Malaria Prevention

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QUESTION

What are the ways in which you can prevent yourself from being infected with malaria?

ANSWER

Malaria prevention consists of a combination of mosquito avoidance measures (since malaria is transmitted by infected mosquitoes) and chemoprophylaxis (medication to prevent the establishment of malaria in your body, if you do get bitten). Although very efficacious, none of the recommended interventions are 100% effective.

Mosquito Avoidance Measures

  • Because of the nocturnal feeding habits of Anopheles mosquitoes, malaria transmission occurs primarily between dusk and dawn.
  • Contact with mosquitoes can be reduced by remaining in well-screened areas, using mosquito bed nets (preferably insecticide-treated nets), using a pyrethroid-containing flying-insect spray in living and sleeping areas during evening and nighttime hours, and wearing clothes that cover most of the body.
  • All travelers should use an effective mosquito repellent.
  • The most effective repellent against a wide range of vectors is DEET (N,N-diethylmetatoluamide), an ingredient in many commercially available insect repellents. The actual concentration of DEET varies widely among repellents. DEET formulations as high as 50% are recommended for both adults and children older than 2 months of age (see the Protection Against Mosquitoes, Ticks, and Other Insects and Arthropods section later in this chapter). DEET should be applied to the exposed parts of the skin when mosquitoes are likely to be present.
  • In addition to using a topical insect repellent, a permethrin-containing product may be applied to bed nets and clothing for additional protection against mosquitoes.

Chemoprophylaxis

      • All currently recommended primary chemoprophylaxis regimens involve taking a medicine before travel, during travel, and for a period of time after leaving the malaria endemic area. Beginning the drug before travel allows the antimalarial agent to be in the blood before the traveler is exposed to malaria parasites.
      • Presumptive antirelapse therapy (also known as terminal prophylaxis) uses a medication towards the end of the exposure period (or immediately thereafter) to prevent relapses or delayed-onset clinical presentations of malaria caused by hypnozoites (dormant liver stages) of P. vivax or P. ovale. Because most malarious areas of the world (except the Caribbean) have at least one species of relapsing malaria, travelers to these areas have some risk for acquiring either P. vivax or P. ovale, although the actual risk for an individual traveler is difficult to define. Presumptive anti-relapse therapy is generally indicated only for persons who have had prolonged exposure in malaria-endemic areas (e.g., missionaries, volunteers).
      • In choosing an appropriate chemoprophylactic regimen before travel, the traveler and the health-care provider should consider several factors. The travel itinerary should be reviewed in detail and compared with the information on where malaria transmission occurs within a given country to determine whether the traveler will actually be traveling in a part of the country where malaria occurs and if significant antimalarial drug resistance has been reported in that location.
      • The resistance of P. falciparum to chloroquine has been confirmed in all areas with P. falciparum malaria except the Caribbean, Central America west of the Panama Canal, and some countries in the Middle East. In addition, resistance to sulfadoxine–pyrimethamine (e.g., Fansidar) is widespread in the Amazon River Basin area of South America, much of Southeast Asia, other parts of Asia, and in large parts of Africa. Resistance to mefloquine has been confirmed on the borders of Thailand with Burma (Myanmar) and Cambodia, in the western provinces of Cambodia, in the eastern states of Burma (Myanmar), on the border between Burma and China, along the borders of Laos and Burma, and the adjacent parts of the Thailand–Cambodia border, as well as in southern Vietnam.
      • Additional factors to consider are the patient’s other medical conditions, medications being taken (to assess potential drug–drug interactions), the cost of the medicines, and the potential side effects.

The medications recommended for chemoprophylaxis of malaria may also be available at overseas destinations. However, combinations of these medications and additional drugs that are not recommended may be commonly prescribed and used in other countries. Travelers should be strongly discouraged from obtaining chemoprophylactic medications while abroad. The quality of these products is not known, and they may not be protective and may be dangerous. These medications may have been produced by substandard manufacturing practices, may be counterfeit, or may contain contaminants. Additional information on this topic can be found in an FDA document

Purchasing Medications Outside the United States.

Prevention of Malaria

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QUESTION

What is the prevention of malaria?

ANSWER

Malaria prevention consists of a combination of mosquito avoidance measures and chemoprophylaxis. Although very efficacious, none of the recommended interventions are 100% effective.

