. The aim of this study was to evaluate the seroprevalence of three zoonotic pathogens (Brucella suis, Mycobacterium avium, and Paslahepevirus balayani, also called hepatitis E virus) in the swine population in the Campania region, Southern Italy. A total of 370 animals from 31 farms were sampled and tested with specific commercial ELISAs. Antibodies against hepatitis E virus were detected in 41.4 % of the animals and in almost all the farms (83.8 %). Mycobacterium avium and Brucella suis were less widespread (seroprevalences of 3.5 % and 0 % at the individual level, 32.3 % and 0 % at the farm level, respectively). The univariate analysis of risk factors showed that sex (males), location (Naples), age (growers and finishers), farm size, and system (intensive) were related to higher hepatitis E virus prevalences. We also found higher seroprevalences in pigs belonging to districts where bovines were the main ruminant species. This variable and age were confirmed as risk factors also in multivariate analysis. The data obtained highlighted how pigs are HEV reservoirs also in southern Italy and that pigs in this region are also exposed to Mycobacterium avium but not to Brucella suis.

Sow reproductive disorders: a key issue affecting the pig industry

Pig farming is essential to global agricultural economies and food security. However, reproductive disorders in sows significantly impact the economic viability and sustainability of the pig industry. These disorders often result from complex interactions between pathogenic and non-pathogenic factors. Preventing abortions is typically more cost-effective than managing and treating them, particularly in intensive pig farming system. This highlights the importance of comprehensively understanding the underlying causes of abortion in sows. This review explores the factors contributing to sow reproductive disorders, including both non-infectious factors (environmental conditions and management practices) and infectious factors (viruses, bacteria, and parasites). We also outline preventive and control strategies, alongside integrated management approaches, by analyzing the underlying causes and pathogenic mechanisms of pregnancy disorders. Overall, implementing the "One Health" concept in large-scale farming provides an effective strategy to reduce the incidence of sow abortion rate, ensure stable livestock production, and maintain a reliable global pork supply.

Tracking sero-molecular trends of swine brucellosis in Hawai'i and the central Pacific

Introduction

Brucellosis is a zoonotic disease of mammals caused by bacterial species of the Brucella genus. The reservoir for disease is typically mammals, with species of Brucella found infecting amphibians, bats, and marine mammals. Brucella spp. can pass directly to humans through contact with infected animals or their products. Brucella spp. can cause chronic debilitating infections in mammals, including humans, and is associated with spontaneous abortions in infected animals, causing reduced fecundity. In Hawai'i, terrestrial species that could harbor Brucella spp. include swine, cattle, horses, and axis deer among others. The numerous feral swine in Hawai'i are known to carry Brucella suis, with evidence supporting infections in cattle. Brucella suis also poses infection risk to humans, dogs, and potentially horses across the state.

Methods

In this study, 3,274 feral swine serum samples collected from 5 of the 8 main islands over a 15-year span were analyzed for exposure to B. suis. Of the 558 watersheds in the state, 77 were sampled as part of this effort. Spatial analysis was used to identify watersheds of concern. MLVA and whole genome SNP analysis was used for molecular epidemiological analysis.

Results

Statewide seropositivity rates were triple that of feral swine found in the conterminous United States. Smoothed positivity rates were highest on Maui, followed by O'ahu, and the island of Hawai'i. Island-by-island analysis found high brucellosis positivity levels associated with specific watersheds and agricultural areas. Local spatial autocorrelation identified hot spots on O'ahu and Hawai'i. MLVA analysis of available B. suis from Hawai'i found molecular epidemiological connections with B. suis found in French Polynesia and the mainland US while differing from those in Tonga, Western Polynesia. Strains from Hawai'i are phylogenetically closest to strains from the United States. MLVA and SNP analysis found B. suis strains from Hawai'i fell into the genetic group that contains biovar 1 B. suis.

Discussion

This work identified islands and watersheds of high brucellosis seropositivity in feral swine of Hawai'i, highlighting the magnitude of the zoonotic risk. Introduction of strains in recent history is unlikely due to modern animal trade and disease control practices. Genomic analysis of strains in Hawai'i and the Pacific area can provide hidden historical and local clues to brucellosis epidemiology in the state.

