Determination of the effect of temperature on the life cycle of Aedes aegypti and Ae. albopictus

Introduction:

Mosquito is a heterothermic animal; thus, the biological activities of the mosquito depends on the environmental temperature. As far as dengue is concerned, the life span, length of the life cycle and gonotrophic cycle are important determinants of the transmission of the disease. This study was designed with the following objectives.

Objectives

General objective 

To determine the effect of temperature on the life cycle, life span and the gonotrophic cycle of Aedes aegypti and Ae. Albopictus.

Specific objectives

1. To determine the time taken for hatching the eggs of Aedes aegypti and Ae. Albopictus at different temperatures.
2. To determine the time taken for completing the different stages of life cycle of Aedes aegypti and Ae. Albopictus (1^st, 2^nd, 3^rd and 4^th stages of larvae, pupae and adult mosquitoes) at different temperatures.
3. To determine the time taken for gonotrophic cycle of Ae. Aegypti and Ae. Albopictus at different temperatures.

Materials and methods

The study area and study sites

The districts of Kandy, Matale and Nuwara Eliya in the Central Province of Sri Lanka are selected for the present study. Since the province shows different temperatures with minimum in Nuwara Eliya and high temperatures in Matale district this area was selected for the study. The study sites are Hawa Eliya in the Nuwara Eliya district, Naula in the Matale district and Akurana in the Kandy district.

Methodology

Eggs of Aedes mosquitoes are collected using ovi traps at the study sites. The egg straps of the traps are brought to the field laboratory, allowed to air dry for two days and count the number of eggs in each strip. Place the egg strips in enamel trays to hatch them to larvae. The larvae are identified to species and Ae. Aegypti and Ae. Albopictus larvae are selected and place them separately in enamel trays to allowed to develop to pupae. Pupae are placed in mosquito cages to develop to adults. After 2 days of emergence, the males and females of each species are separated and place 100 of each sex in different cages. The adult females are fed with blood and the males are fed with sugar solution. Set Ovitraps in the cages with female mosquitoes and note the time of the Gonotropic cycle. Also, count the number of mosquitoes died in the cage every day if any. The eggs collected from the Ovitraps are allowed to hatch and note the time taken to hatch the eggs, time duration of each stage of larvae and the pupae.

Time frame

		Wk 1	Wk 2	Wk 3	Wk 4	Wk 5	Wk 6	Wk 7	Wk 8	Wk 9	Wk 10
1	Setting and collection of Ovitraps	x	x
2	Allow the egg strips to air dry for 2 days and count the number of eggs in each strip separately		x	x
3	Allow the mosquito eggs to hatch and develop into adults				x	x
4	Identify the adult mosquitoes, feed them collect data on gonotrophic cycle and daily survival counts						x	x
5	Collect eggs from each colony and allowed to hatch and develop to adults and collect data on the time duration of different stages of the life cycle								x	x
6	Prepare summary reports										x