Aedes Albopictus - Control and Suppression

Control and Suppression

Aedes albopictus has proven to be very difficult to suppress or to control due to their remarkable ability to adapt to various environments, their close contact with humans, and their reproductive biology.

Efficient monitoring or surveillance is essential to prevent the spread and establishment of the species. In addition to the monitoring of ports, warehouses with imported plants, and stockpiles of tires, rest areas on highways and train stations should be monitored with appropriate methods.

The control of the Asian tiger mosquitoes begins with destroying the places where they lay their eggs, which are never far from where people are being bitten, since they are weak fliers, with only about a 180-meters (200-yard) lifetime flying radius. Locate puddles that last more than three days, sagging or plugged roof gutters, old tires holding water, litter, bird baths, inlets to sewers and drainage systems holding stagnant water and any other possible containers or pools of standing water. Flower pots, standing flower vases, knotholes and other crevices that can collect water should be filled with sand or fine gravel to prevent mosquitoes from laying their eggs in them. Litter can also hold rain water and should be removed.

Any standing water in pools, catchment basins, etc., that cannot be drained, or dumped, can be periodically treated with properly labeled insecticides or Bacillus thuringiensis israelensis (Bti), often formed into doughnut shaped "mosquito dunks". Bti is a bacterium that produces toxins which are effective in killing larvae of mosquitoes and certain other Dipterans, while having almost no effect on other organisms. Bti preparations are readily available at farm, garden, and pool suppliers.

Flowing water will not be a breeding spot, and water that contains minnows is not usually a problem, because the fish eat the mosquito larvae. Dragonflies are also an excellent method of imposing control. Dragonfly larvae eat mosquito larvae in the water, and adults will snatch adult mosquitoes as they fly.

In any case, an efficient surveillance is essential to monitor the presence of tiger mosquitoes and the effect of control programs. So-called ovitraps are normally used for the monitoring of Aedes albopictus. They are black water containers with floating Styrofoam blocks or small wooden paddles that are in contact with the surface of the water. Female tiger mosquitoes lay their eggs on these surfaces. Through the identification of these eggs or of the larvae that hatch from these eggs in the laboratory, the presence and abundance of mosquito species can be estimated. Versions of these traps with an adhesive film (sticky traps) that catch the egg depositing mosquitoes make the analysis much easier and quicker, but are more complicated in terms of handling. The results of ovitraps are often variable and depend on the availability of alternative egg depositing waters. Due to this, it is best to use them in large numbers and in conjunction with other monitoring methods.

To date, there are few effective traps for the adult Asian tiger mosquito. Those traps that catch other species of mosquitoes do not catch tiger mosquitoes efficiently. A new trap type has now been shown to catch significant numbers of Aedes albopictus. This device, with the help of a ventilator, produces an upward air current of ammonia, fatty acids, and lactic acids that takes a similar form and smell of a human body. With the addition of carbon dioxide, the efficacy of the trap is increased. This means there is a suitable tool available for trapping adult tiger mosquitoes and, for example, examining the existence of viruses in the trapped mosquitoes. Previously, the mosquitoes had to be collected from volunteers to be studied, which is ethically questionable, especially during epidemics. Recent research also indicates this trap type may also have a use as a control tool; in a study in Cesena, Italy, the amount of biting tiger mosquitoes was reduced in places where traps were installed.