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Biomedical subjects

F Simondon

Publications and source records attributed to F Simondon.

At least 37 records · Page 2Linked to original sources
PubMed1998

Preschool stunting, age at menarche and adolescent height: a longitudinal study in rural Senegal.

OBJECTIVE: To study the impact of preschool stunting on adolescent height and age at menarche in rural West Africa. DESIGN: A longitudinal, population-based study. SETTING: The Niakhar study area in Central Senegal. SUBJECTS: 1650 children aged 12-17 y with known height-for-age at the age of 2-5 y. MAIN OUTCOME MEASURES: Adolescent height; mean age at menarche of girls estimated by the status quo method. RESULTS: The subjects were divided into three groups of preschool height-for-age: < -2, -2 to -1 and > -1 z-score of the NCHS reference. The mean height during adolescence differed significantly according to preschool height-for-age for both boys and girls (P < 0.001). Relative risk of adolescent stunting according to preschool stunting varied from 2.0-4.0 depending on age and sex. Estimated mean age at menarche was 17.2 (95% fiducial confidence interval: 16.6-18.7), 16.5 (16.1-17.2) and 15.6 (15.2-16.0) y, respectively, for the three groups of preschool height-for-age (P < 0.001). Mean increment from age 5 y to adolescence did not differ significantly among the boys according to preschool stunting, but among the girls aged 16-17 y, the increment was higher for those who had been stunted during preschool life (P < 0.01). CONCLUSION: Some evidence of catch-up growth between the ages of 5 and 17 y was found for stunted girls. The significant delay in sexual maturation of the stunted girls suggests that stunted children of both sexes have a possibility of catch-up growth after the age of 17 y.

Adolescent↗
PubMed1998

[Malaria transmission in the rural zone of Niakhar, Senegal].

The anopheline bioecology and the malaria transmission were studied from January to December 1995 in three villages of the sahelian rural area of Niakhar, Senegal. This area of 29000 inhabitants, has been for several decades, a regional observatory for population and health. The three methods used for collecting mosquitoes were the collection at larval stages, the all night human biting collection, and the pyrethrum spray catch in houses during afternoons. The anophelines collected were, by numerical importance: Anopheles arabiensis, An. rufipes, An. gambiae, An. pharoensis, An. funestus and An. coustani. In the An. gambiae complex, An. arabiensis represented 97% of man biting females and 98% of half gravid resting females (difference not significant); the other reminding species of this complex was always An. gambiae. These two species belonging to the An. gambiae complex were responsible for the totality of the transmission. The anthropophilic index, obtained from half gravid indoor resting An. gambiae s.l., was 83%. The annual biting rate of An. gambiae s.l. varied from 512 to 1558 bites per man per night, depending on the villages. Vectors were observed all year long but their densities were low during the dry season. Vector population presented a notable increase due to the rains, with a maximum of about 10 bites per man per night in September or at the beginning of October; during September the biting rate represented 48% of the annual biting rate. The sporozoitic index of An. gambiae s.l., obtained by ELISA revealing the circumsporozoite protein, was 1.6% for human biting females and 1.8% for half-gravid resting females (difference not significant). Plasmodium falciparum was the only plasmodial species observed among infected anophelines. The annual transmission in the vo villages representative of the Niakhar area were 9 and 12 bites of infected anophelines per man, occurring mainly from August to October. In the third village, not representative of the area regarding permanent breeding places, the transmission was 26 bites of infected anopheline per man per year. These results were discussed in the Senegambian and sahelian contexts.

Animals↗
PubMed1998

Acute and long-term changes in T-lymphocyte subsets in response to clinical and subclinical measles. A community study from rural Senegal.

To investigate the possibility of long-term suppression of T-lymphocyte subsets, we examined children exposed to measles at home during an epidemic in rural Senegal, at time of exposure and 1 and 6 months later. The measles case fatality ratio was 1%. Subclinical measles was common among vaccinated children exposed to measles (45%). Both clinical and subclinical cases of measles showed a significant rise in absolute CD4 count in the incubation period. In the prodromal phase and the first week after the rash, the lymphocyte percentage, the white blood cell count and the absolute CD4 cell numbers were significantly reduced. There was no persistent decrease of absolute CD4 or CD8 numbers at 1 or 6 months after exposure. Measles infection was followed by significant changes in the subset composition, both CD4 and CD8 percentages being significantly higher in the second month after measles than among non-seroresponders. These changes were more marked among girls, since they had significantly higher CD4 percentages and CD4/CD8 ratios than boys in the convalescence phase. In conclusion, measles infection is not associated with a long-term suppression of CD4+ or CD8+ T-lymphocytes.

