Malaria control measures : impact on malaria and anaemia in holoendemic area of rural coastal Tanzania

Abstract

Malaria is a major public health problem in tropical Africa. It is particularly the main killer disease in children below five years and its health impact is most severe in the rural areas. Malarial anaemia is believed to be the main complication in high endemic areas. However both clinical and basic research on this topic has been largely neglected so far. Epidemiological and intervention studies on anaemia and malaria including malaria case-management were therefore conducted in rural areas of Bagamoyo district on the coast of Tanzania.

The aims of these studies were to describe malaria epidemiology especially morbidity of malaria associated with anaemia, mortality in young children and malaria case- management practices. In addition, clinical diagnosis and a simple new dipstick diagnostic test were evaluated. An attempt was then made to evaluate sustainable malaria control measures. The impact of chemotherapy in combination with insecticide treated bed nets and micronutrients with iron on malaria morbidity were evaluated.

The main findings were that in young children the prevalence of parasitaemia was over 80% with frequent high parasite densities and 2.8 malaria episodes/child/annum. Anaemia was prevalent and associated with parasitaemia and clinical malaria episodes. The prevalence of anaemia (PCV < 33%) was > 70% and that of severe anaemia 2.5% (PCV < 20%). Severe anaemia mainly occurred before 18 months of age.

Demographic surveillance of child mortality under five years of age revealed 192 deaths in two years in a population of 3000 under five years. Of these, 148 were infant deaths giving a infant mortality rate of 131/1000 live births (95% CI 101, 154). There were 44 deaths in children 1 to 4 years of age, an annual child mortality rate of 10/1000 (95% CI 6.1, 14.3). Using verbal autopsy questionnaires, 56% of the deaths under 4 years were tentatively attributed to malaria. Most deaths due to malaria were associated with symptoms suggestive of severe anaemia.

At all health care levels 90% of children presenting with fever history were considered as malaria patients and treated with chloroquine. Clinical history taking and physical examination was not adequately performed, especially at the dispensary level. Microscopy where available, was not used to complement the clinical diagnosis and fever history was still the main determining factor for chloroquine treatment (P < 0.0001) . Presumptive clinical malaria diagnoses were reduced by 40% when the medical assistant was asked to perform systematic clinical evaluation and regression analysis showed that the presumptive diagnosis by the medical assistant was then strongly predictive of high parasitaemia (Odds ratio, 4.8, CI, 1.5-21.3). The ParaSight-F-Test showed high sensitivity for high parasite densities and therefore represents a good complement to clinical diagnosis and will further reduce chloroquine use (41 % of fevers were test positive). At primary health care level the use of ParaSight-F-Test was highly feasible and appreciated as a diagnostic tool.

The use of insecticide treated bed nets (ITNs) had a significant impact on malaria morbidity in children under three years. When compared to control children the relative risk of parasitaemia was 0.45 (0.36-0.57), similarly parasitaemia of 5000/1ll was reduced. The relative risks for febrile episode with parasitaemia was 0.39 (0.29-0.53).