Reduce Risk of p.falciparum

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QUESTION:

I am laboratories man. My question is the risk of P. falciparum especially for mother and children is very high.  How can we reduce this risk?

ANSWER:

That’s a crucial question for malaria control. Certainly, as you say, the risk of severe malaria is much greater for young children and for pregnant women. As such, these high risk groups should be targeted during prevention campaigns, as well as for diagnosis and treatment.

There are several methods of prevention, which are suitable for all types of malaria, including P. falciparum. Probably the most effective, and also the most simple, is through the proper use of insecticide-treated bednets. These are often handed out at antenatal clinics to pregnant women, but ensuring that the nets are used properly is more difficult. Proper training, and emphasising that children and pregnant women will benefit most from reduced exposure to mosquitoes, is required. For more on the difficulties and challenges of bednet distribution, you can see Hugo Gouvras’ comment on an earlier question in this Q&A forum – see here: http://www.malaria.com/questions/free-malaria-bednet

The other main method for malaria prevention is through the use of prophylactic drugs, although these have to be taken every day, and so the cost is usually prohibitive for residents of malarial areas. In these areas, there have been successful trials of so-called SP IPT, which stands for sulfadoxine-pyrimethamine intermittent protective treatment. In this regime, malaria in pregnant women is prevented by administering intermittent doses of sulfadoxine-pyrimethamine; usually two doses during the pregnancy (one in the second and one in the third trimester), but monthly doses have also been tested. More frequent doses may be better for women who are also HIV positive, some studies have shown.

Intermittent preventative treatment has also been trialled on young children as a way of reducing the severity and frequency of malarial episodes when the child is most vulnerable. I’m not up to date on the most recent studies on this work, so will ask another one of our experts to comment on the efficacy of IPT, both in children and pregnant women.

Thanks for the question!

How to Prevent Malaria

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QUESTION:

What is the prevention of malaria?

ANSWER:

Malaria can be prevented in a number of ways, the main three of which are bite reduction, prophylaxis and vector control.

Bite reduction just means steering clear of mosquitoes, and specifically those that transmit malaria. These bite mostly between dusk and dawn, so if walking around at these times of day in a malarial area, it is worth wearing long sleeves and pants, and applying an insect repellant – ones containing DEET are the most effective at keeping off mosquitoes, in my opinion, but they also contain very toxic chemicals so should be used with care.

Specifically, 100% DEET shouldn’t be applied directly to bare skin, since it can be absorbed and cause problems for the liver. Natural insecticides, such as those containing citronella, are also an option. At night, it is advised to sleep under a bednet, which prevents mosquitoes from biting you while you sleep. Nets which are infused with pyrethrin, or other insecticides, are recommended.

Pyrethrin spray can also be used on clothing, to stop mosquitoes biting through light cloth. On a broader scale, bite reduction can also be achieved through better screening of windows and doors, and other ‘environmental’ controls.

Prophylaxis, when referring to malaria, means taking certain medication in order to prevent the onset of the disease. Several different drugs exist, and different ones are recommended depending on the type of malaria you are likely to encounter. Moreover, each has different potential side effects, different schedules of ingestion and come at a range of prices.

Since they do cost money, and are sometimes very expensive, prophylaxis against malaria is usually only used by short term visitors to malarial zones, although since pregnant women are more susceptible to malaria, they may choose to take prophylaxis during their term in order to prevent infection – it should be noted that most of the drugs used for malaria prophylaxis are NOT recommended for pregnant women so it is important to check carefully before starting on any of these medications.

For more info on malaria prevention while pregnant, why not check out the Q&A question about pregnancy and travelling to Belize?

For info on malaria prophylaxis in general, there is a Prophylaxis Forum dedicated to this here on this website, so have a look!

Finally, there is vector control. This means reducing the number of mosquitoes around so that there are less to transmit malaria! Spraying households with insecticides has been very effective in reducing malaria transmission in a number of settings, and although it suffers from a lack of cost-effectiveness and sustainability in the long run, may still be very useful in high-endemicity regions or those where drug-resistant malaria is rife.

