| Título: | Previous exposure-dependent factors related to protection against malaria in a Braziliam Amazon migrant population : an open cohort study |
| Autores: | Duarte, Elisabeth Carmen. |
| Fecha: | 1999 |
| Publicador: | McGill University - MCGILL |
| Fuente: |
 |
| Tipo: | Electronic Thesis or Dissertation |
| Tema: |
Biology, Biostatistics. Health Sciences, Public Health. |
| Descripción: | Malaria remains an important public health problem in developing countries. Because of difficulties in control programmes, naturally acquired immunity (NAI) for many is the only factor that limits the number and severity of malaria episodes. To improve scientific knowledge about the determinants of NAI, this study describes the relationship between previous exposure-dependent factors and malaria occurrence in a Brazilian migrant population. Using an open-cohort design, all individuals living in two hypo-endemic rural communities of Peixoto de Azevedo (MT - Brazil) between September 1996 and April 1997 were enrolled. An interview, spleen measurement, blood samples for anti-RESA ELISA-based indices and malaria thick smears were undertaken at baseline. Incident malaria infections were identified through follow-up visits (4-months interval) and lab monitoring. Associations between previous exposure-dependent factors and time to malaria onset or malaria episode frequency were assessed using Cox's proportional hazards or linear regression models. The study population consisted of 521 individuals, mostly males (60.5%), mean age 26.3 (+/-18.0) years, born in hypo or non-endemic malaria areas (63.1%) and living in endemic areas for 11 years, on average. The majority had non-palpable spleens (65.4%) and had experienced malaria during their lifetime (93.0%) and during the last two years (76.1%). A total of 107 (20.5%) individuals were lost to follow-up. The malaria incidence rate was low [101 cases: 4.49 per 100 person-months], and vivax malaria was four times more frequent than falciparum malaria. The anti-RESA index was positively associated (p ≤ 0.003) with indicators of previous-exposure to malaria: age, malaria episodes during lifetime and months lived in mining environments. Higher malaria incidence rates were associated with lower anti-RESA indices [hazard ratio (HR) = 0.979, p = 0.004] and increased malaria episodes during the last two years (HR = 1.049; p < 0 |
| Idioma: | en |
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