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Malaria Elimination Campaigns in the Lake Kariba Region of Zambia: A Spatial Dynamical Model

View Article: PubMed Central - PubMed

ABSTRACT

As more regions approach malaria elimination, understanding how different interventions interact to reduce transmission becomes critical. The Lake Kariba area of Southern Province, Zambia, is part of a multi-country elimination effort and presents a particular challenge as it is an interconnected region of variable transmission intensities. In 2012–13, six rounds of mass test-and-treat drug campaigns were carried out in the Lake Kariba region. A spatial dynamical model of malaria transmission in the Lake Kariba area, with transmission and climate modeled at the village scale, was calibrated to the 2012–13 prevalence survey data, with case management rates, insecticide-treated net usage, and drug campaign coverage informed by surveillance. The model captured the spatio-temporal trends of decline and rebound in malaria prevalence in 2012–13 at the village scale. Various interventions implemented between 2016–22 were simulated to compare their effects on reducing regional transmission and achieving and maintaining elimination through 2030. Simulations predict that elimination requires sustaining high coverage with vector control over several years. When vector control measures are well-implemented, targeted mass drug campaigns in high-burden areas further increase the likelihood of elimination, although drug campaigns cannot compensate for insufficient vector control. If infections are regularly imported from outside the region into highly receptive areas, vector control must be maintained within the region until importations cease. Elimination in the Lake Kariba region is possible, although human movement both within and from outside the region risk damaging the success of elimination programs.

No MeSH data available.


Related in: MedlinePlus

Malaria elimination in the Lake Kariba region is possible under high levels of ITN usage even without distributing MDAs after 2015.The fraction of total study area population living in clusters where no local transmission has occurred over a month-long period is plotted for each month between January 2012 and January 2030. Line indicates the mean and shaded area the range observed over 100 samples from the joint posterior distribution of 10 best-fit habitat availability pairs for each cluster. A simulation results in elimination if no new infections occur in all clusters over a 3-year period. The “elimination” row indicates the fraction of simulations where elimination was observed. (A) If ITN distributions stop after 2015, elimination is never observed to occur. (B) Under an aggressive ITN distribution scenario, elimination becomes likely even without additional MDAs after 2015.
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pcbi.1005192.g007: Malaria elimination in the Lake Kariba region is possible under high levels of ITN usage even without distributing MDAs after 2015.The fraction of total study area population living in clusters where no local transmission has occurred over a month-long period is plotted for each month between January 2012 and January 2030. Line indicates the mean and shaded area the range observed over 100 samples from the joint posterior distribution of 10 best-fit habitat availability pairs for each cluster. A simulation results in elimination if no new infections occur in all clusters over a 3-year period. The “elimination” row indicates the fraction of simulations where elimination was observed. (A) If ITN distributions stop after 2015, elimination is never observed to occur. (B) Under an aggressive ITN distribution scenario, elimination becomes likely even without additional MDAs after 2015.

Mentions: Discontinuing MDAs after the 2015 rounds while maintaining current levels of ITN usage did not result in long-term reduction in regional malaria transmission (Fig 7A, scenario 1). Increasing passive case management rates (scenario 2) established a new baseline of lower transmission during the decades following the end of MDAs in 2015 but could not achieve region-wide elimination. Combining the 2014–15 MDAs with ramp-ups in case management and increased ITN usage resulted in elimination under highly aggressive ITN distribution campaigns but not if ITN ramp-ups followed historical rates of increase (Fig 7B and S11 Fig). Under the ramp-up scenario (scenario 3), transmission rebounded after the last ITN distribution in 2022 to a new baseline largely determined by case management rate. In the aggressive scenario (scenario 4), 87% of simulations resulted in elimination.


Malaria Elimination Campaigns in the Lake Kariba Region of Zambia: A Spatial Dynamical Model
Malaria elimination in the Lake Kariba region is possible under high levels of ITN usage even without distributing MDAs after 2015.The fraction of total study area population living in clusters where no local transmission has occurred over a month-long period is plotted for each month between January 2012 and January 2030. Line indicates the mean and shaded area the range observed over 100 samples from the joint posterior distribution of 10 best-fit habitat availability pairs for each cluster. A simulation results in elimination if no new infections occur in all clusters over a 3-year period. The “elimination” row indicates the fraction of simulations where elimination was observed. (A) If ITN distributions stop after 2015, elimination is never observed to occur. (B) Under an aggressive ITN distribution scenario, elimination becomes likely even without additional MDAs after 2015.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5120780&req=5

pcbi.1005192.g007: Malaria elimination in the Lake Kariba region is possible under high levels of ITN usage even without distributing MDAs after 2015.The fraction of total study area population living in clusters where no local transmission has occurred over a month-long period is plotted for each month between January 2012 and January 2030. Line indicates the mean and shaded area the range observed over 100 samples from the joint posterior distribution of 10 best-fit habitat availability pairs for each cluster. A simulation results in elimination if no new infections occur in all clusters over a 3-year period. The “elimination” row indicates the fraction of simulations where elimination was observed. (A) If ITN distributions stop after 2015, elimination is never observed to occur. (B) Under an aggressive ITN distribution scenario, elimination becomes likely even without additional MDAs after 2015.
Mentions: Discontinuing MDAs after the 2015 rounds while maintaining current levels of ITN usage did not result in long-term reduction in regional malaria transmission (Fig 7A, scenario 1). Increasing passive case management rates (scenario 2) established a new baseline of lower transmission during the decades following the end of MDAs in 2015 but could not achieve region-wide elimination. Combining the 2014–15 MDAs with ramp-ups in case management and increased ITN usage resulted in elimination under highly aggressive ITN distribution campaigns but not if ITN ramp-ups followed historical rates of increase (Fig 7B and S11 Fig). Under the ramp-up scenario (scenario 3), transmission rebounded after the last ITN distribution in 2022 to a new baseline largely determined by case management rate. In the aggressive scenario (scenario 4), 87% of simulations resulted in elimination.

View Article: PubMed Central - PubMed

ABSTRACT

As more regions approach malaria elimination, understanding how different interventions interact to reduce transmission becomes critical. The Lake Kariba area of Southern Province, Zambia, is part of a multi-country elimination effort and presents a particular challenge as it is an interconnected region of variable transmission intensities. In 2012–13, six rounds of mass test-and-treat drug campaigns were carried out in the Lake Kariba region. A spatial dynamical model of malaria transmission in the Lake Kariba area, with transmission and climate modeled at the village scale, was calibrated to the 2012–13 prevalence survey data, with case management rates, insecticide-treated net usage, and drug campaign coverage informed by surveillance. The model captured the spatio-temporal trends of decline and rebound in malaria prevalence in 2012–13 at the village scale. Various interventions implemented between 2016–22 were simulated to compare their effects on reducing regional transmission and achieving and maintaining elimination through 2030. Simulations predict that elimination requires sustaining high coverage with vector control over several years. When vector control measures are well-implemented, targeted mass drug campaigns in high-burden areas further increase the likelihood of elimination, although drug campaigns cannot compensate for insufficient vector control. If infections are regularly imported from outside the region into highly receptive areas, vector control must be maintained within the region until importations cease. Elimination in the Lake Kariba region is possible, although human movement both within and from outside the region risk damaging the success of elimination programs.

No MeSH data available.


Related in: MedlinePlus