Bayesian Evaluation of Three Serological Tests for Detecting Antibodies against Brucella spp. among Humans in the Northwestern Part of Ecuador.

Brucellosis is an important but neglected zoonosis that causes serious economic losses both in livestock and human populations. The aim of the present study was to estimate the true prevalence of brucellosis together with diagnostic sensitivity and specificity of three serological tests in humans of the northwestern part of Ecuador using a Bayesian approach adjusted for the dependencies among the multiple tests to avoid any misinterpretation. In addition, the causal agent responsible for human brucellosis was also identified. Using a total of 3,733 samples collected from humans in this area between 2006 and 2008, the prevalence of human brucellosis and the diagnostic test characteristics of the Rose Bengal fast agglutination test (RBT), Wright's slow agglutination test with ethylenediaminetetraacetic acid disodium salt dehydrate (EDTA) (SAT-EDTA), and indirect ELISA (iELISA) were estimated using a Bayesian approach. The estimated true prevalence of human brucellosis was 1% (credibility interval: 0.4-1.6). The sensitivities of iELISA and RBT were higher than and similar (95.1% and 95.0%, respectively) to those of SAT-EDTA (60.8%). Even though all tests indicated a high specificity (> 99.0%), the specificity of SAT-EDTA was highest (99.9%). The circulating strain in this study area was identified to be Brucella abortus biotype 4 based on culture and microbiological characterization. The RBT and the iELISA are recommended for estimating the true prevalence of human brucellosis and/or for surveillance programs following their high sensitivities and specificities. The proposed strategy supports evidence-based medicine for clinicians and policy-makers to ensure appropriate preventive and control program of brucellosis worldwide.

The unexpected discovery of Brucella abortus Buck 19 vaccine in goats from Ecuador underlines the importance of biosecurity measures.

Very few, mostly old, and only preliminary serological studies of brucellosis in goats exist in Ecuador. In order to assess the current epidemiological situation, we performed a cross-sectional serological study in the goat populations of Carchi (n = 160 animals), Pichincha (n = 224 animals), and Loja provinces (n = 2024 animals). Only two positive serological results (RB negative and SAT-EDTA ≥400 IU/ml) were obtained in lactating goats from the same farm in Quito (Pichincha province). Additionally, milk was sampled from 220 animals in Pichincha province. The present study indicates a low apparent prevalence in Pichincha province and absence in Carchi and Loja provinces. A total of 25 positive milk ring tests (MRT) were obtained in Pichincha province yielding a prevalence of MRT of 11.16%. Subsequent culture was performed on the positive MRT samples. All results were negative, apart from a single sample, obtained from a serologically positive goat in Quito, that was positive for Brucella abortus strain 19 (B19). Several hypotheses are forwarded concerning this unexpected result. The most likely hypothesis is the possible accidental use of a needle, previously used for vaccination of cattle with the said vaccine, for the administration of drug treatment to the goat. This hypothesis underlines the necessity of biosecurity measures to prevent this type of accidents.

Diagnosis of trypanosomatid infections: targeting the spliced leader RNA.

Trypanosomatids transcribe their genes in large polycistronic clusters that are further processed into mature mRNA molecules by trans-splicing. During this maturation process, a conserved spliced leader RNA (SL-RNA) sequence of 39 bp is physically linked to the 5' end of the pre-mRNA molecules. Trypanosomatid infections cause a series of devastating diseases in man (sleeping sickness, leishmaniasis, Chagas disease) and animals (nagana, surra, dourine). Here, we investigated the SL-RNA molecule for its diagnostic potential using reverse transcription followed by real-time PCR. As a model, we used Trypanosoma brucei gambiense, which causes sleeping sickness in west and central Africa. We showed that the copy number of the SL-RNA molecule in one single parasitic cell is at least 8600. We observed a lower detection limit of the SL-RNA assay in spiked blood samples of 100 trypanosomes per milliliter of blood. We also proved that we can detect the trypanosome's SL-RNA in the blood of sleeping sickness patients with a sensitivity of 92% (95% CI, 78%-97%) and a specificity of 96% (95% CI, 86%-99%). The SL-RNA is thus an attractive new molecular target for next-generation diagnostics in diseases caused by trypanosomatids.

Human brucellosis in northwest Ecuador: typifying Brucella spp., seroprevalence, and associated risk factors.

Human brucellosis in Ecuador is underreported and based only on passive surveillance. Since 2008, brucellosis was removed from the list of communicable diseases in the country. Until now, the true human brucellosis picture has not yet been determined. The aim of this study was to determine the seroprevalence of the disease, identify risk factors associated with brucellosis seropositivity in humans, and isolate circulating strains of Brucella spp. in the northwestern part of Ecuador. Between 2006 and 2008, a large transect survey was conducted, based on blood sampling of people from the northwestern part of Ecuador (n=3733) together with an epidemiological inquiry. On the basis of three diagnostic tests used in parallel, the overall seroprevalence was estimated as 1.88% (95% confidence interval [CI] 1.48-2.38). Based on a multivariable random effects logistic regression analysis, the main risk factors associated with human brucellosis seropositivity were contact with livestock (odds ratio [OR]=3.0; CI 1.25-7.08), consumption of fetus and placenta (OR=2.5; CI 1.18-5.22), and involvement in activities at risk for brucellosis infection (OR=1.8; CI 1.00-3.35). Noticeable variation in brucellosis seropositivity among humans within cantons was observed. The circulating strain was Brucella abortus biotype 4. This study emphasized that contact with livestock, consumption of fetus and placenta, and occupational hazard group were all significant risk factors for the transmission of brucellosis among individuals in the northwestern part of Ecuador. Alongside encouraging the launching of educational campaigns against brucellosis, especially in rural areas where 36% of the population lives, controlling this zoonotic disease in animals will directly benefit its prevention in humans, especially because there is no safe and efficacious vaccine against brucellosis in humans.