Malaria is a life-threatening tropical disease spread by mosquitoes in more than 100 countries around the world. This article is part of a two-part series related to malaria and resistance to the disease. In this article, I will explain the symptoms of malaria and how it can be treated, before moving on to the science behind how it spreads both around the body and between humans. I will finally conclude by evaluating different methods for its prevention in LIDCs (Low-income Developing Countries). Next week's article will then explore sickle cell anaemia, firstly by explaining what it is. I will then explore how sickle cell anaemia can give people resistance against malaria and why that is.
Like most illnesses, if malaria is not recognised and treated early it only gets worse, making early detection and treatment essential for survival. Symptoms of malaria include fever-like symptoms such as high temperatures, shivering, headaches and muscle pains, as well as vomiting and diarrhoea. However, as I explain below, the onset of these symptoms only occurs between 7-18 days after infection, thus reducing the time available to react to the illness.
As such, if you live in or plan to travel to at-risk areas (especially tropical areas in Africa, Asia, Central and South America) you are well-advised to stay alert for these symptoms, as well as take appropriate precautions to reduce the risk of infection. As such, the NHS advises travellers to prevent mosquito bites by using insect repellent and covering any exposed skin, as well as taking antimalarial tablets.
Providing that malaria is diagnosed early, survival rates are very high, with virtually everyone being able to make a full recovery. Treatment of malaria is generally carried out by carrying out a blood test to confirm a diagnosis of malaria, followed by prescribing a course of antimalarial tablets (such as doxycycline). The exact treatment given, however, varies as it depends on the type of malaria you have as well as on other factors such as age and the severity of your symptoms.
Contrary to popular belief, malaria is not a disease caused by the species 'mosquito'. Instead, 40 mosquito species of the Anopheles genus are vectors for 5 different species of Plasmodium (a unicellular parasitic protozoan). All that needs to happen for someone to be infected with malaria is to be bitten by a female Anopheles mosquito infected with the Plasmodium parasite.
Plasmodium exhibits three life-cycle stages - gametocytes, sporozoites and merozoites. Gametocytes are the initial form of the protozoa which are found in the mosquito vector. The gametocytes then develop into sporozoites, a motile inactive form of the Plasmodium. These sporozoites are then transmitted to humans through the saliva of mosquitoes feeding on the human bloodstream. The sporozoites then spread through the bloodstream to the cells in the liver called the parenchymal cells (the cells that make up the functional tissue of the organ). In these liver cells, the sporozoites then reproduce asexually forming thousands of merozoites which saturate the parenchymal tissue of the liver. While this originally causes no symptoms, after 7-10 days the merozoites are released back into the bloodstream where they infect red blood cells before replicating inside them asexually to produce 8 to 24 infective merozoites, before bursting and infecting fresh red blood cells with merozoites.
Moreover, some of these merozoites can also leave this asexual reproduction cycle. This occurs when the merozoites in an infected blood cell develop into sexual forms of the protozoa - gametocytes. These gametocytes are then taken up by an uninfected mosquito when it bites an infected human. Once ingested, the gametocytes continue to develop, forming gametes. Fertilisation then occurs and sporozoites develop, beginning the replication cycle all over again.
Malaria kills by catastrophically affecting your red blood cells. Once infected, red blood cells are no longer as elastic as they should be. For that reason, they don't fit properly through the capillaries, clogging up the vessels, leading to organ failure. Because the degree of clogging is dependent on the number of infected blood cells, a greater parasitic count in the blood leads to a higher chance of death.
Furthermore, as the red blood cells are more elastic, they are also more fragile. This property decreases the lifespan of the red blood cells. While in a healthy human, red blood cells last between 100-120 days, infected cells can last for as little as 48 hours. As a result of the haemolysis (red blood cells bursting and spilling their contents into the surrounding environment), the body's capacity to carry oxygen around the body is drastically reduced, leading to fatigue, shortness of breath, anaemia and, in extreme cases, organ failure.
Malaria can be treated with many different kinds of prescription medications. According to Mayo Clinic, the antimalarial drugs used depend on the strain of malaria the patient has, their age and the severity of their symptoms. Different medicines can also be used in those who are pregnant so that the risk to the foetus is reduced. The preferred medication for treating malaria is chloroquine phosphate. However, since some malarial parasites are resistant to this drug, artemisinin-based combination therapies can also be used.
One of the most effective methods of preventing malaria in LIDCs is the distribution of insecticide-treated mosquito nets. Not only are they relatively cheap (around $2 per net), meaning that a large number of nets can easily be distributed, but they are also very effective. This is because the insecticide-treated net provides a physical barrier between humans and mosquitoes. The insecticide is also effective at killing the mosquitos, thus reducing the number of mosquitos in the local area. Indeed, the World Health Organisation estimates that in 2017 about half the population living in areas at risk of malaria in Africa were protected by these nets. Nevertheless, there are setbacks to this method. Without proper training in how to use these nets, incorrect use can severely limit their effectiveness. Furthermore, in areas such as Tanzania, these nets are often used as fishing nets. This significantly harms marine life and, as such, I suggest that the international community provide aid, to make up for the fact that the local water's fish population has been depleted by foreign trawlers meaning local fisherman have to use larger nets to catch enough fish, as well as provide education to locals on sustainable fishing.
Insecticides are also sprayed indoors to reduce malaria transmission. While this is effective, the World Health Organisation notes that the usage of this technique has decreased recently, from 5% in 2010 to 3% in 2017. Furthermore, increased use of insecticides can also be dangerous as it can lead to insecticide resistance. As such, I would suggest that their use should be limited and only be used in areas with a very high risk of malaria.
Governments also need to track malaria outbreaks in their own country and utilise the information that their data provides then, taking action to curb outbreaks before they become too serious. Currently, LIDC governments generally have fairly poor surveillance systems in place to track malaria outbreaks in their countries. Because of this, improving them is definitely essential to combating malaria as, without an effective system in place to track malaria outbreaks, it is very difficult to deploy targeted treatment to those areas.
In conclusion, I would contend that a comprehensive overhaul of malaria treatment in these areas should take place. While the current systems are effective, especially the distribution of insecticide-treated nets, more needs to be done to ensure they are only used for their intended purpose. Moreover, governments in malaria-prone areas must ensure that they can quickly detect malaria outbreaks in their countries as, without doing so, treatment can not be deployed. Nonetheless, the international community should also provide aid and support in combating malaria in LIDCs as, by doing so, not only can we reduce death rates in those areas, but we can also ensure people can stay in work longer, leading to a higher quality of life for society and resulting in a more prosperous country.
Make sure to subscribe to my mailing list so that you get notified when I publish 'part 2' next week about sickle cell anaemia. Thank you for taking the time to read this week's article! Sources;
Schlagenhauf-Lawlor P (2008). Travelers' Malaria. ISBN 978-1-55009-336-0. - Page 71
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