Malaria prophylaxis

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QUESTION:

What name brand medicine should you take if you are traveling to area where malaria is present?

ANSWER:

That depends on a few factors, such as where exactly you are going, whether you have had bad experiences with any malaria preventative drugs (prophylactics) in the past, and how much money you want to spend! Common brand names of malaria prophylactic drugs include Lariam (generic name mefloquine) and Malarone (a combination of atovaquone and proguanil). Doxycycline is also a popular antimalarial, which is often sold under its generic name.

How soon can malaria occur a second time?

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QUESTION:

My son is studying in Tanzania and was diagnosed June 28, 2011 with malaria while taking Malarone. He took Duo-Cotecxin as prescribed for treatment and was feeling much better. He was given a “clear” blood test result. He started taking Malarone July 16, 2011 and on June 18, 2011 was ill again and diagnosed with malaria a second time in less than 6 weeks. Can malaria occur in this way or is there a possibility that the first case of malaria was controlled but not cured with Dus-Cotecxin and then esculated when he started taking Malarone again?

ANSWER:

There are two possibilities in this case; first of all, your son could have had what is called a recrudescence. This is where levels of the parasite in the blood drop to below detectable limits, and the immune system is able to keep the infection at bay. It can occur due to a failure to complete the course of antimalarial drugs, or indeed also due to treatment failure of the medication itself. Although Duo-Cotecxin is one of the recommended artemisinin-based combination therapies (ACTs) on the market for treatment of uncomplicated Plasmodium falciparum malaria, its cure rate is still at 98.7%, meaning that there is still a possibility of the drug not being completely effective in every instance. Moreover, there is a worrying indication that some strains of malaria are actually managing to become resistant even to ACTs.

The other possibility is that your son became re-infected, and it was a separate case of malaria; he was just very unlucky! This is highly unusual while taking Malarone as a prophylaxis, but it is possible. Determining which of these two scenarios occurred is difficult, but some information may be had from the type of blood test he had; clinics in Tanzania regularly use either blood film microscopy or rapid diagnostic tests (RDTs). Microscopy is notoriously insensitive as a diagnostic, and cannot reliably detect malaria parasites below a certain threshold, which depends on the skill and experience of the technician reading the blood slide. Therefore, if your son was declared negative for malaria based on this diagnostic, after the initial treatment, I think there is a good chance he was suffering from a recrudescence or treatment failure. However, if he was diagnosed by RDT, which is very sensitive to even low levels of malaria parasite in the blood, then I would think it might have been re-infection. However, I have concerns about the accuracy of RDTs so soon after infections have been cleared; the tests usually work by binding to malaria antibodies in the blood, which can sometimes persist even after the parasites have all been cleared. As such, you should also check what the diagnostic was the third time he was tested, and if this differed from the other two times; another possibility is that his infection really was cleared through treatment, and then got sick with something other than malaria; if they used an RDT on him at this point to diagnose malaria, they might have got a positive result confounded by his earlier infection. In these cases, you must ensure that the clinician takes a full history and so knows that the patient recently suffered from malaria; it may not be appropriate to use an RDT in this instance.

If your son is still in Tanzania and would like more information on malaria, he can contact us.  I am currently also working in Tanzania and so can perhaps help more if I know the details of his case (where he is based, etc). I would be happy to answer any questions he has.

Causes of malaria, treatment with drugs and emerging resistance

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QUESTION:

What is malaria and what causes it besides bacteria? What is the name of the causal agent for malaria, which drug is used to cure it and how do the pathogens become resistant to the drugs?

ANSWER:

There are many questions in there! Malaria is actually caused by a single-celled animal, called a protozoan; it’s not a bacterial disease. There are different species of these protozoans, which form a genus called Plasmodium; the different species cause different types of malaria, for example Plasmodium falciparum, the most deadly and severe form, and Plasmodium vivax, which is widespread throughout the world but is a less acute infection. These different forms of malaria are each treated with different medications, depending on what is most effective and available; P. vivax, for example, can be treated with chloroquine, whereas in many places, P. falciparum has become resistant to this drug. In areas where resistance to chloroquine has emerged, other drugs are used; in Africa, artemisinin-based combination therapies (ACTs) are commonly used against chloroquine-resistant P. falciparum. Other drugs used to treat malaria include quinine compounds such as quinine sulphate, mefloquine, sulfadoxine-pyrimethamine and medications combining proguanil with atovaquone (marketed as Malarone).

