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).

Repellent for Malaria Mosquitos

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QUESTION

My daughter is leaving for Africa for 5 weeks on a mission trip. Is there a repellent that can be used to ward off these infected mosquitos? Also what can she do to stay safe and protected?

ANSWER

There is no way of warding off only those mosquitoes that are infected with malaria. However, insect repellents which contain DEET (10% or higher) are the most effective against the species of Anopheles mosquito that carry malaria.

From personal experience, I can tell you that “natural” insect repellants that do not contain DEET are just not as effective against these mosquitoes. Your daughter can also spray her clothing with permethrin, which repells insects, and she should wear long-sleeved clothing in the evenings, early mornings and at night, when the malaria mosquitoes are most active. She should also try to sleep every night under a long-lasting insecticide treated bednet, which drastically reduces the number of bites.

In addition, your daughter should look into taking anti-malarial preventative medication, known as malaria prophylaxis. There are a number of different types; the two most commonly recommended for Africa are doxycycline (cheap, effective, but can cause sun sensitivity and so people taking it must be vigilant about using sun block! It also needs to be taken for four weeks after leaving the malarial area) and atovaquone-proguanil (sold as Malarone—this is effective, and has very few side effects, but is often very expensive. It only needs to be taken for a week after returning home), both of which are taken as a daily pill with food.

Malaria in Burkina Faso

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QUESTION

(1)What drug is administered in the first 24 hours after malaria symptoms onset. What side effects have this/these drugs.

(2) I it is not possible to reach a treatment facility etc until 7 days after initial chills, fever etc and there are no symptoms remaining other than tiredness what is the drug of choice?. Local people say it is malaria but there is no diagnostic facility near the location until a week has passed.

The person in question is visiting in Burkina Faso where malaria is endemic. Standard anti malaria treatment was taken, but we are told that this is not always effective.

ANSWER

1) In most parts of sub-Saharan Africa, due to the spread of chloroquine-resistant strains of Plasmodium falciparum (the most widespread and deadly form of malaria), the first-line treatment for uncomplicated malaria infection are artemisinin-based combination therapy (ACTs) drugs, which combine artemisinin or a derivative (such as artemether) with another anti-malarial drug.

One very common combination is artemether with lumefantrine, which is often marketed as Coartem. ACTs have few common side effects, and very few severe ones, but mild side effects which are reported include nausea, dizziness, loss of appetite and vomiting. One severe side effect that has been reported is allergic reaction.

2) If a patient has had suspected malaria but seems to have recovered, they should probably present themselves to a clinic or physician for a blood test. This will determine whether the patient is still currently suffering from malaria; if so, they will probably still be treated with Coartem or another ACT as above. If there is no trace of the malaria parasites in the blood, the patient might want to try a rapid diagnostic test which looks for antibodies to the malaria parasite; this will tell them if they did in fact have malaria before. Some tests can also differentiate between Plasmodium falciparum and other forms of malaria.

This is important because if they test positive for P. vivax or P. ovale, there is a possibility that the malaria parasites are still present in the liver, in a dormant form, even once all the parasites are gone from the blood stream. In this case, the patient may want to consider talking to their doctor about taking primaquine, which kills the dormant liver stages of the parasites.

People with G6PD deficiency cannot take primaquine so in some cases a G6PD deficiency test may be required first. If the patient is found to have had Plasmodium falciparum, but no active infection appears in the blood, they should still monitor their health carefully for several weeks, and perhaps take malaria preventative medication such as doxycycline or Malarone; even after symptoms cease, in some cases a small number of P. falciparum parasites can remain in the blood, at concentrations too low to be seen under the microscope, but which can then flare up at a later date and cause symptoms to reappear. This is called recrudescence; once symptoms reappear, the patient should immediately seek a diagnosis from the doctor to confirm it is malaria, and then take treatment.

