Evaluation of an indirect ELISA for the diagnosis of bovine brucellosis

Comparison of Different Laboratory Methods for Clinical Detection of Brucella Infection

The rapidity, accuracy, and detection abilities of different laboratory methods (tube agglutination test (SAT), indirect ELISA, fluorescence polarization test (FPA), and blood culture methods) to detect Brucella in the laboratory. The study included 95 patients with documented and 42 patients with suspected brucellosis and 56 healthy control subjects. For the tests, the positive rates of Brucella infection detection in the confirmed group were significantly higher than in group with suspected infection (p<0.01) and in healthy controls (p<0.01). There was no significant difference between indirect ELISA and FPA in detecting antibodies to Brucella in acute (χ²=0.335), subacute (χ²=0.660), and chronic cases (χ²=5.332). Among the detection methods, indirect ELISA showed the highest sensitivity (98.9%), specificity (100%), and Youden index (0.989). The sensitivity and specificity of FPA were 96.8 and 96.4%, respectively. In order to easily and rapidly diagnose brucellosis in clinical practice, a combination of detection methods is recommended, in which Brucella antibodies are screened by FPA and then confirmed by indirect ELISA.

Epidemiology and Associated Risk Factors for Brucellosis in Small Ruminants Kept at Institutional Livestock Farms in Punjab, Pakistan

Brucellosis is reportedly endemic in ruminants in Pakistan. Both Brucella abortus and B. melitensis infections have been decumented in domestic animals and humans in the country. This study aimed to identify the burden of anti-Brucella antibodies in small ruminants as well as associated potential risk factors with its occurrence at nine institutional livestock farms in Punjab, Pakistan. The sera collected from equal number of sheep and goats (500 from each species) were screened by indirect-ELISA for anti-smooth-Brucella antibodies followed by a serial detection by real-time PCR. Overall, 5.1% (51/1000) seropositivity was registered corresponding to 5% (25/500) prevalence in goats and 5.2% (26/500) in sheep. Brucella-DNA could not be detected in any of the tested sera by real-time PCR. Multiple logistic regression model indicated that farm location (OR 34.05), >4 years of age (OR 2.88), with history of reproductive disorders (OR 2.69), and with BCS of ≤ 3 (OR 12.37) were more likely to test positive for brucellosis at these farms. A routine screening, stringent biosecurity, and quarantine measures are warranted for monitoring and eradication of the infection. Similarly, isolation and molecular investigation of the etiologic agent(s) are needed to understand the relationship of epidemiology and out-breaks of brucellosis in the country.

Bayesian evaluation of three serological tests for the diagnosis of bovine brucellosis in Bangladesh

We evaluated the performance of three serological tests – an immunoglobulin G indirect enzyme linked immunosorbent assay (iELISA), a Rose Bengal test and a slow agglutination test (SAT) – for the diagnosis of bovine brucellosis in Bangladesh. Cattle sera (n = 1360) sourced from Mymensingh district (MD) and a Government owned dairy farm (GF) were tested in parallel. We used a Bayesian latent class model that adjusted for the conditional dependence among the three tests and assumed constant diagnostic accuracy of the three tests in both populations. The sensitivity and specificity of the three tests varied from 84.6% to 93.7%, respectively. The true prevalences of bovine brucellosis in MD and the GF were 0.6% and 20.4%, respectively. Parallel interpretation of iELISA and SAT yielded the highest negative predictive values: 99.9% in MD and 99.6% in the GF; whereas serial interpretation of both iELISA and SAT produced the highest positive predictive value (PPV): 99.9% in the GF and also high PPV (98.9%) in MD. We recommend the use of both iELISA and SAT together and serial interpretation for culling and parallel interpretation for import decisions. Removal of brucellosis positive cattle will contribute to the control of brucellosis as a public health risk in Bangladesh.

