Shüné Oliver of the National Institute for Infectious Diseases and her colleagues at the National Institute for Infectious Diseases track malaria cases and mosquito behavior in South Africa.
As part of the study, they looked at three key aspects. One is the impact of human activities on mosquito biology. Here, they studied the effects of heavy metal pollution on different life history traits and the expression of resistance in malaria-transmitting Anopheles mosquitoes.
They also studied the impact of climate change on the effectiveness of insecticides against malaria vectors.
Finally, we studied the impact of high temperature on An. arabiensis, the main vector of malaria.
An. arabiensis is very difficult to control. In addition to the insecticide resistance that has been reported, they also tend to avoid insecticide-treated nets and walls. These mosquitoes also tend to bite people outdoors, where there is little protection.
Their work aims to understand the biology of this complex mosquito to track how changes in the environment affect the animal's behavior. This will hopefully inform malaria control strategies and bring us closer to eliminating the disease.
toxin
The larval stage of mosquitoes is aquatic. This vulnerable stage is critical to the health of adult mosquitoes, just as the health of human infants will determine the future health of adult mosquitoes.
Many larval environmental factors have profound effects on adult mosquito fitness. These factors include ambient temperature, crowding levels and access to nutrients. However, human activities have caused water pollution levels to rise, exposing mosquito larvae to more toxins.
This has a big impact on the mosquitoes that transmit malaria. These insects normally breed in clean water but have adapted to breed in polluted water. This means that malaria vectors can now potentially expand into areas where malaria does not normally occur.
Their research shows that contaminated water sources are becoming breeding grounds for mosquitoes that are resistant to a range of toxins. They found that adult mosquitoes exposed to metals during their larval stage develop resistance.
They don't yet know whether insecticide-resistant mosquitoes and infection-susceptible mosquitoes are more likely to spread malaria. But contamination activities lead to an expansion of mosquito ranges and changes in selection procedures.
Insecticides and Mosquito Temperature
Further research they did showed that high temperatures also affect the effectiveness of some pesticides.
Pesticides are commonly used as public health interventions to control malaria vectors in some African countries, including South Africa, Cameroon and Kenya. They are an important component of malaria control policies and strategies for malaria elimination.
Their findings have important implications for determining the effectiveness of currently used pesticides. But their research was conducted under controlled laboratory conditions, so their findings must also be tested in real life. This is because different temperatures have different effects. Environmental conditions also vary and may have an impact on the effectiveness of pesticides.
When it comes to mosquitoes, their research shows that temperature can have a significant impact on the life cycle of these insects. For example, climate change may affect the distribution of malaria vectors. They studied how rising temperatures affect the main malaria vectors. They focused specifically on the relationship between pesticide-resistant vectors and pesticide-susceptible vectors.
Mosquitoes that are resistant are more tolerant of high temperatures than those that are not. This means that as temperatures rise, so do the odds of insecticide-resistant mosquitoes surviving. This will complicate malaria control.
why should we worry
Human activities are driving mosquito evolution. Contaminating activity causes malaria-carrying mosquitoes to expand into areas where they were not previously present. Adaptation to water pollution leads to increased tolerance to pesticides.
Insecticide-resistant or drug-resistant mosquitoes are better able to deal with a wider range of toxic pollutants. It's unclear whether these mosquitoes are more likely to transmit malaria than insecticide-susceptible mosquitoes.
