How to substantiate eradication of bovine brucellosis when aspecific serological reactions occur in the course of brucellosis testing

Molecular evidence of Brucella abortus circulating in cattle, goats, and humans in Central Equatoria State, South Sudan

Brucellosis is a neglected zoonotic disease in most developing countries, including South Sudan. Precise identification of Brucella species is crucial for addressing public health and epidemiological concerns associated with brucellosis. The study aimed to identify Brucella species using real-time polymerase chain reaction (qPCR) from seropositive samples that were acquired from an earlier investigation. A total of 143 genomic DNA samples were extracted from brucellosis Rose Bengal plate test (RBPT) seropositive samples from humans (n = 7), cattle (n = 103) and goats (n = 33). The samples were collected from Terekeka and Juba counties, Central Equatoria State (CES), South Sudan. The qPCR targeting the Brucella-specific IS711 insertion gene at the genus level was performed. Samples with a cycle threshold (Ct) of ≤ 35 were considered positive and subjected to further Brucella speciation assays. Out of 143 DNA samples tested for genus-specific Brucella, 15 (10.5%) were positive including 4 (2.8%) from humans, 10 (6.9%) from cattle, and 1 (0.7%) from goats. Brucella abortus was identified in 5 (33.3%) of the positive samples at the genus level. The overall individual species infection rates with B. abortus were 6.6% (1/15) in humans, 20% (3/15) in cattle, and 6.6% (1/15) in goats. There was no B. melitensis detected in this study. This study identified B. abortus in cattle, goats and humans in CES, South Sudan. The findings suggest that cattle are probably the primary reservoirs for transmission of B. abortus, with infections occurring in goats and humans primarily resulting from cattle spillover.

Brucellosis in camel, small ruminants, and Somali pastoralists in Eastern Ethiopia: a One Health approach

Brucellosis is a neglected bacterial zoonotic disease with economic and public health importance in pastoral communities of sub-Saharan Africa. A cross-sectional study was conducted from December 2021 to April 2022, to estimate the prevalence and identify the associated risk factors causing brucellosis in animals and associated with occupational diseases in humans from three selected districts of "the Somali Pastoral region," Eastern Ethiopia. In this study, 1,000 serum samples were screened for anti-Brucella spp. antibodies using Rose Bengal Plate Test (RBPT) and further confirmed using a competitive enzyme-linked immunosorbent assay (cELISA). A structured questionnaire was used to collect the biodata of tested animals and animal attendants to test the association between explanatory and outcome variables. The overall animal level prevalence was 5% (95% CI, 6.1-7.2.0) in small ruminants, 2.9% (95% CI, 1.5-4.9) in camels, and 2.0% (95% CI, 0.2-3.7) in occupationally linked humans. Herd size and herd history of retained fetal membranes were risk factors associated with Brucella spp. seropositivity in animals (p < 0.05). Disposing of retained fetal membranes was significantly associated (p < 0.05) with Brucella spp. seropositivity in humans. Evidence of brucellosis in various livestock species and associated seropositivity in humans indicates the need for a coordinated One Health approach, considering sociocultural dynamics of pastoral communities in controlling brucellosis to safe guard public health and increase livestock productivity.

Occurrence and Risk Factors of Brucellosis in Commercial Cattle Farms from Selected Districts of the Eastern Coast Zone, Tanzania

Brucellosis is a disease of major socio-economic importance worldwide, particularly in low-income countries. This retrospective study aimed to estimate seroprevalence and risk factors associated with brucellosis in commercial cattle farms in the eastern coast zone of Tanzania (ECZT). A total of 1,052 serum samples collected from 20 commercial farms were subjected to rose bengal plate test (RBPT) and indirect enzyme-linked immunosorbent assay (i-ELISA). Descriptive analysis was employed to determine frequencies and proportions. To establish risk factors, a multivariate logistic regression analysis was carried out using a backward elimination procedure, following a univariate analysis, with 0.1 set as a cut-off point for the selection of putative risk factors. Agreement between RBPT and i-ELISA was determined using a Kappa coefficient (κ). The overall animal-level seroprevalence was 25.9% based on i-ELISA. Logistic regression analysis revealed that odds of infection were significantly higher in females (OR = 1.8, 95% CI: 1.2-2.5, p = 0.002) and in young animals than in adults (OR = 3.6, CI: 2.1-6.2, p < 0.001). In addition, odds of infection were higher during the wet season (OR = 3.4, CI: 3.2-5.2, p < 0.001), in cattle reared in rural farms (OR = 4.8, CI: 2.0-11.5, p < 0.001), in cattle reared in areas, not in contact with wildlife (OR = 2.9, CI: 1.4-2.3, p = 0.004), and in medium-sized farms (OR = 12.5, CI: 6.9-22.9, p < 0.001). These findings confirm that bovine brucellosis was prevalent among commercial cattle farms in the ECZT, posing a serious public health concern to the community living in these settings. The one health approach should be adopted for effective control of brucellosis.

Development of a Multiplex Bead Assay to Detect Serological Responses to Brucella Species in Domestic Pigs and Wild Boar with the Potential to Overcome Cross-Reactivity with Yersinia enterocolitica O:9

The aim of this study was to develop a multiplex bead assay using a Brucella rLPS antigen, a Brucella suis smooth antigen, and a Yersinia enterocolitica O:9 antigen that not only discriminates Brucella-infected from Brucella-uninfected pigs and wild boar, but also overcomes the cross reactivity with Y. enterocolitica O:9. Sera from 126 domestic pigs were tested: 29 pigs were Brucella infected, 80 were non-infected and 17 were confirmed to be false positive serological reactors (FPSR). Sera from 49 wild boar were tested: 18 were positive and 31 were negative. Using the rLPS antigen, 26/29 Brucella-infected domestic pigs and 15/18 seropositive wild boar were positive, while 75/80 non-Brucella infected domestic pigs, all FPSR, and all seronegative wild boar were negative. Using the smooth B. suis 1330 antigen, all Brucella-infected domestic pigs, 9/17 FPSR and all seropositive wild boar were positive, while all non-infected pigs and 30/31 seronegative wild boar were negative. The ratio of the readouts from the smooth B. suis antigen and Y. enterocolitica O:9 antigen enabled discriminating all Brucella infected individuals from the FPSR domestic pigs. These results demonstrate the potential of this assay for use in the surveillance of brucellosis, overcoming the cross-reactivity with Y. enterocolitica.

Brucella activates the host RIDD pathway to subvert BLOS1-directed immune defense

The phagocytosis and destruction of pathogens in lysosomes constitute central elements of innate immune defense. Here, we show that Brucella, the causative agent of brucellosis, the most prevalent bacterial zoonosis globally, subverts this immune defense pathway by activating regulated IRE1α-dependent decay (RIDD) of Bloc1s1 mRNA encoding BLOS1, a protein that promotes endosome-lysosome fusion. RIDD-deficient cells and mice harboring a RIDD-incompetent variant of IRE1α were resistant to infection. Inactivation of the Bloc1s1 gene impaired the ability to assemble BLOC-1-related complex (BORC), resulting in differential recruitment of BORC-related lysosome trafficking components, perinuclear trafficking of Brucella-containing vacuoles (BCVs), and enhanced susceptibility to infection. The RIDD-resistant Bloc1s1 variant maintains the integrity of BORC and a higher-level association of BORC-related components that promote centrifugal lysosome trafficking, resulting in enhanced BCV peripheral trafficking and lysosomal destruction, and resistance to infection. These findings demonstrate that host RIDD activity on BLOS1 regulates Brucella intracellular parasitism by disrupting BORC-directed lysosomal trafficking. Notably, coronavirus murine hepatitis virus also subverted the RIDD-BLOS1 axis to promote intracellular replication. Our work establishes BLOS1 as a novel immune defense factor whose activity is hijacked by diverse pathogens.

