Malaria and Nkadu Luo

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QUESTION

When did professor Nkadu Luo discover that female mosquito causes malaria?

ANSWER

Professor Nkadu Luo is a microbiologist and immunologist in Zambia. Most of her work has been on HIV/AIDS and sickle cell anaemia. She has also been a key figure in promoting screening of blood banks in Zambia for infectious diseases such as HIV and malaria. However, the discovery that female mosquitoes transmit malaria was made much earlier—taxonomists as early as the mid-19th century were aware of differences in the mouthparts between male and female mosquitoes of certain species, which allowed them to determine that they were feeding on different things (female mosquitoes who feed on blood have very specialised mouthparts, for example).

Then, in the late 1890s, a British doctor called Ronald Ross discovered that mosquitoes transmit malaria parasites when they feed on blood. Prof Luo probably learned about the cycle of malaria transmission during her extensive biomedical training.

Symptoms and Causes of Malaria

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QUESTION

What are the symptoms and 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.

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).

There are five kinds of malaria known to infect humans: Plasmodium falciparum, P. vivax, P. ovale, P. malariae and P. knowlesi. The symptoms of malaria differ depending on the type of malaria; P. falciparum  is the most deadly and severe form of the disease. General symptoms of malaria include  include fever and flu-like illness, including shaking chills, headache, muscle aches, and tiredness. Nausea, vomiting, and diarrhea may also occur. Malaria may cause anemia and jaundice (yellow coloring of the skin and eyes) because of the loss of red blood cells.

Symptoms usually appear between 10 and 15 days after the mosquito bite. If not treated, malaria can quickly become life-threatening by disrupting the blood supply to vital organs.

What are the 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.

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).

There are five kinds of malaria known to infect humans: Plasmodium falciparum, P. vivax, P. ovale, P. malariae and P. knowlesi.

Is malaria possible years after bite?

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QUESTION

My child had a fever for 40 days after returning from a cruise 3 years ago. I begged the pediatrician to test for malaria because she got bit by something in Mexico but they laughed at me. She has had swollen lymph nodes on both sides of her neck for 3 years and all the docs tell me you can have swollen lymph nodes forever but now she has them in her groin and under arm on left side. She is pale and tired all the time. I took her back to the pediatrician and her cbc was normal so the dr is blowing it off. Malaria and Lymphoma are on my mind. My question is, Can malaria live in the body that long without it killing you?

ANSWER

Malaria can certainly survive in the body for a long time, but usually would present as recurring episodes of fever rather than enlarged lymph nodes (the malaria parasites reside dormant in the liver). There are two types of malaria that can reside in the body for extended periods: Plasmodium vivax and P. ovale. The former is found in parts Mexico, but cases of malaria are rare, especially in coastal areas. Unfortunately, malaria can only be detected when it enters the blood again – this occurs during the fever episodes. So, if your daughter does have a fever again, it might be worth asking for a malaria test, and specifically to look for P. vivax. If positive, there is a drug, primaquine, which can be taken to kill the remaining liver stages of malaria and prevent further relapses. However, overall, your daughter’s case doesn’t sound like malaria. What was your daughter’s Hb level? Anemia could explain the pallor and lethargy, though your pediatrician should have spotted that on the blood tests.

Headache and Chills with Malaria

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QUESTION

Could a person be infected by malaria without symptoms of headache and chills?

ANSWER

Malaria symptoms vary considerably, depending on the type of malaria, the severity of the infection and the patient’s natural immunity. It is certainly possible for a patient to have malaria without experiencing headache and chills; some people infected with certain forms of malaria, such as Plasmodium malariae, may not even experience severe fever and barely realise they are infected. However, most cases of malaria, especially in sub-Saharan Africa, are caused by Plasmodium falciparum, which is a faster-acting, more severe form of malaria and usually results in fever and chills, often accompanied by headache and nausea.

Are Anti-malaria pills necessary if no mosquito bites?

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QUESTION

We had a weekend in the Kruger Park and all of us took anti malaria pills beforehand. None of us was bitten or even saw a mosquito, do we need to carry on taking them for so long?

ANSWER

Since you say “so long”, I assume you are either taking doxycycline or Lariam, both of which are taken for four weeks after leaving the malarial area. Unless you are experiencing severe side effects, it is always recommended to continue taking prophylactic medication for the full course, the reason being that the malaria parasite has a latent period of up to a few weeks, and the prophylactics only kill the parasite after this latent stage. Even though you didn’t see any mosquitoes, the possibility remains that you got bitten and did not notice – ultimately, you can weigh up the slight inconvenience of taking the pills for a while longer versus the slight risk, but enormous inconvenience of getting malaria!

Since you have taken malaria prophylactics, please take a moment to fill out the Malaria Medication Side-effects Survey: Treatment and Prophylaxis!

Thank you!

Pregnant Women and Malaria

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QUESTION

Why are pregnant women and children at the highest risk of getting malaria?

ANSWER

The reason why pregnant women and children are at greater risk of contracting malaria is due to their reduced levels of immunity. Children living in malarial areas have less immunity than adults because they have had less exposure to malaria, and so their immune systems have not had a chance to develop antibodies to protect against the disease. Pregnant women, although they may normally have good immunity, witness changes in their immune systems during pregnancy in order for the woman to carry the child.

