Search

Background: The objective of this study was to investigate Brucella infection in farm animals in Saham, Oman, with reference to a survey carried out by the Ministry of Agriculture & Fisheries (MAF) for Brucellosis during the period of May to July 2016 in Saham, following an outbreak of human brucellosis. We wanted to apply different serological, bacteriological and molecular tests in a time frame (phase 1, 2 & 3) with reference to the pivotal time of a human brucellosis outbreak to ascertain the status of the disease in Saham area where the MAF survey was conducted. Blood samples were collected from farm animals and sera were screened in parallel for Brucella antibodies using different serological tests., Results: Using the RBT test, phase 1 sera showed seropositivity in sheep at 2.6%, (95% CI: 0.5-13.5%), in camel (5.9%, 1.1-27.0%), but not in sera from goats and cattle (0%). Using I-ELISA, seropositivity in goat was 3.1% (0.6-15.8%), with no positive sheep and cattle. Using c-ELISA for camel we found a seropositivity of 5.9% (1.1-27.0%). Furthermore, CFT seropositivity in goats was 21.9% (CI: 11.3-38.9), cattle and sheep sera were negative and camel was 5.9% (1.1-27.0%). In phase 2, the seropositivity in goats was 1.9% (1.4-2.6%), sheep 4.5% (3.5-5.8%), cattle 1.1%, (0.5-2.3%) and camels 18.2% (5.1-47.7%), Phase 3 sera were collected 6 months after the human brucellosis outbreak. With RBT, the seropositivity in goats was 3% (1.0-8.5%), sheep 2% (0.6-7.1%) cattle 1% (0.2-5.5%). With I-ELISA, goats & camels were negative, sheep were 3% (1.0-8.5%) and cattle 1% (0.2-5.5%). Moreover, B. melitensis was isolated from a bronchial lymph node of the RBT and I-ELISA seropositive cow and confirmed by Multiplex PCR and biochemical tests., Conclusion: Using a retrospective study analysis of animal sera and following up after a human brucellosis outbreak, the present study showed a slight decrease in seropositivity of infected animals after the MAF implemented test and slaughter policy. The most interesting finding in this study was the isolation, identification and molecular characterization of Brucella melitensis in a cow (spillover), which is not a preferential host for Brucella melitensis.

Background: Brucella ovis causes an infectious disease responsible for infertility and subsequent economic losses in sheep production. The standard serological test to detect B. ovis infection in rams is the complement fixation test (CFT), which has imperfect sensitivity and specificity in addition to technical drawbacks. Other available tests include the indirect enzyme-linked immunosorbent assays (I-ELISA) but no I-ELISA kit has been fully evaluated.The study aimed to compare an I-ELISA kit and the standard CFT. Our study was carried out on serum samples from 4599 rams from the South of France where the disease is enzootic. A Bayesian approach was used to estimate tests characteristics (diagnostic sensitivity, Se and diagnostic specificity, Sp). The tests were then studied together in order to optimise testing strategies to detect B. ovis., Results: After optimising the cut-off values in order to avoid doubtful results without deteriorating the concordance between the results of the two tests, the I-ELISA appeared to be slightly more sensitive than CFT (Se I-ELISA=0.917 [0.822; 0.992], 95% Credibility Interval (CrI) compared to Se CFT=0.860 [0.740; 0.967], 95% CrI). However, CFT was slightly more specific than I-ELISA (Sp CFT=0.988 [0.947; 1.0], 95% CrI) compared to Sp I-ELISA =0.952 [0.901; 1.0], 95% CrI).The tests were then associated with two different interpretation schemes. The series association increased the specificity of screening and could be used for pre-movement testing in rams from uninfected flocks. The parallel association increased sequence sensitivity, thus appearing more suitable for eradicating the disease in infected flocks., Conclusions: The high sensitivity and acceptable specificity of this I-ELISA kit support its potential interest to avoid the limitations of CFT. The two tests could also be used together or combined with other diagnostic methods such as semen culture to improve the testing strategy. The choice of test sequence and interpretation criteria depends on the epidemiological context, screening objectives and the financial and practical constraints.