Seroprevalence and risk factors of brucellosis in Arabian horses

Background

Brucellosis, as a zoonotic disease, mainly occurs in horses by Brucella abortus, Brucella canis and Brucella suis. The disease in equines is often asymptomatic, but the clinical signs in horses are mostly characterized by bursitis, arthritis and tenosynovitis.

Objectives

This study, thus, aimed to determine the seroprevalence of brucellosis and its associated risk factors in the Arabian horses of Khuzestan province, South‐west Iran.

Methods

To that end, the blood samples randomly collected from 180 Arabian horses were analyzed for the presence of anti‐Brucella antibodies by Rose Bengal plate test (RBPT), serum agglutination test (SAT), 2‐mercaptoethanol test (2‐ME) and a commercial i‐ELISA kit.

Results

The ROC curve analysis showed that the best cut‐off point for S/P values in i‐ELISA turned out to be 26.25%. The results showed that the overall seroprevalence of brucellosis based on parallel interpretation of the test results was 12.22% (Positive/Tested = 22/180). The prevalence of acute and chronic brucellosis was 8.3 and 3.9%, respectively. The seroprevalence of brucellosis with RBPT and i‐ELISA methods was 1.11% (2/180) and 7.22% (13/180), respectively. According to what SAT revealed, 9.44% (17/180) of sera had a titer of 40 or greater, and at 2‐ME, 7.22% of samples (13 out of 180 samples) depicted a titer of 40. The results of i‐ELISA, SAT and 2‐ME were significantly different from those of RBPT (p < 0.01); however, there was no significant difference between i‐ELISA, SAT and 2‐ME in findings (p > 0.05).

Conclusions

The results of this study recommend that i‐ELISA be used for screening purposes of brucellosis in horses. The findings confirmed that Arabian horses are natural hosts for the Brucellae. It is, thus, necessary to adopt appropriate prevention and control programs by health authorities and horse owners so as to reduce the distribution and transmission of the infection in the regions where brucellosis is prevalent.

Occurrence and risk factors of brucellosis among domestic animals: an artificial neural network approach

Brucellosis is a zoonotic infectious disease with a worldwide distribution. This cross-sectional study aimed to determine the occurrence of Brucella in milk and blood samples of ruminants and the importance factors associated with animal brucellosis in Eastern Iran. A total of 200 paired samples, including blood (100) and milk (100), were obtained from the goats, sheep, and cows in Eastern Iran. Serum agglutination (SAT) and 2-mercapto ethanol (2-ME) tests were performed on the sera. A multiplex-polymerase chain reaction (m-PCR) assay was performed to identify the following species of Brucella, including B. abortus biovar 1, 2, 4, 3b, 5, 6, and 9, B. abortus S19, B. melitensis, and B. melitensis Rev.1 vaccine strain. B. abortus RB51 vaccine strain was also investigated in a second PCR assay. Risk factors for infection with Brucella spp. including the effect of abortion, contact with the wild animals, herd type, age, and previous vaccination in predicting blood contamination with B. abortus biovar 1, 2, and 4 were modeled by use of the artificial neural network. A total of 23 samples were seropositive regarding SAT and 2-ME tests. In total, B. abortus was detected in 35% and 15% of blood and milk samples, respectively, by the m-PCR assay. One sample of each of milk and blood was detected to have B. melitensis. Some samples were simultaneously contaminated with two Brucella species or two biovars of B. abortus. B. abortus S19 and B. melitensis Rev.1 vaccine strains were also detected in milk and blood samples. The sensitivity and specificity of the ANN model were 81% and 62%, respectively. In conclusion, B. abortus had higher frequency than B. melitensis in blood and milk samples. ANN determined herd type, previous vaccination, and age of the animal as the largest predictors of blood contamination with B. abortus.

Seroprevalence of Bovine Brucellosis and Associated Risk Factors in Western Ethiopia

Background

Brucellosis is a contagious bacterial disease, which affects domestic animals, humans, and wildlife in Ethiopia and other countries.

Methods

A cross-sectional study design using a simple random sampling technique was conducted in Diga, Guto, Gida, and Sibu Sire districts of East Wollega Zone, Western Oromia, from November 2019 to July 2020 to determine the prevalence of bovine brucellosis and identify associated risk factors. A lottery method was used during serum collection and risk factors identified during interview.

Results

A total of 1152 serum samples were collected from cattle of 6 months age and above. Serum samples were tested by enzyme linked immunosorbent assay (I-ELISA). An overall seroprevalence of brucellosis was 1.82% (21/1152). Statically significant variation (P<0.05) in seroprevalence of bovine brucellosis was recorded among potential risk factors such as breed [P≤0.05; OR:8.905; CI:1.568–50.573], parity [P≤0.05; OR:0.017; CI:0.042–5.195], retained fetal membrane [P≤0.001; OR:0.018; CI:0.00–2.169], and abortion history [P≤0.001; OR:0.030; CI:0.004–0.212]. Conversely, seroprevalence variations in sex, district, villages, body condition score, and age were statistically insignificant (P>0.05).

Conclusion

The current study revealed bovine brucellosis is posing a threat to livestock with no strict control and prevention scheme in place. Therefore, public awareness creation about the zoonotic importance of the disease is crucial and the Government should establish legislation, support, control, and prevention of the disease recommended.

Cross-sectional study of Brucella spp. using real-time PCR from bovine whole blood in Colombia

A cross-sectional study was conducted in Colombia to recover Brucella spp. DNA from bovine whole-blood samples through probe-based real-time PCR (qPCR). By an SNP-based assay, vaccine strains were differentiated from field strains. The associated factors were evaluated using logistical regression models. A total of 656 random cows from 40 herds were selected and analyzed using serology and PCR. The qPCR assay detected 9.5% (n = 62/656; 95% CI: 7.3, 12.0) of the animals with Brucella-DNA presence, while the serological test detected a 6.6% (n = 43/656; CI: 4.8, 8.7). 62.5% (n = 25/40; 95% CI: 45.8, 77.3) of positive cases were detected at the herd-level by the qPCR, while only 27.5% (n = 11/40; 95% CI: 14.6, 43.9) were detected by the serological test. All positive samples were identified as field Brucella strains employing the SNP-based assay. In the final regression model at the animal-level, five variables were associated with Brucella-DNA presence: the use of bulls for mating recorded history of reproductive problems, pregnant cows, parlor milking, and cows belonging to farms ≤200 m from the main road. At the herd-level, two variables were associated with Brucella-DNA presence: recorded history of reproductive problems and the use of bulls for mating. Given the fluctuant brucellosis prevalence in endemic areas, updated epidemiological studies are necessary to evaluate the disease dynamic and if established prevention and control measures have been effective or need to be adjusted. The increase in the prevalence of brucellosis in animal reservoirs creates an important risk of transmission in humans.

