Malaria is a deathly, insect-borne disease that is transmitted through mosquito bites. Mosquitoes have a habit of being exceptionally irritating and even though they might be all around us, it’s important to understand that they are not just annoying little pests that bite us, but that certain mosquito species are the vectors for billions of cases every year of a publicly significant health problem. This article will cover insights into the biology of mosquitoes, the life cycle of the mosquito that carries disease, and how science and partially cultural exploitation of the mosquito is preventing many deaths from a dreaded disease – malaria. The mosquito has historically been around for millions of years and is a flighted fish with a predatory nature.
The Malaria-Causing Mosquitoes
The main malaria mosquitoes are females of the type Anopheles. This genus of mosquitoes encompasses several closely related species. Three of the most nefarious are Anopheles gambiae, Anopheles funestus, and Anopheles stephensi. They are ubiquitous throughout the tropical and subtropical regions of the world, yet they are concentrated in sub-Saharan Africa.
Unlike their male counterparts, which feed exclusively on nectar, female Anopheles mosquitoes need an additional blood meal for egg production. This is the mechanism by which Plasmodium parasites, the causal agents of malaria, are transmitted.
The Life Cycle of Malaria-Carrying Mosquitoes
The life cycle of the mosquito that catches malaria is the key to understanding how malaria is transmitted and how it can be controlled. The life cycle of the malaria mosquito can be divided into four sections: egg, larva, pupa, and adult. Each stage provides an opportunity to intervene.
1. Egg Stage
Female Anopheles lay their eggs on the surface of stagnant or slowly flowing water and they are small, oval-shaped, and float on in the water, mostly in clusters or singly, and are dark colored which makes them somewhat easier to spot in the water.
2. Larval Stage
Three or four days later, the eggs hatch into larvae (known as the ‘wriggler’ stage), which feed on microorganisms and organic material in the water. Larvae are especially sensitive to environmental impacts at this stage, which is an optimal period for targeted interventions.
3. Pupal Stage
After the larval stage, the mosquito pupae. Pupae are also called ‘tumblers’, and often sink to the bottom and tumble about in the water before emerging. This is an intermediate stage between larva and adult. Pupae neither eat nor move much (imagine what it would be like to be stuck inside a body that was essentially an infant but without any eyes, ears, antennae, or legs?) and serve as a sort of holding pattern.
4. Adult Stage
In just a few days, the adult mosquito has emerged from its pupal covering. It must rest on the water’s surface to allow its new wings to dry and expand before it can fly. Female mosquitoes need a blood meal to mature eggs, which they take after mating and laying around 200 eggs. After maturation on land, ready to mate and feed, a mosquito lays its eggs in a new body of water – and the cycle begins again.
How Malaria is Transmitted
Picture courtesy http://en.wikipedia.orgMalaria transmission begins when a female Anopheles mosquito feeds on a person with the malaria infection. When an infected mosquito takes a blood meal, thousands of Plasmodium parasites enter its salivary gland and are injected into the skin and blood of a new human host the human host, the parasites travel to the liver, reproduce, and escape into the bloodstream, where they infect red blood cells. This is the moment at which the classical symptoms of malaria express themselves.
After taking a blood meal from an infected person, a mosquito captures the parasites, they undergo development in the mosquito’s abdomen, and then migrate to the mosquito’s salivary glands. The disease is then passed on to the next person the mosquito bites.
Breaking the Chain: The Role of Insecticide-Treated Nets
One of the most effective ways to prevent transmission is the use of insecticide-treated nets (ITNs), which physically keep the mosquito away from the person sleeping under it. Here’s how ITNs interfere with the malaria transmission chain:
1. Reducing Mosquito Bites
ITNs are specifically designed to be used in bed while sleeping. Anopheles mosquitoes are active during the hours that people are sleeping. Because of this simple fact, if there is a physical barrier between the mosquito and the human, then the mosquito is unable to take a bite – and a mosquito that cannot bite cannot transmit malaria. In short, when ITNs are used correctly, they cut the mosquito bite rate to almost zero.
2. Killing Mosquitoes
ITNs are treated with insecticides, which are chemicals that kill or keep insects away from something. A mosquito landing on an ITN is exposed to this insecticide, which is why the mosquito dies. Fewer mosquitoes around means less chance of malaria spreading.
3. Interrupting the Transmission Cycle
Every mosquito bite prevented, every mosquito killed, breaks a chain in the malaria transmission cycle. If there are fewer mosquitoes, there are fewer opportunities for Plasmodium parasites to be transferred from one person to the next. Your neighbors are also better protected, thereby reducing malaria incidence in your community.
The Impact of ITNs on Malaria Control
Their widespread use has made ITNs one of the most successful mosquito-driven malaria-control interventions. In programs where ITNs are properly used, malaria cases as well as deaths can be reduced by between 37 to as much as 50 percent. The intervention works on at least two fronts: directly preventing mosquito bites on humans and killing mosquitoes.
1. Community-Wide Benefits
But ITNs also confer indirect benefits: when large numbers of people in a community use ITNs, as noted earlier, the mosquito population is generally reduced, resulting in a reduction of malaria cases in the community – a type of protective benefit known as ‘community-wide protection’.
2. Cost-Effectiveness
Over the long term, ITNs manifest in disease control. The extra benefit covers the original cost of buying and treating a net with insecticide many times over. ITNs include the purchase and initial treatment, while the long-lasting effectiveness of the insecticide drives much of the extra benefit. Users can enjoy protection against malaria for years because the insecticide remains effective for an average of three to five years.
Challenges and Considerations
While ITNs are highly effective, their success depends on several factors:
1. Proper Usage
For ITNs to work properly, they have to be used properly as well. That means ensuring that every individual in the household uses the nets consistently and that the nets are maintained properly. Nets with holes should be repaired or replaced with new nets.
2. Insecticide Resistance
Insecticide resistance is a major issue when it comes to ITNs. Insecticides break down over time, causing mosquitoes to develop resistance to them. This means that ITNs need constant monitoring, and new insecticides need to be developed regularly. It also means that combining ITNs with other malaria control strategies can help reduce the emergence of resistance. These are much finer points and not the broad debate monopolizing headlines.
3. Accessibility and Distribution
Making sure that ITNs are available to people and that they use the ITNs is also very important. In some areas, such as remote areas or poor areas where people are not accustomed to visiting clinics, it can be a challenge to distribute ITNs. Developing better distribution channels and getting people to understand the importance of ITNs are ongoing efforts.
The ecology of the mosquitoes that carry malaria can be an eye-opener on the spread of malaria and how its transmission can be prevented. The four stages of the mosquito life cycle as an egg, larva, pupa, and adult are important points of intervention in the control of the disease. The mosquito bites that cause malaria can be prevented through insecticide-treated nets. Mosquitoes themselves can be killed by insecticide-treated nets. Malaria transmission can be interrupted with insecticide-treated nets.
The use of ITNs has been effective and cost-effective in fighting against malaria, but insecticide resistance and accessibility are just some factors to overcome or improve on to maintain and enhance their usefulness in malaria control. If ITNs are coupled with other malaria control measures and if people use them correctly and widely, we will maintain a significant reduction in malaria cases and future global health improvements.
In summary, even though we are not yet fully rid of it, the fight against malaria goes on. Knowing the life cycle of the mosquito remains one of the most crucial steps, but in the future other powerful apparatus like insecticide-treated nets will help to break the chain of malaria transmission. We all can combine our efforts to achieve the goal of controlling and eventually eradicating this deadly disease on Earth.
