Multiple mechanisms of resistance to pyrethroids in Anopheles gambiae s.l populations in Niger.

INTRODUCTION: We performed a transversal study to map resistance of malaria vectors (Anopheles mosquitoes) to insecticides in Niger within the frame of the National Malaria Control Program funded by the World Health Organization (WHO). METHOD: Larvae of Anopheles gambiae s.l were collected from November to December 2013 in seven locations selected on the basis of different patterns of use of insecticides and environment. WHO susceptibility test tubes were used on females Anopheles to detect resistance to insecticides. Eight insecticides were tested. Percentages of knockdown during exposure time to pyrethroids and DDT and mortality after 24hours of observation for all tested insecticides were calculated. PCR and biochemical tests were carried out to identify the species and mechanisms of resistance (Kdr allele frequencies and activity of detoxification enzymes). RESULTS: In all sites, Anopheles gambiae s.l was susceptible to bendiocarb and malathion but resistant to the five pyrethroids and DDT (24-hour mortality rate was <90%). The Kdr mutation was present in the molecular form M of Anopheles gambiae with an average frequency of 58%. Biochemical tests showed the activity of various enzyme families (esterase, oxidase, and glutathione s-transferase). CONCLUSION: This study showed multiple resistance of Anopheles mosquitoes to insecticides in Niger. A rigorous management of this resistance is imperative to preserve the efficacy of pyrethroids as it is the only class of insecticides used for insecticide-treated nets.

Analysing cross-sectional data with time-dependent covariates: the case of age at first birth in South Africa.

Analysing time-dependent independent variables requires the use of process-oriented statistical models. Yet social scientists--especially those in poor countries--have often had to use data collected at a single point in time, making their task difficult. Making several assumptions about the covariates, the present study uses survival analysis and other statistical techniques to analyse the 1996 South African population census data and examine the effects of selected independent variables on the timing of parenthood in the country. It was found that the onset of parenthood occurs late in South Africa compared with the pattern in most other African societies. While education plays a role in the postponement of parenthood within racial groups, it fails to explain the differences between African and Coloured women on the one hand, and White and Asian women on the other hand, a finding that suggests the existence of two regimes of family formation in South African society.

Analysis of life-time migration in the former Transkei, Eastern Cape.

PIP: The authors analyze internal migration in Transkei, South Africa. They "attempt to provide answers and explanations to the following issues: trends and patterns of internal migration, including migration fields of the sample urban places at varying stages (moves) in the migration cycle; characteristics of the migration process, including information sources or destinations (and whether destinations were visited before migration occurred), and reasons for migrating; individual characteristics of migrants including age-sex composition, education, marital status, economic activity, and time spent looking for a job; migration differentials, including household incomes, tenure of housing, household size, household composition, and fertility." (EXCERPT)^ieng

The effect of nuptiality status variables on fertility: the Kenyan experience.

"This paper examines the relationship between fertility and nuptiality in Kenya using data from the Kenya Fertility Survey 1977/78. The results show that completed fertility (the cumulative fertility at the end of the reproductive period 15-49) decreases with the rise in age at first marriage. Type of union is also found to affect marital stability, frequency of marriage and consequently completed fertility. Regardless of type of union, women whose first union is still continuing have higher fertility than those women whose first union was dissolved and who married once or several times after. Highest fertility is experienced by women married only once and...in monogamous unions. The results also show that polygamously married older women among the rural populations experience higher fertility than their counterparts in the urban areas regardless of age." (SUMMARY IN AFR)

Bongaarts' proximate determinants of fertility applied to group data from the Kenya Fertility Survey 1977/78.

PIP: The objective of this analysis is to quantify the effects of the proximate determinants on marital fertility in Kenya, and to find out whether the level of fertility, both at the national and subnational level, can be accounted for using the model developed by Bongaarts. The analysis is based on data from the Kenya Fertility Survey, undertaken in 1977/78, and which included a nationally representative sample of 8100 women of reproductive ages (15-50). The model was applied using 4 steps: 1) estimating the intermediate fertility variables; 2) estimating the indices; 3) estimating TFR, on the assumption that fertility, in the absence of all 4 intermediate variables, would be 15.3 births; and 4) comparing the model estimates with the observed TFR. The results at the national level fit the model well. At subnational level, the results also fit well for all but Nairobi, metropolitan, coast, and Muslim populations. The findings suggest that variations in the proportion married among the population, level of contraceptive use and postpartum lactational infecundability can account for much but not all of the observed marital fertility differentials. Modernization through education and urbanization has had offsetting effects on fertility, by reducing lactation and increasing contraception. However, the proportion using contraception, limited mainly to those with secondary and higher education or metropolitan residence, is to small to have an appreciable impact on the overall level of fertility. The low level of marital fertility observed particularly among the metropolitan, coast and Muslim categories of the population may be attributed to the prevalence of venereal diseases and unreported contraception as well as induced abortion.^ieng