Study on Seroprevalence and Associated Factors of Bovine Brucellosis in Selected Districts of Afar National Regional State, Afar, Ethiopia

Bovine brucellosis is among the top five diseases primarily threatening both public health and livestock economy. Available data are limited to central and highland areas of the country leaving documented literature on the disease in cattle to be found hardly in pastoral and agropastoral regions of the country. As a result, the magnitude and extent of the disease remained to be investigated. A cross-sectional study design was conducted on local Afar cattle aged six months and above from February 2017 to January 2019 in selected districts of Afar region. Technically, study districts and kebeles were selected purposively whereas simple random sampling technique was applied to select cattle owners and individual animals for sample collection. An average of 8 ml whole blood was drawn of jugular vein into plain vacutainer tube using sterile needle. Using Thrusfield formula, a total of 420 blood samples were collected. The sera were tested by RBPT and CFT tests for detection of Brucella antibodies. Data were analyzed using Stata v14.0. Of the 420 sera tested by RBPT, 50 were positive for Brucella antibodies providing an overall animal level prevalence of 11.9% and those RBPT positive sera were further retested by specific and sensitive confirmatory CFT test and 24 of the retested samples had come positive for the disease providing an overall individual animal seroprevalence of 5.7% over the three districts. Of the 3 associated factors (sex, age, and district) considered, only sex had significantly associated (P < 0.05 : 0.036) with the disease. To estimate the strength of sex impact, odds ratio was generated using bivariate and multivariate logistic regression analyses with 95% CI and P < 0.05 providing OR of 2.484 (1.061–5.815) and 2.514 (1.041–6.07), respectively. Hence, the computations revealed that male cattle were 2.484 and 2.514 times more likely at higher risk for the disease as compared to their female counterparts.

Brucellosis in ruminants and pastoralists in Borena, Southern Ethiopia

Brucellosis is a bacterial zoonotic disease that has important veterinary and public health consequences as well as economic impact in sub Saharan Africa including Ethiopia. A cross-sectional study was conducted in four selected districts of Borena Pastoral setting in Southern Ethiopia from October 2017 to February 2018 to estimate the prevalence of brucellosis and assess associated risk factors in cattle, sheep, goats and occupationally associated humans. A total of 750 cattle, 882 sheep and goats and 341 human subjects were screened for evidence of brucellosis using the Rose Bengal Test (RBT) with positive results confirmed by Competitive-ELISA(c-ELISA). Structured questionnaires were used for collection of metadata from individual animals, herders and animal attendants to test the association between explanatory and outcome variables. The overall animal level prevalence was 2.4% (95% confidence interval, CI: 1.4-3.7) in cattle, 3.2% (95% CI: 2.1-4.6) in sheep and goats, and 2.6% (95% CI: 1.2-5) in humans occupationally linked to livestock production systems. Herd size, parity, and history of abortion were risk factors associated with Brucella seropositivity (P<0.05) in cattle whereas in sheep and goats the results showed that district, age group, flock size, and history of abortion were significantly associated risk factors with Brucella seropositivity (P<0.05). Assisting calving and presence of seropositive animals in a household (P<0.05) were significantly associated with Brucella seropositivity in humans. Evidence of brucellosis in various animal species and the associated human population illustrates the need for a coordinated One Health approach to controlling brucellosis so as to improve public health and livestock productivity.

Evaluation of the sensitivity and specificity of the lateral flow assay, Rose Bengal test and the complement fixation test for the diagnosis of brucellosis in cattle using Bayesian latent class analysis

This study was conducted to evaluate the sensitivity (Se) and specificity (Sp) of the Rose Bengal test (RBT), complement fixation test (CFT), the serum lateral flow assay (LFA_serum) and the blood lateral flow assay (LFA_blood) for the detection of antibodies to Brucella spp. using Bayesian latent class models (BLCMs). Sera and whole blood were collected from naturally infected cattle reared in smallholder, small-scale commercial and large-scale commercial farms in Zimbabwe (n = 1022) and Botswana (n = 770). The BLCMs were fitted under the assumption that conditional dependences existed between the tests. Based on the conditional dependence model, the RBT had the highest Se of 0.897 (95 % Probability Intervals: 0.854; 0.932) compared to 0.827 (0.773; 0.872), 0.812 (0.76; 0.858) and 0.809 (0.785; 0.832) for the LFA_serum, LFA_blood and CFT, respectively. The CFT recorded a higher Sp of 0.999 (0.995; 1.000) than the LFA_serum 0.996 (0.99; 1.000), the LFA_blood 0.984 (0.976; 0.991) and the RBT 0.969 (0.959; 0.978). The data indicated that both the Se and Sp of RBT and CFT and the Sp of LFA_serum and LFA_blood were conditionally independent, while the Se appeared to be conditionally dependent. These results indicated that none of the evaluated tests had perfect Se and Sp and consequently could not be used alone for the diagnosis of brucellosis in cattle from the studied farming sectors. Thus, based on high Se and Sp, respectively, a brucellosis testing regimen using the RBT (screening) and the LFA (confirmatory) may be considered.

Brucella melitensis B115-based ELISA to unravel false positive serologic reactions in bovine brucellosis: a field study

Background

Brucellosis is a zoonosis whose incidence is not declining worldwide despite the global effort to control the disease. Accurate and precise diagnosis is a crucial step in any prophylaxis program but single tests to unequivocally detect animals infected with Brucella spp. are currently unavailable. In Italy, serological diagnosis of bovine brucellosis is performed with two official tests: a rapid agglutination test (i.e., Rose Bengal Plate test, RBPT) and a complement fixation test (CFT) that detect antibodies directed mainly to the smooth lipopolysaccharide (S-LPS). Neither of the two tests is able to avoid the detection of false positive serological reactions (FPSRs) caused by bacteria sharing S-LPS components with Brucella spp. and responsible for the single reactors (SR) phenomenon. A B. melitensis R strain-based ELISA showed a good diagnostic performance in unravelling FP animals; however, since a limited number of animals were analyzed in that study, a large field study was conducted here to discriminate between Brucella-infected from FP animals, with the final aim of reducing the unnecessary slaughter of the latter. An ELISA based on a R strain of Brucella, i.e., Brucella melitensis B115, was employed to measure specific IgG responses in a collection of bovine sera (n = 648). Sera were obtained from 180 farms (either officially brucellosis-free or not brucellosis-free) recruited during an extended period of time (2014–2018) and were preliminarily assayed with the official tests by the Italian Reference Centers and then subjected to the ELISA.

Results

Negative sera, when subjected to the ELISA, gave O.D. values below the cutoff; SR sera, i.e. RBPT positive and CFT negative, as well as double positive (DP) sera, i.e. RBPT and CFT positive, gave O.D. values that were below the cutoff. All positive sera, i.e. from Brucella-infected animals, were RBPT positive and CFT positive (ICFTU ranging from 20 to 1280) and gave ELISA O.D. values above the cutoff.

Conclusions

The B. melitensis B115-based ELISA systematically unravelled all false positive (FP) sera while confirming the diagnosis in Brucella-infected animals. Thus, the test employed in the present study may complement the official assays to avoid the costly slaughter of FP animals.

