Biomedical subjects
Publications and source records attributed to F Simondon.
A nutritional survey performed in the Senegal mid valley in 1983 including 610 individuals shows that mild to moderate protein-energy malnutrition, specific deficiencies and anemia are still present. In addition new health hazards such as overweight and perhaps high blood pressure, raise and may burden public health welfare in that area.
Using data on incidence and secondary attack rates, we examined the protective efficacy of high-titre Edmonston-Zagreb (EZ) and Schwarz (SW-HT) measles vaccines administered at 5 months. Control children were assigned to placebo at age 5 months and standard Schwarz (SW-std) measles vaccine at 9-10 months of age. A large proportion of measles cases was verified serologically. Though high-titre vaccines seemed to be protective before 10 months of age, a significant reduction in disease could not be demonstrated due to low incidence of measles. After 10 months of age, SW-std given at 10 months gave a vaccine efficacy of 100% and induced better protection than SW-HT (P = 0.030) and EZ-HT (P = 0.128) administered at 5 months. In studies of secondary attack rates in the compound, vaccine efficacy was 91% (75%-97%) for EZ-HT, 85% (40%-96%) for SW-HT, and 100% for SW-std. Attack rates were correlated with intensity of exposure (P = 0.0006), being much higher for children exposed in the same hut than for those living in the same compound but in a different household (relative risk = 3.36 [1.32-8.57]). The attack rate was significantly lower among vaccinated than unvaccinated children with no detectable measles antibody (relative risk = 0.41 [0.18-0.93]). In rural areas with a high coverage in the surrounding community, a single dose at 9-10 months may provide sufficient protection. Since high-titre vaccines have been associated with higher mortality than SW-std, further improvements in measles control before 9 months may require two-dose strategies with standard vaccines.
Vaccine efficacy and mortality in successive cohorts of children who routinely received either Edmonston-Zagreb high-titre (EZ-HT) or Schwarz standard (SW-STD) measles vaccines have been examined in a rural area of Senegal. The 2 vaccines were equally protective against measles infection (vaccination efficacy: EZ-HT 94%; SW-STD 93%). Children who did not attend a scheduled session to receive measles vaccine had a higher mortality rate between 9 months and 2 years of age than did children receiving either EZ-HT (mortality ratio [MR] = 1.81, 95% confidence interval [CI] 1.06-3.08) or SW-STD measles vaccine (MR = 1.74, 95% CI 0.95-3.21). Children of either sex vaccinated with EZ-HT had lower mortality than their equivalents who had not received any measles vaccine. There was no difference in overall mortality between recipients of EZ-HT and SW-STD (MR = 0.96, 95% CI 0.70-1.30). Using a Cox regression analysis to adjust for sex, age and significant background factors (season and death of mother), mortality rates tended to be lower for male recipients of EZ-HT than for boys receiving SW-STD (MR = 0.73, 95% CI 0.50-1.11) and higher for girls receiving EZ-HT than for girls receiving SW-STD (MR = 1.30, 95% CI 0.81-2.09) (test of interaction between sex and vaccine, P = 0.067). The tendency to reduced survival benefit for girls following receipt of high-titre measles vaccines substantiated observations from randomized trials in Guinea-Bissau, Senegal and Haiti. Existing data provide little support for the notion that high-titre vaccine is deleterious but it may not have the same beneficial effects as standard-titre measles vaccine.
Growth and maturation during adolescence has not been well described in rural African populations, although it may represent the missing link between high levels of preschool stunting and nearly 'normal' adult heights. In 1995 the homes of subjects aged 10.3-17.5 years, living in a rural area of Senegal, were visited, and all adolescents present, 1527 boys and 1126 girls, were included in the analysis. A number of girls were absent because they worked in the capital city Dakar. Resident girls (n = 705) had significantly higher means than boys for all anthropometric variables (weight, body mass index, arm circumference and muscle arm circumference, triceps and subscapular skinfolds), except for height and head circumference. Girls who had just returned from seasonal migration to Dakar (n = 415) were, on average, 2 kg heavier, but not taller, than resident girls (p < 0.0001). The girls fell off in height from 11 to 13 years compared to the NCHS reference and then 'caught up' until the age of 17, while boys fell off during the entire age span. Mean age at menarche was estimated at 16.1 years (95% fiducial CI: 15.8-16.4) from status quo data by probit analysis. No significant difference was found between residents and migrants. Postmenarcheal girls had better nutritional status than premenarcheal girls in terms of height, weight, body mass index, percentage body fat and arm muscle circumference (p < 0.0001). In conclusion, puberty, as assessed by age at menarche, is delayed by about 3 years in this population, probably due to malnutrition.
