Bio-larvicides

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QUESTION

Why is there no mention here of all the work being done on biolarvicides – the low cost solution for malaria control?

ANSWER

Actually, we had a question a while ago about the ECOWAS program in West Africa, which centers around the use of biolarvicides. A link to that question, and the answer, is provided here: http://www.malaria.com/questions/ecowas-malaria.

The most common form of biolarvicides are those using various microbes, notably Bacillus species, which target mosquito larvae but are harmless to other non-target organisms. A recent study in the Gambia showed very high success rates in killing Anopheles gambiae larvae, when a microbial larvicide using Bacillus thuringiensis var. israelensis strain AM65-52 was applied weekly. Some practitioners are concerned about the amount of effort and man-power a weekly application of larvicide might require, plus the training necessary for correct identification of habitat, but the study in the Gambia seemed to show good compliance once personnel were suitable trained. A link to the study, which is freely available via the Malaria Journal, is available here: http://www.malariajournal.com/content/6/1/76.

 

What measures can local people take to limit malaria infection?

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QUESTION

What measures can local people take to limit malaria infection?

ANSWER

People living in malarial areas can do a lot to protect themselves from getting malaria.  There are community programs for vector control (to control or eliminate mosquitoes) that include draining swamps to remove mosquito breeding habitat, spraying with insecticide, and using biological control techniques. In addition, to prevent  people from getting mosquito bites,   communities can educate families to screen their windows (if possible), to sleep under long lasting insecticide treated bednets, to cover their arms and legs with clothing  and to avoid being outdoors during dawn and dusk when mosquitoes are biting. Communities can also educate people to identify signs and symptoms of malaria and to seek early treatment to avoid serious disease and possibly death.  See Malaria Prevention and Control for more information.

Mosquito Larvae Eradication

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QUESTION

What measures can be taken to eradicate mosquito larvae?

ANSWER

The main methods to control mosquito larval populations are by reducing areas available for adults to breed and also directly killing larvae. So, for example, adult mosquitoes need standing, stagnant water in order to lay their eggs. Getting rid of these sources of standing water, for example by filling in unwanted ditches and removing empty containers that can become filled with rainwater, therefore reduces the available breeding habitat for mosquitoes. Similarly, dripping a small amount of oil on top of standing water creates a thin film of oil over the surface of the water, preventing adults from laying eggs. In addition, the oil prevents the larvae from gaining access to air, suffocating them and killing them. There are other methods for killing larvae too. Directly spraying insecticides onto water is one method, but often not very specific, and can have a negative effect on other forms of aquatic life. One popular method for biocontrol is to introduce other animals which eat mosquito larvae, thus keeping numbers down. Examples include certain species of fish, as well as small crustaceans called copepods.

P. knowlesi versus P. falciparum: Treatment and Prevention

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QUESTION

I would like to know about the P. knowlesi – treatment compared to P. falciparum? preventive medicine?

ANSWER

At this point in time, P. knowlesi is completely susceptible to chloroquine, and so can be treated successfully using this drug. P. falciparum, on the other hand, is known to have widespread resistance to chloroquine, and so the World Health Organization recommends that chloroquine should not be used to treat P. falciparum malaria. Instead, for non-complicated malaria, the WHO recommends treatment with artemisinin-based combination therapies (ACTs). These drugs can also be used against other forms of malaria, including P. knowlesi, particularly if the hospital also treats cases of P. falciparum regularly and so has supplies of ACTs on hand. One study even showed that treatment with ACTs (specifically artemether-lumefantrine) was more effective than chloroquine in treating P. knowlesi. Severe cases of either infection should be treated with intravenous artesunate or quinine.

Prevention for both is roughly similar – chemoprophylaxis should be taken by people travelling to an area where transmission of these types of malaria occurs. However, given P. knowlesi‘s susceptibility to chloroquine, this drug is effective as a prophylactic for this malaria species, whereas it is not appropriate for P. falciparum, given high levels of resistance. In terms of prevention of mosquito bites, this differs due to the types of mosquito vectors each of these species of malaria uses. P. knowlesi is only found in south-east Asia, where the mosquitoes that transmit it tend to be forest dwelling. As such, people who spend time in the forest in the evening and at night are most at risk of contracting P. knowlesi. Wearing long-sleeved clothing and insecticide while in the forest may help prevention in this case. P. falciparum is found throughout the world, and uses many different species of mosquito vector. In Africa, the mosquitoes which transmit P. falciparum tend to rest indoors and thus bite people at night while they are sleeping. Therefore, in these settings, it is especially beneficial to sleep under a long-lasting insecticide treated bednet. Indoor residual spraying, which coats the inside walls of a house with insecticide to kill indoor-resting mosquitoes, can also be beneficial.

Mosquito Larvae Eradication

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QUESTION

What measures can be taken to eradicate the mosquito larvae?