Another approach to vector control is to eliminate habitat for the mosquito larvae. The larvae breed in pools of stagnant water, such as ditches or puddles; filling these in can reduce the number of larvae that can mature into biting mosquitoes. Obviously, some water sources, such as wells and irrigation ditches, are required by communities, particularly in rural areas, and so cannot be removed. As such, larval control is probably mostly an effective strategy in urban transmission settings.

Finally, on a slight tangent to traditional vector control, there has long been interest in the idea of controlling malaria through manipulation of mosquito genetics in such a way that populations could be replaced with individuals that cannot transmit the disease. A research article on this subject is available on this website. See: Malaria Control with Transgenic Mosquitos.

 

How Many Types of Human Malaria?

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QUESTION:

How many types of malaria infect humans?

ANSWER:

There are four main types of malaria which infect humans: Plasmodium falciparum, P. vivax, P. malariae and P. ovale. P. ovale additionally can be split into two sympatric sub-species, P. o. curtisi and P. o. wallikeri. Each of these five kinds has a subtly different life cycle which results in slight variations in symptoms and also in treatment. For more information on this, check out the Q&As on malaria symptoms and malaria treatment; CDC is also a site worth checking out.

Additionally to the four species above, there are observations of a number of other Plasmodium species being able to infect humans, although much less frequently. The most reported of these is P. knowlesi, found in SE Asia, which usually infects macaque monkeys but is capable of crossing over into humans and causing severe quotidien malaria, and may even result in death. The number of cases of P. knowlesi appears to be on the rise in some regions, although the cause of this is not quite clear. For an introduction to P. knowlesi, you should read Christina Faust’s blog.

The list of other species of Plasmodium that have been reported to infect humans (sometimes only experimentally in the lab) includes P. brasilianum, P. cynomolgi, P. eylesi, P. inui, P. rhodiani, P. schwetzi, P. semiovale, P. simium and P. tenue.

Mosquitoes with Malaria

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QUESTION:

Do mosquitoes with malaria get sick like people do?

ANSWER:

That’s a great question! As far as I know, the jury is still out in terms of what overall effect being infected with malaria has on mosquitoes, and to a large extent, it appears to vary due to lots of factors, such as the compatibility between the mosquito and the particular type of malaria parasite, the intensity of malarial infection, and even environmental conditions, to name but a few. However, what is clear is that mosquitoes don’t seem to get ‘sick’ like we do, with fevers, chills and the like—their immune system is just too different from ours! Instead, with mosquitoes, it’s more a question of whether malaria decreases their lifespan, reduced their reproductive success, or other such effects.

A meta-analysis (Ferguson & Read, 2002, ‘Why is the effect of malaria parasites on mosquito survival still unresolved?’, in Trends in Parasitology) of studies that looked on the effect of malaria on mosquito survival demonstrated that 41% of studies reported a detrimental effect of malaria on mosquitoes, whereas 59% reported no effect (none reported a positive effect, which is interesting).

Also worth noting is that the length of the study seemed to have an effect on whether it would report a detrimental effect; this might be due to early stages of infection with malaria not having a negative impact on the host, while the malaria parasite is developing; then, once it is mature, it may be that the parasite’s virulence towards its host increases. Similarly, at this stage in its life cycle, the parasite might induce changes in the mosquito’s behaviour, encouraging it to feed more, which can result in higher mortality to the mosquito (think of swatting away annoying, biting mosquitoes, whereas you’re less likely to go for ones that leave you alone!).

More recently, a study by EJ Dawes and colleagues at Imperial College, London (2009, ‘Anopheles mortality is both age- and Plasmodium-density dependent: Implications for malaria transmission, in Malaria Journal) found evidence for the age of the mosquito and the intensity of malaria parasitism influencing mortality of the insects. Similarly, another research group found that infected female mosquites had significantly lower fecundity than non-infected mosquitoes (Gray & Bradley, 2006, ‘Malarial infection in Aedes aegypti: Effects on feeding, fecundity and metabolic rate’, in Parasitology). These examples begin to swing the balance of the debate in favour of malaria having a negative impact on mosquitoes, at least at certain points in the timeline of an infection (i.e. near the beginning, and then after parasite maturation).