Given that a baby is genetically distinct from its mother, the mother’s immune system has to be modulated in order to ensure that the body’s defenses do not act against the baby, as they would some other foreign object such as an infection. While this immune modulation allows the mother to carry her foetus, it does leave her vulnerable to other infections, such as malaria. In areas of high malaria transmission, the mother may still retain enough immunity to not present with severe symptoms of malaria. In these cases, the dangers of malaria in pregnancy come from resulting anemia in the mother, as well as passage of malaria antigens or the parasite itself through the placenta and to the foetus, which can result in problems for the baby.

Interestingly, a study came out last year which showed evidence that using long-lasting insecticide treated bednets increased malaria prevalence in older children and adults, probably because the nets protected against even sub-clinical exposure to malaria and therefore the levels of natural immunity in people using the nets declined over time, leaving them more susceptible to infection. However, this result has been controversial, as in other studies community-wide coverage of bednets has reduced overall malaria incidence due to reduced transmission.

Post-infection Malaria Medication

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QUESTION

My daughter has recently returned from a trip to Borneo. Even with aggressive preventive anti-mosquito behaviour (long sleeves/pants, deet applications and mosquito netting) but not anti-malarial medication, she received over 30 bites. She is now exhibiting some symptoms (body aches, headache and severe fatigue). She has an appointment at the doctors in 2 days time. Is there some kind of post-trip medication (like doxycycline) she can take as a precaution even if the malarial test comes back negative at this early of a time. Thanks.

ANSWER

The important thing to note here is that if your daughter has symptoms of malaria, then she should be diagnosed and, if positive, treated with medication aimed at curing active malaria. Doxycycline is NOT a drug used for the treatment of malaria, so there is no point taking it if she is already exhibiting symptoms.

Furthermore, some types of malaria found in Borneo (notably P. falciparum and P. knowlesi) can become more severe very quickly – 2 days may be too long to wait. If you live in an area where malaria transmission occurs, you may be able to buy a self-testing kit (also known as a rapid diagnostic test, or RDT) for malaria in a local pharmacy. Otherwise, if your daughter’s symptoms get worse, you should take her to an emergency room and explain her travel history and subsequent risk of having malaria.

There is no substitute for taking prophylactic malaria medicine; it might be that if your daughter had started taking prophylactic medicine as soon as she started receiving multiple mosquito bites, then she may have been protected to some degree. However, malaria has a latent period, and so she would have had to continue taking the medication for a period of time after returning home as well – with doxycycline, this means taking the drug for a further four weeks.

Malaria in Africa

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QUESTION

What is the current problem for malaria in Africa?

ANSWER

Malaria is a particularly severe problem in Africa due to a number of reasons. First of all, transmission in many parts of Africa occurs year round, due to favourable conditions for the development of the mosquitoes malaria requires as its vector.

Secondly, the dominant and most widespread species of malaria in Africa is Plasmodium falciparum, which is most fast-acting and deadly form of the disease.

Thirdly, Africa has a very young population; birth rates are high across much of the continent, and in many countries, more than 40% of the population is under 15 years old. Given that young children are are higher risk of malaria than adults, this also increases the burden of malaria in Africa compared to other parts of the world.

Finally, access to health care and malaria control interventions in Africa has been plagued by more general issues of slow development. While national health systems are slowly emerging, many countries are still reliant on foreign aid and NGOs to provide even basic health services.

Even where these organisations can provide health care, they often face challenges such as reaching remote populations without good road access, finding ways to provide medical services without reliable electricity or communications networks and maintaining supply chains of diagnostic tools and crucial medicine.

However, signs of progress are being seen. Long-lasting insecticide treated bednets have been put forward as a key preventative measure against malaria, and to date millions have been distributed to people living in malarial areas in Africa, and particularly to high risk groups such as young children and pregnant women.

Simultaneously, other control initiatives, such as indoor residual spraying, are gaining traction and being deployed in more areas. An emphasis on local capacity building has encouraged community involvement in drug distribution and access to health care initiatives, as well as training local health workers in diagnostic methods in rural areas.

Encouraging reports from groups such as Malaria No More and the Roll Back Malaria consortium suggest that the number of deaths from malaria in Africa last year was the lowest in history, and efforts are underway to reduce that number to zero, worldwide, by the year 2015.

Malaria Distribution

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QUESTION

What countries have malaria?

ANSWER

Prior to the advent of modern methods for controlling malaria, it was present on every continent in the whole except Antarctica. The transmission of malaria depends on an appropriate climate, both for the development of the parasite and the mosquitoes that it requires as a vector. This limits malaria to areas that are sufficiently warm and with sufficient rainfall to provide pools of stagnant water for the development of mosquito larvae.

In practice, this means that malaria can be transmitted year round in the tropics (apart from areas of high altitude and deserts), most of the year in the sub-tropics (predominantly during rainy periods) and even seasonally in temperate latitudes (during the warmer months). As a result, malaria has historically been present in the United States and even in England, at a latitude of over 50 degrees north.

However, modern control measures, such as insecticide spraying and epidemiological surveillance, has greatly reduced transmission of malaria in many parts of the world, and especially in temperate regions where the force of infection was already lower than elsewhere in the world. As such, nowadays malaria is confined to tropical and sub-tropical Central and South America, certain Caribbean islands (such as Haiti), sub-Saharan Africa (apart from most of Namibia and South Africa), parts of the Middle East, the Indian sub-continent, south-east Asia (excluding major cities such as Singapore) and many of the Indo-Pacific islands (including Papua New Guinea). Of these, by far the largest number of deaths from malaria occur in sub-Saharan Africa.

See the CDC’s interactive map of malaria distribution for more information.