Seroprevalence of Chlamydia abortus and Brucella spp. and risk factors for Chlamydia abortus in pigs from China

Chlamydiosis and brucellosis induced abortions have resulted in significant economic losses in the global livestock industry. Although there have been numerous reports on these two diseases in ruminants in China, limited information is available regarding the prevalence of Chlamydia abortus (C. abortus) and Brucella spp. infection in pigs. This study aimed to investigate the prevalence of C. abortus and Brucella spp. infections in pig serum using serology and to identify potential risk factors. In total, 2816 serum samples were collected from 12 provinces in China. The presence of C. abortus antibodies was determined using an enzyme-linked immunosorbent assay (ELISA), while the presence of Brucella spp. antibodies was examined using the Rose Bengal Plate Test (RBPT) and the Standard Agglutination Test (SAT). The seroprevalences of C. abortus and Brucella spp. were 8.38 % (236/2816) and 0.11 % (3/2816), respectively. Geographical location, season, and age were found to be risk factors associated with C. abortus infection in pig herds in China (p<0.01), and the seropositive rate for C. abortus in sow herds was strongly associated with the occurrence of abortion (p<0.01). Overall, in China, pigs exhibit a higher seroprevalence of C. abortus, whereas the prevalence of Brucella is limited. This study represents the first comprehensive survey of C. abortus and Brucella spp. in pig herds in China that established potential risk factors and provided data for the prevention and control of intraspecies and interspecies transmission of C. abortus to humans.

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.

Brucellosis and One Health: Inherited and Future Challenges

One Health is the collaborative efforts of multiple disciplines to attain optimal health for people, animals and the environment, a concept that historically owes much to the study of brucellosis, including recent political and ethical considerations. Brucellosis One Health actors include Public Health and Veterinary Services, microbiologists, medical and veterinary practitioners and breeders. Brucellosis awareness, and the correct use of diagnostic, epidemiological and prophylactic tools is essential. In brucellosis, One Health implementation faces inherited and new challenges, some aggravated by global warming and the intensification of breeding to meet growing food demands. In endemic scenarios, disease awareness, stakeholder sensitization/engagement and the need to build breeder trust are unresolved issues, all made difficult by the protean characteristics of this zoonosis. Extended infrastructural weaknesses, often accentuated by geography and climate, are critically important. Capacity-building faces misconceptions derived from an uncritical adoption of control/eradication strategies applied in countries with suitable means, and requires additional reference laboratories in endemic areas. Challenges for One Health implementation include the lack of research in species other than cattle and small ruminants, the need for a safer small ruminant vaccine, the need to fill in the infrastructure gap, the need for realistic capacity-building, the creation of reference laboratories in critical areas, and the stepwise implementation of measures not directly transposed from the so-called developed countries.

Immunoassay-based evaluation of rOmp28 protein as a candidate for the identification of Brucella species

Introduction. Brucellosis is an important bacterial zoonosis, re-emerging as a serious public health concern in developing countries. Two major species, Brucella melitensis and Brucella abortus, cause recurrent facile infection in human. Therefore, rapid and accurate diagnosis for early disease control and prevention is needed in areas with low disease burden.Hypothesis. This study evaluated the sandwich enzyme-linked immunosorbent assay (ELISA) (S-ELISA) immunoassay for potential use of whole-cell (WC) and recombinant outer-membrane protein (rOmp28)-derived IgG polyclonals in sensitive detection of Brucella.Aim. Immunoassay-based WC detection of Brucella species in important sub-clinical matrices at lower limits of detection.Methodology. We purified recombinant rOmp28 with Ni-NTA gel affinity chromatography and produced IgG polyclonal antibodies (pAbs) using BALB/c mice and New Zealand white female rabbits against different antigens (Ags) of Brucella. Checkerboard sandwich ELISA and P/N ratio (optical density of 'P' positive test sample to 'N' negative control) were used for evaluation and optimization of the study. The pAbs were characterized using Western blot analysis and different matrices were spiked with WC Ag of Brucella.Results. Double-antibody S-ELISA was developed using WC Ag-derived rabbit IgG (capture antibody at 10 µg ml^-1) and rOmp28-derived mice IgG (detection antibody at 100 µg ml^-1) with a detection range of 10² to 10⁸ cells ml^-1 and a limit of detection at 10² cells ml^-1. A P/N ratio of 1.1 was obtained with WC pAbs as compared to 0.6 and 0.9 ratios with rOmp28-derived pAbs for detecting B. melitensis 16M and B. abortus S99, respectively. An increased P/N ratio of 4.4 was obtained with WC Ag-derived rabbit IgG as compared to 4.2>4.1>2.4 ratios obtained with rabbit IgGs derived against cell envelope (CE), rOmp28 and sonicated antigen (SA) of Brucella with high affinity for rOmp28 Ag analysed on immunoblots. The rOmp28-derived mice IgG revealed two Brucella species at P/N ratios of 11.8 and 6.3, respectively. Upon validation, S-ELISA detected Brucella WCs in human whole blood and sera samples with no cross-reactivity to other related bacteria.Conclusion. The developed S-ELISA is specific and sensitive in early detection of Brucella from different matrices of clinical and non-clinical disease presentation.