A systematic review of current immunological tests for the diagnosis of cattle brucellosis

Brucellosis is a worldwide extended zoonosis with a heavy economic and public health impact. Cattle, sheep and goats are infected by smooth Brucella abortus and Brucella melitensis, and represent a common source of the human disease. Brucellosis diagnosis in these animals is largely based on detection of a specific immunoresponse. We review here the immunological tests used for the diagnosis of cattle brucellosis. First, we discuss how the diagnostic sensitivity (DSe) and specificity (DSp), balance should be adjusted for brucellosis diagnosis, and the difficulties that brucellosis tests specifically present for the estimation of DSe/DSp in frequentistic (gold standard) and Bayesian analyses. Then, we present a systematic review (PubMed, GoogleScholar and CABdirect) of works (154 out of 991; years 1960-August 2017) identified (by title and Abstract content) as DSe and DSp studies of smooth lipopolysaccharide, O-polysaccharide-core, native hapten and protein diagnostic tests. We summarize data of gold standard studies (n = 23) complying with strict inclusion and exclusion criteria with regards to test methodology and definition of the animals studied (infected and S19 or RB51 vaccinated cattle, and Brucella-free cattle affected or not by false positive serological reactions). We also discuss some studies (smooth lipopolysaccharide tests, protein antibody and delayed type hypersensitivity [skin] tests) that do not meet the criteria and yet fill some of the gaps in information. We review Bayesian studies (n = 5) and report that in most cases priors and assumptions on conditional dependence/independence are not coherent with the variable serological picture of the disease in different epidemiological scenarios and the bases (antigen, isotype and immunoglobulin properties involved) of brucellosis tests, practical experience and the results of gold standard studies. We conclude that very useful lipopolysaccharide (buffered plate antigen and indirect ELISA) and native hapten polysaccharide and soluble protein tests exist, provided they are applied taking into account the means available and the epidemiological contexts of this disease: i) mass vaccination; ii) elimination based on vaccination combined with test-and-slaughter; and iii) surveillance and existence of false positive serological reactions. We also conclude that the insistence in recent literature on the lack of usefulness of all smooth lipopolysaccharide or native hapten polysaccharide tests in areas where S19 vaccination is implemented is a misinterpretation that overlooks scientific and practical evidence.

Development of an improved competitive ELISA based on a monoclonal antibody against lipopolysaccharide for the detection of bovine brucellosis

Background

Brucellosis is the most common bacterial zoonosis, and serological tests are routinely used in brucellosis control and eradication programs. In order to improve the accuracy of serological diagnostic method used in bovine brucellosis detection, this study developed an improved competitive ELISA with higher specificity and good sensitivity.

Results

This study prepared 12 monoclonal antibodies against smooth Brucella lipopolysaccharide. One monoclonal antibody 3 F9, presented C epitope specificity, was used to develop a competitive ELISA for the serological detection of bovine brucellosis. The competitive ELISA, a commercial competitive ELISA kit, the rose-bengal plate agglutination test, and a microplate agglutination test were all used in the detection of 6 hyperimmune antisera against other commonly cross-reacted bacterial pathogens and 110 clinical bovine serum samples. The results of the test comparisons indicated that the competitive ELISA had higher specificity than the commercial competitive ELISA kit and RBT, and comparable sensitivity with the commercial ELISA kit.

Conclusions

This study provided a valuable detection tool with high specificity and good sensitivity, which prevent the wrong-culling of bovines in the eradication campaigns of bovine brucellosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0436-3) contains supplementary material, which is available to authorized users.

A case-control study of risk factors for bovine brucellosis seropositivity in Peninsular Malaysia

Bovine brucellosis was first reported in Peninsular Malaysia in 1950. A subsequent survey conducted in the country revealed that the disease was widespread. Current knowledge on the potential risk factors for brucellosis occurrence on cattle farms in Malaysia is lacking. Therefore, we conducted a case-control study to identify the potential herd-level risk factors for bovine brucellosis occurrence in four states in the country, namely Kelantan, Pahang, Selangor and Negeri Sembilan. Thirty-five cases and 36 controls of herds were selected where data on farm management, biosecurity, medical history and public health were collected. Multivariable logistic regression identified that Brucella seropositive herds were more likely to; have some interaction with wildlife (OR 8.9, 95% CI = 1.59–50.05); originated from farms where multiple species such as buffalo/others (OR 41.8, 95% CI = 3.94–443.19) and goat/sheep (OR 8.9, 95%Cl = 1.10–71.83) were reared, practice extensive production system (OR 13.6, 95% CI 1.31–140.24) and have had episodes of abortion in the past (OR 51.8, 95% CI = 4.54–590.90) when compared to seronegative herds. Considering the lack of information on the epidemiology of bovine brucellosis in peninsular Malaysia and absence of information on preventing the inception or spread of the disease, this report could contribute to the on-going area-wise national brucellosis eradication program.

