Review of Le Port A, et al. (2011), ‘Prevention of Malaria during Pregnancy: Assessing the Effect of the Distribution of IPTp Through the National Policy in Benin’, American Journal of Tropical Medicine and Hygiene, Vol 84 (Issue 2): pp 270-275
Is there malaria in North America?
QUESTION:
Are there malaria-infected mosquitoes in North America?
ANSWER:
North America is usually defined as including Canada, the United States and Mexico. Of these, Mexico has known regions of regular malaria transmission; specifically the regions bordering Guatemala and Belize in the south (Chiapas, Quintana Roo and Tabasco), rural areas in the tropical lowlands slightly further north (parts of Oaxaca, Nayarit and Sinaloa) and a very localised section of northern Mexico, located across the states of Chihuahua, Sonora and Durango. Travellers to these areas are recommended to take measures to prevent against malaria infection, such as minimising mosquito bites or taking prophylactic medication. Both P. falciparum and P. vivax are known to be transmitted in Mexico, so you should consult with a travel physician before deciding which form of preventative (prophylactic) medication to take, depending on the length of your stay, your budget and the type of malaria most commonly found in the area to which you are travelling.
Malaria was once also widespread in the southern USA, though a concerted public health campaign that started in 1947 (mainly consisting of reducing the number of mosquitoes through insecticide spraying and control of stagnant water bodies) greatly reduced transmission and led to the disease being considered eliminated by the 1950s. Occasionally, small pockets of transmission will be reported, though stringent diagnosis and treatment quickly places these outbreaks under control once more.
However, there are additional cases of malarial mosquitoes occasionally also reported even from northern parts of the United States and Canada; these are when mosquitoes are accidentally transported from malarial regions, for example in airplanes, in luggage or in shipping containers. These mosquitoes almost never transmit the disease to people, and in most temperate regions, do not live long enough to be a public health threat or to enable the persistance of the disease.
Causes of malaria, treatment with drugs and emerging resistance
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.
Do I have malaria?
QUESTION:
Hi, I went to Ivory Coast August/2003 back March/2004, took some pills to help prevent Malaria on my trip but ran out and did not get more. While I was there I got many mosquito bites.
Around October/03 became very sick, got tested for malaria at the hospital in Quebec but negative. Now May/2011 still have all the same symptoms, flu like symptoms, feeling cold most of the time, chills headaches, tired.
Is there any way I got it? I’ve gone to doctors and doctors and no one can seem to find what is causing this? I am tired of taking tylenols all the time for the body ache. My wife is from there and she’s so sure that I got it from seeing how I am since she’s been around it all her life. Can you help me?
ANSWER:
There are definitely types of malaria that can cause relapses of symptoms many months or even years after an initial infection. These types are not common in the Ivory Coast but if you had many mosquito bites then it is certainly possible that you were exposed. What kind of test did you have for malaria when you returned to Canada?
Often, the test is by looking at a microscope slide of your blood under the microscope—the problem with this test is that it is not very sensitive for low levels of malaria, for example, after the worst of infection, and especially with the types of malaria that cause relapse (these types, P. ovale and P. malariae being the ones you might expect from Ivory Coast, tend to cause less severe illness than the more common type of malaria in Africa, called P. falciparum, doesn’t relapse in the same way, but results in much higher levels of the malaria parasite in the blood, which makes it easier to diagnose on blood slides). Also, since malaria is relatively rare in northern countries like Canada, laboratory technicians are not as experienced at diagnosing the parasite as they are in countries where malaria is endemic.
Having said that, there are of course lots of other illnesses which also cause symptoms similar to that of malaria – fevers, chills, etc. What I would recommend is that you re-visit the doctor, and ask for a more sophisticated test for malaria. Mention that you have had a relapse of symptoms—this should prompt them to use more sensitive tests, such as PCR or a rapid diagnostic test, and to look specifically for P. ovale or P. malariae. Not only will this answer your question about whether you have malaria, but it will allow the doctors to give you the appropriate treatment for your current symptoms (probably chloroquine) as well as treatment to prevent any further relapses (primequine).
Hope this helps!
Causes of malaria
QUESTION:
What are the causes of malaria?
ANSWER:
Malaria is caused by parasites of the genus Plasmodium. These are single-celled animals known as protozoans (from the Greek ‘protos’ and ‘zoia’ which together mean ‘first animal’) and they are transmitted via mosquitoes that feed on blood; the parasites need both mosquito and human hosts to complete their life cycle (see below a graphic of the complete life cycle, courtesy of CDC). In the process of reproducing, the malaria parasites destroy human red blood cells, which is what causes the clinical symptoms of disease that the patient experiences, such as fever, headaches and nausea.
