Effect of irrigation systems on temporal distribution of malaria vectors in semi-arid regions

Abstract

Previous research models have used climate data to explain habitat conditions of Anopheles mosquitoes transmitting malaria parasites. Although they can estimate mosquito populations with sufficient accuracy in many areas, observational data show that there is a tendency to underestimate the active growth and reproduction period of mosquitoes in semi-arid agricultural regions. In this study, a new, modified model that includes irrigation as a factor was developed to predict the active growing period of mosquitoes more precisely than the base model for ecophysiological and climatological distribution of mosquito generations (ECD-mg). Five sites with complete sets of observational data were selected in semi-arid regions of India for the comparison. The active growing period of mosquitoes determined from the modified ECD-mg model that incorporated the irrigation factor was in agreement with the observational data, whereas the active growing period was underestimated by the previous ECD-mg model that did not incorporate irrigation. This suggests that anthropogenic changes in the water supply due to extensive irrigation can encourage the growth of Anopheles mosquitoes through the alteration of the natural water balance in their habitat. In addition, it was found that the irrigation systems not only enable the active growth of mosquitoes in dry seasons but also play an important role in stabilizing the growth in rainy seasons. Consequently, the irrigation systems could lengthen the annual growing period of Anopheles mosquitoes and increase the maximum generation number of mosquitoes in semi-arid subtropical regions.

Combining GIS application and climatic factors for mosquito control in Eastern Province, Saudi Arabia

“…In a comparison of the two regression models (adults and larvae) and climatic factors, it seems that larvae are more influenced by the presence of vegetation, waste material, water reservoirs and ditches. The presence of floating and terrestrial vegetation, poor environmental sanitation and extensive irrigation activities that create water reservoirs such as ditches are among the major environmental factors for mosquito abundance and their wide distribution in many habitats (Ohta and Kaga, 2014, Alahmed, 2012, Calhoun et al, 2007, Chaikoolvatana et al, 2007).…”

Influence of Climatic Factors on the Abundance and Profusion of Mosquitoes in Eastern Province, Saudi Arabia

“…Calhoun et al [41] reported a higher number of Culex larvae in oily/rusty water when compared to clean water. Similarly, Ohta and Kaga [42] found that substantial irrigation activities enhance mosquito growth, lengthen mosquito annual growing periods, and raise mosquito maximum generation numbers by altering natural water in their environment. It was also shown that irrigation systems not only aid mosquito growth during dry seasons but also help to stabilize growth during rainy seasons.…”

“…It seems that Culex and Anopheles larvae are more influenced by the presence of vegetation, waste material, water reservoirs, and ditches. The presence of floating and terrestrial vegetation, poor environmental sanitation, and extensive irrigation activities that create water reservoirs such as ditches are among the major environmental factors for mosquito abundance and their wide distribution in many habitats [39,41,42,49].…”

Investigating the Impact of Irrigation on Malaria Vector Larval Habitats and Transmission Using a Hydrology‐Based Model

“…The lag can be attributed to the time for infiltration to occur, runoff to accumulate in low‐lying areas, and the development time for parasite growth. In addition, past observations have proven that irrigation plays the same function as rainfall in providing larval habitats to support vector growth (Herrel et al., 2001 ; Ohta & Kaga, 2014 ). Hence, irrigation in the dry season in our study created a pseudo‐early rainy season, which causes earlier onset of mosquito breeding and an extended malaria transmission.…”