Causes of Malaria

by

QUESTION:

What causes malaria?

ANSWER:

Malaria is a disease caused by a parasitic single-celled animal known as Plasmodium. There are different species of Plasmodium, which cause different kinds of malaria. The main types which infect humans are P. falciparum, P. vivax, P. ovale and P. malariae. The parasite is transmitted by certain species of mosquito; the parasite lives in the human blood stream and so goes in to the mosquito when the insect feeds. When the same individual mosquito then feeds on another person, it transmits parasites into a new host.

The symptoms of malaria are caused by the actions that the parasite undertakes while in the human host. For example, part of its reproductive cycle involves invading and then multiplying inside red blood cells. Once several cycles of reproduction have occurred, the new parasites burst out of the red blood cell, destroying it. The cycles are times so that all the new parasites burst out of the red blood cells at the same time; this coordinated destruction of the red blood cells, either every 24, 48 or 72 hours, depending on the malaria species, causes the one day, two day or three day cycles of fevers and chills that characterise malaria infection episodes.

What is malaria?

by

QUESTION:

What is malaria?

ANSWER:

To answer your question, I have copied below the answer to an earlier post, published on the 1st of May, 2011, which also asked “What is malaria?”:

Malaria is a disease caused by parasites of the genus Plasmodium. Transmitted by mosquitoes, there are several different kinds of malaria distributed throughout the tropical and sub-tropical regions of the world, causing somewhere between 300-500 million cases of disease each year, and as many as 1 million deaths. In fact, malaria is one of the biggest killers of children under the age of five in sub-Saharan Africa, one of the regions of the world where the burden from malaria is the highest. Malaria is usually an acute disease, manifesting itself with severe fever, chills, headache and often nausea as well. Some types of malaria can have relapsing episodes over a time period of many years.

Having said this, malaria is easily preventable, through avoiding mosquito bites by wearing appropriate clothing and sleeping under insecticide-treated bednets, or through taking preventative medication (called prophylaxis). Malaria is also treatable once symptoms appear, through ingesting safe, effective and relatively cheap drugs. With such control measures at hand, you may ask why malaria is still such a huge problem in our world; the answer is that delivering control strategies and treatment to populations most at risk is difficult, and often countries with high malaria burdens don’t have efficient and effective health systems in place to coordinate control efforts.

International non-governmental organisations such as the World Health Organisation, as well as a multitude of non-profit organisations such as the Malaria Consortium and Malaria No More, work tirelessly to bring malaria control and treatment to the places that need it most, with the aim to eradicate malaria as a disease of public health importance.

 

In which country did malaria start?

by

QUESTION:

In which country did malaria start?

ANSWER:

That’s an interesting question! In terms of the evolution of the disease, the different types of malaria probably evolved in different places; it is hypothesised for example, that P. falciparum evolved from a related strain of malaria that is found in gorillas in central Africa, so the human form also probably originates from that area. Although an exact date for the origin of P. falciparum is still under debate, it was probably sometime around 10,000 years ago,  long before modern countries existed in the region!

As for when malaria was first recorded in human populations, it was known in ancient China, as long ago as 2700 BCE, when the ancient Chinese medical text, Nei Ching, was written. Two and a half thousand years later, in around 200 BCE, there are descriptions of the use of Artemisia annua for the treatment of malarial-type fevers; extracts from this plant, known as artemisinins, are still used for the treatment of malaria today.

Malaria was also known from Europe by the 4th century BCE when it was described by ancient Greek writers. The Romans too were aware of malaria and the risks it posed; they even associated the disease with stagnant water (required by mosquitoes to breed, though it is unclear whether they actively understood the association between mosquito bites and the fevers), which led to extensive public drainage works in order to eliminate bodies of standing water.

Given the lack of written histories, it is more difficult to determine the earliest understanding of malaria in the Americas. However, when the Spanish arrived in the 15th century, they learned of local remedies that the indigenous populations had for various fevers; one of these natural medicines was the bark of a tree of the genus Chichona. More commonly called quinine, this compound is still used as an anti-malarial in modern times.

Nowadays, vector control measures, efficient health monitoring systems and treatment availability has much reduced and in some cases even eradicated the transmission of malaria from most of the United States, Europe and even large parts of China. The greatest burden of the disease continues to be in the tropical regions of the world, and in particular, in sub-Saharan Africa.

Can malaria come back?

by

QUESTION:

If you had malaria once, can it return for a second time without being in a malaria area?

ANSWER:

Yes. There are several ways in which malaria can come back without being re-infected again. The blood forms of the parasites can sometimes persist at low numbers, so that the patient no longer has any symptoms; if these blood forms begin to reproduce again, the patient will once again begin to feel sick and have malaria symptoms. This is known as ‘recrudescence’ and can occur as quickly as within the same year as the initial infection but also as long as fifty years later, depending on the type of malaria! Treating the infection thoroughly, and being tested for parasites after treatment, is one way to avoid recrudescence.