Malaria in Thailand: Phrae and Nan

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QUESTION

We are traveling in Phrae and Nan (in Thailand) in the period of December-Januar. Is there any risk for malaria. We are travelling with kids (9 months, 6 and 8 year) and want to avoid risky areas. Can we travel safely in that region? Thank you for your reply.

ANSWER

Thanks for your question. Phrae and Nan are two districts in northern Thailand—the latter shares a border with Laos. While most of the very touristy destinations in Thailand (i.e. Bangkok and the coastal regions) are considered to have very low levels of malaria, and perhaps no transmission at all, I’m afraid that the areas bordering Laos, Myanmar and Cambodia do have malaria and so if you visit, you should take appropriate preventative precautions.

It is worth noting that some parts of Thailand are known to have mefloquine (sold as Lariam) and chloroquine resistant strains of malaria, although I have just looked it up and it doesn’t appear that Phrae and Nan are within these regions. However, it would still be worth seeing a physician or visiting a travel clinic to get specific advice for your family, and particularly what anti-malarials are appropriate for your children—a lot of that will depend on personal preference, such as how frequently you are comfortable taking medication and also how much you are prepared to spend.

Some, such as Lariam, are also frequently associated with side effects, which may affect your decision. If you do take anti-malarials on your trip, please take the Malaria Medication Side-effects Survey: Treatment and Prophylaxis. We are trying to collect information from travellers to record people’s experiences with the different types available.

In addition to preventative anti-malaria medication (known as prophylaxis), there are other preventative measures you can take, such as sleeping under a long-lasting insecticide-treated bednet, wearing long-sleeved clothing (especially in the evenings and at night when malarial mosquitoes tend to bite) and using insect-repellent on any exposed skin. You can also spray clothing with permethrin, a chemical which repels insects and prevents them from biting through thin cloth.

Antimalarial Drug Therapeutic Life

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QUESTION

Why do some antimalarial drugs have long therapeutic life while others have short therapeutic lives?

ANSWER

Different anti-malarial drugs target slightly different aspects of the malaria Plasmodium parasite, and so are made with different chemical structures.

The differences in therapeutic life across different malaria drugs has to do with the specific pharmacokinetic properties of the chemical compounds from which the drugs are made. Even drugs designed around the same principal chemical compound can persist for different amounts of time in the human body, depending on the other chemicals with which the active compound is bound. The length of time it takes for a chemical compound to halve in concentration, or for its pharmacological effect to reduce by half, in the human blood stream is known as its “half life.”

For example, the common anti-malarial drug chloroquine has a half life of about 10 days, and is based on a chemical compound called 4-aminoquinoline. However, another drug also based on 4-aminoquinoline, called amodioquine, has a half life of only 10 hours.

Proguanil (combined with atovaquone in the drug Malarone) is dihydrofolate reductase inhibitor with a half life of about 16 hours, while mefloquine (sold as Lariam), is made from quinoline methanol and has a half life ranging from 10-40 days. These differences in length of therapeutic action also affect the efficacy of the compounds against malaria at various stages in its progression, and can also be implicated in the propensity to resistance developing to the drug in the malaria parasite.

Child with Fever – Malaria Symptoms?

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QUESTION

Three yrs old boy having fever every 20 days for past 5 times. Remains for 2-3 days. Can it be malaria?
Never got blood tested.

ANSWER

Recurrence of malaria every 20 days is not that common, but could be caused by two different events: (1) true relapse, whereby the boy is infected with either Plasmosium vivax or Plasmodium ovale, and the parasite is disappearing from his blood but re-emerging from dormant forms in the liver (called hypnozoites), or (2) what is known as recrudescence, whereby the parasite never disappears fully from the blood, but reduced enough to stop symptoms from being felt, then flares up again.

Both options can be treated, but require a blood test, to ensure that malaria is the correct diagnosis and also to distinguish between options 1 and 2 above, and different treatment will be required.

A blood test should be performed during a period where the boy is experiencing symptoms, as with both options above, if the infection is not “active” (i.e. few or no parasites are visible in the blood) a blood test may prove negative. Rapid diagnostic tests which look for antibodies might be a good choice in this instance, as they may detect even a non-active infection.