Bovine brucellosis in Argentina and bordering countries: update

Bovine brucellosis is a zoonotic disease spread worldwide. The infection in cattle is predominantly caused by Brucella abortus and is usually detected in pregnant females through abortions. The disease is endemic in Argentina; however, infection in humans is underestimated and often not reported. The prevalence of bovine brucellosis in countries bordering Argentina is quite variable: 0.04% in Uruguay, 10.20% in the north and 0.06% in the south of Brazil, 0.2% in Chile, 3.15% in Paraguay and 2.27% in Bolivia. In 1999, the Argentine National Control and Eradication Program was implemented. Its strategies include identification of vaccinated animals, compulsory vaccination with B. abortus S19 of 100% of 3- to 8-month-old females, negative serological tests before animal movements and categorization of farms in terms of their brucellosis status. The epidemiological surveillance in milk is performed through the milk ring test and the indirect ELISA. The result of a national brucellosis survey performed in 2004 indicates that 12.4% (95% CI: 10.89-14.0) of Argentine beef farms are seropositive to Brucella and that the apparent prevalence in cattle is 2.10% (95% CI: 1.90-2.40). The official serological diagnostic tests are as follows: buffered plate antigen test, as screening, serum agglutination test, 2-mercaptoethanol and fluorescence polarization assay, competitive ELISA, as confirmatory tests, and complement fixation test, as definitive test. Santa Fe and a district in Córdoba have 'Outstanding Plans'. Tierra del Fuego is a 'Zone free from bovine brucellosis'. One question arising when studying the Argentine situation is why the disease remains endemic if good regulations exist to control and eradicate it. In future, some different aspects might be evaluated to understand it, and further studies should be performed to prioritize, select and refine control strategies.

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.

Comparison of diagnostic tests for the detection of Brucella spp. in camel sera

BACKGROUND

Brucellosis in livestock causes enormous losses for economies of developing countries and poses a severe health risk to consumers of dairy products. Little information is known especially on camel brucellosis and its impact on human health. For surveillance and control of the disease, sensitive and reliable detection methods are needed. Although serological tests are the mainstay of diagnosis in camel brucellosis, these tests have been directly transposed from cattle without adequate validation. To date, little information on application of real-time PCR for detection of Brucella in camel serum is available. Therefore, this study was performed to compare the diagnostic efficiency of different serological tests and real-time PCR in order to identify the most sensitive, rapid and simple combination of tests for detecting Brucella infection in camels.

FINDINGS

A total of 895 serum samples collected from apparently healthy Sudanese camels was investigated. Sudan is a well documented endemic region for brucellosis with cases in humans, ruminants, and camels. Rose Bengal Test (RBT), Complement Fixation Test (CFT), Slow Agglutination Test (SAT), Competitive Enzyme Linked Immunosorbant Assay (cELISA) and Fluorescence Polarization Assay (FPA) as well as real-time PCR were used. Our findings revealed that bcsp31 kDa real-time PCR detected Brucella DNA in 84.8% (759/895) of the examined samples, of which 15.5% (118/759) were serologically negative. Our results show no relevant difference in sensitivity between the different serological tests. FPA detected the highest number of positive cases (79.3%) followed by CFT (71.4%), RBT (70.7%), SAT (70.6%) and cELISA (68.8%). A combination of real-time PCR with one of the used serological tests identified brucellosis in more than 99% of the infected animals. 59.7% of the examined samples were positive in all serological tests and real-time PCR. A subpopulation of 6.8% of animals was positive in all serological tests but negative in real-time PCR assays. The high percentage of positive cases in this study does not necessarily reflect the seroprevalence of the disease in the country but might be caused by the fact that the camels were imported from brucellosis infected herds of Sudan, accidentally. Seroprevalence of brucellosis in camels should be examined in confirmatory studies to evaluate the importance of brucellosis in this animal species.

