Abstract
Objective: Cystic echinococcosis (CE) is a parasitic zoonosis caused by Echinococcus granulosus sensu lato. Immunodiagnostic techniques such as Western blot (WB) or enzyme-linked immunosorbent assay (ELISA), with different antigens, can be applied to the diagnosis of sheep for epidemiological surveillance purposes in control programs. However, its use is limited by the existence of antigenic cross-reactivity between different species of taeniidae present in sheep. Therefore, the usefulness of establishing surveillance systems based on the identification of infection present in a livestock establishment, known as the (Epidemiological) Implementation Unit (IU), needs to be evaluated. Materials and Methods: A new ELISA diagnostic technique has been recently developed and validated using the recombinant EgAgB8/2 antigen for the detection of antibodies against E. granulosus. To determine detection of infection at the IU level using information from this diagnostic technique, simulations were carried out to evaluate the sample size required to classify IUs as likely infected, using outputs from a recently developed Bayesian latent class analysis model. Results: Relatively small samples sizes (between 14-29) are sufficient to achieve a high probability of detection (above 80%), across a range of prevalence, with the recently recommended Optical Density cut-off value for this novel ELISA (0.496), which optimizes diagnostic sensitivity and specificity. Conclusions: This diagnostic technique could be potentially used to identify the prevalence of infection in an area under control, measured as the percentage of IUs with the presence of infected sheep (infection present), or to individually identify the IU with ongoing transmission, given the presence of infected lambs, on which control measures should be intensified.