Incidence of Human Taenia solium Larval Infections in an Ecuadorian Endemic Area: Implications for Disease Burden Assessment and Control

Abstract

BackgroundHuman cysticercosis is a zoonotic disease causing severe health disorders and even death. While prevalence data become available worldwide, incidence rate and cumulative incidence figures are lacking, which limits the understanding of the Taenia solium epidemiology.Methodology/Principal findingsA seroepidemiological cohort study was conducted in a south-Ecuadorian community to estimate the incidence rate of infection with and the incidence rate of exposure to T. solium based on antigen and antibody detections, respectively. The incidence rate of infection was 333.6 per 100,000 person-years (95% CI: [8.4–1,858] per 100,000 person-years) contrasting with a higher incidence rate of exposure 13,370 per 100,000 person-years (95% CI: [8,730–19,591] per 100,000 person-years). The proportion of infected individuals remained low and stable during the whole study year while more than 25% of the population showed at least one antibody seroconversion/seroreversion during the same time period.Conclusions/SignificanceUnderstanding the transmission of T. solium is essential to develop ad hoc cost-effective prevention and control programs. The estimates generated here may now be incorporated in epidemiological models to simulate the temporal transmission of the parasite and the effects of control interventions on its life cycle. These estimates are also of high importance to assess the disease burden since incidence data are needed to make regional and global projections of morbidity and mortality related to cysticercosis.

High Prevalence of Asymptomatic Neurocysticercosis in an Endemic Rural Community in Peru

“…Given the rapid rate of seroconversion of the LLGP-EITB from positive to negative, this suggests a highly endemic state with frequent ongoing exposure to T . solium eggs in the study community [21,22]. The lack of clustering of positive serology or brain calcifications in our study also suggests widespread exposure to the parasite.…”

Seroprevalence of Porcine Cysticercosis in Ludewa District, Njombe, Tanzania

“…In the piggery industry, infection by the parasite (porcine cysticercosis (PC)) denies people from pork protein and causes huge economic loss because of veterinary costs, reduced pork production and total condemnation of PC detected pork carcases [2]. Infection of the larval form in human (human cysticercosis (HC)), among other parts of the body, in the central nervous system (CNS) results into neurocysticercosis which is the major cause of acquired epilepsy in T. solium endemic areas [3] [4]. Humans may harbour adult pork tapeworms in the intestine and hence taeniasis for many years without significant health symptoms.…”

Monitoring the outcomes of interventions against Taenia solium: options and suggestions

“…Two recent studies undertaken in Zambia and Ecuador have revealed that many antigen ELISA‐positive patients among people living in areas that are endemic for transmission of T. solium have only transient positive reactions and are likely to revert to being seronegative. These responses may have been due to infections that never fully establish but led to transient antibody responses and the short‐term presence of circulating antigen.…”

“…However, as discussed above in relation to antibody detection tests, there is no direct evidence to support this view. The communities in Zambia and Ecuador where longitudinal studies were undertaken using antigen ELISA would be likely to have been endemic for transmission of several taeniid cestode parasites involving humans, dogs or other carnivores as definitive hosts, not just T. solium . There is potential for exposure of humans to the eggs of a number of these species, any of which could possibly cause a transient immunological response detected in the T. solium antigen ELISA.…”