Preparation and evaluation of a lateral flow immunochromatographic nanogold diagnostic kit for brucellosis in sheep

Background and Aim

Brucellosis is a zoonotic disease with a worldwide distribution. It has a serious impact on the health of humans and animals, along with a negative impact on the economy. This study aimed to prepare and evaluate the diagnostic performance of a lateral flow immunochromatographic test (LFIT) nanogold diagnostic kit for detecting brucellosis in sheep.

Materials and Methods

A rapidly developed LFIT, in which lipopolysaccharide conjugates with nanogold molecules, was placed on the conjugate pad. One hundred ovine serum samples were tested to detect Brucella antibodies (Ab) using the prepared lateral flow immunochromatography assay (LFA) kit and Rose Bengal test. The evaluation of specificity, sensitivity, and accuracy for LFIT and Rose Bengal plate test was conducted using the P04310-10 IDEXX brucellosis ovine/caprine Ab enzyme-linked immunosorbent assay (ELISA) test (gold standard).

Results

The lower amount of Brucella Ab in the ovine serum samples was detected and was 1.58 S/P ratio ELISA titer/100 μL using LFIT and with Rose Bengal to detect 1.86 S/P ratio ELISA. The results showed that the developed LFIT had high specificity with no cross-reactivity with other tested bacteria. The calculated sensitivity, specificity, and accuracy of LFIT and Rose Bengal test using the P04310-10 IDEXX brucellosis ovine/caprine Ab ELISA test (gold standard) were 74% and 89%, 81% and 59%, and 76.9% and 66%, respectively.

Conclusion

The present results showed interesting results implying that the LFIA strip test could be used as a substantial diagnostic tool for field screening ovine Brucella as an essential step in the control of brucellosis. However, further studies for the validation of the present findings are necessary.

First Report of Brucella Seroprevalence in Wild Boar Population in Serbia

Brucellosis is one of the most important bacterial zoonotic diseases worldwide, characterized in domestic animals by long-term reproductive disorders. As known, wild boars (Sus scrofa) are natural hosts for Brucella suis biovar 2, in which the infection passes in inapparent form, increasing the pathogen transmission risk to domestic pigs, other domestic animals and humans. So far, no studies regarding brucellosis in wild boars in Serbia have been published. During the hunting season 2020/2021, 480 sera of wild boars living in Serbia were collected and tested for the presence of anti-Brucella antibodies. For the serological survey, the Rose Bengal Test (RBT) and competitive enzyme-linked immunosorbent assay (c-ELISA) were used. Of the 480 sera, 45 sera tested positive, indicating the acquired Brucella seroprevalence in wild boars of 9.4%. The greatest numbers of Brucella seropositive animals were detected in the eastern parts of the country and in one of the central districts, i.e., Pomoravski, Branicevski, Borski and Juznobanatski. This study provides the first data regarding brucellosis in the wild boar population in Serbia, revealing the seroprevalence of Brucella, thus indicating that wild boars as natural hosts and/or vectors of Brucella likely present a risk for the infection of other animals.