How is Malaria Spread?

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QUESTION

How is malaria spread?

ANSWER

Malaria is caused by a parasite called Plasmodium, which is transmitted via the bites of infected mosquitoes. In the human body, the parasites multiply in the liver, and then infect red blood cells. Usually, people get malaria by being bitten by an infective female Anopheles mosquito. Only Anopheles mosquitoes can transmit malaria and they must have been infected through a previous blood meal taken on an infected person. When a mosquito bites an infected person, a small amount of blood is taken in which contains microscopic malaria parasites. About 1 week later, when the mosquito takes its next blood meal, these parasites mix with the mosquito’s saliva and are injected into the person being bitten.

Because the malaria parasite is found in red blood cells of an infected person, malaria can also be transmitted through blood transfusion, organ transplant, or the shared use of needles or syringes contaminated with blood. Malaria may also be transmitted from a mother to her unborn infant before or during delivery (“congenital” malaria).


Causes of Malaria

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QUESTION

What are the causes of malaria?

ANSWER

Malaria is caused by a parasite called Plasmodium, which is transmitted via the bites of infected mosquitoes. In the human body, the parasites multiply in the liver, and then infect red blood cells. Usually, people get malaria by being bitten by an infective female Anopheles mosquito.

Only Anopheles mosquitoes can transmit malaria and they must have been infected through a previous blood meal taken on an infected person. When a mosquito bites an infected person, a small amount of blood is taken in which contains microscopic malaria parasites. About 1 week later, when the mosquito takes its next blood meal, these parasites mix with the mosquito’s saliva and are injected into the person being bitten.

Following the infective bite by the Anopheles mosquito, a period of time (the “incubation period”) goes by before the first symptoms appear. The incubation period in most cases varies from 7 to 30 days. The shorter periods are observed most frequently with P. falciparum and the longer ones with P. malariae.

Because the malaria parasite is found in red blood cells of an infected person, malaria can also be transmitted through blood transfusion, organ transplant, or the shared use of needles or syringes contaminated with blood. Malaria may also be transmitted from a mother to her unborn infant before or during delivery (“congenital” malaria).


What are Gametocytes?

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QUESTION

What are Gametocytes?

ANSWER

Gametocytes are the sexually reproductive form of the malaria parasite. They circulate in the blood of the human/mammal host and are picked up by the mosquito when it takes a blood meal.

Inside the mosquito, the gametocytes undergo sexual reproduction in the mosquito midgut, producing oocysts which attach to the midgut wall and produce sporozoites, which are the stage that are infective to humans when the mosquito takes another blood meal (the sporozoites are passed into the blood via the saliva of the mosquito).

How to get malaria?

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QUESTION

How do we get malaria?

ANSWER

Malaria is caused by a parasite called Plasmodium, which is transmitted via the bites of infected mosquitoes. In the human body, the parasites multiply in the liver, and then infect red blood cells. Usually, people get malaria by being bitten by an infective female Anopheles mosquito. Only Anopheles mosquitoes can transmit malaria and they must have been infected through a previous blood meal taken on an infected person. When a mosquito bites an infected person, a small amount of blood is taken in which contains microscopic malaria parasites. About 1 week later, when the mosquito takes its next blood meal, these parasites mix with the mosquito’s saliva and are injected into the person being bitten.

Because the malaria parasite is found in red blood cells of an infected person, malaria can also be transmitted through blood transfusion, organ transplant, or the shared use of needles or syringes contaminated with blood. Malaria may also be transmitted from a mother to her unborn infant before or during delivery (“congenital” malaria).

Causes of Malaria

by

QUESTION

What causes malaria?

ANSWER

Malaria is caused by a parasite called Plasmodium, which is transmitted via the bites of infected mosquitoes. In the human body, the parasites multiply in the liver, and then infect red blood cells.

Usually, people get malaria by being bitten by an infective female Anopheles mosquito. Only Anopheles mosquitoes can transmit malaria and they must have been infected through a previous blood meal taken on an infected person. When a mosquito bites an infected person, a small amount of blood is taken in which contains microscopic malaria parasites. About 1 week later, when the mosquito takes its next blood meal, these parasites mix with the mosquito’s saliva and are injected into the person being bitten.

Because the malaria parasite is found in red blood cells of an infected person, malaria can also be transmitted through blood transfusion, organ transplant, or the shared use of needles or syringes contaminated with blood. Malaria may also be transmitted from a mother to her unborn infant before or during delivery (“congenital” malaria).

 


 

Malaria Mosquito

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QUESTION

Which mosquito causes malaria?

ANSWER

Malaria mosquito vector map CDC

Map of the main global mosquito vectors of malaria (image courtesy of CDC)

It is important to note that mosquitoes do not CAUSE malaria—the disease itself is caused by microscopic, single-celled animals called Plasmodium. These Plasmodium parasites live and reproduce inside the mosquito, and when the mosquito bites a person, the parasites are transferred into that person’s blood via the mosquito’s saliva. If another mosquito bites a person with malaria, they will pick up the parasites from the person’s blood, and the cycle continues.

Malaria parasites are simply transmitted by mosquitoes, and specifically of the genus Anopheles, of which a variety of different species are capable of transmitting it to humans. In Africa, the species most responsible for transmission is An. gambiae, which actually consists of a group of very similar and closely related species; the group as a whole is known as the An. gambiae species complex. An. funestus is also a wide-spread and important vector species in Africa. Below is a map, courtesy of the CDC, which shows the distribution of some of the main malaria vector mosquitoes worldwide.

