by Malaria Q&A
QUESTION
Is malaria infectious or noninfectious?
ANSWER
Malaria is considered an infectious disease because it can be transmitted from one person to another, via the bite of an infected mosquito. Since the parasite that causes malaria is passed through the blood, it can also be transmitted via organ transplant, blood transfusion, or via pregnancy (so-called “congenital” malaria).
by Malaria Q&A
QUESTION
Why are pregnant women and children at the highest risk of getting malaria?
ANSWER
The reason why pregnant women and children are at greater risk of contracting malaria is due to their reduced levels of immunity. Children living in malarial areas have less immunity than adults because they have had less exposure to malaria, and so their immune systems have not had a chance to develop antibodies to protect against the disease. Pregnant women, although they may normally have good immunity, witness changes in their immune systems during pregnancy in order for the woman to carry the child.
Given that a baby is genetically distinct from its mother, the mother’s immune system has to be modulated in order to ensure that the body’s defenses do not act against the baby, as they would some other foreign object such as an infection. While this immune modulation allows the mother to carry her foetus, it does leave her vulnerable to other infections, such as malaria. In areas of high malaria transmission, the mother may still retain enough immunity to not present with severe symptoms of malaria. In these cases, the dangers of malaria in pregnancy come from resulting anemia in the mother, as well as passage of malaria antigens or the parasite itself through the placenta and to the foetus, which can result in problems for the baby.
Interestingly, a study came out last year which showed evidence that using long-lasting insecticide treated bednets increased malaria prevalence in older children and adults, probably because the nets protected against even sub-clinical exposure to malaria and therefore the levels of natural immunity in people using the nets declined over time, leaving them more susceptible to infection. However, this result has been controversial, as in other studies community-wide coverage of bednets has reduced overall malaria incidence due to reduced transmission.
by Malaria Q&A
QUESTION
Can one get malaria through contact with the infected person or is it airborne?
ANSWER
Malaria cannot be transmitted through direct contact with an infected person, nor is it airborne! It is actually transmitted directly via the bite of an infected mosquito. Only certain female mosquitoes, of the genus Anopheles, can carry malaria. The mosquito picks up the malaria parasite (there are five different types of malaria that infect humans, though all are transmitted in exactly the same way) when it feeds on the blood of an infected person. The parasite then undergoes a cycle of reproduction in the mosquito, before new parasites migrate once again to the mosquitoes salivary glands. From here, they are able to escape into the blood of a new human host when the mosquito takes another blood meal by biting the person.
Since malaria is transmitted by blood, there have been a some reports of malaria transmission via organ donor or blood transfusion, though most countries now screen for malaria before using donated blood or organs. Additionally, if a pregnant woman gets malaria, the parasite can be passed to her baby either across the placenta or during delivery; this is called “congenital malaria”, and can be quite harmful to the baby. As such, and also because pregnant women themselves are especially vulnerable to malaria, many campaigns have dedicated themselves to providing pregnant women with long-lasting insecticide treated bednets and other measures to prevent and treat malaria.
by Malaria Q&A
QUESTION:
What are the drugs for a pregnant woman who has malaria for the first to third trimester?
ANSWER:
The treatment of malaria in pregnant women has become more challenging in recent years, as many types of malaria are developing resistance to the standard arsenal of drugs. In locations where the dominant form of malaria is still chloroquine-sensitive, chloroquine can be used safely throughout pregnancy.
However, given the high levels of chloroquine-resistance, other drug regimens may be required. Currently, first-line treatment options for uncomplicated malaria caused by Plasmodium falciparum (many strains of which are resistant to chloroquine), is quinine plus clindamycin (doxycycline is contraindicated in pregnant women). In the second and third trimesters, artesunate plus clindamycin can be administered, or the artemisinin-based combination therapy (ACT) commonly used in that region, although some of these combinations, particularly those containing artemether, have limited safety testing in pregnant women. In general, the paucity of controlled, randomized trials has posed a problem to creating safe and effective recommendations for the treatment of malaria in pregnant women.
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
by Malaria Q&A
QUESTION:
Can malaria spread from one person to another?
ANSWER:
Usually, no. In most cases, the malaria parasite has to first pass from a human host into a mosquito as the mosquito takes a blood meal, and then from the mosquito into another human via the mosquito’s saliva. This severely limits the amount of person-to-person transmission that exists. In fact, the only mechanisms for direct transmission between humans are when malaria parasites are passed between a mother and her unborn child via the placenta (congenital transmission) and through unscreened blood transfusions.