The emergence of resistance to these drugs is a worrying phenomenon with respect to malaria; it is such a widespread and deadly disease, that the consequences of failed treatment are very high. Resistance can be caused by many factors, at the level of the drug, the human host, the mosquito host and also the malaria parasite itself. For example, poor drug compliance during treatment can lead to a failure to clear an infection completely, allowing the remaining parasites, which were less susceptible to the drug, to survive and reproduce. With successive generations, natural selection will lead to the evolution of strains of malaria parasites which are firmly resistant to that drug. The same process occurs when mass drug administration programmes, for example in areas of high malaria endemicity, give people sub-therapeutic doses of medication (in other words, doses of the drug that are too low to kill the parasite). Another problem is when people are not checked for their infection status after having been treated for malaria; if treatment fails for some reason, they will still have parasites in their blood, and should be treated again to ensure that all the malaria has been killed. If this doesn’t happen, the parasites can carry on reproducing, as in the processes described above. For these reasons, it is crucially important for people to be given accurate doses of medication, to ensure that they complete the full course of treatment, and that once treatment has been completed, they are accurately tested as negative for the malaria parasite. Finally, there are factors related to the affinity of the malaria parasite to its vector mosquito hosts which can lead to the emergence of drug resistant strains. For example, it has been shown that strains of malaria which are resistant to chloroquine are better able to survive and reproduce inside their mosquito hosts, leading to a greater population size of resistant parasites compared to drug-susceptible ones. It is for these reasons that malaria treatment and control programmes are now being very careful with the ways in which they administer drugs and monitor infections, in order to limit any further reisstance developing; similarly, pharmaceutical and biochemical researchers are constantly on the look-out for new compounds or methods of killing malaria parasites, which can be developed into new forms of treatment.

Malaria effects on body’s digestive system

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QUESTION:

How does Malaria affect the digestive system?

ANSWER:

Malaria does not usually affect the digestive system directly, although nausea and abdominal pain can be symptoms of the disease, usually due to the high fevers caused by the infection. Having said that, some of the drugs given as treatment or prevention of malaria are also known to have gastrointestinal side effects; both chloroquine and proguanil (one of the active ingredients in Malarone) are known to cause nausea and abdominal pain as common side effects, and both can also sometimes (in rare cases) result in gastrointestinal bleeding. It is recommended that these medications be taken with food, to reduce the likelihood of experiences any such side effects.

Malaria Prevention for Seniors

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QUESTION:

I am a healthy senior citizen (73 years) and I am considering a trip with Semester at Sea. One of the ports they plan to visit is Ghana. I see the CDC says Ghana is a “high risk” area for malaria.

I think I remember being told (at the U of W Travel Medicine Clinic) a few years ago that the malaria drugs are problematic for Seniors.

With the Semester at Sea ship stopping at Takoradi, Ghana, how high a risk is malaria and what preventative measures could/should I take?

I have had no malaria treatment (preventive or due to illness) in the past.

Thank you.

ANSWER:

It is correct that Ghana is a high risk zone for malaria, and wise of you to investigate ways to prevent infection. This is especially the case given that there is evidence to suggest that senior citizens and travellers over the age of 60 may be more at risk of serious complications from malaria. As such, it is especially important for these high risk groups, which also includes pregnant women and children, to be well aware of ways to reduce the risk of exposure and infection.

Having said that, I have done some research and I don’t think there is any evidence that the standard drugs for preventing malaria work less well in older people. In fact, one study I found suggested that younger people were more likely to report side effects from taking malaria preventative medicine (see Mittelholzer et al., “Malaria prophylaxis in different age groups” in volume 3 of the Journal of Travel Medicine, published in 2006).

The only potential problem could be cross-reaction of the malaria drugs with other prescribed medicine. As such, I would recommend you enquire with your doctor prior to the trip, to ask about being prescribed drugs to prevent malaria that are appropriate for the region you are travelling to (probably Malarone, Lariam or doxycycline, since you will be travelling to an area with chloroquine-resistant forms of malaria) that furthermore won’t harmfully interact or have reduced efficacy when ingested alongside other medication you might already be taking.

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 Prevention

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Photo by Matthew Naythons, MD

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. [Read more…]

Malaria Treatment

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Malaria can be a severe, potentially fatal disease (especially when caused by Plasmodium falciparum) and treatment should be initiated as soon as possible.

Patients who have severe P. falciparum malaria or who cannot take oral medications should be given the treatment by continuous intravenous infusion.

Most drugs used in treatment are active against the parasite forms in the blood (the form that causes disease) and include:

  • chloroquine
  • atovaquone-proguanil (Malarone®)
  • artemether-lumefantrine (Coartem®)
  • mefloquine (Lariam®)
  • quinine
  • quinidine
  • doxycycline (used in combination with quinine)
  • clindamycin (used in combination with quinine)
  • artesunate (not licensed for use in the United States, but available through the CDC malaria hotline)

In addition, primaquine is active against the dormant parasite liver forms (hypnozoites) and prevents relapses. Primaquine should not be taken by pregnant women or by people who are deficient in G6PD (glucose-6-phosphate dehydrogenase). Patients should not take primaquine until a screening test has excluded G6PD deficiency.

How to treat a patient with malaria depends on:

  • The type (species) of the infecting parasite
  • The area where the infection was acquired and its drug-resistance status
  • The clinical status of the patient
  • Any accompanying illness or condition
  • Pregnancy
  • Drug allergies, or other medications taken by the patient

If you have or suspect you have malaria, you should contact your doctor immediately.

Source: Centers for Disease Control (CDC)