Adolescent↗
PubMed1998

Mothers prolong breastfeeding of undernourished children in rural Senegal.

BACKGROUND: Breastfeeding, when prolonged beyond infancy, is a risk factor for low nutritional status in most cross-sectional samples from less developed countries. Therefore, it has been suggested that prolonged breastfeeding impairs growth. To test whether, on the contrary, breastfeeding is prolonged because the child is already undernourished, nutritional status prior to weaning was compared according to age at weaning. METHODS: Precise dates of birth and weaning were collected weekly through continuous demographic surveillance in a rural area of Senegal. Weight and length at 9-10 months were measured during vaccination sessions (coverage: 78%) from 1989 to 1996. Eight infants weaned before 9 months were excluded, and the duration of breastfeeding of the remaining 4515 children was compared according to nutritional status at 9-10 months by survival analysis. RESULTS: Length-for-age during infancy was associated with duration of breastfeeding: the median duration was 25.0 months for z-scores <-2, 24.1 months for z-scores -2 to -1, 23.4 months for z-scores -1 to 0 and 22.7 months for z-scores >0 (P for trend <0.0001). Weight-for-length during infancy was also associated with duration of breastfeeding (P for trend <0.0001), though the differences among groups were smaller. The relationships remained at the same significance levels after adjustment for season of birth, mother's age, parity, height, occupation and education. CONCLUSION: Duration of breastfeeding is not determined by characteristics of the mothers only. Women prolong breastfeeding for undernourished children and reduce the duration for well-nourished children, probably because they are aware of the mortality risk following weaning.

Anthropometry↗
PubMed1998

Evaluation of an immunoglobulin G enzyme-linked immunosorbent assay for pertussis toxin and filamentous hemagglutinin in diagnosis of pertussis in Senegal.

The enzyme-linked immunosorbent assay is widely employed for the serological diagnosis of pertussis. It is generally concluded that a significant increase in specific immunoglobulin G (IgG) or IgA against the pertussis toxin (PT) or against filamentous hemagglutinin (FHA) in paired sera correlates with Bordetella pertussis infection. However, this type of diagnosis of pertussis has mainly been applied to unvaccinated children, with timely sampling of acute- and convalescent-phase sera. In current practice and in epidemiological studies, such criteria are not always fulfilled. The aim of this study was to analyze the significance of decreases in IgG antibody titers against PT and FHA between paired sera observed in suspected cases of pertussis infection. Serological results from paired sera were available for 460 children experiencing at least 8 days of cough. An anti-PT IgG decrease was observed in 25% of the children, more frequently than the anti-FHA IgG decrease. Fourteen percent of the serologic decreases were observed in children with culture-confirmed infection, and 59% of the decreases were observed in children with confirmation criteria according to World Health Organization recommendations. Most of the decreases were observed when serum samples were collected according to a standard recommended schedule. Serologic decreases were observed more frequently among vaccinated children than among unvaccinated children. This difference, which was highly significant (P < 0.00001), was explained by the different kinetics of the antibody responses between vaccinated and unvaccinated children. The importance of the antibody response for the evaluation of vaccine efficacy, namely a bias toward higher absolute vaccine efficacy when this response is not taken into account, is discussed. This study supports an earlier recommendation that a significant decrease in PT or FHA should be added to the diagnostic criteria for pertussis.

Enzyme-Linked Immunosorbent Assay↗
PubMed1997

Decline in measles case fatality ratio after the introduction of measles immunization in rural Senegal.

