What type of mosquito causes malaria

The natural history of malaria involves cyclical infection of humans and female Anopheles mosquitoes. In humans, the parasites grow and multiply first in the liver cells and then in the red cells of the blood.

The blood stage parasites are those that cause the symptoms of malaria. When certain forms of blood stage parasites gametocytes, which occur in male and female forms are ingested during blood feeding by a female Anopheles mosquito, they mate in the gut of the mosquito and begin a cycle of growth and multiplication in the mosquito. When the Anopheles mosquito takes a blood meal on another human, anticoagulant saliva is injected together with the sporozoites, which migrate to the liver, thereby beginning a new cycle.

More on: Anopheles Mosquitoes. More on: Malaria Parasites. More on: Human Factors and Malaria. For malaria transmission to occur, conditions must be such so that all three components of the malaria life cycle are present:.

In rare cases malaria parasites can be transmitted from one person to another without requiring passage through a mosquito from mother to child in "congenital malaria" or through transfusion, organ transplantation, or shared needles.

Climate is a key determinant of both the geographic distribution and the seasonality of malaria. Without sufficient rainfall, mosquitoes cannot survive, and if not sufficiently warm, parasites cannot survive in the mosquito. Anopheles lay their eggs in a variety of fresh or brackish bodies of water, with different species having different preferences. Eggs hatch within a few days, with resulting larvae spending days to develop into adults in tropical areas.

If larval habitats dry up before the process is completed, the larvae die; if rains are excessive, they may be flushed and destroyed.

Life is precarious for mosquito larvae, with most perishing before becoming adults. Life is usually short for adult mosquitoes as well, with temperature and humidity affecting longevity. Only older females can transmit malaria, as they must live long enough for sporozoites to develop and move to the salivary glands. Thus, malaria transmission is much more intense in warm and humid areas, with transmission possible in temperate areas only during summer months.

In warm climates people are more likely to sleep unprotected outdoors, thereby increasing exposure to night-biting Anopheles mosquitoes. During harvest seasons, agricultural workers might sleep in the fields or nearby locales, without protection against mosquito bites. The types species of Anopheles present in an area at a given time will influence the intensity of malaria transmission.

Not all Anopheles are equally efficient vectors for transmitting malaria from one person to another. Those species that are most prone to bite humans are the most dangerous, as bites inflicted on animals that cannot be infected with human malaria break the chain of transmission.

If the mosquito regularly bites humans, the chain of transmission is unbroken and more people will become infected. Some species are biologically unable to sustain development of human malaria parasites, while others are readily infected and produce large numbers of sporozoites the parasite stage that is infective to humans. Many of the most dangerous species bite human indoors. For these species insecticide treated mosquito nets and indoor residual spray whereby the inner walls of dwellings are coated with a long-lasting insecticide are effective interventions.

Both of these interventions require attention to insecticide resistance, which will evolve if the same insecticide is used continuously in the same area. Characteristics of the malaria parasite can influence the occurrence of malaria and its impact on human populations, for example:. Plasmodium falciparum predominates in Africa south of the Sahara, one reason why malaria is so severe in that area. A certain species of malaria called P. Humans living in close proximity to populations of these macaques may be at risk of infection with this zoonotic parasite.

Malaria transmission has been eliminated in many countries of the world, including the United States. However, in many of these countries including the United States Anopheles mosquitoes are still present. Thus the potential for reintroduction of active transmission of malaria exists in many non-endemic parts of the world. All patients must be diagnosed and treated promptly for their own benefit but also to prevent the reintroduction of malaria.

Biologic characteristics present from birth can protect against certain types of malaria. Two genetic factors, both associated with human red blood cells, have been shown to be epidemiologically important.

Persons who have the sickle cell trait heterozygotes for the abnormal hemoglobin gene HbS are relatively protected against P. Because P. In general, the prevalence of hemoglobin-related disorders and other blood cell dyscrasias, such as Hemoglobin C, the thalassemias and G6PD deficiency, are more prevalent in malaria endemic areas and are thought to provide protection from malarial disease.

Persons who are negative for the Duffy blood group have red blood cells that are resistant to infection by P. Since the majority of Africans are Duffy negative, P. In that area, the niche of P. Other genetic factors related to red blood cells also influence malaria, but to a lesser extent. More on: Sickle Cell and Malaria.

Acquired immunity greatly influences how malaria affects an individual and a community. After repeated attacks of malaria a person may develop a partially protective immunity.

In areas with high P. As these antibodies decrease with time, these young children become vulnerable to disease and death by malaria. If they survive repeated infections to an older age years they will have reached a protective semi-immune status. Thus in high transmission areas, young children are a major risk group and are targeted preferentially by malaria control interventions. In areas with lower transmission such as Asia and Latin America , infections are less frequent and a larger proportion of the older children and adults have no protective immunity.