The other way in which malaria can come back is through ‘recurrence’, which is when the malaria parasite enters a dormant phase which resides in the liver. Again, the patient will feel no symptoms while the malaria is dormant, but once these liver stages change into the blood stages and reproduce, symptoms will reoccur. This form of relapse only occurs with Plasmodium vivax and P. ovale infections, and can be prevented through taking an additional form of medication, called primequine, at the same time as the normal malaria drugs when diagnosed. This extra medicine kills the liver forms of malaria and thus prevents recurrence. For more details on this, please see the comments I made, on behalf of Dr Etty Villanueva, on the post ‘Malaria Symptoms and Causes’, published on the 22nd of February, 2011.

Malaria in Southern United States

by

QUESTION:

Why is there not a prevalence of malaria in the southern United States when we are bitten almost daily by the “little beasts?”

ANSWER:

Malaria once was relatively common in the southern United States. Transmission used to be possible due to the favorable climatic conditions for the development both of the mosquito as well as the malaria parasite. Huge advances in the control and treatment of malaria were made directly as a result of increased interest in the disease after the US occupation of Cuba and the building of the Panama Canal in the early years of the 20th century. This vastly reduced the number of cases of the disease, but the final, concerted effort to eradicate malaria came in the 1940s.

This was due to a federal public health program called the National Malaria Eradication Program (NMEP), and as a result of its actions, malaria transmission was halted throughout the United States by 1951. The program was launched in 1947, coordinated by the newly formed Communicable Disease Center (now the Center for Disease Control and Prevention, or CDC) and mostly involved reducing the number of mosquitoes in and around people’s homes. This was done through the wide-spread spraying of DDT—during the years of NMEP, it has been estimated that more than 6.5 million homes were sprayed with the insecticide. Alongside spraying, mosquito breeding habitats were also removed, through wetland drainage, and human monitoring and treatment efforts were stepped up. By 1949, malaria was no longer considered a disease of public health importance, and it was declared eradicated from the United States in 1951.

Having said that, the species of mosquito that transmit malaria still exist in the USA, and particularly in the southern states, which means that there is always a risk of small, localized outbreaks of the disease, particularly during hot and wet seasons.

Climate change may also increase the zones where malaria is at risk of being able to develop within the United States. For this reason, the CDC continually monitors the small number of cases reported each year in the USA (there were about 1500 cases in 2007—all but four of these cases, however, were the result of travelers to malarial areas outside of the USA bringing the disease back with them) to ensure that they are prepared and well-informed should an outbreak arise.

Does malaria spread from a person to another?

by

QUESTION:

Can malaria spread from one person to another?

ANSWER:

Usually, no. In most cases, the malaria parasite has to first pass from a human host into a mosquito as the mosquito takes a blood meal, and then from the mosquito into another human via the mosquito’s saliva. This severely limits the amount of person-to-person transmission that exists. In fact, the only mechanisms for direct transmission between humans are when malaria parasites are passed between a mother and her unborn child via the placenta (congenital transmission) and through unscreened blood transfusions.

Congenital malaria is the more common type of human-to-human transmission; across various surveys of newborns in West Africa, between 8-24% were found to be infected with malaria parasites.

All four main species of human malaria (P. falciparum, P. vivax, P. ovale and P. malariae) have been implicated in congenital transmission. Infection with malaria during pregnancy not only puts the mother at greater risk of severe disease episodes (probably through reduced immunocompetence during pregnancy) but may also negatively impact the baby; although in endemic areas it is rare for babies to be symptomatic for malaria when acquired congenitally, even if they have parasitaemia, they have been shown to have a higher mortality rate than non-infected newborns. In non-endemic areas, babies with congenital malaria often display symptoms, which usually manifest themselves between 2 and 8 weeks after birth. Both quinine and artemisinin-based therapies have been successfully used to treat congenital malaria.

Malaria infection as a result of blood transfusion was first identified in 1911 and is one of the most common illness transmitted via transfusion, although the risk of being infected, particularly in non-endemic countries, is very low.

As it is difficult to screen blood directly for malaria infection, a number of standards have been put in place by blood-collection services to reduce the risk of obtaining blood containing malaria parasites. For example, in many places, you will not be allowed to donate whole blood if you have visited an endemic malarial region in the last three months, nor should you donate if you have previously had malaria unless you have been symptom-free for at least three years.

Due to the longevity of Plasmodium malariae in the blood, you are unlikely to be able to donate blood if you have ever been confirmed as positive for P. malariae. Serological screening of blood for malaria antibodies has recently been shown to be a sensitive method for testing for malaria in blood, although it is expensive and therefore not cost-effective for screening every sample, especially in non-endemic countries. However, it can be effective and efficient to avoid wastage when employed together with a travel-based questionnaire to ascertain donors who are high-risk for malaria.