CONCLUSION

We suggest combining bcsp31 real-time PCR with either FPA, CFT, RBT or SAT to screen camels for brucellosis.

Development and evaluation of an indirect enzyme-linked immunosorbent assay for the detection of antibodies against Campylobacter fetus in cattle

Campylobacteriosis is a zoonosis that occurs worldwide. Infection with Campylobacter fetus (C. fetus) causes infertility and abortion in sheep and cattle. The current study focuses on the SapA gene of C. fetus that encodes surface array proteins and plays an important role in the virulence of C. fetus. The SapA-N (1398bp) and SapA-C (1422bp) fragments were amplified from the C. fetusSapA gene using polymerase chain reaction (PCR), and the corresponding recombinant proteins rSapA-N and rSapA-C were expressed in Escherichia. coli BL21 cells. Results of Western blotting and enzyme-linked immunosorbent assay (ELISA) showed that the immunological activity of rSapA-N was higher than that of rSapA-C (P<0.05). Therefore, rSapA-N was selected to establish an indirect ELISA for detecting antibodies against C. fetus. The diagnostic criteria were as follows: S/P0.45: positive; S/P<0.4: negative; 0.45>S/P0.4: suspected. The specificity and sensitivity of our method were 94.3% and 88.6%, respectively. Moreover, no cross-reactions were observed between rSapA-N and serum samples that were positive for other bovine bacterial pathogens diseases such as Mycobacterium avium subspecies paratuberculosis. One hundred and two serum samples from cows that had experienced abortion were tested. Four and 2 C. fetus-positive serum samples were found among the 70 bovine brucellosis-positive samples and the 32 infectious bovine rhinotracheitis (IBR)-positive samples, respectively. The findings suggest that the rSapA-N-based ELISA method has immense potential in future applications.

EVALUACIÓN ENTRE CUATRO TÉCNICAS SEROLÓGICAS PARA EL DIAGNÓSTICO DE INFECCIONES CAUSADAS POR BRUCELLA ABORTUS EN BOVINOS

ABSTRACT Serum samples from 200 vaccinated adult bovine females from two herds were analyzed by buffered antigen acidified plate test (AAT) (Rose Bengal Plate Test), indirect enzyme-linked immunosorbent assay (ELISAI), 2-mercaptoethanol test (2-ME) and complement fixation test (FC). For ELISAI, the fixed value of 45 percent positivity (PP) was used. Group A was composed of 100 animals, with description of reproductive disturbances compatible with brucellosis and reagent to the AAT. Group B was composed of 100 animals serologically free of B. abortus for at least two years. Additionally, all serum samples were tested using the AAT, the 2-ME and the FC to confirm negative status. The combination of two tests, FC and 2ME was used as the gold standard. The relative sensitivity and specificity and the Kappa were calculated for each test. The result of kappa for 2-ME in relation to the FC and of the AAT and the ELISAI in relation to the gold standard was, respectively, 0.78, 0.86 And 0.84. The relative sensitivities (Sr) were, respectively, 84.1% (53/63), 100% (53/53) and 98.1% (52/53), and the relative specificities (Er) were 93.3% (111/119), 90.1% (100/111) and 90.1% (100/111). For comparison between the ELISAI and the AAT, there was obtained a Kappa of 0.91, Sr of 93% (93/100) and Er of 98% (98/100). Conclusions: 1 The option of constituting the gold standard based on at least two tests was the most suitable for this study; 2 The ELISAI resulted in values of Sr and Er similar to the AAT. Therefore, the AAT and the ELISAI are good for screening in regard to the diagnosis of brucellosis.

BRUCELOSE EM BÚFALOS

RESUMO A bubalinocultura é uma atividade econômica relevante no Brasil. Considerando a importância do Programa Nacional de Controle e Erradicação da Brucelose e Tuberculose para a evolução das cadeias produtoras de bovinos e bubalinos e tendo em vista a escassez de estudos sobre o sorodiagnóstico da brucelose na espécie bubalina, procedimento no qual apóia-se o processo de certificação de rebanhos livres e monitorados, é apresenta uma revisão sobre brucelose bubalina. Neste trabalho são discutidos os seguintes temas: 1a bubalinocultura no Brasil; 2revisão e aspectos históricos da brucelose bovina e bubalina; 3revisão sobre o sorodiagnóstico da brucelose em bovinos e bubalinos.

