Effect of Salinity on Mosquito ( Aedes ) Oviposition Preference and Survival of Larvae: A Laboratory-based Study

Vector control measures assume utmost importance in the absence of specific treatment against clinically complicated Dengue virus infections. Preventive measures such as reduction of mosquito larvae breeding hot spots also include spraying of insecticides. However, insecticides pose a risk to the general population as well as to the environment. A search for a suitable environmentally friendly substitute for insecticides has been one of the goals of all researchers round the globe.

To investigate the possibility of using salt in existing vector control programs, we investigated the effect of different concentrations of saline water on mosquito larva in the present study.

Larvae of Aedes aegypti were subjected to six different doses of salt solutions ranging from 0.5% to 3% for the larval bioassay. The lethal concentrations (LC50 and LC90 values) for 50% and 90% mortality were computed. Simultaneously, gravid females, A. aegypti mosquitoes, were released into the cage for egg-laying, and from the 4th day onward, the eggs were counted. Egg-hatching tests were also done in the salt solution to assess the influence of salinity on egg hatching.

The findings imply that a salt concentration of 1%-2% is lethal for A. aegypti . With a salinity content of more than 2%, no egg-laying was observed. After control, the maximum emergence (64.5%) was recorded in a water bowl containing 8% saltwater (66%). The threshold concentration was found to be between 0.5% and 1.0%, after which the mortality of the hatched larvae rose sharply, reaching 100% in 24 h at 2.0% concentration. At a salinity of 2%, common salt sodium chloride (NaCl) was shown to be efficient in killing A. aegypti larvae.

Unlike other insecticides, salt is nontoxic, crystalline, cost-effective, stable, and easy to implement. More studies on this aspect of salt may be undertaken in the future to assess its efficacy in field conditions.