You might ask why mosquitoes that are commonly infected with malaria don’t become resistant to infection, given that they seem to suffer ill-effects when they are parasitised—well, some recent research may have provided the answer to that one. Researchers looking at population growth rates in malaria-susceptible mosquitoes versus those resistant to infection noticed significantly slower growth rates in the resistant population, suggesting that in terms of reproduction, resistance at a population level might come at a cost to growth (Voordouw et al., 2009, ‘Rodent malaria-resistant strains of the mosquito, Anopheles gambiae, have slower population growth than -susceptible strains’, in BMC Evolutionary Biology). However, there may be ways in which this effect can be by-passed, in order to control malaria transmission at the level of the mosquito; one group of researchers recently published the results of a study, where they showed that when resistant and susceptible male mosquitoes rae released into a population of females (bearing in mind only the females feed on blood, and so males are not implicated in transmission), the females tend to mate first with the earlier-hatching resistant males, and moreover, lay a greater number of eggs with these males! So it may be that research on the effect of malaria on mosquitoes can be used in the future to decrease malaria transmission, which would be a hugely positive step for public health in many parts of the world.

It would be great if any malaria researchers out there would comment on the above answer, especially if there are more up-to-date examples of research on the effect of malaria on mosquitoes!

Malaria Self-Diagnosis

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QUESTION:

I live in Nigeria and was wondering if there are ways to find out if I malaria without going to the doctor or a hospital?

ANSWER:

The current “gold-standard” for malaria diagnosis, at least of active infections, is through microscropy, where a trained technician looks at a droplet of your blood on a slide, and sees if any of your red blood cells are infected with the malaria parasite. Given the expertise required for this procedure, it is usually only available through a doctor or in a hospital setting. Moreover, this technique is not reliable for very low numbers of parasites, though most active malaria infections will be positively diagnosed.

However, in the last ten years, there has been a rise in the availability and effectiveness of so-called rapid diagnostic tests (RDTs) for malaria, which can be self-administered and so are able to be bought in a pharmacy and used at home. There are a wide variety of these tests, which work by using antibodies to detect the antigens produced by the malaria parasites. As such, the tests seem to be able to detect even low levels of parasitaemia, and in some cases can even tell you which kind of malaria you have. The tests usually come with all necessary materials, which include a lancet for pricking the fingertip for a drop of blood, although you should always check that everything is within the packaging (I have bought tests in Uganda which came without the buffer solution; this had to be purchased separately in this case). The WHO maintains a list of currently available RDTs (PDF).

Make sure the test you purchase is suitable for the type of malaria that is found in your region; many only test for P. falciparum, for example, which might not be appropriate for a region with high levels of P. vivax or other species.

Malaria – Free Bednets?

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QUESTION:

Why do people have to pay for the bed nets?  I think that is mean to the people and they should get them for free.

ANSWER:

You have hit on a very important and on-going debate in the malaria control community. In many places around the world, organisations such as UNICEF have distributed free, insecticide-treated bednets, and especially to mothers—pregnant women and children under five are the groups most at risk from dying from malaria.

In 2010, UNICEF reported that together with its partners (WHO, the EU and the World Bank, to name a few) 5.5 million free bednets have been distributed in DR Congo alone. Similarly, in Mozambique, the Malaria Consortium has been working in a partnership with DFID and the public sector to distribute 400,000 bednets to pregnant women as part of an ante-natal service, again targeting some of the most at-risk people.

However, you are right to say that in some cases, people have to pay for bednets; in some of the poorest countries in the world, this can seem like an unjustifiable expense. However, there are some arguments in favor of having people buy their bednets.

For example, some people argue that a purely public donation initiative is unsustainable, and in order to have an on-going distribution campaign, the private sector has to be involved at some level, and this usually means charging a fee for each bednet. Moreover, forcing people to buy their own nets would free up donor funds for other purposes. Similarly, it is thought in some circles that having payment encourages suppliers to continue producing and selling nets. Finally, there are suggestions that purchasing a bednet increases their value to the recipient, who subsequently uses their net more frequently and more reliably in the manner in which it is intended (and not, for example, as a spare fishing net, as I’ve seen in parts of Uganda!).