Generalized malaria life cycle (courtesy of CDC: www.cdc.gov)
There are four main species of Plasmodium that infect humans: P. falciparum, P. vivax, P. malariae and P. ovale. P. falciparum causes the most severe manifestations of the disease and is responsible for the majority of human deaths from malaria. There is a fifth type of malaria, P. knowlesi, which usually infects macaque monkeys but has been known to pass into humans as well.
For more on this, please see Christina Faust’s excellent blog post about her research.
Malaria in Malaysia
QUESTION:
Is there malaria in Malaysia?
ANSWER:
Yes, there is malaria in Malaysia, although efficient vector control campaigns, alongside a well-functioning health system which effectively diagnoses and treats malaria cases has vastly reduced the transmission of the disease in peninsular Malaysia at least. Transmission is still a problem in rural, interior areas, and especially in Sabah and Sarawak.
The history of malaria control in Malaysia is actually something of a success story; back in 1961, there were over 240,000 reported cases of malaria across the country; this was reduced to about 40,000 cases by 1980, due to the measures mentioned briefly above, and in 2008, that number had further dropped to only about 7,000 cases a year.
The fatality rate of malaria in Malaysia is also very low, being about 0.09%, or about 50 deaths a year, which is a testament to the effectiveness of national health systems at monitoring for the disease. Having said that, Plasmodium falciparum, the most severe type of malaria, is present in Malaysia—it was this that was responsible for all the reported fatalities in 2008. As such, if you are visiting or living in rural regions of Malaysia, where malaria transmission still is relatively high, it is recommended that you take preventative measures against the disease, such as sleeping under an insecticide-treated bednet, or taking prophylactic (preventative) medicine. This latter measure is usually only worthwhile if you are visiting a malaria area for a relatively short time, as the drugs can be quite expensive.
If you have visited these rural areas, and have symptoms of malaria, such as fever and chills, within two weeks of returning, you should go to the hospital or visit a physician immediately for diagnosis. If it is malaria, the doctor will be able to provide you with the most appropriate medicine for the type of malaria that you have.
What are the strains of malaria?
QUESTION:
What are the different strains of malaria?
ANSWER:
Malaria is caused by small, single-celled parasites called protozoans, and specifically ones of the genus Plasmodium. There are many, many species of Plasmodium, which infect a wide variety of different species, from lizards and birds to rodents, bats and primates. Of all the species of malaria, four main ones infect humans – these are P. falciparum, P. vivax, P. ovale and P. malariae. A fifth species, P. knowlesi, usually infects macaque monkeys in South East Asia but has been known to cross over to humans. Each of these species causes slightly different manifestations of the disease in humans, and even within the species, there are regional strains and variations. Probably the most distinct internal division within a malaria species is within P. ovale, where two sub-species are currently recognised: P. ovale curtisi and P. ovale wallikeri. These two forms are identical morphologically (that is, in the way they look under the microscope) but can be differentiated genetically.
Can malaria kill you?
QUESTION:
Can malaria kill you?
ANSWER:
YES! Malaria, especially of the kind caused by Plasmodium falciparum parasites, can be an extremely severe illness and even deadly. Somewhere between 700,000 and 1 million people die of malaria every year, and the majority of these are children under the age of five years old, which is the age group most susceptible to severe malaria attacks. Pregnant women are also at elevated risk, due to their compromised immune systems. Therefore, preventing malaria in young children and pregnant women is the single most effective way to reduce the number of malaria fatalities; in highly endemic areas, this is usually achieved through the distribution of insecticide-treated bednets, to sleep under at night to reduce mosquito bites, or preventative medication such as intermittent preventive therapy (IPT).
Given the seriousness of malaria, it is prudent to check with a doctor or go to hospital if you live in a malaria endemic area and come down with symptoms of the disease such as high fever, chills and nausea. The majority of malaria cases are easily treated with oral medication, given swift and accurate diagnosis.
Treating Malaria by Health Extension Workers: A Case Study from Ethiopia
For many years the World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF) have been promoting an Integrated Management of Childhood Illness (IMCI) training package to ensure that nurses and doctors are capable of treating sick children at health facilities. Over the years, with the realization that many children did not have access to health facilities and therefore were not being ttreated, the two organizations published a Joint Statement on Managing Pneumonia in Community Settings (2004)[1]. This groundbreaking document calls on countries to bring treatment of childhood illness – pneumonia as well as malaria and diarrhea closer to communities that need it, by empowering trained community health workers to identify and manage these problems. Many countries have followed this advice with excellent results. Here is a story from Ethiopia.
Aminata is a health extension worker (HEW) at the Tebisa health post, located in a rural, hilly area of East Amhara, some 400 kilometers away from Addis Ababa, the capital city of Ethiopia. Aminata received training on integrated community based management of common childhood illnesses (iCCM) in early 2011. After the training, she carried the essential materials and supplies with her back to the health post, and started treating children suffering from pneumonia, malaria, diarrhoea and/or severe acute malnutrition. In the last two months, she has treated 35 children under five.