ANSWER

The usual, traditional method of eradicating mosquito larvae is through the application of insecticides. However many of these are known to have severe negative effects on water quality, particularly through being non-selectively toxic and therefore killing lots of other aquatic life as well as the mosquitoes. Moreover, some are known for their effects on animals further up the foodchain; the most famous example of this being DDT, which was used to kill adult mosquitoes. It was discovered that this pesticide resulted in birds laying eggs that had very thin shells, preventing the chicks from hatching successfully. As such, it was banned in most developed countries. Modern insecticides used for mosquito larva reduction have been developed to target mosquitoes specifically; a popular one in the USA is methoprene, which interferes with the mosquitoes’ growth hormones, preventing development into adults. Microbial compounds, which are not dangerous to other organisms, are also sometimes used.

Another approach is through the use of natural enemies of the mosquito larvae, notably certain species of fish and dragonflies. These will eat mosquito larvae and pupae, thus naturally reducing numbers, and with little undue effect on water quality (although in some contexts, such as reservoir water, there may be concerns with stocking the water source with large numbers of fish).

Community Based Management for Malaria

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QUESTION

what are the methods for community based management for malaria?

ANSWER

Community-based management of malaria revolves around three main principles: prevention, diagnosis and treatment.

Prevention mainly revolves around stopping mosquitoes from biting people. Methods for this include distribution of long-lasting insecticide treated bednets (and teaching people to use them properly!), indoor residual spraying to stop mosquitoes from living in houses, screening houses properly and removing sources of stagnant water from the community to stop mosquitoes from breeding. Collectively, these methods are considered “vector control”. They have benefit for the individuals who practice the methods, as well as collective benefit at the community level from reduced transmission. Within the community, pregnant women and young children, who are most at risk of severe infection, are often targeted for preventive measures. In addition, transmission of malaria from a pregnant mother to her unborn child can be prevented through chemoprophylaxis, administered usually twice during pregnancy, in a process known as intermittent preventive therapy (IPT).

Diagnosis and treatment involves educating people about the symptoms of malaria so that if they suspect they are infected, they know how and where to seek appropriate medical care. The community therefore has to provide a clinic or hospital that is sufficiently equipped to do accurate diagnosis, which requires blood testing. Clinicians should also be able to identify which type of malaria the patient is infected with, since this determines treatment. Identification of the type of malaria is usually done via looking at the blood of the patient under a microscope, a process which requires a significant amount of training. The type of treatment depends on the severity of infection as well as the type of parasite they are infected with.

All of the above interventions depend on sustained investment in community health care, training of local health workers and clinicians and education the community about the transmission of malaria and how this can be interrupted.

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.

Socio-Economic and Environmental Conditions Contributing to Malaria

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QUESTION

what socio-economic and environmental conditions contribute to the disease?

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.

Where Does Malaria Occur?

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QUESTION

Where does malaria occur?

ANSWER

Malaria has at some stage or another occurred on every continent of the world except Antarctica. Currently, cases of human malaria are mainly found in Central and South America, parts of the Caribbean, sub-Saharan Africa, parts of the Middle East, south Asia, south-east Asia, and the Pacific Islands of Oceania. Control efforts, mainly consisting of reducing populations of vector mosquitoes, has eliminated transmission from North America, most of Europe, most of North Africa and parts of the Middle east and Asia. Currently, the vast majority of malaria mortalities occur in sub-Saharan Africa, and mainly in children under the age of five.

How to Prevent Malaria

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QUESTION

How to prevent malaria?

ANSWER

There are a number of ways to prevent malaria. These can be placed into two categories: medication and vector protection.

For medication, there are drugs you can take to prevent the malaria parasite from developing after someone is bitten by an infected mosquito. These drugs are known as “chemoprophylaxis.”

There are several different kinds, such as doxycycline, mefloquine (marketed as Lariam), atovaquone-proguanil (marketed as Malarone) and chloroquine—the type you use depends on the type of malaria present in the area. For example, in much of Africa and India, malaria is resistant to chloroquine, so this cannot be used as a prophylactic. In parts of Thailand, resistance to mefloquine has emerged. However, if the appropriate type of prophylaxis is used, it is very effective against malaria.

The problem is that these drugs have not been tested for long-term use, can be expensive and may have side-effects. Therefore they are of limited use for people who live in areas where malaria is endemic, and are more appropriate for travelers who are in malarial areas for short amounts of time. However, anti-malarial medication may be used in a very specific way for people at particularly high-risk for malaria, such as pregnant women and young children. In these cases, the high-risk individuals receive a dose or series of doses of malaria medication in order to prevent malaria. This form of prevention is known as intermittent preventive therapy (IPT).

Vector prevention involves protecting oneself against getting bitten by mosquitoes. This can involve wearing long-sleeved clothing in the evenings and at night, when malaria mosquitoes are most active, or wearing insect repellent on exposed skin. Indoor residual spraying, whereby repellent and insecticides are sprayed inside the house, can also be used to bring down the number of mosquitoes.

Another very effective technique for preventing malaria is to sleep under a long-lasting insecticide-treated bednet. The mesh acts as a barrier against the mosquitoes, and the insecticide impregnated in the mesh further repels the mosquitoes and prevents them from biting through the mesh.