The epidemiology of measles has been investigated in Niakhar, a rural area of Senegal, during two periods, 1983-1986 and 1987-1990. Following a major increase in immunization coverage beginning in 1987, the case fatality ratio for all ages declined fourfold from the first to the second period (relative risk (RR) = 0.24, 95% confidence interval (CI) 0.13-0.46). The measles incidence for children under 10 years of age declined by 69% (95% CI 65-72) and the risk of dying of measles by 91% (95% CI 82-95). Vaccinated children who contracted measles had significantly lower case fatality ratio than unvaccinated children with measles (p = 0.038). Children infected by an immunized case tended to have lower case fatality ratio than those infected by an unimmunized index case (p = 0.104) and immunized index cases generated fewer secondary cases than unimmunized index cases (p < 0.001). Respiratory complications were more common in secondary cases infected by an index case with respiratory complications than by an index case without such complications (RR = 1.60, 95% CI 1.08-2.37), which suggests that severe cases give rise to further severe cases. As expected, there was a significant increase in the proportion of vaccinated cases in the second period (RR = 1.41, 95% CI 1.00-1.98). Mean age at infection increased from 4 to 7 years between the two periods and the change in age structure accounted for 20% of the decline in case fatality ratio. Measles immunization may contribute to lower mortality directly through reduced incidence and indirectly through increases in age at infection, less severe infection for immunized cases and changes in transmission patterns leading to reduced severity of measles.

Child↗
PubMed1997

A randomized double-blind trial comparing a two-component acellular to a whole-cell pertussis vaccine in Senegal.

A randomized, double-blind trial comparing a diphtheria-tetanus-acellular pertussis vaccine (DTaP) (pertussis toxoid and filamentous hemagglutinin) with a whole-cell vaccine (DTwP) was conducted. A case-contact study was nested in the trial to estimate absolute efficacy. From 1990 through 1994, 4181 children were randomized to receive one of the vaccines at 2, 4, and 6 months. Severe adverse events were monitored weekly during two visits after vaccination. Fewer serious adverse events were observed after DTaP. Surveillance for cough illnesses persisting more than 7 days, in children under 15 years of age, was made by weekly home visits. Examining physicians, blind to vaccination status, took samples for culture and serologic testing. Pertussis was defined as 21 or more days of cough confirmed by culture, serology, or contact with a culture-confirmed person. Beginning 28 days after the third vaccine dose, the overall ratio of pertussis incidence in the DTaP group relative to the DTwP group (RRac/wc) was 1.54 (95% CI, 1.23-1.93). In children younger than 18 months of age, RRac/wc was 1.16 (95% CI, 0.77-1.73) and 1.76 (95% CI, 1.33-2.33) in children older than 18 months, which suggests a shorter duration of protection with the acellular vaccine (P = 0.090). Absolute efficacy estimates derived from the case-contact study confirmed the lower protection afforded by the acellular vaccine compared with the whole-cell vaccine: 31% (95% CI, 7-49) versus 55% against the protocol case definition, and 85% (95% CI, 66-93) versus 96% for the more severe WHO case definition. Although vaccination with DTaP provided a lower degree of protection than the highly effective DTwP, this difference was less prominent before 18 months of age, the customary age for a fourth dose. The safer DTaP vaccine may prove a valuable substitute for whole-cell vaccines when used in a schedule that includes a booster-dose.

Adult↗
PubMed1997

Age at introduction of complementary food and physical growth from 2 to 9 months in rural Senegal.

OBJECTIVE: To compare nutritional status and physical growth among infants according to age at introduction of complementary food (CF). DESIGN: A longitudinal observational study. SETTING: Three health clinics in a rural area of Senegal. SUBJECTS: During immunization sessions, 522 infants were recruited at 2-3 months. Complete data on three visits were available for 420 infants (4 visits: n = 361); 73 were lost to follow-up and 29 had incomplete data. MAIN OUTCOME MEASURES: Increments in length and weight between adjacent visits. RESULTS: Infants complemented at 2-3 months (n = 50) had significantly lower length-for-age (P = 0.014), weight-for-length (P < 0.001) and arm circumference (P < 0.0001) at 2-3 months than predominantly breastfed infants (n = 370), after adjustment for residence, mother's age and education of parents. The growth in weight and length from 2-3 to 9-10 months did not differ. The infants complemented by 4-5 months, but not yet at 2-3 months, (n = 94) had a slightly lower length increment from 4-5 to 6-7 months (1.42 vs 1.53 cm/mo, p < 0.05) compared to infants predominantly breastfed at 4-5 months (n = 276). The infants first complemented by 6-7 months (n = 122) had increments from 6-7 to 9-10 months similar to those of predominantly breastfed infants (n = 154). CONCLUSION: Introduction of CF by 2-3 months was associated with a low nutritional status, but not with slow growth from 2-3 to 9-10 months. Introduction of CF by 4-5 months was associated with slightly slower linear growth compared to later introduction.

Age Factors↗
PubMed1997

The Senegal pertussis trial: safety and surveillance of adverse reactions.