Modelling the immunopathophysiology of Brucella melitensis and its lipopolysaccharide in mice infected via oral route of exposure

Brucella melitensis is one of the leading zoonotic pathogens with significant economic implications in animal industry worldwide. Lipopolysaccharide, however, remains by far the major virulence with substantial role in diseases pathogenesis. Nonetheless, the effect of B. melitensis and its lipopolysaccharide on immunopathophysiological aspects largely remains an enigma. This study examines the effect of B.melitensis and its lipopolysaccharide on immunopathophysiological parameters following experimental infection using mouse model. Eighty four (n = 84) mice, BALB/c, both sexes with equal gender distribution and 6-8 weeks-old were randomly assigned into three groups. Group 1-2 (n = 72) were orally inoculated with 0.4 mL containing 10⁹ CFU/mL of B. melitensis and its LPS, respectively. Group 3 (n = 12) was challenged orally with phosphate buffered saline and served as a control group. Animals were observed for clinical signs, haematological and histopathological analysis for a period of 24 days post-infection. We hereby report that B.melitensis infected group demonstrated significant clinical signs and histopathological changes than LPS infected group. However, both infected groups showed elevated levels of interleukins (IL-1β and IL-6) and antibody levels (IgM and IgG) with varying degrees of predominance in LPS infected group than B. melitensis infected group. For hormone analysis, low levels of progesterone, estradiol and testosterone were observed in both B. melitensis and LPS groups throughout the study period. Moreover, in B. melitensis infected group, the organism was re-isolated from the organs and tissues of gastrointestinal, respiratory and reproductive systems thereby confirming the infection and transmission dynamics. This report is the first detailed investigation comparing the infection progression and host responses in relation to the immunopathophysiological aspects in a mouse model after oral inoculation with B. melitensis and its lipopolysaccharide.

Prevalence of Caprine brucellosis in Anhui province, China

Background and Aim

Brucellosis is one of the most widespread zoonotic diseases globally. Studies indicated the existence of Brucella infection in goats in some province of China. Thus this study aimed to estimate the prevalence of brucellosis in goats of Anhui Province, China.

Materials and Methods

Serum and milk samples obtained from goats in different regions of Anhui province were studied through rose Bengal plate test (RBPT), serum agglutination test (SAT), milk ring test (MRT), and polymerase chain reaction (PCR).

Results

The investigation frequency of brucellosis using RBPT, SAT, MRT, and PCR methods was 3.9% (n=7), 4.45% (n=8), 11.67% (n=7), and 86.67% (n=156), respectively. The prevalence recorded for brucellosis in sex-wise animals as in females 5.55%, 6.67%, 11.67%, and 78.8% through above methods, while in males, it was 2.23% and 2.23% by RBPT and SAT. However, in age-wise animals, the results 6.36%, 7.27%, 11.67%, and 74.5% were perceived positive by RBPT, SAT, MRT, and PCR in adult females, respectively, but young males and females (up to 9 months) were considered free from brucellosis.

Conclusion

These results show that prevalence of brucellosis was relatively higher in females than male's goats and SAT was relatively specific and accurate as compared to RBPT and MRT, but for diagnosis of brucellosis, molecular method (PCR) is recommended.

Evaluation of DNA vaccine encoding BCSP31 surface protein of Brucella abortus for protective immunity

Brucellosis is a highly contagious and zoonotic disease and has a considerable impact on animal health and economy of a country, principally in Pakistan, where rural income largely depends upon livestock farming and dairy products. The disease burden is more in underdeveloped/developing countries due to the low economy and limited access to the diagnostic facilities. In Pakistan, the prevalence of Brucella abortus is very high, so it is the need of the hour to control this disease through more advanced methods. This study was designed with the aim to construct the DNA based vaccine of gene encoding antigenic surface protein (BCSP₃₁). For this purpose, the BCSP₃₁ gene was amplified, purified and ligated in pTZ57 R/T (cloning vector). Dubbed BCSP₃₁-pTZ57 R/T vector was transformed into competent cells (DH5α). After plasmid extraction, the plasmid and pET-28a vector was restricted with EcoRI and BamHI. Again, ligation was done and dubbed pET-28a-BCSP₃₁ transformed into E. coli (BL21). After expression, the protein was purified and used for evaluation of immunogenic response. The protective and immunogenic efficacy of the vaccine was evaluated in rabbits (n = 20). The rabbits were divided into four equal groups. Groups A-C were given purified protein diluted in normal saline @ 750, 1500 and 3000 μg/0.2 mL, respectively through intraconjunctival route. Group D was given 0.2 mL normal saline through intraconjunctival route. Specific immunoglobulin G (IgG) responses were measured through indirect ELISA on a weekly basis. The titer of IgG against the antigen was significantly (p < 0.05) higher in vaccinated groups A-C as compared to group D (control group) in a dose dependent manner. Moreover, log units of protection produced by DNA based vaccine in the rabbits (3.02) also indicated the protective efficacy of the DNA vaccine against B. abortus challenge. The response of this vaccine in rabbit suggested its potential effectiveness against Brucella abortus in large animals.

Comparisons of brucellosis between human and veterinary medicine

Brucellosis is the world's most widespread zoonosis, but also ranks as one of the seven most neglected diseases, according to the World Health Organization. Additionally, it is recognized as the world's most common laboratory-acquired infection. There are a reported 500,000 incident cases of human brucellosis per year. However, true incidence is estimated to be 5,000,000 to 12,500,000 cases annually. Once diagnosed, focus is directed at treating individual patients with antibiotic regimes, yet overall neglecting the animal reservoir of disease. Countries with the highest incidence of human brucellosis are Syria (1,603.4 cases per 1,000,000 individuals), Mongolia (391.0), and Tajikistan (211.9). Surveillance on animal populations is lacking in many developed and developing countries. According to the World Animal Health Information Database, Mexico had the largest number of reported outbreaks, 5,514 in 2014. Mexico is followed by China (2,138), Greece (1,268), and Brazil (1,142). The majority of these outbreaks is Brucella abortus, the etiologic agent of bovine brucellosis. Brucellosis is an ancient disease that still plagues the world. There are still knowledge gaps and a need for better diagnostics and vaccines to make inroads towards control and eradication.

Rapid visual isothermal nucleic acid-based detection assay of Brucella species by polymerase spiral reaction

AIM

The aim of this study was to develop polymerase spiral reaction (PSR) for rapid, sensitive and specific detection of Brucella sp.

METHODS AND RESULTS

Polymerase spiral reaction assay was developed using specifically designed primers targeting the conserved multicopy IS711 gene of Brucella sp. The assay could be performed within 60 min at an isothermal temperature of 64°C. The lower limit of detection of PSR was 11·8 fg and conventional PCR was 1·18 pg of Brucella abortus genomic DNA. Thus, PSR was found to be 100-fold more sensitive than conventional PCR and was comparable to real-time PCR. The specificity of PSR was tested with other non-Brucella bacteria and also with some bacterial and viral pathogens causing abortions. The assay was found to be specific as it did not detect any putative pathogens other than Brucella sp. Fifty-six clinical samples suspected for brucellosis (aborted fetal stomach content) were screened with PSR to validate the applicability of the test to detect Brucella DNA. The same samples were also screened with conventional PCR and real-time PCR. Of 56 samples, 25 samples were found to be positive with both PSR as well as real-time PCR, whereas only 20 samples were found positive with conventional PCR.

