A mosquito net is a protective screen draped over a sleeping area to shield the occupant from biting insects. This physical barrier prevents contact with mosquitoes, flies, and other pests, thereby reducing the transmission of insect-borne diseases like malaria, dengue fever, and Zika virus. The use of these nets is a successful public health intervention.
The Physical Structure
Standard mosquito nets are constructed from durable synthetic fibers, most commonly polyester, polyethylene, or nylon. Polyester is the most popular material due to its low weight and durability compared to cotton alternatives. Thread thickness is measured in denier (D); a standard net often uses a 75-denier thread for strength and resilience.
The net’s effectiveness is determined by its mesh count, which is the number of holes per square inch of fabric. Higher mesh counts block smaller insects but can decrease airflow. Nets are manufactured in various forms, including conical shapes suspended from a single point or rectangular box shapes.
The Barrier Principle
The mechanism of a mosquito net relies entirely on the principle of physical exclusion. To be effective, the mesh openings must be small enough to block disease-carrying mosquitoes, such as the Anopheles species, while allowing for adequate air circulation. The World Health Organization (WHO) recommends a minimum mesh count of 156 holes per square inch for nets used in areas with malaria transmission. This density ensures that harmful mosquitoes cannot penetrate the barrier.
A finer mesh with a count of 285 holes per square inch is often considered ideal, as it blocks even smaller biting midges without compromising breathability. The net must be completely intact, as even a small tear or hole compromises the entire barrier, allowing insects to enter.
Types of Nets and Effective Installation
Mosquito nets are broadly categorized into untreated nets, which rely purely on the physical barrier, and Long-Lasting Insecticidal Nets (LLINs). LLINs are pre-treated with a synthetic insecticide, typically a pyrethroid like permethrin or deltamethrin, which is either coated onto the fibers or incorporated within them during manufacturing. This treatment adds a chemical layer of defense, offering protection even if a mosquito contacts the net.
The pyrethroid acts as a contact poison, causing a lethal or repelling effect on mosquitoes and other insects that land on the fabric. Newer generation LLINs often include a synergist like piperonyl butoxide (PBO) alongside the pyrethroid to combat growing insecticide resistance. PBO inhibits the enzymes mosquitoes use to detoxify the insecticide, restoring the net’s killing power. LLINs are designed to withstand multiple washes over several years before the insecticide loses its efficacy.
Effective Installation
For maximum protection, proper installation is necessary to establish an effective barrier. The net must be hung so that it does not touch the body, as mosquitoes can bite through the mesh where it presses against the skin. The sides of the net must be tucked securely under the mattress or sleeping mat to prevent insects from gaining access from below.