Plasmodium falciparum clinical malaria in Dielmo, a holoendemic area in Senegal: no influence of acquired immunity on initial symptomatology and severity of malaria attacks.

Abstract

Abstract. Six hundred eighty-nine Plasmodium falciparum malaria attacks were observed during a three-year period among 226 inhabitants of the village of Dielmo, Senegal, an area of high malaria transmission. Malaria attacks were defined as clinical episodes with fever (body temperature Ն 38.0ЊC) or reporting of fever or headache or vomiting, associated with a parasite:leukocyte ratio above an age-dependent pyrogenic threshold identified in this population. The symptom frequencies were tested against age, gender, and parasite density using a random-effect logistic regression model and the study of distinguishable clinical presentations was carried out by multi-correspondence analysis. There was little difference between the severity of symptoms during the initial course of attacks in young children and adults, and this severity was not correlated with the duration of the pathologic episode. It was not possible to distinguish objectively different malaria attack types according to the severity of clinical manifestations. In contrast, the duration of fever, symptoms, and parasite clearance were significantly longer among the youngest children than among the oldest children and adults. These findings suggest that of the two components of protective immunity, anti-parasite immunity and anti-toxic immunity, only the first would play a major role as age increases. They suggest also that the initial clinical presentation of malaria attacks is not predictive of the level of protective immunity.The main goal of the current malaria control strategies is to prevent malaria mortality by diagnosing and treating clinical manifestations of the disease as early as possible. 1 This depends not only on the availability of efficient health services but also on the knowledge and the attitude of the patients or of their parents and on their perception of the initial symptoms that influence their therapeutic approach at home. Although a number of studies have been published on the signs and symptoms of clinical malaria in endemic populations, almost all of these studies were conducted in hospitals or outpatient clinics. Few detailed data are available on the range of clinical manifestations of malaria at the community level, their relative frequency, and their value in diagnosing the disease and initiating treatment. Since access to health facilities is difficult for most rural populations of tropical Africa, a better knowledge of clinical malaria at the community level could help to develop simple rules that would be necessary for reducing malaria mortality in these populations.A better knowledge of the whole range of malaria morbidity would also determine whether different clinical forms of nonsevere malaria attacks exist. The distinction between forms of malaria attacks that differ in the severity of clinical expression could have implications for the evaluation of control methods. The assessment of the clinical efficiency of malaria drugs or vaccines could vary according to the clinical forms that have been chosen to evaluate them...

The public health impact of chloroquine resistance in Africa

“…In semi-immune children and adults, the peaks of high parasitemia that are responsible for fever are spontaneously controlled within a few hours or days, and symptoms would disappear rapidly even if no malaria treatment were available. 39,40 …”

Evaluation of the pyrogenic threshold for Plasmodium falciparum malaria in naive individuals.

“…This value is within the range commonly used by other investigators. 5,6,12 However, it should be noted from plots of parasitemia and temperature over time (Figure 1), that the parasites elicited a host response reflected by elevations in body temperature at levels much lower then the fever threshold. Thus, different clinical definitions of fever would be expected to alter the results presented.…”

Parasite density and malaria morbidity in the Pakistani Punjab.

“…12,15 In fact, investigators reporting results from sub-Saharan Africa generally only include high densities of P. falciparum parasitemia (adjusted for age) as part of the definition for malaria disease. 6,[23][24][25] Nevertheless, the results of adjusted multiple logistic regression models showed that a clinical diagnosis of malaria by the examining physician: a history of fever, rigors, headache, and an elevated temperature or a palpable spleen in children were all highly associated with the presence of malaria parasites and the density of parasites in the blood in a monotonic dose-response manner. This association was present with either P. falciparum or P. vivax infections although the strength of association was greater with the former.…”