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

Gatton, Michelle L.; Cheng, Qin

doi:10.4269/ajtmh.2002.66.467

Cited by 52 publications

(56 citation statements)

References 12 publications

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“…Tolerance to malaria parasites may be acquired after a single infection, as the pyrogenic threshold during an infection in non-immune hosts increases between the first and second fever episodes [9]. Moreover, a larger proportion of patients remained asymptomatic during the reinfection (11.5%) compared with the initial infection (1.8%) [9], suggesting the persistence of tolerance mechanisms after the infection ends.…”

Section: Tolerance To Malaria Infectionmentioning

confidence: 99%

“…Differences noted between Plasmodium falciparum strains and isolates in their maximum parasitemia [8], pyrogenic thresholds [9], multiplication rates [10], and cytoadhesion leading to sequestration in vital organs [11] suggest that there might be parasite factors that contribute to the development of asymptomatic infection.…”

Section: Malaria Parasite Factorsmentioning

confidence: 99%

“…However, this has not been demonstrated in other areas with intense seasonality or in low-transmission settings [15], questioning the reliability of parasite densities in distinguishing malaria attacks from other causes of fever. Moreover, significant differences have been observed between the pyrogenic thresholds for different P. falciparum strains [9], suggesting that some strains may induce a febrile response in the host at lower parasite densities compared with other strains. Possible explanations for these differences include variations in the virulence of the strains in inducing an inflammatory response, in their potential for cytoadhesion and sequestration, in the degree of synchronization of parasite populations, or in the length of the replication cycle.…”

Section: Box 1 Asymptomatic Malariamentioning

confidence: 99%

“…Surveillance tools based on these factors might guide the selection of the most effective elimination strategies to target the asymptomatic reservoir of malaria transmission. been shown to cover a wide spectrum of parasite densities ranging from 10 to 200 000 parasites/ml [9], varying as a function of transmission intensity, age, or host ethnicity [9]. In high-transmission areas, clinical illness is not often associated with parasitemia of P. falciparum below 10 000 parasites/ml [14].…”

mentioning

confidence: 99%

“…Infections may remain asymptomatic if major disruptions of physiological functions are prevented by tolerance mechanisms. Such tolerance developed by the host is likely to be multifactorial and includes the neutralization of parasite toxins and other virulence factors and immunoregulatory mechanisms that reduce the damage triggered by excessive immune responses of the host (i.e., immunopathology) as well as cellular and systemic adaptive responses that limit the deleterious effects associated with stress imposed by pathogens and/or host immunity (Box 3).Tolerance to malaria parasites may be acquired after a single infection, as the pyrogenic threshold during an infection in non-immune hosts increases between the first and second fever episodes [9]. Moreover, a larger proportion of patients remained asymptomatic during the reinfection (11.5%) compared with the initial infection (1.8%) [9], suggesting the persistence of tolerance mechanisms after the infection ends.…”

mentioning

confidence: 99%

See 4 more Smart Citations

Malaria Parasites in the Asymptomatic: Looking for the Hay in the Haystack

Galatas

Bassat

Mayor

2016

Trends in Parasitology

116

122

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With malaria elimination back on the international agenda, programs face the challenge of targeting all Plasmodium infections, not only symptomatic cases. As asymptomatic individuals are unlikely to seek treatment, they are missed by passive surveillance while remaining infectious to mosquitoes, thus acting as silent reservoirs of transmission. To estimate the risk of asymptomatic infections in various phases of malaria elimination, we need a deeper understanding of the underlying mechanisms favoring carriage over disease, which may involve both pathogen and host factors. Here we review our current knowledge on the determinants leading to Plasmodium falciparum symptomless infections. Understanding the host-pathogen interactions that are most likely to affect transitions between malaria disease states could guide the development of tools to tackle asymptomatic carriers in elimination settings. Being AsymptomaticPeaceful coexistence with the infected host, rarely causing clinical symptoms, is a common but poorly understood phenomenon that occurs for many human pathogens [1]. Because such asymptomatic cases of infection occur without eventual overt symptoms, they do not come to clinical attention, thus representing a large hidden reservoir of active infection that permits their persistence and eventual spread to other human hosts. This is the case for many malaria infections in semi-immune individuals from endemic areas, which commonly cause a mild febrile illness or no apparent symptoms at all, while keeping parasite numbers at low densities [2] (Box 1).Carriage of asymptomatic malaria (see Glossary) infections, being at the same time difficult to detect and to manage, has considerable implications for the design and use of malaria elimination strategies. Symptomless infections that persist during the dry season in areas of seasonal transmission have been suggested to seed the malaria outbreaks after annual rains when mosquitoes reappear [3]. Similarly, asymptomatic parasitemia may potentially contribute to persistence of transmission in low-transmission settings [4]. However, the precise contribution of asymptomatic malaria to transmission in areas that have achieved substantial reductions in the malaria burden remains a matter of debate [5], as is the assumption that detecting and targeting these individuals for radical treatment, as opposed to using mass drug administration approaches, would be an efficient and effective tactic. Moreover, eradication in Europe, North America, and other parts of the world using no better diagnostics than microscopy [6] suggest that key determinants of success might not be finding the last parasite. From a practical point of view, the proportion of asymptomatic infections in certain situations and phases of malaria elimination may impose the need for modifications of detection methods (active versus passive case detection) [7] if, for example, symptom-based surveillance at health facilities is insufficient and mass blood surveys are necessary to inform the design of elimination i...

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Section: Tolerance To Malaria Infectionmentioning

confidence: 99%