Congenital malaria is the more common type of human-to-human transmission; across various surveys of newborns in West Africa, between 8-24% were found to be infected with malaria parasites.
All four main species of human malaria (P. falciparum, P. vivax, P. ovale and P. malariae) have been implicated in congenital transmission. Infection with malaria during pregnancy not only puts the mother at greater risk of severe disease episodes (probably through reduced immunocompetence during pregnancy) but may also negatively impact the baby; although in endemic areas it is rare for babies to be symptomatic for malaria when acquired congenitally, even if they have parasitaemia, they have been shown to have a higher mortality rate than non-infected newborns. In non-endemic areas, babies with congenital malaria often display symptoms, which usually manifest themselves between 2 and 8 weeks after birth. Both quinine and artemisinin-based therapies have been successfully used to treat congenital malaria.
Malaria infection as a result of blood transfusion was first identified in 1911 and is one of the most common illness transmitted via transfusion, although the risk of being infected, particularly in non-endemic countries, is very low.
As it is difficult to screen blood directly for malaria infection, a number of standards have been put in place by blood-collection services to reduce the risk of obtaining blood containing malaria parasites. For example, in many places, you will not be allowed to donate whole blood if you have visited an endemic malarial region in the last three months, nor should you donate if you have previously had malaria unless you have been symptom-free for at least three years.
Due to the longevity of Plasmodium malariae in the blood, you are unlikely to be able to donate blood if you have ever been confirmed as positive for P. malariae. Serological screening of blood for malaria antibodies has recently been shown to be a sensitive method for testing for malaria in blood, although it is expensive and therefore not cost-effective for screening every sample, especially in non-endemic countries. However, it can be effective and efficient to avoid wastage when employed together with a travel-based questionnaire to ascertain donors who are high-risk for malaria.
It is worth mentioning that transmission of malaria via plasma only is very uncommon, and so frequent travellers or residents in malarial areas, who may be denied the right to donate whole blood, should ask about the possibility of donating plasma instead.
by Malaria Q&A
QUESTION:
A child of what age can be affected from cerebral malaria or malaria?
ANSWER:
People of all ages can be affected by malaria, which is what makes it such a public health burden in so many places.
Severe symptoms of the disease, such as the manifestation of cerebral malaria that you mention, can also be seen in children of all ages as well as adults. However, generally, younger children tend to have more serious attacks of malaria, and the disease is most deadly in children under the age of 5, who have not had a chance to build up natural, protective immunity to malaria. This lack of immunity is why malaria is also particularly severe in travellers, who have not been exposed during their childhood. Similarly, changes in the body’s immune response and blood chemistry during pregnancy make pregnant women, no matter what their age, very vulnerable to malaria infection.
QUESTION:
I am laboratories man. My question is the risk of P. falciparum especially for mother and children is very high. How can we reduce this risk?
ANSWER:
That’s a crucial question for malaria control. Certainly, as you say, the risk of severe malaria is much greater for young children and for pregnant women. As such, these high risk groups should be targeted during prevention campaigns, as well as for diagnosis and treatment.
There are several methods of prevention, which are suitable for all types of malaria, including P. falciparum. Probably the most effective, and also the most simple, is through the proper use of insecticide-treated bednets. These are often handed out at antenatal clinics to pregnant women, but ensuring that the nets are used properly is more difficult. Proper training, and emphasising that children and pregnant women will benefit most from reduced exposure to mosquitoes, is required. For more on the difficulties and challenges of bednet distribution, you can see Hugo Gouvras’ comment on an earlier question in this Q&A forum – see here: http://www.malaria.com/questions/free-malaria-bednet
The other main method for malaria prevention is through the use of prophylactic drugs, although these have to be taken every day, and so the cost is usually prohibitive for residents of malarial areas. In these areas, there have been successful trials of so-called SP IPT, which stands for sulfadoxine-pyrimethamine intermittent protective treatment. In this regime, malaria in pregnant women is prevented by administering intermittent doses of sulfadoxine-pyrimethamine; usually two doses during the pregnancy (one in the second and one in the third trimester), but monthly doses have also been tested. More frequent doses may be better for women who are also HIV positive, some studies have shown.
Intermittent preventative treatment has also been trialled on young children as a way of reducing the severity and frequency of malarial episodes when the child is most vulnerable. I’m not up to date on the most recent studies on this work, so will ask another one of our experts to comment on the efficacy of IPT, both in children and pregnant women.
Thanks for the question!