CONCLUSIONS

The results of this study indicated that the PSR assay is a simple, rapid, sensitive and specific method for the detection of Brucella sp. that may improve diagnostic potential in clinical laboratories or can be used at diagnostic laboratories with minimal infrastructure.

SIGNIFICANCE AND IMPACT OF THE STUDY

The PSR assay, because of its simplicity and low cost, can be preferred to other molecular methods in the diagnosis of infectious diseases.

Activation of Host IRE1α-Dependent Signaling Axis Contributes the Intracellular Parasitism of Brucella melitensis

Brucella spp. are intracellular vacuolar pathogens that causes brucellosis, a worldwide zoonosis of profound importance. We previously demonstrated that the activity of host unfolded protein response (UPR) sensor IRE1α (inositol-requiring enzyme 1) and ER-associated autophagy confer susceptibility to Brucella melitensis and Brucella abortus intracellular replication. However, the mechanism by which host IRE1α regulates the pathogen intracellular lifestyle remains elusive. In this study, by employing a diverse array of molecular approaches, including biochemical analyses, fluorescence microscopy imaging, and infection assays using primary cells derived from Ern1 (encoding IRE1) conditional knockout mice, we address this gap in our understanding by demonstrating that a novel IRE1α to ULK1, an important component for autophagy initiation, signaling axis confers susceptibility to Brucella intracellular parasitism. Importantly, deletion or inactivation of key signaling components along this axis, including IRE1α, BAK/BAX, ASK1, and JNK as well as components of the host autophagy system ULK1, Atg9a, and Beclin 1, resulted in striking disruption of Brucella intracellular trafficking and replication. Host kinases in the IRE1α-ULK1 axis, including IRE1α, ASK1, JNK1, and/or AMPKα as well as ULK1, were also coordinately phosphorylated in an IRE1α-dependent fashion upon the pathogen infection. Taken together, our findings demonstrate that the IRE1α-ULK1 signaling axis is subverted by the bacterium to promote intracellular parasitism, and provide new insight into our understanding of the molecular mechanisms of intracellular lifestyle of Brucella.

Immunological response to Brucella abortus strain 19 vaccination of cattle in a communal area in South Africa

Brucellosis is of worldwide economic and public health importance. Heifer vaccination with live attenuated Brucella abortus strain 19 (S19) is the cornerstone of control in low- and middle-income countries. Antibody persistence induced by S19 is directly correlated with the number of colony-forming units (CFU) per dose. There are two vaccination methods: a 'high' dose (5-8 × 1010 CFU) subcutaneously injected or one or two 'low' doses (5 × 109 CFU) through the conjunctival route. This study aimed to evaluate serological reactions to the 'high' dose and possible implications of the serological findings on disease control. This study included 58 female cases, vaccinated at Day 0, and 29 male controls. Serum was drawn repeatedly and tested for Brucella antibodies using the Rose Bengal Test (RBT) and an indirect enzyme-linked immunosorbent assay (iELISA). The cases showed a rapid antibody response with peak RBT positivity (98%) at 2 weeks and iELISA (95%) at 8 weeks, then decreased in an inverse logistic curve to 14% RBT and 32% iELISA positive at 59 weeks and at 4.5 years 57% (4/7 cases) demonstrated a persistent immune response (RBT, iELISA or Brucellin skin test) to Brucella spp. Our study is the first of its kind documenting the persistence of antibodies in an African communal farming setting for over a year to years after 'high' dose S19 vaccination, which can be difficult to differentiate from a response to infection with wild-type B. abortus. A recommendation could be using a 'low' dose or different route of vaccination.

Detection of Brucella spp. in milk from seronegative cows by real-time polymerase chain reaction in the region of Batna, Algeria

Aim:

The aim of this study was to detect Brucella spp. DNA in milk samples collected from seronegative cows using the real-time polymerase chain reaction (PCR) assay for diagnosis of brucellosis in seronegative dairy cows to prevent transmission of disease to humans and to reduce economic losses in animal production.

Materials and Methods:

In this study, 65 milk samples were investigated for the detection of Brucella spp. The detection of the IS711 gene in all samples was done by real-time PCR assay by comparative cycle threshold method.

Results:

The results show that of the 65 DNA samples tested, 2 (3.08%) were positive for Brucella infection. The mean cyclic threshold values of IS711 real-time PCR test were 37.97 and 40.48, indicating a positive reaction.

Conclusion:

The results of the present study indicated that the real-time PCR appears to offer several advantages over serological tests. For this reason, the real-time PCR should be validated on representative numbers of Brucella-infected and free samples before being implemented in routine diagnosis in human and animal brucellosis for controlling this disease.

Molecular Detection of Brucella spp. from Milk of Seronegative Cows from Some Selected Area in Bangladesh

Brucellosis is endemic in Bangladesh both in humans and in animals. A number of reasons complicate the diagnosis, as bovine brucellosis can be diagnosed by various serological tests. But the tests have a limitation; when the organism remains intracellular, the disease goes into chronic stage and the antibody titres may decline. The present study was conducted for isolation and detection of Brucella spp. by polymerase chain reaction (PCR) from seronegative cows. A total of 360 dairy cows from three geographical regions were screened serologically by Rose Bengal Plate Test (RBPT) where 24 samples were serologically positive and the rest of the samples were serologically negative. Among the 24 seropositive individuals, 11 were culture positive and 6 were culture positive from serologically negative dairy cows. The overall seroprevalence of brucellosis in cattle was 6.6% and in disease condition a higher prevalence was recorded in abortion (28.07%) followed by infertility (13.33%). To confirm the Brucella spp. in seronegative dairy cattle, the isolates were extracted and PCR was conducted, which produced 905 bp amplicon size of 6 Brucella spp. from milk sample. So, for the detection or eradication of brucellosis, a bacteriological test and a PCR technique should be performed with the serological test of milk.

Evaluation of three serological tests for diagnosis of bovine brucellosis in smallholder farms in Pakistan by estimating sensitivity and specificity using Bayesian latent class analysis

The present study aimed to estimate the herd-level sensitivity (Se) and specificity (Sp) of three commonly used serological tests in naturally-infected cattle and buffalo in smallholder farms in Pakistan. Between February and June 2015, a cross-sectional study was carried out in five districts of Punjab (Kasur, Okara, Pakpattan, Jhelum, and Bhakkar) and two districts of Sindh (Badin and Thatta). Serum samples from mixed farms of cattle (n=441) and buffalo (n=621) were collected and tested using the Rose Bengal test (RBT), indirect ELISA (I-ELISA) and competitive ELISA (C-ELISA). A Bayesian latent class analysis (LCA) approach was used to estimate the Se and Sp of these three serological tests and the true herd-level prevalence in each district. The model was fitted under the assumption of conditional independence between three tests and also conditional dependence by including covariances between the two ELISAs. In addition, the model was fitted using three different shapes of beta distributions to incorporate prior information in the model. The test with the highest Se was the C-ELISA, with a range from 76.3% (95% PCI (Posterior Credibility Interval), 62.6-88.2%) to 81.4% (95% PCI, 68.2-92.8%). The RBT was found to have the highest Sp (99.1-99.4%) of the tests. The highest estimated herd-level prevalence, 45% (95% PCI, 32-59%), was found in Jhelum district and the lowest in Thatta district, 1.1% (95% PCI 0.04-6.0%). The results of this study identified some discrepancy between the published literature on the level of Se of these tests, especially for RBT. It appears that RBT has lower Se and higher Sp when used in the field conditions of the present study. Consequently, it is recommended that none of the evaluated tests should be performed in isolation for the diagnosis of bovine brucellosis in the field conditions of Pakistan, but the use of tests in combination, with RBT and C-ELISA used in parallel returning optimal Se and Sp, is warranted.