My Malaria Refuses to Go Away

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QUESTION

The symptoms started about 2 months ago and I have used all kind of drugs. I have completed lumartem dose twice and I have used Coartem, I even took chloroquine injection and I am well for a few days and it comes back to the way it use to be, because of so many antibiotics I have taken I now have swellings in my body and in my leg and its making my leg ache and making walking difficult. What do I do?

ANSWER

Are you sure you have malaria? The most important thing is to get diagnosed accurately, either at a clinic or by a trained diagnostician. The most common form of diagnosis is a blood film on a slide, read under the microscope, but this can require expertise for accurate diagnosis. Another option is a rapid diagnostic test, now available in many places, which tests for the antibodies to malaria.

In my experience, in many places clinics will diagnose malaria purely on clinical symptoms, such as fever, which actually are very general to many diseases and so not necessarily mean malaria! So if you have been diagnosed without a blood test, go back to the clinic/doctor and demand a blood test.

There are no known strains of malaria that are resistant to Coartem which is why I suspect you may have something else, perhaps in addition to the initial malaria infection. Moreover, the drugs used to treat malaria are not antibiotics, and should not result in swollen legs; again, you should see a doctor or clinician before taking any further medication.

Malaria Medication Side Effects

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QUESTION

My mother is an old patient of arthritis. She has also had a long stint with asthma and tuberculosis. She has presently been diagnosed with urine infection but was treated with malaria medicines artesunate and primaquine phosphate.

What side effects could she possibly develop by wrong administration of malaria medicines?
ANSWER

Luckily there are few major side effects associated with either artesunate or primaquine. Mild side effects of the former include ones similar to malaria: nausea, headache, loss of appetite and vomiting. Side effects of primaquine are very similar to this, but can also include intense itching and anemia in some people (mainly of Mediterranean or African descent). The main thing to be aware of with primaquine is that it can be dangerous for people with G6DP deficiency, so patients should be tested for this before taking primaquine.

How soon can I take Coartem if I suspect Malaria?

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QUESTION

Does one have to wait for the symptoms of Malaria to show before taking Coartem? Will the Coartem still be effective in killing the malaria before it has entered the red blood cells and the fever has broken?

ANSWER

I believe that Coartem is only effective against the blood form of the parasite, hence why it is not effective in treating the liver forms of Plasmodium vivax and Plasmodium ovale.

More to the point, if you don’t have symptoms of malaria you shouldn’t take any medication to treat it—improper use of treatment medication can lead to resistance to Coartem developing in the malaria parasite, which would be a tragedy as it is currently the front-line treatment for many millions of people affected by malaria around the world.

On a personal level, taking Coartem unnecessarily can also lead to unpleasant side effects. As such, you should always get tested and diagnosed as positive for malaria before taking treatment. As a rule of thumb, if you don’t have symptoms, you probably don’t have malaria (though if you live in a highly endemic area, you may be able to tolerate a certain burden of malaria without symptoms…but then you would also be very familiar with the symptoms). Generally speaking, testing asymptomatic people isn’t worthwhile.

Can malaria affect one’s mental fitness?

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QUESTION

Can malaria affect ones mental fitness?

ANSWER

Given that malaria is often associated with severe fever and flu-like illness, I would say that is usually enough to prevent someone from feeling completely mentally fit! However, in addition to these general symptoms, there are other specific ways in which malaria can affect a patient’s mind.

With a particular type of malaria, called Plasmodium falciparum (the most common form in Africa and the most deadly worldwide), the disease can sometimes progress to what is called cerebral malaria, where the malaria parasite stick to red blood cells that clog up the tiny red blood cells in the brain. This condition is very serious, and can lead to impaired mental function, loss of consciousness, coma and even death.  Luckily, these effects are usually reversible and there are rarely permanent mental consequences of infection with malaria if treated promptly and effectively.