Is Malaria Transmitted by Female Mosquitoes?

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QUESTION

Is malaria caused by only female mosquitoes?

ANSWER

Malaria is only transmitted by female mosquitoes, yes. This is because only female mosquitoes of the genus Anopheles (the genus that transmits malaria in mammals, including humans) feed on blood, and the parasite that causes malaria (called Plasmodium) spends part of its life cycle in the blood. Therefore, when a female mosquito feeds on an infected person, when she sucks up their blood, she also takes up some of the Plasmodium parasites. These parasites mature inside the mosquito, and then, when the mosquito goes to bite another person, she passes some of the mature Plasmodium parasites into that new person’s blood while she feeds. The Plasmodium parasites may then be able to undergo further development in the new host, which may lead to the person experiencing a malaria infection. So, while technically female mosquitoes don’t cause malaria (since the disease is caused by the Plasmodium parasite), female mosquitoes are required to pass it between one person and another.

Mosquitoes Transmission via Feces

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QUESTION

Can a mosquito give you malaria after having being on an infected person’s feces?

ANSWER

No. Malaria can only be transmitted via blood. As such, transmission via mosquitoes occurs when a mosquito feeds on the blood of an infected person, then bites someone who is not infected, and transfers the malaria parasite in the bite (this cannot happen straight away – the malaria parasite has to undergo some changes in the mosquito first).

Ingestion of Malaria Blood

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QUESTION

If someone were to eat/ingest the blood of an infected individual would they become infected with malaria? If an infected person’s blood was on their hands and they handled food, would eating the food put others at risk for malaria?

ANSWER

No, you would not get infected with malaria, as the malaria parasites must be transmitted into a person’s blood directly in order for them to be infected. As such, most transmission only occurs via mosquitoes: when a mosquito bites a person infected with malaria, it may pick up some of the malaria parasites while it feeds on the person’s blood. When it then goes to bite another person, after the parasite has replicated and changed inside the mosquito, it can pass the malaria on to the next person, again when it bites them and drinks the person’s blood.

Additionally, in some cases malaria can be transmitted by blood transfusion or organ donation, or from a mother to her unborn baby via the placenta, or through blood passed in childbirth. If you ate/drank malaria-infected blood, the parasites would be broken down and destroyed by your stomach acid.

Malaria: Mode of Transmission

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QUESTION

What is the mode of transmission of Malaria?

ANSWER

Malaria is transmitted normally via the bite of an infected mosquito. These mosquitoes, always female and of the genus Anopheles, carry malaria parasites in their salivary glands. The parasites, at this part of their life cycle known as sporozoites, are introduced into the host’s blood when the mosquito takes a blood meal. From there, the sporozoites travel to the liver, reproduce (this process may take several weeks), then finally re-enter the blood stream. At this point, the patient will begin to experience symptoms. Eventually, the malaria parasites change again, into gametocytes, which are picked up by another mosquito, again when it bites the infected person. In this way, the life cycle of the malaria parasite continues.

Because malaria reproduces in the blood and in the liver, in some cases malaria can be transferred via organ transplant or blood transfusion. In addition, malaria parasites can cross the placenta, and so can be transmitted from a mother to her unborn child, either in the womb or during childbirth. This is known as congenital malaria.

Malaria Treatment and Prevention Methods

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QUESTION

I work in Central Africa republic.I was recently diagnosed with malaria (p.falciparum) after a blood test—my 4th attack in 15 months and given Co-Arinate. Two days after completing my dose I went for a 2nd blood test and the trophozoite count was 720/mm3.

The doctor prescribed co-artem and said if I don’t get better he shall transfuse quinine. Whats your comment on the treatment? Do these malaria medications/attacks have a long term effect on ones liver? What prophylaxis should I consider to prevent future attacks.

ANSWER

I will forward your question on to one of the medical professional who advises our website. However, normal procedure after treatment failure or incomplete treatment with one type of anti-malarial medication would be to try another type of medication first; Co-Arinate might not have been an ideal first choice given that many types of malaria around the world are showing signs of resistance to pyrimethamine, the combination drug in Co-Arinate.

Co-Artem would be a better first choice drug, given that there is no convincing evidence for resistance to its combination compound, lumefantrine. Quinine could be a potential next step though I would imagine Co-Artem will be successful—make sure the drugs have not expired and are in their original packaging, as counterfeit medication is a problem in many parts of the world.

Regarding prevention, a key method is to sleep under a long-lasting insecticide treated bednet; make sure it is re-dipped in insecticide every year or so to maintain its efficacy. The mosquitoes which transmit malaria tend to feed at night, and so protecting yourself and your home during the evening, night and early morning is crucial. Maintaining good screens on all windows and doors can be a very effective way of preventing mosquitoes from entering, and in many parts of the world, people spray inside with insecticides to reduce the number of mosquitoes yet further. Wearing long-sleeved clothing at night and in the evenings can also prevent bites.