Detection and characterization of Brucella spp. in bovine milk in small-scale urban and peri-urban farming in Tajikistan

Brucellosis is one of the most common zoonoses globally, and Central Asia remains a Brucella hotspot. The World Health Organization classifies brucellosis as a neglected zoonotic disease that is rarely in the spotlight for research and mainly affects poor, marginalized people. Urban and peri-urban farming is a common practice in many low-income countries, and it increases the incomes of families that are often restrained by limited economic resources. However, there is a concern that the growing number of people and livestock living close together in these areas will increase the transmission of zoonotic pathogens such as Brucella. This study investigates the presence of Brucella DNA in bovine milk in the urban and peri-urban area of Dushanbe, Tajikistan. Brucella DNA was detected in 10.3% of 564 cow milk samples by IS711-based real-time PCR. This finding is concerning because consumption of unpasteurized dairy products is common in the region. Furthermore, Brucella DNA was detected in the milk of all seropositive cows, but 8.3% of the seronegative cows also showed the presence of Brucella DNA. In addition, sequence analysis of the rpoB gene suggests that one cow was infected with B. abortus and another cow was most likely infected with B. melitensis. The discrepancies between the serology and real-time PCR results highlight the need to further investigate whether there is a need for implementing complementary diagnostic strategies to detect false serological negative individuals in Brucella surveillance, control, and eradication programmes. Furthermore, vaccination of cattle with S19 in addition to vaccination of small ruminants with Rev 1 might be needed in order to control Brucella infections in the livestock population but further research focusing on the isolation of Brucella is required to obtain a comprehensive understanding of the Brucella spp. circulating among the livestock in this region.

Immuno-pathophysiological responses of mouse model to experimental infection with Brucella melitensis and its lipopolysaccharides via intraperitoneal route

Brucella melitensis is one of the major zoonotic pathogens with significant economic implications worldwide. The pathogenicity is complex and not always well understood. Lipopolysaccharide (LPS) remains the major virulent factor of B. melitensis and responsible for the mechanism by which the pathogen causes its deleterious effects. In this study, 84 mice of 6-8 weeks old of both sexes were divided equally into 3 groups; namely Brucella melitensis infected group, lipopolysaccharide (LPS) infected group and control group. The former two groups contained 36 mice each with equal gender distribution. The control group consisted of 12 mice only. Animals in B. melitensis infected group, a single inoculum of 0.4 ml containing 10⁹ of B. melitensis were intraperitoneally challenged while animals in LPS group, a single dose of 0.4 ml containing LPS extracted from the B. melitensis were intraperitoneally inoculated. Animals in control group received intraperitoneally, a single dose of 0.4 ml phosphate buffered saline (PBS) of pH7. Animals that were infected intraperitoneally with B. melitensis demonstrated significant clinical presentation; gross and histo-pathological evidence than LPS infected group. However, both infected groups showed elevated levels of interleukins (IL-1β and IL6), antibody levels (IgM an IgG) as early as 3 days post-infection with predominance in LPS infected group. In contrast, low levels of sex related hormonal changes in which LPS infected group showed the least concentration were also detected throughout the experimental period. In conclusion, B. melitensis can be transmitted via gastrointestinal, respiratory and reproductive tract. Moreover, LPS stimulated significantly the innate and acquired immune system without significant systemic dysfunction, suggesting potentiality of the protective properties of this component as alternative vaccine for brucellosis infection.

The Case for Live Attenuated Vaccines against the Neglected Zoonotic Diseases Brucellosis and Bovine Tuberculosis

Vaccination of humans and animals with live attenuated organisms has proven to be an effective means of combatting some important infectious diseases. In fact, the 20th century witnessed tremendous improvements in human and animal health worldwide as a consequence of large-scale vaccination programs with live attenuated vaccines (LAVs). Here, we use the neglected zoonotic diseases brucellosis and bovine tuberculosis (BTb) caused by Brucella spp. and Mycobacterium bovis (M. bovis), respectively, as comparative models to outline the merits of LAV platforms with emphasis on molecular strategies that have been pursued to generate LAVs with enhanced vaccine safety and efficacy profiles. Finally, we discuss the prospects of LAV platforms in the fight against brucellosis and BTb and outline new avenues for future research towards developing effective vaccines using LAV platforms.

Evaluation of three competitive ELISAs and a fluorescence polarisation assay for the diagnosis of bovine brucellosis

Bovine brucellosis is an infectious disease of worldwide public health and economic importance. The usual tests for the diagnosis of this disease include the Rose-Bengal test (RBT), complement fixation test (CFT), serum agglutination test (SAT) and indirect ELISA. New tests such as competitive ELISAs (C-ELISA) and fluorescence polarisation assay (FPA) have been developed. However, C-ELISA may correspond to different protocols and a wide variation may exist in their diagnostic performance. The aim of this study was to evaluate three commercially available C-ELISA kits (C-ELISA1-3) and FPA for the diagnosis of bovine brucellosis and compare test performance with RBT, CFT, indirect ELISA and FPA. Sera submitted to EU laboratories in 2011 from 5111 adult cattle were tested. Individual test sensitivities (Se) and specificities (Sp) were estimated. Threshold assessment using the receiver operating characteristic method was also performed. The most sensitive tests were FPA (99.0%; 95% confidence interval [CI], 97.9-100%), C-ELISA1 (98.4%; 95% CI, 97.0-99.8%) and RBT (97.7%; 95% CI, 95.9-99.3%). The most specific tests were CFT (99.98%; 95% CI, 99.93-100%), SAT (99.98%; 95% CI, 99.93-100%) and RBT (99.89%; 95% CI, 99.79-99.99%). Among the new tests, none of the three C-ELISA kits studied could be recommended as a single screening test because of their low specificity, especially when used in a herd. C-ELISA3 could not be recommended as confirmatory test on individual animals to determine whether false positive serological test results had occurred.

Seroprevalence of bovine brucellosis and associated risk factors in and around Alage district, Ethiopia

Brucellosis is a zoonotic disease with economic and public health impact, particularly for human and animal populations within developing countries that relay on livestock production. A cross sectional study was conducted between October 2013 and March 2014 in and around Alage district to determine the seroprevalence of bovine brucellosis and associated risk factors. A total of 804 sera samples; 421 from cattle managed under extensive production system and 383 from cattle managed under intensive production system were collected. Multistage cluster sampling method was employed to sample unvaccinated cattle above 6 months of age. Rose Bengal Plate Test and c-ELISA were used in serial for detection of antibodies against Brucella species. The overall seroprevalence was 2.4 %, and herd level seroprevalence was 45.9 %. A prevalence of 3.3 and 1.3 % was recorded in the extensive and intensive farms respectively. Among the three sites, seropositivity of 3.4 % in Naka, 3.3 % in Negelewudisha and 1.3 % in Alage were recorded. Risk factors such as age, sex, number of service per conception, calving interval and reproductive status were associated with serostatus of brucellosis. Taken as a whole, cattle in both intensive and extensive production systems are endemically infected by brucellosis at low level in the study areas. This warrants the need of integrated intervention strategies to minimize the spread of the disease in animals and reduce the risk of transmission to humans.