I believe a study in Malawi showed that by asking people in urban areas, who have a bit more disposable income, to purchase full-price bednets, the program was able to generate sufficient funds to offer bednets at a highly subsidized cost in rural, poorer areas of the country; by asking people to purchase the nets, the program believed bednet usage among its recipients was higher overall, than if the nets had been given out for free.

I think the organization that tried this approach was called PSI (Population Services International)—they also offered nurses a small monetary incentive to sell bed nets (at the small sum of 50 cents each) to the rural women who attended pre-natal clinics, thus encouraging them to offer the nets widely to pregnant women.

As the final word, a study in Kenya recently showed that as costs for services such as bednets increased, demand for the service among the poorest sectors of the population declined sharply. Instead, it seemed most economical and efficient to target high-risk groups with free bednets, who are also incentivized to use the product properly and value the protection it confers, such as pregnant women in ante-natal settings, rather than doling them out to the community at large.

So we’re back to where I started with this response; the great job that many organizations out there are doing in distribution insecticide-treated bednets to the people who need it the most, and who can’t afford to buy them themselves, although it is worth bearing in mind that alternative models of bednet funding and distribution might prove equally beneficial and potentially more sustainable, at least in certain areas.

I’m also going to ask Hugo Gouvras to weigh in on this one—he works for Malaria No More, an organization that has recently launched an innovative mechanism for accelerating funding provision for bednet distribution to Africa. Hopefully he can update anything that I have said which is old news, and provide additional information!

Malaria in Brazil

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QUESTION:

Is there Malaria in Brazil? If so, what pills do I need to take?

ANSWER:

Yes, there is malaria in many parts of Brazil, and more than one type: about 75% of cases in Brazil are caused by Plasmodium vivax, whereas the rest are from infections with P. falciparum, the more acute and dangerous species of malaria. Brazil does have good information as to the distribution of malaria across the country; in terms of affected states, the full list is as follows:

Acre, Amapa, Amazonas, Maranhao (western part), Mato Grosso (northern part), Para (except Belem City), Rondonia, Roraima, and Tocantins.

This includes cities within the above districts, such as Boa Vista, Macapa, Manaus, Maraba, Porto Velho and Santarem, and particularly on the outskirts where transmission is highest. It is worth noting that malaria is not considered to be a problem in the region of Iguassu Falls.

In terms of malaria prevention, the CDC recommends Larium (mefloquine is the generic name), Malarone (atovaquone or proguanil are the generic names) or doxycycline, due to the presence of chloroquine-resistant P. falciparum in some areas. Deciding between which of these to take depends on a number of factor, including cost, known side-effects, and, not least of all, personal preference. For a discussion on the pros and cons of these various form of prophylaxis, check out the discussion “Malaria Prophylaxis” on this website.

Malaria in Thailand

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QUESTION:

I am going to Thailand. Do I need to take Malaria medication there?

ANSWER:

Like many other countries, that depends on where in Thailand you are planning to go. The country on the whole has been successful in containing malaria, mostly through successful mosquito control initiatives and a great initiative of government-sponsored “malaria clinics”  dotted around the country, which diagnosed and treated thousands of people.

Now, malaria is more or less constrained to the border regions with Myanmar, Laos and Cambodia, and if you plan to travel to these areas, prophylaxis is recommended (malarone or doxycycline are best since the area has chloroquine-resistant strains of Plasmodium falciparum, the most quick-acting and dangerous form of malaria). There are a few cases of malaria from coastal areas every year, but bite prevention is probably sufficient to reduce the risk of infection – make sure to wear insect repellant, especially at night and dusk/dawn, and if possible sleep under an insecticide-treated bednet.

Finally, remember if you do take prophylaxis, and as per the manufacturer’s instructions, there is only a tiny risk of contracting malaria. But if you do find yourself with symptoms when you get back (see the ‘What are the symptoms of malaria?’ question in this Q&A forum for a description of the more common signs of malarial infection), it’s definitely worth getting checked out!