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The impact of IPTi and IPTc interventions on malaria clinical burden - in silico perspectives.

Aguas R, Lourenço JM, Gomes MG, White LJ - PLoS ONE (2009)

Bottom Line: Here, we simulate several schemes of intervention under different transmission settings, while varying immunity build up assumptions.However, even when significant rebound effects are predicted to occur, the overall intervention impact is positive.On the contrary, IPTc has a significant potential to reduce transmission, specifically in areas where it is already low to moderate.

View Article: PubMed Central - PubMed

Affiliation: Instituto Gulbenkian de Ciência, Oeiras, Portugal. ricaguas@igc.gulbenkian.pt

ABSTRACT

Background: Clinical management of malaria is a major health issue in sub-Saharan Africa. New strategies based on intermittent preventive treatment (IPT) can tackle disease burden by simultaneously reducing frequency of infections and life-threatening illness in infants (IPTi) and children (IPTc), while allowing for immunity to build up. However, concerns as to whether immunity develops efficiently in treated individuals, and whether there is a rebound effect after treatment is halted, have made it imperative to define the effects that IPTi and IPTc exert on the clinical malaria scenario.

Methods and findings: Here, we simulate several schemes of intervention under different transmission settings, while varying immunity build up assumptions. Our model predicts that infection risk and effectiveness of acquisition of clinical immunity under prophylactic effect are associated to intervention impact during treatment and follow-up periods. These effects vary across regions of different endemicity and are highly correlated with the interplay between the timing of interventions in age and the age dependent risk of acquiring an infection. However, even when significant rebound effects are predicted to occur, the overall intervention impact is positive.

Conclusions: IPTi is predicted to have minimal impact on the acquisition of clinical immunity, since it does not interfere with the occurrence of mild infections, thus failing to reduce the underlying force of infection. On the contrary, IPTc has a significant potential to reduce transmission, specifically in areas where it is already low to moderate.

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Related in: MedlinePlus

Targeted interventions according to endemic level.The IPTi intervention outcome (red line) is compared with a population without intervention in equilibrium conditions (black line), and a tailored schedule for the administration of anti-malarial drugs (blue line). These simulations are performed for a high transmission transmission setting.
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pone-0006627-g003: Targeted interventions according to endemic level.The IPTi intervention outcome (red line) is compared with a population without intervention in equilibrium conditions (black line), and a tailored schedule for the administration of anti-malarial drugs (blue line). These simulations are performed for a high transmission transmission setting.

Mentions: In Figure 3 we analyse the impact of IPTi at a specific point of the transmission spectrum, focusing on the importance of tailored interventions. In these simulations we assumed that, while treated, the risk of infection upon challenge, and the chance to build up clinical immunity upon infection is 0.5. We present in red an IPTi schedule concomitant with the EPI vaccination ages, and in blue the simulated intervention scenario that resulted in higher impact in terms of proportion of clinical cases prevented. The predicted optimal schedule for a three-dose intervention over the first year of life for this specific transmission setting is to give prophylactic treatment at 3, 5 and 7 months of age. Whereas in intermediate transmission areas, targeted interventions seem to harness little benefit (not shown), in high transmission regions a tailored schedule may be responsible for the prevention of 8.3% of cases of clinical malaria over all age classes, which contrasts with the 5.6% obtained under the EPI schedule.


The impact of IPTi and IPTc interventions on malaria clinical burden - in silico perspectives.

Aguas R, Lourenço JM, Gomes MG, White LJ - PLoS ONE (2009)

Targeted interventions according to endemic level.The IPTi intervention outcome (red line) is compared with a population without intervention in equilibrium conditions (black line), and a tailored schedule for the administration of anti-malarial drugs (blue line). These simulations are performed for a high transmission transmission setting.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2722080&req=5

pone-0006627-g003: Targeted interventions according to endemic level.The IPTi intervention outcome (red line) is compared with a population without intervention in equilibrium conditions (black line), and a tailored schedule for the administration of anti-malarial drugs (blue line). These simulations are performed for a high transmission transmission setting.
Mentions: In Figure 3 we analyse the impact of IPTi at a specific point of the transmission spectrum, focusing on the importance of tailored interventions. In these simulations we assumed that, while treated, the risk of infection upon challenge, and the chance to build up clinical immunity upon infection is 0.5. We present in red an IPTi schedule concomitant with the EPI vaccination ages, and in blue the simulated intervention scenario that resulted in higher impact in terms of proportion of clinical cases prevented. The predicted optimal schedule for a three-dose intervention over the first year of life for this specific transmission setting is to give prophylactic treatment at 3, 5 and 7 months of age. Whereas in intermediate transmission areas, targeted interventions seem to harness little benefit (not shown), in high transmission regions a tailored schedule may be responsible for the prevention of 8.3% of cases of clinical malaria over all age classes, which contrasts with the 5.6% obtained under the EPI schedule.

Bottom Line: Here, we simulate several schemes of intervention under different transmission settings, while varying immunity build up assumptions.However, even when significant rebound effects are predicted to occur, the overall intervention impact is positive.On the contrary, IPTc has a significant potential to reduce transmission, specifically in areas where it is already low to moderate.

View Article: PubMed Central - PubMed

Affiliation: Instituto Gulbenkian de Ciência, Oeiras, Portugal. ricaguas@igc.gulbenkian.pt

ABSTRACT

Background: Clinical management of malaria is a major health issue in sub-Saharan Africa. New strategies based on intermittent preventive treatment (IPT) can tackle disease burden by simultaneously reducing frequency of infections and life-threatening illness in infants (IPTi) and children (IPTc), while allowing for immunity to build up. However, concerns as to whether immunity develops efficiently in treated individuals, and whether there is a rebound effect after treatment is halted, have made it imperative to define the effects that IPTi and IPTc exert on the clinical malaria scenario.

Methods and findings: Here, we simulate several schemes of intervention under different transmission settings, while varying immunity build up assumptions. Our model predicts that infection risk and effectiveness of acquisition of clinical immunity under prophylactic effect are associated to intervention impact during treatment and follow-up periods. These effects vary across regions of different endemicity and are highly correlated with the interplay between the timing of interventions in age and the age dependent risk of acquiring an infection. However, even when significant rebound effects are predicted to occur, the overall intervention impact is positive.

Conclusions: IPTi is predicted to have minimal impact on the acquisition of clinical immunity, since it does not interfere with the occurrence of mild infections, thus failing to reduce the underlying force of infection. On the contrary, IPTc has a significant potential to reduce transmission, specifically in areas where it is already low to moderate.

Show MeSH
Related in: MedlinePlus