As a general rule, most malaria carrying mosquitoes bite at night; mosquitoes that spread Dengue and Dengue Hemorrhagic Fever (DHF) bite during the day. (In some cases people travelling through dark forests during daylight hours can be bitten by malaria infected mosquitoes.)
Mosquito nets, if properly used and maintained, can provide a physical barrier to infected mosquitoes, both in daylight hours if people are sleeping or resting during the day and at night.
At the present time there are 3 basic types of mosquito nets, untreated nets, Insecticide Treated Nets (ITNs) and Long Life Insecticide treated Nets (LLINs). ITNs are nets that need to be treated once a year with a special chemical solution that ensures their continued effectiveness.
LLINs are nets that do not have to be treated for three years or more.
Whilst an ordinary mosquito net will protect a person from mosquito bites, the ITN and LLIN are much preferred as the chemical in the nets also kills the mosquito without harming the person underneath the net. Currently permethrin is the chemical most commonly used to treat mosquito nets, although new chemicals are constantly under development. Permethrin is a man-made insecticide, structurally similar to a naturally-occurring chemical called pyrethrum. Pyrethrum was initially derived from the crushed dried flowers of the daisy Chrysanthemum, whose insecticidal properties have been recognized since the 18th century. Permethrin is safe to use if handled properly.
Maintenance of ITNs is very important if they are to remain fully effective. This means that the nets need to be re-treated with insecticide and that any tears that occur in the net are promptly repaired.
Cost is also a significant factor. For people living in developed economies insecticide treated nets (ITNs) are relatively cheap to buy, however, in developing nations the actual cost of buying the net and re-treating it is prohibitive for many families living in abject poverty.
