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Incorporating the effects of humidity in a mechanistic model of Anopheles gambiae mosquito population dynamics in the Sahel region of Africa.

Yamana TK, Eltahir EA - Parasit Vectors (2013)

Bottom Line: In this case, relative humidity had little effect on the mosquito population.In this case, the decrease in mosquito survival due to relative humidity improved the model's ability to reproduce the seasonal pattern of observed mosquito abundance.Future modeling work should account for these effects of relative humidity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Massachusetts Institute of Technology, 15 Vassar Street, Cambridge, MA 02139, USA. tkcy@mit.edu

ABSTRACT

Background: Low levels of relative humidity are known to decrease the lifespan of mosquitoes. However, most current models of malaria transmission do not account for the effects of relative humidity on mosquito survival. In the Sahel, where relative humidity drops to levels <20% for several months of the year, we expect relative humidity to play a significant role in shaping the seasonal profile of mosquito populations. Here, we present a new formulation for Anopheles gambiae sensu lato (s.l.) mosquito survival as a function of temperature and relative humidity and investigate the effect of humidity on simulated mosquito populations.

Methods: Using existing observations on relationships between temperature, relative humidity and mosquito longevity, we developed a new equation for mosquito survival as a function of temperature and relative humidity. We collected simultaneous field observations on temperature, wind, relative humidity, and anopheline mosquito populations for two villages from the Sahel region of Africa, which are presented in this paper. We apply this equation to the environmental data and conduct numerical simulations of mosquito populations using the Hydrology, Entomology and Malaria Transmission Simulator (HYDREMATS).

Results: Relative humidity drops to levels that are uncomfortable for mosquitoes at the end of the rainy season. In one village, Banizoumbou, water pools dried up and interrupted mosquito breeding shortly after the end of the rainy season. In this case, relative humidity had little effect on the mosquito population. However, in the other village, Zindarou, the relatively shallow water table led to water pools that persisted several months beyond the end of the rainy season. In this case, the decrease in mosquito survival due to relative humidity improved the model's ability to reproduce the seasonal pattern of observed mosquito abundance.

Conclusions: We proposed a new equation to describe Anopheles gambiae s.l. mosquito survival as a function of temperature and relative humidity. We demonstrated that relative humidity can play a significant role in mosquito population and malaria transmission dynamics. Future modeling work should account for these effects of relative humidity.

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Climate in Banizoumbou and Zindarou. Ground observations of daily average meridional wind speed, daily total rainfall, and daily averages of relative humidity and temperature are shown for Banizoumbou (red) and Zindarou (blue) for the year 2006. Postive values (above the yellow line) indicate wind blowing from the south while negative values (below the yellow line) indicate wind from the north.
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Figure 1: Climate in Banizoumbou and Zindarou. Ground observations of daily average meridional wind speed, daily total rainfall, and daily averages of relative humidity and temperature are shown for Banizoumbou (red) and Zindarou (blue) for the year 2006. Postive values (above the yellow line) indicate wind blowing from the south while negative values (below the yellow line) indicate wind from the north.

Mentions: In this paper, we investigated the effects of relative humidity on simulated mosquito population dynamics in two villages in Niger, West Africa. These two villages, Banizoumbou (13.53° N, 2.66° E) and Zindarou (13.43° N, 2.92° E), were the subject of extensive field activities and numerical model simulations using HYDREMATS (Hydrology, Entomology and Malaria Transmission Simulator), a spatially explicit, mechanistic model of malaria transmission [1,2]. The two villages are approximately 30 km apart, and there is little difference in climate between the two. Climate data for 2006 are shown in Figure 1. The rainy season in the region is dictated by the migration of the West African Monsoon. From approximately November through April, Harmattan winds from the Northeast bring dry air from the Sahara desert. From May through October, the monsoon brings moist air from the Southwest [3]. This shift in wind direction as measured in Banizoumbou and Zindarou in 2006 is shown in the upper left panel of Figure 1, where positive values of the meridional wind speed indicate wind blowing from the south, while negative values indicate wind blowing from the north. The moist air from the south leads to high relative humidity and rainfall as shown in the lower left and upper right panels of Figure 1, respectively.