More broadly speaking, you can try to make sure that stagnant water sources, such as empty containers or barrels, are removed, as mosquitoes require still water to breed. Reducing the presence of stagnant water will therefore reduce mosquito numbers; treating standing water with larvacides or adding fish that eat mosquito larvae can also help.

Malaria Hosts

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QUESTION

Which are malaria hosts and how does malaria have an effect on one of them?

ANSWER

The parasite which causes malaria (called Plasmodium) requires two different hosts—a vertebrate intermediate host, such as a human, and an insect definitive host, also known as the vector. For the types of malaria which infect humans and other mammals, the vector is always a mosquito of the genus Anopheles.

However, there are other types of malaria which infect birds and reptiles, and these can use other genera of mosquito as their vectors, and some parasites closely related to Plasmodium can even use sandflies and other types of insects as their vectors too.

In humans, malaria usually causes disease, characterized by high fever, chills, aches and nausea. However, the presentation of symptoms and their severity depends on a number of factors, such as the type of Plasmodium (P. falciparum is the most dangerous to humans), the immune status of the host and the infective dose received from the vector.

Many mammals are also susceptible to malaria, such as macaque monkeys, and with them as well the effect of the parasite depends on a number of factors. For example, for macaques in south-east Asia, many will be co-infected with several different types of malaria simultaneously, though none appear to cause disease. However, if macaques from other parts of tje world, such as the Himalayas, are experimentally infected with these same types of malaria, they will get sick and possibly even die. As such, evolutionary history also plays a part in terms of how severe malaria will be in a particular host.

For the insect vector, infection with malaria parasites does not appear to have a strong deleterious effect, though some studies have shown reduced survival in mosquitoes infected with malaria. Also, changes in behavior have been observed. For example, some studies have shown that mosquitoes which are infected with malaria are more likely to continue seeking for food (i.e. through biting a host) even if they have recently fed than mosquitoes which are uninfected, or infected with non-transmissable life stages of malaria. This suggests that in some way the malaria parasite is manipulating the vector’s behavior in order to increase its own chances of being passed on to a new host.

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).

Do I need malaria tablets to live in Nigeria?

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QUESTION

Do I need malaria tablets to live in Nigeria? I was born and bred in the UK and want to go back to live in Nigeria for about 2 years, do I need malaria tablets?

ANSWER

It is not usually recommended to take malaria tablets for long periods of time (i.e. more than a few months). People living for extended periods in areas with malaria should focus on other methods of prevention, such as sleeping under a long-lasting insecticide-treated bednet.

The mosquitoes that carry malaria, Anopheles, feed mostly in the evenings and at night, so it is particularly important to protect yourself during these times. Screening windows and doors tightly can help prevent mosquitoes form entering, as can air conditioning inside the house (it makes the climate less suitable for the mosquitoes).

In many parts of Africa, insecticide is sometimes sprayed indoors, again to prevent mosquitoes from being inside the house. Personal protection is also important; wearing long-sleeved clothing, particularly at dawn, dusk and at night, can prevent mosquitoes from biting you, as can wearing mosquito repellent, particularly kinds containing the chemical DEET.

Regarding tablets to prevent malaria, if you really want to pursue this option, the only medication which is recommended for long-term use is doxycycline, but you should consult with your doctor about its suitability for periods of longer than 6 months, and they should also explain to you the possible side effects associated with taking it.

While the above mentioned forms of prevention should be the mainstay of your efforts to avoid malaria, it is also important to know what the symptoms are and what to do if you suspect you might be infected.

Malaria is characterized by high fever, chills, aches and nausea most commonly, and if you think you may be infected, you should immediately go to a doctor or a clinic for diagnosis. The doctor/clinician should take a blood sample and either look at it under a microscope to look for malaria parasites or they will use a drop of blood in a rapid diagnostic test. In both cases, you should only take medication to treat malaria if you are positively diagnosed.

Malaria Socio-Economic Issues

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QUESTION

What are the socio-economic issues on the spread of malaria?

ANSWER

Malaria transmission requires the presence of Anopheles mosquitoes; as such, conditions which favor the growth and persistence of these mosquitoes will also be hotspots for malaria transmission, provided the climate is also sufficiently warm for the development of the parasite within the mosquito.

Rural areas without sophisticated water and sanitation systems often utilize streams or ponds for everyday water needs; if these produce stagnant patches of water, they can be an ideal location for the development of mosquito larvae.

Similarly, if rural farmers dig canals or ditches to irrigate their fields, these can become breeding areas. Urban areas tend to have less standing water, apart from cisterns, so in many cases transmission is less prevalent in urbanized locations.

As a further socio-economic factor, preventing mosquitoes from entering the house and biting people is  key way to prevent infection. Rich people in malarial areas may be more able to have fully screened houses, possibly even with air-conditioning, which will prevent mosquitoes from establishing in the house. They may also be more likely to have access to a long-lasting insecticide treated bednet, which further reduces mosquito bites, and also access to accurate diagnostic screening and treatment, if they do happen to get infected.

All of these factors contribute to making malaria burden highest in some of the world’s poorest areas, with the highest levels of mortality in sub-Saharan Africa.