Gilles Pison

Impact of chloroquine resistance on malaria mortality

Over 12 years, from 1984 to 1995, we conducted a prospective study of overall and malaria specific mortality among three rural populations in the Sahel, savanna and forest areas of Senegal. The emergence of chloroquine resistance has been associated with a dramatic increase in malaria mortality in each of the studied populations. After the emergence of chloroquine resistance, the risk of malaria death among children 0-9 years old in the three populations was multiplied by 2.1, 2.5 and 5.5, respectively. This is the first study to document malaria mortality at the community level in Africa before and after the emergence of chloroquine resistance. Findings suggest that the spread of chloroquine resistance has had a dramatic impact on the level of malaria mortality in most epidemiological contexts in tropical Africa.

Increased risk of death from measles in children with a sibling of opposite sex in Senegal.

OBJECTIVE--To examine whether contracting measles from a sibling of the opposite sex affects mortality. DESIGN--Prospective registration during 15-20 years of all births and deaths, including 243 measles related deaths. Measles infection was not registered; however, as in fatal cases measles was probably contracted from a maternal sibling the risk of dying during measles outbreaks was examined in families with two boys, two girls, or a boy and a girl. SETTING--31 small villages in two rural areas of eastern Senegal. SUBJECTS--766 children living in families with two children aged under 10 years during outbreaks of measles, 107 (14%) of whom died of measles. MAIN OUTCOME MEASURE--Deaths from measles, size of village, age and sex of maternal siblings. RESULTS--The interval between outbreaks in the same village was greater than 10 years. The risk of dying of measles was significantly related to age, increasing with the age difference between siblings and decreasing with the size of village. In a multiple logistic regression analysis adjusting for these background factors, children in families with a boy and a girl had a significantly higher mortality than children in families with two boys or two girls (odds ratio = 1.81, 95% confidence interval 1.17 to 2.82). The increase in risk was the same for boys and girls in families with two children one of whom was a boy and one a girl. CONCLUSION--Cross sexual transmission may be an important determinant of severity of measles infection.

Lower Mortality for Female-Female Twins Than Male-Male and Male-Female Twins in Rural Senegal

Twins have been registered prospectively for 12–22 years in 42 small villages in the Bandafassi area of Eastern Senegal. We studied 98 pairs of twins to test whether twins in opposite-sex pairs have higher postneonatal mortality than same-sex twins. Neonatal mortality for twins was 41.3%; mortality for infants and for children under age 5 years was 53.0% and 66.8%, respectively. Neonatal mortality was identical for same-sex and opposite-sex twin pairs, but much higher for boys than girls [relative risk = 1.8; 95% confidence interval (CI) = 1.2–2.6]. There was clustering of double neonatal deaths for all types of twins. In the postneonatal period, female-female twins had lower mortality than other twin types. Twins had higher postneonatal mortality as long as the co-twin was alive [mortality rate ratio (MR) = 2.6; 95% CI = 1.0–6.7]. Girls had excess mortality when the co-twin was of the opposite sex (MR = 4.3; 95% CI = 1.2–15.3), whereas there was no difference for boys. In conclusion, contact with a co-twin of the opposite sex increased child mortality for female twins. Our data are not sufficient to determine whether this difference is specific for girls or applies to boys as well.