In the Senegal pertussis trial, common adverse reactions were actively monitored during the pilot phase II study, while the frequency of severe adverse reactions was monitored as a secondary objective within the phase III efficacy trial. Since the trial was conducted in Niakhar, an area in rural West Africa under intensive surveillance, the safety monitoring during the study was incorporated within the general surveillance system. This was a two-step procedure: detection of a potential reaction by a field worker, followed by confirmation report by a physician. The frequency of severe reactions was low among both pertussis vaccine groups, receiving either the two-component acellular vaccine or the whole-cell vaccine currently used in the Senegal Expanded Programme on immunisation. Among severe reactions, only persistent crying was found to be at a significantly higher rate in the whole-cell group. Common adverse reactions were more frequent in the whole-cell group.

Crying↗
PubMed1996

[A non-specific, beneficial effect of measles vaccination. Analysis of mortality studies from developing countries].

The study examined whether the reduction in mortality after standard titre measles immunization in developing countries can be explained by the prevention of acute measles and its long-term consequences. All studies comparing mortality of unimmunised children and children immunised with standard titre measles vaccine in developing countries were included; ten cohort and two case-control studies from Bangladesh, Benin, Burundi, Guinea-Bissau, Haiti, Senegal, and Zaire. We examined the protective efficacy of standard titre measles immunization against all cause mortality. Furthermore, by restricting the analysis to children who had not developed measles, we examined how much of the difference in mortality between immunised and unimmunised children could be explained by prevention of measles disease. In the ten cohort studies, protective efficacy against death after measles immunization was found to be in the range of 30-86%. Efficacy was highest in the studies with short follow-up and where children were immunised in infancy (range: 44-100%). Vaccine efficacy against death was much greater than the proportion of deaths attributed to acute measles disease. In four studies from Guinea-Bissau, Senegal and Burundi, vaccine efficacy against death remained almost unchanged when measles cases were excluded from the analysis. Hence, the reduction in mortality among immunized children cannot be explained by the prevention of acute and long-term consequences of measles. In contrast to the effect of measles vaccine, studies from Guinea-Bissau, Senegal and Benin suggest that diphtheria-tetanus-pertussis and polio vaccinations are not associated with reduction in mortality. These observations suggest that standard titre measles vaccine may confer a beneficial effect which is unrelated to the specific protection against measles disease.

Cohort Studies↗
PubMed1996

No long-term excess mortality after measles infection: a community study from Senegal.

Because measles immunization has been found in all studies to reduce mortality with more than the share of deaths attributed to acute measles, the authors examined mortality after measles infection in a study in a rural area of Senegal that included 6,924 unimmunized children, whom 1,118 developed measles. Age-adjusted post-measles mortality was similar to the mortality of unvaccinated, uninfected children (mortality ratio (MR) = 1.04, 95% confidence interval (CI) 0.80-1.35). When controlling for source of infection, mortality rate was significantly different for children who contracted measles from a person outside the home (index cases vs. unvaccinated, uninfected MR = 0.27, 95% CI 0.09-0.85) and for children infected at home (secondary cases vs. unvaccinated, uninfected MR = 1.10, 95% CI 0.80-1.51). Hence, secondary cases had markedly higher long-term mortality than did index cases (MR = 4.13, 95% CI 1.26-13.58). These estimates were essentially unchanged when the effects of season, period, separation from mother, size of community, and size of compound were investigated using a multivariate Cox regression model. The authors conclude that measles infection was not associated with increased mortality after the acute phase of infection and that index cases had lower mortality than uninfected, unvaccinated children. The reduction in mortality after measles immunization can therefore not be explained by the prevention of post-measles mortality.

Age Factors↗
PubMed1996

Comparative safety and immunogenicity of an acellular versus whole-cell pertussis component of diphtheria-tetanus-pertussis vaccines in Senegalese infants.

A diphtheria and tetanus toxoid two-component acellular pertussis vaccine (DTaP), consisting of 25 micrograms glutaraldehyde-detoxified pertussis toxin (PT) and 25 micrograms native filamentous hemagglutinin (FHA), was compared with diphtheria and tetanus toxoid whole-cell pertussis vaccine (DTwP) in a randomized, double-blind manner in 286 Senegalese infants inoculated at two, four, and six months of age. In infants receiving DTaP a significantly lower rate of local reactions, crying and fever was observed than in infants receiving DTwP. One month after the third dose, the geometric mean titres for FHA antibodies were higher in the DTaP group, whereas increases in PT antibody titres were higher in the DTwP group. More than 90% of the infants had a fourfold or more increase in antibodies to both PT and FHA with either vaccine. Diphtheria, tetanus, and polio antibody responses were also measured and found to be comparable between the two groups. The results of this pilot study support the implementation of a field trial to compare the protective efficacy of these vaccines against pertussis in the same setting.

