Today is World Malaria Day 2015, which highlights the continued fight against a disease that affects millions of people across the world. In this post, we’ve pulled together some facts and information from sources across the web.
Malaria is caused by parasitic protozoans and transmitted between people through the bites of mosquitos. The parasites belong to the genus Plasmodium, with four species causing malaria in humans: P. falciparum, P. vivax, P. malariae and P. ovale. The vast majority of malaria cases are caused by P. falciparum, which also causes the highest numbers of deaths. In 2013, the WHO estimated that there were 198 million cases of malaria, which resulted in an estimated 584,000 deaths.
The malaria parasites have a cyclical lifecycle that begins with the bite of a mosquito. At this point immature parasites known as sporozoites are injected into the blood; these travel through the bloodstream to the liver where they multiply asexually in liver cells, turning into the next stage of the parasites’ lifecycles, known as merozoites.
These merozoites burst out of the liver cells and re-enter the bloodstream where they go on to invade, reproduce and burst out of red blood cells. Some of these merozoites change again into the sexual forms of the parasite, known as gametocytes. Feeding mosquitos ingest these gametocytes, which reproduce and ultimately form new sporozoites, which travel to the mosquitos’ salivary glands, starting the cycle again.
Symptoms of malaria can vary between species, but they are split into two categories: ‘uncomplicated’, or ‘severe’. Severe malaria is a potentially fatal form of the disease that requires urgent medical attention.
Sadly, large swathes of those affected by malaria are unable to get the treatment they require. The majority of malaria cases are found in low- and middle-income countries, with the WHO estimating that 90% of all malaria deaths occur in Africa.
Malaria is spread by female mosquitos of the genus Anopheles. There are around 30 species of Anopheles mosquito capable of transmitting human malaria. Controlling the mosquito vector is an important weapon in the fight against malaria. Anopheles mosquitos bite at night, so the use of insecticide-treated mosquito nets (ITNs) is an effective way of controlling the disease. The use of ITNs has increased in sub-Saharan Africa over the past 10 years, with 49% of the population having access to one in 2014, compared to 3% in 2004. However, there is a worrying trend towards the mosquitos developing resistance to the insecticides used in the nets, with 53 countries around the world reporting resistance since 2010.
Another option to control the disease is to use drugs. The rediscovery of an ancient Chinese treatment for malaria, derived from the wormwood plant, revolutionised malaria treatment. Known as artemisinin, this compound is now combined with other drugs to form artemisinin-based combination therapies (ACTs). Sadly, in Southeast Asia, P. falciparum parasites resistant to artemisinin have been detected. The fight against resistance in this part of the world is expertly described in this article in Mosaic. If these resistant parasites are able to spread to other countries, particularly those in Africa, the effect will be disastrous.
Researchers have for decades been working on a vaccine for malaria. One vaccine has recently completed its final trials – although it has only shown partial efficacy, researchers hope that it will save the lives of thousands of children.
Each of these approaches has their merits and each their failings – what works for one area might not for another. There are numerous hurdles that need to be overcome if we are to defeat malaria. As recently as this week, researchers have suggested that there may have been an extra 10,900 malaria deaths in 2014 in West Africa, as local health services have struggled to cope with the Ebola outbreak.
On World Malaria Day 2015 the WHO will be announcing new strategic targets to tackle the disease, calling for a 90% reduction in cases and deaths in 2030 compared to today. In 2013, an estimated 584,000 died of the disease, mostly children under 5 years of age. That works out about one death per minute. The world has come a long way in the fight against malaria, but we’re not there yet.
The Society for General Microbiology has developed the fact file Malaria – A Global Challenge, and educational resource suitable for KS4 and post-16 students. You can find it here.