- A Health Extension Worker (HEW) with Almaz and her family. Photo: Dr. L. Pearson
One of the children suffering from malaria is a five year old girl, Almaz (which means diamond in Amharic). She developed fever one night in April. Her mother took her to the health post and she was seen immediately. Aminata checked her temperature (39.0 OC), and respiratory rate (children sometimes have pneumonia and malaria at the same time) and pricked her finger to obtain a drop of blood to perform a Rapid Test for Malaria (RTM) to look for malaria parasites [Ed: Rapid Diagnostic Tests, or RDTs, are another, more general term for these tests].
Almaz did not have rapid breathing, an indication of pneumonia, but she did have falciparum malaria (the most severe and deadly of the types of malaria found in humans, and caused by the Plasmodium falciparum parasite). She was given Coartem (Arthemeter-Lumefentrine) treatment by mouth for three days. Aminata gave the first dose of medicine and gave the mother the rest of the tablets, explaining when to give them. Aminata made a point to discuss how important it is to feed a sick child so they do not lose weight, and to be alert to certain ‘danger signs’ in case the child is not getting better, in which case they should return immediately to the health post.
On the second day of treatment her mother brought her back to the health post for a follow up check. Almaz’s mother expressed her gratitude. “If the HEWs are not providing treatment for sick children, I would have to carry Almaz to the health center some 4 hours away by foot. I would also have to pay for the treatment. We were frustrated before iCCM started because we were not able to help children with malaria and pneumonia”.
- Malaria medicine available, for free, at the Tebisa health post in Ethiopia. Photo: Dr L. Pearson
“The communities trust and support us even more now”, said Aminata. “Now the mothers are so happy, they even bring the children for immunization without us having to push them”.
In the next two years, about 20,000 HEWs will be trained and supported to provide iCCM in 10,000 rural villages. Hundreds and thousands of young children in Ethiopia will benefit from the iCCM programme jointly supported by the government of Ethiopia, Catalytic Initiative of Canada, UNICEF and other development partners. Program implementation will focus on remote and harder to reach villages and households, to ensure every child is covered, no matter where they are and who they are.
The iCCM is be an important opportunity to further improve quality of care provided at the health posts, and accelerate toward the achievement of Millennium Development Goal 4, to reduce deaths of children under 5 by two-thirds by 2015.
Wolbachia Bacteria Reduce Parasite Levels and Kill the Mosquitos that Spreads Malaria
Wolbachia are bacteria that infect many insects, including mosquitoes. However, Wolbachia do not naturally infect Anopheles mosquitoes, which are the type that spreads malaria to humans. Researchers at the Johns Hopkins Bloomberg School of Public Health found that artificial infection with different Wolbachia strains can significantly reduce levels of the human malaria parasite, Plasmodium falciparum, in the mosquito, Anopheles gambiae. The investigators also determined that one of the Wolbachia strains rapidly killed the mosquito after it fed on blood. According to the researchers, Wolbachia could potentially be used as part of a strategy to control malaria if stable infections can be established in Anopheles.
“This is the first time anyone has shown that Wolbachia infections can reduce levels of the human malaria parasite (Plasmodium falciparum) in Anopheles mosquitoes,” said Jason Rasgon, PhD, senior author of the study and associate professor with the Johns Hopkins Malaria Research Institute and the Bloomberg School’s W. Harry Feinstone Department of Molecular Microbiology and Immunology.
For the study, Rasgon and his colleagues infected Anopheles gambiae mosquitoes with two different Wolbachia strains (wMelPop and wAlbB). After infection, Wolbachia disseminated widely in the mosquitoes and infected diverse tissues and organs. Wolbachia also seemed to actively manipulate the mosquito’s immune system to facilitate its own replication. Both Wolbachia strains were able to significantly inhibit malaria parasite levels in the mosquito gut. Although not virulent in sugar-fed mosquitoes, the wMelPop strain killed most mosquitoes within a day after the mosquito was blood-fed.
“These experiments show that Wolbachia could be used in multiple ways to control malaria, perhaps by blocking transmission or by killing infected mosquitoes,” said Rasgon.
Worldwide, malaria afflicts more than 225 million people. Each year, the disease kills nearly 800,000, many of whom are children living in Africa.
In addition to Rasgon, the authors of “Wolbachia infections are virulent and inhabit the human malaria parasite Plasmodium falciparum in Anopheles gambiae” include Grant Hughes and Ping Xue of the Johns Hopkins Malaria Research Institute, and Ryuichi Koga and Takema Fukatsu of the National Institute of Advanced Industrial Science and Technology in Tsukuba, Japan.
Funding was provided by the Johns Hopkins Malaria Research Institute and the National Institute of Allergy and Infectious Diseases. The study is published in the May 19, 2011 edition PLoS Pathogens.
Source: Johns Hopkins Bloomberg School of Public Health