In such areas, malaria disease can be found in all age groups, and epidemics can occur. Anemia in young children in Asembo Bay, a highly endemic area in western Kenya. Anemia occurs most between the ages of 6 and 24 months.

After 24 months, it decreases because the children have built up their acquired immunity against malaria and its consequence, anemia. The mother had malaria, with infection of the placenta. Pregnancy decreases immunity against many infectious diseases.

Women who have developed protective immunity against P. Malaria during pregnancy is harmful not only to the mothers but also to the unborn children. The latter are at greater risk of being delivered prematurely or with low birth weight, with consequently decreased chances of survival during the early months of life. For this reason pregnant women are also targeted in addition to young children for protection by malaria control programs in endemic countries.

More on: Malaria During Pregnancy. Human behavior, often dictated by social and economic reasons, can influence the risk of malaria for individuals and communities. For example:. Human behavior in endemic countries also determines in part how successful malaria control activities will be in their efforts to decrease transmission. The governments of malaria-endemic countries often lack financial resources.

As a consequence, health workers in the public sector are often underpaid and overworked. They lack equipment, drugs, training, and supervision. The local populations are aware of such situations when they occur, and cease relying on the public sector health facilities.

Conversely, the private sector suffers from its own problems. Regulatory measures often do not exist or are not enforced. This encourages private consultations by unlicensed, costly health providers, and the anarchic prescription and sale of drugs some of which are counterfeit products. Correcting this situation is a tremendous challenge that must be addressed if malaria control and ultimately elimination is to be successful.

The sickle cell gene is caused by a single amino acid mutation valine instead of glutamate at the 6th position in the beta chain of the hemoglobin gene. Inheritance of this mutated gene from both parents leads to sickle cell disease and people with this disease have shorter life expectancy.

On the contrary, individuals who are carriers for the sickle cell disease with one sickle gene and one normal hemoglobin gene, also known as sickle cell trait have some protective advantage against malaria.

Malaria parasites about to burst out of red blood cell. Image credit: Will Hamilton. A smear of blood being taken on a slide for examination under the microscope. Image credit: Shutterstock. This video introduces you to the disease malaria, taking you through the life cycle of the parasite that causes it and why it is such a huge problem in the developing world.

Infectious diseases are caused by microorganisms such as viruses, bacteria, fungi or parasites and can spread between individuals. In Malaria Challenge you can explore the different stages of malaria and how scientists are trying to find new ways of preventing and treating this deadly tropical disease.

If you have any other comments or suggestions, please let us know at comment yourgenome. Can you spare minutes to tell us what you think of this website? Open survey. In: Facts Targeting Disease. Malaria is a life-threatening disease caused by a parasite that is transmitted through the bite of infected female Anopheles mosquitoes. The parasite that causes malaria is a microscopic, single-celled organism called Plasmodium.

Most cases and deaths are in sub-Saharan Africa. In , malaria was present in 91 countries and territories. Early treatment of malaria will shorten its duration, prevent complications and avoid a majority of deaths. Because of its considerable drag on health in low-income countries, malaria disease management is an essential part of global health development.

Treatment aims to cure patients of the disease rather than to diminish the number of parasites carried by an infected person. The best available treatment, particularly for P. However, the growing potential for parasite resistance to these medicines is undermining malaria control efforts see below. There are no effective alternatives to artemisinins for the treatment of malaria either on the market or nearing the end of the drug development process.

Drug resistance to commonly used antimalarial drugs has spread very rapidly. In order to avoid this for artemisinins, they should be used in combination as ACTs, and artemisinin monotherapy use of one artemisinin drug versus the more effective combination pill should not be used. The less effective single-drug treatment increases the chance for parasites to evolve and become resistant to the medicine.

Intensive monitoring of drug potency is essential to protect against the spread of resistant malaria strains to other parts of the world. WHO recommends continuous monitoring and is assisting countries as they work to strengthen drug observation efforts. Prevention focuses on reducing the transmission of the disease by controlling the malaria-bearing mosquito. Two main interventions for vector control are:. These core interventions can be locally complemented by other mosquito vector control methods for example, reducing standing water habitats where insects breed, among other approaches.

Insecticide resistance Mosquito control efforts are being strengthened in many areas, but there are significant challenges, including:. There are no equally effective and efficient insecticide alternatives to DDT and pyrethroids, and the development of new pesticides is an expensive, long-term endeavour.

Vector management practices that enforce the sound management of insecticides are essential. Insecticide resistance detection should be a routine feature of national control efforts to ensure that the most effective vector control methods are being used.

Beyond the human toll, malaria wreaks significant economic havoc in high-rate areas, decreasing Gross Domestic Product GDP by as much as 1.