Evaluation of the sensitivity and specificity of an enzyme-linked immunosorbent assay for diagnosing brucellosis in African buffalo (Syncerus caffer)

Brucellosis is a disease of veterinary and public health importance worldwide. In sub-Saharan Africa, where the bacterium Brucella abortus has been identified in several free-ranging wildlife species, successful disease control may be dependent on accurate detection in wildlife reservoirs, including African buffalo (Syncerus caffer). We estimated the sensitivity and specificity of a commercial enzyme-linked immunosorbent assay (ELISA) (IDEXX Brucellosis Serum Ab test, IDEXX Laboratories, Westbrook, Maine, USA) for B. abortus based on a data set of 571 serum samples from 258 buffalo in the Kruger National Park, South Africa. We defined a pseudogold standard test result as those buffalo that were consistently positive or negative on two additional serologic tests, namely, the rose bengal test (RBT) and the complement fixation test (CFT). The ELISA's cutoff value was selected using receiver operating characteristics analysis, the pseudogold standard, and a threshold criterion that maximizes the total sensitivity and specificity. Then, we estimated the sensitivity and specificity of all three tests using Bayesian inference and latent class analysis. The ELISA had an estimated sensitivity of 0.928 (95% Bayesian posterior credibility interval [95% BCI] = 0.869-0.974) and specificity of 0.870 (95% BCI = 0.836-0.900). Compared with the ELISA, the RBT had a higher estimated sensitivity of 0.986 (95% BCI = 0.928-0.999), and both the RBT and CFT had higher specificities, estimated to be 0.992 (95% BCI = 0.971-0.996) and 0.998 (95% BCI = 0.992-0.999), respectively. Therefore, no single serologic test perfectly detected the antibody. However, after adjustment of cutoff values for South African conditions, the IDEXX Brucellosis Serum Ab Test may be a valuable additional screening test for brucellosis in Kruger National Park's African buffalo.

A molecular scheme for Yersinia enterocolitica patho-serotyping derived from genome-wide analysis

Yersinia enterocolitica is a food-borne, gastro-intestinal pathogen with world-wide distribution. Only 11 serotypes have been isolated from patients, with O:3, O:9, O:8 and O:5,27 being the serotypes most commonly associated with human yersiniosis. Serotype is an important characteristic of Y. enterocolitica strains, allowing differentiation for epidemiology, diagnosis and phylogeny studies. Conventional serotyping, performed by slide agglutination, is a tedious and laborious procedure whose interpretation tends to be subjective, leading to poor reproducibility. Here we present a PCR-based typing scheme for molecular identification and patho-serotyping of Y. enterocolitica. Genome-wide comparison of Y. enterocolitica sequences allowed analysis of the O-antigen gene clusters of different serotypes, uncovering their formerly unknown genomic locations, and selection of targets for serotype-specific amplification. Two multiplex PCRs and one additional PCR were designed and tested on various reference strains and isolates from different origins. Our genotypic assay proved to be highly specific for identification of Y. enterocolitica species, discrimination between virulent and non-virulent strains, distinguishing the main human-related serotypes, and typing of conventionally untypeable strains. This genotyping scheme could be applied in microbiology laboratories as an alternative or complementary method to the traditional phenotypic assays, providing data for epidemiological studies.

Brucella antibody seroprevalence in Antarctic seals (Arctocephalus gazella, Leptonychotes weddellii and Mirounga leonina)

Brucellosis is a worldwide infectious zoonotic disease caused by Gram-negative bacteria of the genus Brucella, and Brucella infections in marine mammals were first reported in 1994. A serosurvey investigating the presence of anti-Brucella antibodies in 3 Antarctic pinniped species was undertaken with a protein A/G indirect enzyme-linked immunosorbent assay (iELISA) and the Rose Bengal test (RBT). Serum samples from 33 Weddell seals Leptonychotes weddelli were analysed, and antibodies were detected in 8 individuals (24.2%) with the iELISA and in 21 (65.6%) with the RBT. We tested 48 southern elephant seal Mirounga leonina sera and detected antibodies in 2 animals (4.7%) with both the iELISA and the RBT. None of the 21 Antarctic fur seals Arctocephalus gazella was found positive. This is the first report of anti-Brucella antibodies in southern elephant seals. The potential impact of Brucella infection in pinnipeds in Antarctica is not known, but Brucella spp. are known to cause abortion in terrestrial species and cetaceans. Our findings suggest that Brucella infection in pinnipeds is present in the Antarctic, but to date B. pinnipedialis has not been isolated from any Antarctic pinniped species, leaving the confirmation of infection pending.

Investigating the use of protein saver cards for storage and subsequent detection of bovine anti-Brucella abortus smooth lipopolysaccharide antibodies and gamma interferon

Brucella abortus, a smooth strain of the genus Brucella, is the causative agent of bovine brucellosis. To support the ongoing development of diagnostic tests for bovine brucellosis, the use of Protein Saver cards (Whatman) for bovine blood serum and plasma sample collection has been evaluated. These cards offer significant logistical and safety alternatives to transporting and storing liquid samples and may aid in diagnostic programs and validation studies. To evaluate the utility of these cards, 204 bovine blood serum samples from Brucella-infected and noninfected animals were stored on and eluted from the Protein Saver cards. Anti-Brucella smooth lipopolysaccharide (sLPS) antibody titers for the serum eluates were compared to those of the unprocessed original serum samples by indirect enzyme-linked immunosorbent assay (ELISA). The results showed a highly significant correlation between titers from the serum eluates and the unprocessed sera. Therefore, under these circumstances, serum eluates and unprocessed serum samples may be used interchangeably. Blood plasma from 113 mitogen-stimulated whole-blood samples was added to and eluted from the Protein Saver cards. The gamma interferon (IFN-γ) titers in the plasma eluates were compared to those of the unprocessed plasma samples obtained by IFN-γ ELISA. The results showed a significant correlation between the plasma eluates and the unprocessed plasma samples. To derive a signal in the plasma eluate, it was necessary to develop a novel and highly sensitive ELISA for the detection of IFN-γ. The serum samples stored on cards at room temperature over a 10-day period showed little variation in antibody titers. However, the plasma eluates showed a progressive loss of IFN-γ recovery over 10 days when stored at room temperature.

