Evolution of malaria mortality and morbidity after the emergence of chloroquine resistance in Niakhar, Senegal

Abstract

Background: Recently, it has been assumed that resistance of Plasmodium to chloroquine increased malaria mortality. The study aimed to assess the impact of chemoresistance on mortality attributable to malaria in a rural area of Senegal, since the emergence of resistance in 1992, whilst chloroquine was used as first-line treatment of malaria, until the change in national anti-malarial policy in 2003.

Methods: The retrospective study took place in the demographic surveillance site (DSS) of Niakhar. Data about malaria morbidity were obtained from health records of three health care facilities, where diagnosis of malaria was based on clinical signs. Source of data concerning malaria mortality were verbal autopsies performed by trained fieldworkers and examined by physicians who identified the probable cause of death.

Results: From 1992 to 2004, clinical malaria morbidity represented 39% of total morbidity in health centres. Mean malaria mortality was 2.4 per thousand and 10.4 per thousand among total population and children younger than five years, respectively, and was highest in the 1992-1995 period. It tended to decline from 1992 to 2003 (Trend test, total population p = 0.03, children 0-4 years p = 0.12 - children 1-4 years p = 0.04- children 5-9 years p = 0.01).

Conclusion: Contrary to what has been observed until 1995, mortality attributable to malaria did not continue to increase dramatically in spite of the growing resistance to chloroquine and its use as first-line treatment until 2003. Malaria morbidity and mortality followed parallel trends and rather fluctuated accordingly to rainfall.

Figure 1

Niakhar study area.

Figure 2

Evolution of consultations for malaria in health care facilities and deaths attributable to malaria in Niakhar area (1992-2004). The purple line represents the clinical malaria morbidity in dispensaries per 1,000 person-year at risk (py). The orange line represents the malaria mortality per 1,000 py in the population.

Figure 3

Malaria consultations and annual rainfall in Niakhar area, 1992-2004. The purple line represents the clinical malaria morbidity in dispensaries per 1,000 person-year at risk (py). The green line represents the annual rainfall (mm) in Niakhar village.

Figure 4

Evolution of malaria mortality and resistance to chloroquine between 1992 and 2004 in Niakhar area. The orange line represents the malaria mortality per 1,000 person-year (py) in the population. Red bars represent the rate of chloroquine resistance (%) measured at day 14 after treatment by chloroquine. Pink bars represent the rate of chloroquine resistance (%) measured at day 7 after treatment by chloroquine. (a) 1993, 1994, 1995: in vivo chemosensitivity studies, Diohine village, Niakhar DSS [5]. (b) 1996: in vivo chemosensitivity study, Diohine village, Niakhar DSS [7]. (c) 1998 and 2001: in vivo chemosensitivity studies, Kaolack sentinel site, 50 km from Fatick [8].