There are a number of reasons why climate, in certain physical and social environments, could have an impact on the epidemiology of malaria. Events, such as floods or drought, are related to the number of malaria cases and deaths, both seasonally and interannually. At a smaller scale, this study analyses the relation between climate variability and the variability in the number of deaths attributable to malaria in Niakhar, Senegal. The Niakhar area has a population of 30,000 and has been under demographic surveillance system since 1984. The rainfall in this region is highly seasonal, with a rainfall maximum in August and almost no rain between October/November and May/June. In addition to this seasonal cycle, rainfall also varies greatly from year to year (interannual variation). Over the 13 years, there were 661 deaths attributed to malaria with a marked interannual variability (range from 23 to 100, with a median of 43). There was also a strong seasonality in mortality, with nearly all deaths (89.1%) occurring between August and December. The number of deaths peaks in October, two months after the rainfall peak. Standardised monthly values were calculated for each climatic series (rainfall, relative humidity, temperature) as well as standardised five-month and monthly values of the number of deaths attributed to malaria between August and December. Correlation coefficients were calculated between these standardised values. The correlation between the variability in August rainfall and the variability in the number of deaths attributed to malaria between August and December was positive and statistically significant (r = +0.61, p = 0.02). In addition, highly significant cross-correlations were found between monthly rainfall series and monthly mortality series at one- and two-month lag (r = + 0.43, p = 0.0004 for one-month lag; r = + 0.26, p = 0.03 for two-month lag). This correlation is somewhat lower than the correlation of August rainfall alone with August to December mortality, but the result adds confidence to the signal given the increased degrees of freedom in the analysis. Similar, but slightly weaker, results were found when precipitation data were replaced with surface humidity data. Results with temperature were less clear; while temperature could in some circumstances have a direct impact on malaria, in this case here it is possible that the weak negative correlation between malaria deaths and temperature arises mainly because precipitation is physically connected to both the indices, correlating positively with malaria and negatively with temperature. The availability of a continuous demographic and medical survey since 1984 in a region of highly variable rainfall has created a rare opportunity to analyse with some confidence a climate versus malaria relationship. The findings are consistent with our understanding of the proposed link between rainfall and conditions for the reproduction of the malaria vector, leading to a lag time (here of one to two months) between anomalies of rainfall and deaths attributable to malaria. These results may have practical implications in Sub-Saharan regions marked by a great seasonal and interannual variability in rainfall by providing a simple tool to forecast the impact of climate variability on malaria mortality.
To study the immunological effect of total dietary restriction, BALB/c mice were limited to reduced body growth or maintained at practically constant body weight between 21 and 61 days of age by giving them 70% (R70%) or 55% (R55%) of the average daily food intake of the control group fed ad libitum. Thymus and spleen weight were decreased, but thymus size was maintained in proportion to body weight in R70% mice, whereas the ratio of thymus weight to body weight was significantly decreased in R55% mice. In restricted mice, splenocytes showed a lower percentage of B lymphocytes and a higher percentage of T lymphocytes. Results of stimulation showed that proliferation capacity was increased for B lymphocytes and decreased for T lymphocytes in restricted mice. Our data show the importance of studying the thymus over a period, because normal thymus growth was first greatly impaired by dietary restriction, and subsequent thymus involution was delayed, showing that an isolated comparison between the thymus of growing mice is not enough. Our data show the interest of determining the percentage of lymphocyte populations parallel to their response to mitogen stimulation.