Antibodies, Bacterial↗
PubMed1996

Five year follow-up of morbidity and mortality among recipients of high-titre measles vaccines in Senegal.

At 3-5 years of age, female recipients of Edmonston-Zagreb high-titre (EZ-HT) and Schwarz high-titre (SW-HT) measles vaccine had lower survival rates than female recipients of Schwarz standard measles vaccine (SW-STD) in Guinea-Bissau, Senegal and Haiti. In Senegal, the children who received high-titre vaccines have now been followed to the age of 5-7 years to determine whether the difference in mortality persisted, and whether differences in vaccine efficacy were apparent. At this age there was no difference in mortality between female recipients of high-titre and standard titre measles vaccines. There was no indication that high-titre EZ-HT vaccine at 5 months (EZ-HT,5m) provided suboptimal protection, as vaccine efficacy after exposure was 97% and 95%, respectively, for EZ-HT,5m and SW-STD,10m vaccines, whereas SW-HT,5m vaccine had an efficacy of 81%. The difference in mortality between recipients of high-titre vaccines and SW-STD observed in several studies during the first few years after vaccination may be explained by non-specific beneficial effects of the standard measles vaccine rather than a harmful effect of the high-titre vaccines.

Female↗
PubMed1996

Effect of early, short-term supplementation on weight and linear growth of 4-7-mo-old infants in developing countries: a four-country randomized trial.

The effect of supplementation on growth was tested by means of four similar controlled randomized trials in the Congo (n = 120), Senegal (n = 110), Bolivia (n = 127), and New Caledonia (n = 90). Four-month-old infants were randomly allocated to supplement or control groups. A cereal-based precooked porridge was offered twice daily for 3 mo and consumption was monitored. Both groups were free to eat local food. At 7 mo of age, all infants were still breast-fed in the Congo, Senegal, and Bolivia compared with 47% in New Caledonia. Mean daily consumption of the supplement varied among countries (558-790 kJ/d). Mean length at 4 mo was lowest in Bolivia, higher in Senegal and the Congo, and near the National Center for Health Statistics reference in New Caledonia. The mean 4-7 mo length increment was 0.48 cm higher for supplemented than for control infants in Senegal (P < 0.05), whereas weight increments did not differ. No significant effect was found in the other countries.

Body Height↗
PubMed1996

Child mortality following standard, medium or high titre measles immunization in West Africa.

BACKGROUND: The World Health Organization (WHO) recommended the use of high titre measles vaccine in 1989. Subsequent long term follow-up of several trials yielded results suggesting higher mortality among children inoculated with medium and high titre vaccines compared to standard titre vaccines, although none of the individual trials found significant differences in mortality. METHODS: Long term survival after standard, medium and high titre measles vaccines has been investigated in a combined analysis of all West African trials with mortality data. In trials from Guinea-Bissau, The Gambia and Senegal, children received medium or high titre vaccines from 4 months of age and were compared to control groups recruited at the same time later receiving standard titre vaccine from 9 months of age. All children were followed up to at least 3 years old. RESULTS: Combining trials of high titre vaccines showed higher mortality among the high titre group compared to the standard group: mortality ratio (MR) = 1.33 (95% CI : 1.02-1. 73). Mortality among recipients of medium titre vaccines was not different from that in the standard vaccine group, MR = 1.11 (95% CI: 0.54-2.27). In a combined analysis by sex, the adjusted mortality ratios comparing high titre vaccine with standard vaccine were 1.86 (95% CI : 1.28-2.70) for females and 0.91 (95% CI : 0.61-1.35) for males. The trials were not designed to study long term mortality. Adjustments for several possible sources of bias did not alter the results. CONCLUSIONS: The combined analysis showed a decreased survival related to high titre measles vaccine compared with standard titre vaccines, though solely among females. As a result of these studies from West Africa and a study from Haiti, WHO has recommended that high titre measles vaccine no longer be used.

Age Distribution↗