Incorporating the effects of humidity in a mechanistic model of Anopheles gambiae mosquito population dynamics in the Sahel region of Africa.

Yamana TK, Eltahir EA - Parasit Vectors (2013)

Climate in Banizoumbou and Zindarou. Ground observations of daily average meridional wind speed, daily total rainfall, and daily averages of relative humidity and temperature are shown for Banizoumbou (red) and Zindarou (blue) for the year 2006. Postive values (above the yellow line) indicate wind blowing from the south while negative values (below the yellow line) indicate wind from the north.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750695&req=5

Figure 1: Climate in Banizoumbou and Zindarou. Ground observations of daily average meridional wind speed, daily total rainfall, and daily averages of relative humidity and temperature are shown for Banizoumbou (red) and Zindarou (blue) for the year 2006. Postive values (above the yellow line) indicate wind blowing from the south while negative values (below the yellow line) indicate wind from the north.
Mentions: In this paper, we investigated the effects of relative humidity on simulated mosquito population dynamics in two villages in Niger, West Africa. These two villages, Banizoumbou (13.53° N, 2.66° E) and Zindarou (13.43° N, 2.92° E), were the subject of extensive field activities and numerical model simulations using HYDREMATS (Hydrology, Entomology and Malaria Transmission Simulator), a spatially explicit, mechanistic model of malaria transmission [1,2]. The two villages are approximately 30 km apart, and there is little difference in climate between the two. Climate data for 2006 are shown in Figure 1. The rainy season in the region is dictated by the migration of the West African Monsoon. From approximately November through April, Harmattan winds from the Northeast bring dry air from the Sahara desert. From May through October, the monsoon brings moist air from the Southwest [3]. This shift in wind direction as measured in Banizoumbou and Zindarou in 2006 is shown in the upper left panel of Figure 1, where positive values of the meridional wind speed indicate wind blowing from the south, while negative values indicate wind blowing from the north. The moist air from the south leads to high relative humidity and rainfall as shown in the lower left and upper right panels of Figure 1, respectively.

Bottom Line: In this case, relative humidity had little effect on the mosquito population.In this case, the decrease in mosquito survival due to relative humidity improved the model's ability to reproduce the seasonal pattern of observed mosquito abundance.Future modeling work should account for these effects of relative humidity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Massachusetts Institute of Technology, 15 Vassar Street, Cambridge, MA 02139, USA. tkcy@mit.edu

ABSTRACT

Background: Low levels of relative humidity are known to decrease the lifespan of mosquitoes. However, most current models of malaria transmission do not account for the effects of relative humidity on mosquito survival. In the Sahel, where relative humidity drops to levels <20% for several months of the year, we expect relative humidity to play a significant role in shaping the seasonal profile of mosquito populations. Here, we present a new formulation for Anopheles gambiae sensu lato (s.l.) mosquito survival as a function of temperature and relative humidity and investigate the effect of humidity on simulated mosquito populations.

Methods: Using existing observations on relationships between temperature, relative humidity and mosquito longevity, we developed a new equation for mosquito survival as a function of temperature and relative humidity. We collected simultaneous field observations on temperature, wind, relative humidity, and anopheline mosquito populations for two villages from the Sahel region of Africa, which are presented in this paper. We apply this equation to the environmental data and conduct numerical simulations of mosquito populations using the Hydrology, Entomology and Malaria Transmission Simulator (HYDREMATS).

Results: Relative humidity drops to levels that are uncomfortable for mosquitoes at the end of the rainy season. In one village, Banizoumbou, water pools dried up and interrupted mosquito breeding shortly after the end of the rainy season. In this case, relative humidity had little effect on the mosquito population. However, in the other village, Zindarou, the relatively shallow water table led to water pools that persisted several months beyond the end of the rainy season. In this case, the decrease in mosquito survival due to relative humidity improved the model's ability to reproduce the seasonal pattern of observed mosquito abundance.

Conclusions: We proposed a new equation to describe Anopheles gambiae s.l. mosquito survival as a function of temperature and relative humidity. We demonstrated that relative humidity can play a significant role in mosquito population and malaria transmission dynamics. Future modeling work should account for these effects of relative humidity.

Show MeSH
Related in: MedlinePlus