What are mosquito larvae?

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QUESTION

What are mosquito larvae?

ANSWER

Larvae are one of the life stages of mosquitoes; they are baby mosquitoes, if you will. Adult mosquitoes lay eggs as a “raft” on the surface of a body of fresh water—they prefer still and stagnant pools. These eggs then hatch into the mosquito larvae, which live in the freshwater pool until they form a pupa, just under the surface. These pupae then hatch into adults again, completing the life cycle.

Mosquito larvae are omnivorous, eating algae and small organisms also living in the water. Despite living immersed in water, they require oxygen to breathe, which they inhale using two different methods: Aedes and Culex mosquitoes (the vectors of a number of diseases, including West Nile disease, dengue fever, yellow fever, encephalitis and filarisasis) have a specialised breathing organ, a bit like a snorkel, called a siphon, which they use to suck in air, whereas Anopheles mosquitoes (the main vectors of malaria) lack this organ and so have to lie next to the surface to take in air. The larvae moult four times while they live in water; after the fourth time, they are ready to pupate and become adults. The entire larval stage of a mosquito’s life usually take between one and two weeks, depending on the ambient temperature.

History of Fighting Malaria

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QUESTION

What are some examples of attempts of fighting this disease that happened in the past?

ANSWER

The battle against malaria has been going on, in one form or another, for literally thousands of years. The ancient Chinese mention the symptoms of the disease in a medical scroll as early as 2700 BCE – even more remarkably, a herb called Artemesia has been used in traditional Chinese medicine for more than 2000 years to treat malaria, and compounds extracted from that same herb are the basis for some of the most effective modern medications, known as artemisinin-based combination therapies (ACTs). Indigenous tribes in the Americas also had traditional medicines to treat malaria; having conquered the New World, the Spanish learned of a bark, from the Cinchona tree, which could cure malaria. Quinine, extracted from this same tree bark, is still used today to treat malaria.

However, back then the causes of malaria were not known—it wasn’t until the late 19th century that a more complete understanding of malaria would emerge. The first key development in this process was the observation of the parasites that cause malaria in a patient’s blood, which was first done by Charles Louis Alphonse Laveran in 1880.

A few years later, in 1897, a British army doctor called Ronald Ross discovered that the parasite was transmitted via the bite of infected mosquitoes, of the genus Anopheles. This latter finding allowed for the emergence of the first programmes for malaria control, which focused on vector control, through insecticide use and elimination of water bodies used by the mosquito larvae. An early example of the success of this approach came in the building of the Panama Canal; started in 1906, progress was initially slow, due to the enormous proportion of workers who fell ill from yellow fever and malaria. With vector control, the number of cases plummeted, and the canal was finally opened in 1914.

While prophylactic quinine had also been part of the control strategy during the building of the Panama Canal, it played a much more secondary role to vector control. Using similar strategies, focusing primarily on killing adult mosquitoes through insecticide spraying (mainly DDT), the United States of America successfully eliminated malaria from its shores in the early 1950s. Prior to this, transmission had occurred across most of the south-east of the country.

In the last 50 years, access to early diagnosis and effective treatment have gained a more prominent role among many malaria control strategies, although prevention is still seen as crucial. Many developing countries, where malaria is still rife, have set up national control programmes, which seek to ensure that all communities have access to adequate care and information about malaria prevention.

A key tool in the prevention arsenal has been the long-lasting insecticide treated bednet; sleeping underneath one prevents bites from the mosquitoes that carry malaria, which are most active in the evenings and at night, especially in children and pregnant women, who are among the people most at risk from infection. Bednet distribution has been a major focus of many malaria campaigns, and very successful in many places; in 2008, for example, bednet coverage was estimated at over 80% of the at-risk population in Djibouti, Mali, Ethiopia and Sao Tome and Principe.

How does malaria enter the body?

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QUESTION:

What is the portal of entry for malaria?

ANSWER:

Malaria enters its human hosts via the bite of mosquitoes of the genus Anopheles. The malaria parasites are present in the mosquitoes saliva, and enter into the human bloodstream when the mosquito bites to take a blood meal.

Once in the human body, the malaria parasite then undergoes a number of different life stages, involving reproduction in the liver as well as inside red blood cells. Once the malaria parasite has undergone reproduction in the red blood cells, the new parasites burst out and back into the blood stream, where they can be ingested by another mosquito biting again. Inside the mosquito, the malaria parasites undergo more reproduction and life stage changes, until they are ready to be transferred into a human host again, via another bite. In this way, the cycle continues.

What does malaria cause?

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QUESTION:

What does malaria cause?

ANSWER:

Malaria is a disease. It is caused by tiny single-celled parasites called Plasmodium, which are transmitted through the bite of infected Anopheles mosquitoes. There are many symptoms that occur as a result of infection with malaria, namely fever, chills, headaches and nausea, among others. Malaria can be a very serious disease, especially if not treated promptly, and so when spending time in malaria-infection areas (such as many areas of low to moderate elevation in the tropics and sub-tropics) precautions should be taken to avoid mosquito bites and thus infection. If a person finds themselves suffering from some of the above symptoms after being in a malaria transmission region, it is crucially important they get diagnosed straight away; if they do indeed have malaria, then they can be given treatment to facilitate a quick and safe recovery.