Mosquito Avoidance Measures

  • Because of the nocturnal feeding habits of Anopheles mosquitoes, malaria transmission occurs primarily between dusk and dawn.
  • Contact with mosquitoes can be reduced by remaining in well-screened areas, using mosquito bed nets (preferably insecticide-treated nets), using a pyrethroid-containing flying-insect spray in living and sleeping areas during evening and nighttime hours, and wearing clothes that cover most of the body.
  • All travelers should use an effective mosquito repellent.
  • The most effective repellent against a wide range of vectors is DEET (N,N-diethylmetatoluamide), an ingredient in many commercially available insect repellents. The actual concentration of DEET varies widely among repellents. DEET formulations as high as 50% are recommended for both adults and children older than 2 months of age (see the Protection Against Mosquitoes, Ticks, and Other Insects and Arthropods section later in this chapter). DEET should be applied to the exposed parts of the skin when mosquitoes are likely to be present.
  • In addition to using a topical insect repellent, a permethrin-containing product may be applied to bed nets and clothing for additional protection against mosquitoes.

Read the full article about Malaria Prevention.

What does the goverment do to help malaria?

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QUESTION

Does the goverment help malaria?

ANSWER

Many governments around the world assist in controlling malaria. Some countries, like Australia and the United States, used to have malaria transmission occur within their own borders, but through dedicated control programs, have managed to eradicate the disease locally. In these cases, the government coordinated huge programs of draining standing water, spraying insecticides and ensuring that health clinics were equipped to diagnose and quickly treat any human cases.

Nowadays, the governments of the US and Australia, along with many other countries which do not have malaria, still assist in the fight against malaria by funding malaria control programs in other countries, either directly (for example, the US funds international health projects through the US Agency for International Development) or indirectly, through international organisations like the World Health Organisation and the Global Fund for HIV, TB and Malaria. They also provide training in technical expertise to scientists, doctors and clinicians from malaria-endemic countries.

The governments of countries which have malaria are also deeply engaged in fighting the disease, mostly through their respective Ministries of Health, which often have specific malaria departments. In India, for example, malaria control is carried out by the National Vector Borne Disease Control Programme (NVBDCP), which is part of the Directorate General of Health Services. The NVBDCP carries out a multi-pronged strategy to combat malaria, including early case detection and treatment, vector control (with spraying, biological control and personal protection), community participation, etc. In Uganda, the Malaria Control Programme also carries out the above activities, and also provides intermittent preventative treatment against malaria for young children and pregnant women and has in the past engaged in large-scale distribution of long-lasting insecticide treated bednets. Both countries also explicitly include monitoring and evaluation as part of their control strategies, to make sure that any interventions or control efforts they make are having a positive impact on reducing malaria morbidity and mortality.

Geographic Range of Malaria

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QUESTION

Has the geographic range of malaria increased over the past 20 – 30 years? I have read that preventative measures have helped lower rates of infection, but I’m interested in the extension of the range itself.

ANSWER

That is a very interesting question, and one that garners quite a lot of debate. Preventative measures have actually also helped to limit the range of malaria globally. For example, malaria used to be relatively common in the Mediterranean basin and south-eastern United States, but control measures (mainly based around killing mosquitoes and removing suitable mosquito habitat) has largely eradicated malaria from these areas.

However, there is concern that on-going and future climate change has and will change the  distribution of malaria globally. For example, some predictions have suggested that malaria might be able to re-establish itself in the Mediterranean and Middle East, due to higher rainfall and higher winter minimums of temperature. Additionally, malaria may be able to spread to higher altitudes in areas where it is already present at low elevations. This is of huge concern in places like Kenya: Nairobi, the capital city (with around 5million people), sits at 1660 m altitude, and as such currently has generally negligible levels of malaria transmission. However, if climate change enables malaria to move up to this altitude, a huge number of people will be at additional risk of infection. Worryingly, there is some evidence from the Kenyan highlands that these changes are already underway.

Having said this, there are also parts of the world which might see malaria transmission ease as a result of climate change. This is particularly the case where rainfall is expected to decrease, or change significantly in relation to temperature. Moreover, some scientists think that on-going control efforts, particularly with respect to the distribution of bednets, vector control and greater coverage of diagnosis and treatment will continue to reduce the geographical spread of malaria over and beyond the changes associated with climate change. These scientists have compiled a map of Plasmodium falciparum transmission now as compared to data from before control interventions were rolled out—the reduction of transmission risk in many parts of the world, are clear to see (see below).

changing plasmodium falciparum map

Maps showing changes in transmission risk and endemicity of Plasmodium falciparum malaria between approximately 1900 (a) and now (b). (c) shows the balance of change in malaria transmission between the two time periods: the higher the negative number, the greater the reduction in malaria transmission. A positive number indicates increased malaria transmission. The different classes of malaria transmission risk are as follows: hypoendemic, prevalence < 10%; mesoendemic, PR ≥ 10% and < 50%; hyperendemic, prevalence ≥ 50% and < 75%; holoendemic, prevalence ≥ 75%. Image reproduced here from Gething et al., (2010), 'Climate change and the global malaria recession', in Nature, volume 465, pages 342-345.