It is worth mentioning that transmission of malaria via plasma only is very uncommon, and so frequent travellers or residents in malarial areas, who may be denied the right to donate whole blood, should ask about the possibility of donating plasma instead.

What is malaria?

by

QUESTION:

What is malaria?

ANSWER:

Malaria is a disease caused by parasites of the genus Plasmodium. Transmitted by mosquitoes, there are several different kinds of malaria distributed throughout the tropical and sub-tropical regions of the world, causing somewhere between 300-500 million cases of disease each year, and as many as 1 million deaths. In fact, malaria is one of the biggest killers of children under the age of five in sub-Saharan Africa, one of the regions of the world where the burden from malaria is the highest. Malaria is usually an acute disease, manifesting itself with severe fever, chills, headache and often nausea as well. Some types of malaria can have relapsing episodes over a time period of many years.

Having said this, malaria is easily preventable, through avoiding mosquito bites by wearing appropriate clothing and sleeping under insecticide-treated bednets, or through taking preventative medication (called prophylaxis). Malaria is also treatable once symptoms appear, through ingesting safe, effective and relatively cheap drugs. With such control measures at hand, you may ask why malaria is still such a huge problem in our world; the answer is that delivering control strategies and treatment to populations most at risk is difficult, and often countries with high malaria burdens don’t have efficient and effective health systems in place to coordinate control efforts.

International non-governmental organisations such as the World Health Organisation, as well as a multitude of non-profit organisations such as the Malaria Consortium and Malaria No More, work tirelessly to bring malaria control and treatment to the places that need it most, with the aim to eradicate malaria as a disease of public health importance.

 

Treatment for Malaria

by

QUESTION:

How do you treat malaria?

ANSWER:

Malaria can be treated with a number of different types of medication; which one to use depends on the type of malaria you have, as well as whether resistant strains are known to occur in your area. Below I have copied the response I wrote to a similar question on malaria treatment, posted on the 2nd of May, 2011:

In most cases of non-Plasmodium falciparum malaria (the most deadly form of malaria, found throughout the world but most prevalent in sub-Saharan Africa), and even in some places where P. falciparum has not yet developed resistance, treatment with chloroquine is sufficient.

The dosage will depend on body weight (usually approximated by age). Where there is a risk of chloroquine-resistant malaria occurring, treatment of non-complicated cases will usually consist of orally-administered artemisinin-based combination therapy (or ACT) – again, the dosage will depend on age/weight.

For severe malaria, parenteral ingestion of drugs is required. For the treatment of cerebral malaria, caused by P. falciparum, quinine is the traditional drug of choice, though artemisinin has also been shown to be effective. Anti-convulsants and anti-pyretics (to reduce fever) should also be administered.

In cases of infection with P. vivax or P. ovale, the parasite can become dormant in the liver and result in a relapse of the disease if not treated properly. As such, patients with either of these forms of malaria should also be treated with primaquine.

If you have, or suspect you have a health problem, you should visit a physician for a medical diagnosis and treatment.

Malaria Statistics

by

QUESTION:

What are the statistics of malaria?

ANSWER:

If you mean the number of cases worldwide and the number of deaths, then the statistics are as follows: the World Health Organization estimates that approximately half the world’s population are at risk from malaria infection, and as a result, there are somewhere between 300 and 500 million cases of malaria every year, worldwide.

However, this may be an underestimate, since many people don’t seek help when they have malarial symptoms. The same is true of number of deaths per year from malaria – it is currently estimated that between 700,000 and 800,000 people die every year from the disease, but as with the number of cases, there may be unreported deaths as well. Organisations such as Malaria No More seek to eliminate deaths from malaria by the year 2015.

If you have more specific questions regarding the statistics of malaria, please feel free to ask!

Which doctor first linked Anopheles to cases of malaria?

by

QUESTION:

Which doctor first found that Anopheles mosquitoes transmitted malaria?

ANSWER:

The first person to show conclusively that malaria could be transmitted by Anopheles mosquitoes was Ronald Ross (later knighted in 1911 for his services to medicine).

Working in the Presidency General Hospital in Calcutta (Sir Ronald was born in India and joined the Indian Medical Services in 1881 after studying medicine in London), he observed malaria parasites in the salivary glands of mosquitoes that had been fed on infected birds. This was in 1898, and he was awarded the Nobel Prize for Medicine and Physiology in 1902 based on this discovery. A medical board in 1900 later confirmed his findings, and provided recommendations for the control of malaria, some of which were instrumental in limiting the impact of the disease on workers employed to construct the Panama Canal.

The parasite that causes malaria, of the genus Plasmodium, had been identified in 1880 by the French doctor Charles Louis Alphonse Laveran, who had observed the parasites in the red blood cells of infected patients in Algeria.