Bayesian estimation of true prevalence, sensitivity and specificity of indirect ELISA, Rose Bengal Test and Slow Agglutination Test for the diagnosis of brucellosis in sheep and goats in Bangladesh

The true prevalence of brucellosis and diagnostic test characteristics of three conditionally dependent serological tests were estimated using the Bayesian approach in goats and sheep populations of Bangladesh. Serum samples from a random selection of 636 goats and 1044 sheep were tested in parallel by indirect ELISA (iELISA), Rose Bengal Test (RBT) and Slow Agglutination Test (SAT). The true prevalence of brucellosis in goats and sheep were estimated as 1% (95% credibility interval (CrI): 0.7-1.8) and 1.2% (95% CrI: 0.6-2.2) respectively. The sensitivity of iELISA was 92.9% in goats and 92.0% in sheep with corresponding specificities of 96.5% and 99.5% respectively. The sensitivity and specificity estimates of RBT were 80.2% and 99.6% in goats and 82.8% and 98.3% in sheep. The sensitivity and specificity of SAT were 57.1% and 99.3% in goats and 72.0% and 98.6% in sheep. In this study, three conditionally dependent serological tests for the diagnosis of small ruminant brucellosis in Bangladesh were validated. Considerable conditional dependence between IELISA and RBT and between RBT and SAT was observed among sheep. The influence of the priors on the model fit and estimated parameter values was checked using sensitivity analysis. In multiple test validation, conditional dependence should not be ignored when the tests are in fact conditionally dependent.

Yersinia enterocolitica serotype O:9 cultured from Swedish sheep showing serologically false-positive reactions for Brucella melitensis

In a herd of 20 sheep in Sweden, a country where brucellosis has never been diagnosed in sheep or goats, a total of six sheep were found serologically positive to Brucella melitensis in two different rounds of sampling. Yersinia enterocolitica serotype O:9 could at the time of the second sampling be isolated from four sheep, one of them at the same time serologically positive for B. melitensis. The article describes the case and gives some background information on brucellosis and Y. enterocolitica in general as well as a more specific description of the Swedish surveillance program for B. melitensis and the test procedures used. The problem with false-positive reactions, in particular its implications for surveillance programs in low prevalence or officially brucellosis-free countries, is discussed.

A review on camel brucellosis: a zoonosis sustained by ignorance and indifference

In many developing countries of Asia and Africa, camels are one of the most important sources of income for the nomadic population. With increasing urbanization, camel milk and meat have gained a wider market and commercialization and consumption of camel products are on the rise. Camel brucellosis can be encountered in all camel rearing countries with exception of Australia. High animal and herd prevalences have been reported from numerous countries, which not only pose a continuous risk for human infection, but also increase the spread of infection through uncontrolled trade of clinically inconspicuous animals. This short review aims at providing an overview on diagnostic investigations, as well as the public health and economic impact of brucellosis in old world camels.

A serological and bacteriological survey of brucellosis in wild boar (Sus scrofa) in Belgium

Background

Brucellosis is frequently reported among wild boar populations in Europe. The aim of the study was to assess the epidemiological situation in Belgium, regarding the steady increase of wild boar populations over the last decades. Several serological tests were used and compared with culture and IS711 polymerase chain reaction (PCR), to determine the most suitable combination of diagnostic tools for conducting a successful prevalence study in wildlife.

Results

An indirect enzyme-linked immunosorbent assay (iELISA) was used on 1168 sera from hunter-killed wild boar sampled between 2003 and 2007 in 4 natural regions of southern Belgium. Results gave an apparent prevalence of 54.88% (95% CI 52.03-57.73). Prevalence was significantly affected by age and by the year of study, but not by sex nor by the region of sampling. The relative sensitivities of the complement fixation test (CFT), the Rose Bengal test (RBT), and the slow agglutination test (SAT) versus the iELISA differed widely between tests, reaching 62.67%, 46.68%, and 34.77%, respectively. The relative specificities of the CFT, RBT and SAT versus the iELISA were respectively 99.01%, 92.49%, and 99.1%. From seropositive animals (iELISA), 9% were positive by culture and 24% by PCR when testing spleen and/or tonsils. Sensitivity of the PCR was higher on tonsils than on spleen. All bacterial isolates were identified as Brucella suis biovar 2.

Conclusions

Brucellosis is widespread among wild boar in southern Belgium, with seroprevalences having increased over ten years, and constitutes a growing risk of spillback to outdoor-farmed pig herds. The iELISA showed a better sensitivity than the CFT, RBT and SAT. Serological tests must be associated with direct diagnosis and PCR proved more sensitive than culture under wildlife sampling conditions. Spleen and tonsils are lymphoid tissues usually sampled in multi-disease monitoring programs. They remain top-grade organs for direct diagnosis of brucellosis, with a preference for tonsils.

An evaluation of the capability of existing and novel serodiagnostic methods for porcine brucellosis to reduce false positive serological reactions

Porcine brucellosis is a zoonotic disease of truly global significance because even in countries without the disease the occurrence of false positive serological reactions (FPSRs) creates significant problems. Statutory diagnostic testing is required in many disease free countries or regions and is often a prerequisite for the movement of live animals. Currently this testing is dependent almost entirely on serological assays and these may result in a significant number of FPSRs. The aim of this study was to examine existing and novel serodiagnostic assays to evaluate their diagnostic sensitivity and resilience to FPSRs. The existing assays evaluated were the RBT, smooth lipopolysaccharide (sLPS) indirect (i) ELISA, sLPS competitive (c) ELISA, and the FPA. The novel assays evaluated were the sLPS TR-FRET assay, a rough (r) LPS iELISA, a recombinant protein BP26 iELISA and a cytoplasmic protein extract (Brucellergene™) iELISA. Four populations of sera were evaluated: those from Brucella suis infected swine (n=34), randomly selected samples from non-infected swine (n=161), sera from non-infected swine within herds exhibiting FPSRs (n=132) and sera from swine experimentally infected with Yersinia enterocolitica O:9 (n=4). The results show that all the assays dependent on the sLPS O-polysaccharide (OPS) for their sensitivity (the RBT, sLPS ELISAs, FPA and the sLPS TR-FRET) had significantly reduced diagnostic specificity when applied to the FPSR population, the RBT being most affected. Of the two rapid homogeneous assays, the TR-FRET was diagnostically superior to the FPA in this study. Neither of the protein based iELISAs demonstrated sufficient diagnostic sensitivity to resolve the FPSRs. The rLPS iELISA showed no cross reaction with the FPSRs and had diagnostic sensitivity similar to that of the OPS based assays.

Interference in diagnostic tests for brucellosis in cattle recently vaccinated against leptospirosis

The aim of the current study was to verify if cattle vaccinated against leptospirosis may react in diagnostic tests for brucellosis. Sixty cows were divided into 5 groups, each comprising 12 animals. Four groups were given different vaccines against leptospirosis, while the control group received only saline. Two doses of vaccine were given, as recommended by the manufacturers. Serum samples were collected on the first day of immunization (day 0) and on postvaccination days 7, 14, 21, 28, 35, 42, 49, 56, 96, and 126. All the serum samples were tested for brucellosis and leptospirosis. Twenty animals were reactive at least once to the Rose Bengal test, but by day 96, no further reactions were elicited by this test. Twenty-six samples were reactive to the Rose Bengal test, but only 7 remained positive in confirmatory tests: 1 to the 2-mercaptoethanol test, 2 to the fluorescence polarization assay, and 6 to indirect enzyme-linked immunosorbent assays. None of the samples was reactive in the complement fixation test. None of the animals in the control group was reactive. A significant difference was found between the control group and the groups vaccinated against leptospirosis, according to Fisher exact test. However, the groups were found to respond independently of the vaccine brand. The results indicate that cattle vaccinated against leptospirosis may show reactivity on screening tests for brucellosis.