US Army Doctor William Crawford Gorgas: Sent to Panama to fight Malaria

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QUESTION

What was the doctor’s name who was sent to Panama to fight Malaria when Panama Canal was being built?

ANSWER

I believe the person you are referring to is Dr. William Crawford Gorgas. Dr Gorgas was the chief sanitary officer for the Panama Canal project and had gained experience in controlling vector borne diseases while working in Havana, Cuba, where yellow fever was a problem.

It had also been shown a few years earlier, in 1898, that mosquitoes carried malaria as well. In Panama, Dr Gorgas focused his efforts on controlling mosquitoes, through drainage of standing water, adding larvicide and oil to remaining water and hand-collection of adult mosquitoes. In addition, Dr Gorgas screened all government buildings and workers’ quarters to prevent mosquitoes from entering, and gave workers prophylactic quinine. He was assisted in these endeavours by Dr Joseph Augustin LePrince and Dr Samuel Taylor Darling; together, their efforts led to the elimination of yellow fever from the canal zone and a great decrease in the number of malaria cases, though malaria continued to be a problem throughout the construction of the Panama Canal.

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.

Does Malaria Still Exist?

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QUESTION

does malaria still exist?

ANSWER

Yes, malaria still exists, and is responsible for 250 million cases of illness every year, of which about 700,000 result in death. So it is a very serious global health problem!

Some countries, such as the United States, have managed to successfully eliminate malaria through a combination of vector control strategies (i.e. spraying for mosquitoes, reducing the presence of water bodies where mosquitoes breed, etc) and better health infrastructure for diagnosis and treatment. This strategy has also been successful in other settings, such as the Mediterranean and much of the Middle East, as well as even in some high transmission tropical settings such as Malaysia (particularly in urban areas).

The widespread distribution of long-lasting insecticide treated bednets has further assisted in malaria prevention in high transmission areas. However, much of the rest of the world is still struggling to control malaria, though the number of deaths is dropping every year, and some organisations hope to reduce malaria mortality to zero by the year 2015.

If you have taken medications for malaria, please help Malaria.com by taking our Malaria Survey. Thank you!

Malaria Prevention

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QUESTION

what is the prevention of malaria?

ANSWER

There are many ways in which to prevent malaria. I’ll break them down into three categories: 1) medical prevention, 2) protection from getting mosquito bites and 3) vector control.

1) Medical prevention

Malaria can be prevented using certain medications. Taking drugs to prevent a disease is known as “chemoprophylaxis”, and so these drugs are often referred to as “malaria prophylactics”. There are several different types of malaria prophylactic: the most common ones are chloroquine, a mix of atovaquone and proguanil (marketed as Malarone), mefloquine (marketed as Lariam) and doxycycline. The mode of taking these medications vary (Lariam is taken once a week, for example, whereas the others are usually taken once every day), and they also have different restrictions and side effects. Chloroquine is not effective in areas where local forms of malaria have become resistant, for example, and Lariam is not recommended for people with a history of mental instability, as it is known to cause hallucinations and otherwise impair consciousness. Here on Malaria.com, we are actually currently running a survey on side effects of malaria prophylactic drugs, so if you have ever taken medication to prevent malaria, please take the survey: Malaria Medication Side-effects Survey: Treatment and Prophylaxis

It is worth noting that these drugs have not been tested for long term use, plus they can be expensive if taken for an extended period of time. As such, they may not be appropriate for people living in endemic areas for malaria. However, medication can be useful for preventing malaria in high risk groups, even when they are living in a malaria endemic area. One example is the use of intermittent preventive treatment (IPT) for preventing malaria infection in pregnant women, infants and young children. For more information on this, please see the review article written by Dr Felicia Lester for this website: http://www.malaria.com/research/malaria-pregnancy-preventive-treatment

2) Protection from getting mosquito bites

This section links in with the more general vector control strategies, which will be discussed below. Since malaria is transmitted through the bite of infected mosquitoes, preventing mosquito bites is a very effective way of reducing malaria incidence. One of the most popular methods for personal protection, especially in areas where malaria is endemic, is through sleeping under a mosquito bednet. The mesh prevents mosquitoes from being able to fly close to the person sleeping; however, if there are holes in the net, or the person skin is pressed directly against the mesh, the mosquito may still be able to bite them. This is where insecticide-treated bednets come in – they are impregnated with mosquito repellents to stop mosquitoes from biting through the mesh or passing through holes. Newly developed long-lasting insecticide treated bednets (LLINs) are even more effective, in that they don’t require “re-dipping” to maintain the level of repellent in the fibres, and so can protect a person for several years without losing efficacy. These LLINs have been instrumental in reducing cases of severe and fatal malaria, especially among pregnant women and young children, who are often targeted by bednet distributors.

