RESUMO

Echinococcosis is a zoonotic disease relevant to public health in many countries, on all continents except Antarctica. The objective of the study is to describe the registered cases and mortality from echinococcosis in Brazil, from 1995 to 2016. The records of two national databases, the Hospital Information System (HIS) and the Mortality Information System (MIS), were accessed during the period of 1995-2016. Demographic, epidemiological, and health care data related to the occurrence of disease and deaths attributed to echinococcosis in Brazil are described. The results showed that 7955 records of hospitalizations were documented in the HIS, during the study period, with 185 deaths from echinococcosis, and 113 records of deaths were documented in the MIS Deaths in every state of Brazil in the period. When comparing between states, the HIS showed great variability in mortality rates, possibly indicating heterogeneity in diagnosis and in the quality of health care received by patients. Less severe cases that do not require specialized care are not recorded by the information systems, thus the true burden of the disease could be underrepresented in the country. A change in the coding of disease records in the HIS in the late 1990s, (the integration of echinococcosis cases with other pathologies), led to the loss of specificity of the records. The records showed a wide geographic distribution of deaths from echinococcosis, reinforcing the need to expand the notification of the disease in Brazil. Currently, notification of cases is compulsory in the state of Rio Grande do Sul.

RESUMO

The accuracy of screening tests for detecting cystic echinococcosis (CE) in livestock depends on characteristics of the host-parasite interaction and the extent of serological cross-reactivity with other taeniid species. The AgB8 kDa protein is considered to be the most specific native or recombinant antigen for immunodiagnosis of ovine CE. A particular DNA fragment coding for rAgB8/2 was identified, that provides evidence of specific reaction in the serodiagnosis of metacestode infection. We developed and validated an IgG Enzyme Linked Immunosorbent Assay (ELISA) test using a recombinant antigen B sub-unit EgAgB8/2 (rAgB8/2) of Echinoccocus granulosus sensu lato (s.l.) to estimate CE prevalence in sheep. A 273 bp DNA fragment coding for rAgB8/2 was expressed as a fusion protein (∼30 kDa) and purified by affinity chromatography. Evaluation of the analytical and diagnostic performance of the ELISA followed the World Organisation for Animal Health (OIE) manual, including implementation of serum panels from: uninfected lambs (n = 79); experimentally infected (with 2,000 E. granulosus s.l. eggs each) sheep with subsequent evidence of E. granulosus cysts by necropsy (n = 36), and animals carrying other metacestode/trematode infections (n = 20). The latter were used to assess the cross-reactivity of rAgB8/2, with these animals being naturally infected with Taenia hydatigena, Thysanosoma actinioides and/or Fasciola hepatica. EgAgB8/2 showed cross-reaction with only one serum sample from a sheep infected with Ta. hydatigena out of the 20 animals tested. Furthermore, the kinetics of the humoral response over time in five 6-month old sheep, each experimentally infected with 2,000 E. granulosus s.l. eggs, was evaluated up to 49 weeks (approximately one year) post infection (n = 5). The earliest detectable IgG response against rAgB8/2 was observed in sera from two and four sheep, 7 and 14 days after experimental infection, respectively. The highest immune response across all five animals was found 16 to 24 weeks post infection.

RESUMO

Taenia solium is an important cause of acquired epilepsy worldwide and remains endemic in Asia, Africa, and Latin America. Transmission of this parasite is still poorly understood despite the design of infection experiments to improve our knowledge of the disease, with estimates for critical epidemiological parameters, such as the probability of human-to-pig infection after exposure to eggs, still lacking. In this paper, a systematic review was carried out and eight pig infection experiments were analyzed to describe the probability of developing cysts. These experiments included different pathways of inoculation: with ingestion of proglottids, eggs, and beetles that ingested eggs, and direct injection of activated oncospheres into the carotid artery. In these experiments, different infective doses were used, and the numbers of viable and degenerated cysts in the body and brain of each pig were registered. Five alternative dose-response models (exponential, logistic, log-logistic, and exact and approximate beta-Poisson) were assessed for their accuracy in describing the observed probabilities of cyst development as a function of the inoculation dose. Dose-response models were developed separately for the presence of three types of cysts (any, viable only, and cysts in the brain) and considered for each of the four inoculation methods ("Proglottids", "Eggs", "Beetles" and "Carotid"). The exact beta-Poisson model best fit the data for the three types of cysts and all relevant exposure pathways. However, observations for some exposure pathways were too scarce to reliably define a dose-response curve with any model. A wide enough range of doses and sufficient sample sizes was only found for the "Eggs" pathway and a merged "Oral" pathway combining the "Proglottids", "Eggs" and "Beetles" pathways. Estimated parameter values from this model suggest that a low infective dose is sufficient to result in a 50% probability for the development of any cyst or for viable cyst infections. Although this is a preliminary model reliant on a limited dataset, the parameters described in this manuscript should contribute to the design of future experimental infections related to T. solium transmission, as well as the parameterization of simulation models of transmission aimed at informing control.

Assuntos

RESUMO

Echinococcus granulosus sensu lato is a globally prevalent zoonotic parasitic cestode leading to cystic echinococcosis (CE) in both humans and sheep with both medical and financial impacts, whose reduction requires the application of a One Health approach to its control. Regarding the animal health component of this approach, lack of accurate and practical diagnostics in livestock impedes the assessment of disease burden and the implementation and evaluation of control strategies. We use of a Bayesian Latent Class Analysis (LCA) model to estimate ovine CE prevalence in sheep samples from the Río Negro province of Argentina accounting for uncertainty in the diagnostics. We use model outputs to evaluate the performance of a novel recombinant B8/2 antigen B subunit (rEgAgB8/2) indirect enzyme-linked immunosorbent assay (ELISA) for detecting E. granulosus in sheep. Necropsy (as a partial gold standard), western blot (WB) and ELISA diagnostic data were collected from 79 sheep within two Río Negro slaughterhouses, and used to estimate individual infection status (assigned as a latent variable within the model). Using the model outputs, the performance of the novel ELISA at both individual and flock levels was evaluated, respectively, using a receiver operating characteristic (ROC) curve, and simulating a range of sample sizes and prevalence levels within hypothetical flocks. The estimated (mean) prevalence of ovine CE was 27.5% (95%Bayesian credible interval (95%BCI): 13.8%-58.9%) within the sample population. At the individual level, the ELISA had a mean sensitivity and specificity of 55% (95%BCI: 46%-68%) and 68% (95%BCI: 63%-92%), respectively, at an optimal optical density (OD) threshold of 0.378. At the flock level, the ELISA had an 80% probability of correctly classifying infection at an optimal cut-off threshold of 0.496. These results suggest that the novel ELISA could play a useful role as a flock-level diagnostic for CE surveillance in the region, supplementing surveillance activities in the human population and thus strengthening a One Health approach. Importantly, selection of ELISA cut-off threshold values must be tailored according to the epidemiological situation.