RESUMO
This study examines the age-dependency of the relationships between human infection with whipworm (Trichuris trichiura) and parasite-specific antibody level measured by ELISA against an extract of adult worms after preincubation of the sera with Ascaris lumbricoides adult worm extract. The convex age-profile of parasite infection intensity is shown to be mirrored by age-dependent change in age-class mean levels of IgG (all subclasses except IgG3), IgA, IgM and IgE. Mean antibody levels rise with increasing acquisition of infection in childhood. Immunoblot analysis of selected sera from different age-classes indicates that antigen recognition is similarly dependent on infection intensity. In individual children, antibody levels correlate positively with acquisition of infection, consistent with a simple model of antigen dosage specifying the magnitude of the humoral immune response. In adults, IgG4 correlates positively and IgA negatively with intensity of infection, suggesting involvement of these isotypes in functional roles of immune blockade or effector mechanisms, respectively.(AU)
Assuntos
Humanos , Pré-Escolar , Criança , Adolescente , Adulto , Pessoa de Meia-Idade , Anticorpos , Anticorpos Anti-Helmínticos , Tricuríase , Trichuris , Fatores Etários , Ensaio de Imunoadsorção EnzimáticaRESUMO
A seroepidemiological study of the prevalence of mumps virus specific antibodies reveals a pattern of endemic persistence on the island of St. Lucia in the West Indies. In the unvaccinated population the proportion seropositive rose rapidly in the child age classes to attain a stable plateau close to unity in value in the teenage and adult age groups. The average age at infection was estimated to be between 3 and 4 years of age and the average duration of detactable levels of maternally derived antibodies was approximately 3 months. Analyses based on mathematical models of the transmission dynamics of the virus suggest that in excess of 75 percent of each cohort of 1-to 2-year-old children must be effectively immunized to eliminate mumps virus transmission. A mumps radial haemolysis test, developed for quantitive measurements of antibody, is discussed. (AU)
Assuntos
Humanos , Lactente , Pré-Escolar , Criança , Adolescente , Adulto , Pessoa de Meia-Idade , Idoso , Masculino , Feminino , Caxumba/transmissão , Fatores Etários , Caxumba/epidemiologia , Caxumba/prevenção & controle , Vírus da Caxumba/imunologia , Testes Sorológicos/métodos , Vacinação , Santa LúciaRESUMO
The study examines the distribution of Trichuris trichiura infection in a village community in St. Lucia, West Indies. The infection intensity of the same age-stratified population was assessed (by drug expelled worm burden and faecal egg count) at the intiation of the study, and after 17 months of reinfection following treatment. The frequency distribution of worm numbers per person was similar at both periods of sampling. There was a significant correlation between the initial infection intensity of an individual, and the intensity acquired by the same individual following the 17 month period of reinfection. This relationship was observed in a broad range of host age classes. The study provides firm evidence that individuals are predisposed to heavy (or light) T. trichiura infection. (Summary)
Assuntos
Humanos , Lactente , Pré-Escolar , Criança , Adolescente , Adulto , Fezes/parasitologia , Tricuríase/parasitologia , Trichuris/isolamento & purificação , Mebendazol/uso terapêutico , Contagem de Ovos de Parasitas , Recidiva , Tricuríase/tratamento farmacológico , Tricuríase/epidemiologia , Índias OcidentaisRESUMO
The gastrointestinal helminth infection status of an age-stratified sample from a single Caribbean community was assessed using anthelmintic expulsion techniques. The same sample was re-assessed in a similar manner after a 17 month period of re-infection. The age-prevalence profile of Ascaris lumbricoides was convex while that of Trichuris trichiura was asymptotic. The age-intensity profiles of both species were convex. These differing patterns are attributed to differences in the absolute worm burdens of the 2 species. The frequency distributions of infection intensity were similar for both species, and largely independent of host age. The basic reproductive rate of A. lumbricoides (R. = 1-1.8) was similar to that recorded elsewhere and much lower than that of T. trichiura (R. = 4-6), implying that the latter is intrinsically more resistant to control. Individual hosts were predisposed to high (or low) intensity infection with either species, although predisposition to both species simultaneously was not conclusively demonstrated. Futher studies are required to determine the cause of these observations.(AU)