Other methods for preventing mosquito bites include wearing long-sleeved clothing and personal application of mosquito repellent, particular those containing a percentage of DEET, which is a very effective insecticide. These measures should be especially taken in the evening, early morning and at night, which is when the Anopheles mosquitoes that carry malaria are most active.

3) Vector control

Finally, malaria can be prevented from reducing numbers of mosquitoes directly. Some methods target the adult mosquitoes; one such initiative is indoor residual spraying (IRS), whereby the inside of a house is sprayed with an insecticide to kill mosquitoes. Twelve different insecticides are approved by the World Health Organisation for this purpose, though pyrethroids are among the most popular, as they can be used on a variety of surfaces, do not leave a visible stain and can also protect against other insect pests, such as bedbugs.

Other methods for vector control focus on other parts of the mosquito lifecycle. Mosquito larvae require stagnant freshwater for their development, so some projects have worked to eliminate standing water sources, such as unnecessary ditches and puddles, which reduces the amount of habitat available for mosquitoes to lay their eggs and sustain larvae. Other programmes have spread insecticides directly in stagnant water to kill the larvae, or sought to introduce fish or other aquatic organisms, such as copepods, which consume mosquito eggs and larvae. This latter biological control approach is popular because it can also supply an area with fish for local consumption, and doesn’t contaminate water sources with chemicals.

Malaria in Africa

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QUESTION

Why do Africans catch malaria more than others?

ANSWER

There are a number of reasons why malaria is more widespread in Africa than in many other parts of the world. However, it is worth mentioning that other parts of the world, such as India and south-east Asia, also have very high prevalence of malaria, especially in rural areas.

The high transmission of malaria is Africa is predominantly due to two factors: climate and control measures, or rather, the lack of them.

Malaria is spread by mosquitoes of the genus Anopheles, and so in order to persist, an area must have a suitable temperature for the development of both the mosquito as well as the malaria parasite. This limits malaria transmission to the sub-tropics and tropics, primarily. The area must also have sufficient rainfall and areas of standing water, since the malaria mosquitoes lay their eggs in stagnant water, which the larvae live in until they pupate into adults. This means that malaria transmission cannot occur in desert regions.

Unfortunately, a large portion of Africa, and particularly West, Central and East Africa, are climatically very well suited to the development of mosquitoes and thus the transmission of malaria.

In addition, many countries in Africa are not as developed as other tropical countries. This means that health resources have not been as focused on control efforts in Africa—for example, Malaysia very successfully reduced malaria transmission by a huge amount through a combination of vector control (namely spraying households with insecticides and filling up stagnant water pools so larvae couldn’t develop), distribution of bednets (which reduces mosquito biting rate) and better diagnoses and treatment facilities.

All of these efforts are beginning to be developed and rolled out in Africa as well, so hopefully in the near future we will also see a dramatic reduction in malaria transmission in Africa.

Use of Fish for Malaria Eradication

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QUESTION

Why is very little research being done on the possibility of mosquito fish being used as a means of controlling the hatching of new eggs?

ANSWER

Actually there is a lot of scientific literature on the use of fish as a biological control of mosquitoes, usually through consumption of the mosquito larvae or pupae while they are in freshwater. The most common species used for this purpose are the guppy (Poecilia reticulata) and the appropriately named mosquito fish (Gambusia affinis). Other fish groups, like cyprinodontids (i.e. Aphanius species), tilapia and minnows will also eat mosquito larvae.

In addition, other freshwater predators, such as copepods, have been shown to be highly effective in  killing mosquito in laboratory and field experiments, though results are sometimes inconsistent (see Lardeaux, 2008 “Biological control of Culicidae with the copepod Mesocyclops aspericornis and larvivorous fish (Poeciliidae) in a village of French Polynesia,” in Medical and Veterinary Entomology, vol 6, issue 1, pages 9-15, for a comparison of the anti-mosquito effect of these different groups).

The Lardeaux paper also describes the failure of the program: despite introduction of larvivorous animals, biting rates of mosquitoes did not significantly reduce, indicating some of the complications that can be associated with biological control programs.

However, in Vietnam, field studies have shown significant reductions of local Aedes mosquitoes associated with the presence of copepods in standing water sources, which shows the potential positive effects of incorporating natural biological control agents within part of an integrated vector control strategy (Nam et al., 2000 “National progress in dengue vector control in Vietnam: Survey for Mesocyclops (Copepoda), Micronexa (Corixidae) and fish as biological control agents,” in the American Journal of Tropical Medicine and Hygiene, vol 62, issue 1, pages 5-10).

Another example of successful introduction of fish as biological control agent comes from Ethiopia (Fletcher et al., 1992 “Control of mosquito larvae in the port city of Assab by an indigenous larvivorous fish, Aphanius dispar,” in Acta Tropica, vol 52, issue 2-3, pages 155-166).