A longitudinal study to identify constraints to dairy cattle health and production in rural smallholder communities in Northern Vietnam

The objective of the study was to investigate constraints to dairy cattle health and production in rural smallholder communities in northern Vietnam, one of the target areas of the Vietnam government's dairy development programme. A total of 99 dairy farms (11 per commune) were recruited from 9 of 32 communes in Ba Vi District, using random two-stage cluster sampling. After the initial questionnaire interviews were conducted, farms were visited at three monthly intervals over a period of 1 year. Information on several health and production parameters relating to the study cattle was collected. Using multiple indicator modelling, it was found that Fasciola infestation, farmers who had been involved in dairying for longer (not indicative of better management skills), larger herd size, and cattle being kept in a shed were linked to reduced reproductive performances.

Comparison of three serological tests in the diagnosis of Brucella infection in unvaccinated cattle in Eritrea

Three serological methods, the Rose-Bengal test (RBT), the complement-fixation test (CFT) and an indirect enzyme-linked immunosorbent assay (I-ELISA) were compared for the detection of Brucella-infected animals in unvaccinated cattle herds in Eritrea. In this study, 71 herds first were classified as positive or negative for Brucella infection on the basis of at least one animal being seropositive by RBT and CFT. All the 159 RBT-positive samples from the 26 seropositive herds and 214 RBT-negative samples randomly selected from the seropositive herds and from the 45 negative herds were tested further by CFT and I-ELISA. Using the ELISA titer as main predictor, and incorporating the RBT results, a logistic model was built to predict the CFT-negative or -positive status of individual sera and to estimate sensitivity and specificity. Whilst the ELISA titers (< or =20) accurately predicted all the negative sera in herds that were also negative by the CFT, the number of seropositive animals was higher by ELISA in herds that had positive animals. Serum samples which give higher degrees of agglutination with the RBT need not be re-tested with CFT; consideration of the seropositive status of a herd should be taken into consideration on defining the cut-off optical density readings for ELISA.

Field evaluation of an indirect ELISA for detection of brucellosis in lowland Bolivia

Bovine brucellosis exists endemically at an estimated prevalence of 10% in the developing dairy industry of Santa Cruz in tropical Bolivia. This paper describes field testing of an FAO/IAEA indirect ELISA for brucellosis, as a possible replacement confirmatory test for the complement fixation test (CFT). The ELISA and CFT were compared on sera from 3 cattle populations: a non-vaccinated negative population, an S19-vaccinated negative population, and a brucellosis-positive population of unknown vaccination status. The CFT and ELISA showed excellent specificities of 100% and 98% respectively against the negative non-vaccinated group. The CFT maintained a specificity of 98% against the S19-vaccinated negative group, but ELISA specificity fell to 83% using a cut-off of 20% of positive control, and 94% using a cut-off of 40% of positive control. Against sera from the positive population, the ELISA gave many more positive reactions than the CFT, probably a combination of both higher sensitivity and lower specificity. It is concluded that as Santa Cruz is entering a phase of brucellosis control rather than eradication, the extra sensitivity of the ELISA is not valuable enough to risk a higher level of false positive reactions, especially as S19 vaccination is being increasingly used.

An indirect ELISA using a monoclonal anti IgG1 enzyme conjugate for the diagnosis of bovine brucellosis

An indirect ELISA using a monoclonal anti-IgG1 enzyme conjugate for diagnosis of bovine brucellosis was evaluated. Three groups of sera from negative non-vaccinated, from negative vaccinated and from positive cows were used. The specificity of the ELISA for negative non-vaccinated cows was 99.2 and 99.6% for negative but vaccinated cows. The sensitivity of this technique estimated with positive sera was 99.5%. The ELISA evaluated appears to be a very useful tool in the diagnosis of bovine brucellosis, particularly for regions where little epidemiological information is available about this disease and where large numbers of sera should be tested to obtain such information.