25 Apr 2019

World Malaria Day

First off, Happy World Malaria Day! A day that allows us to recognize all those globally who have worked tirelessly to find a cure for Malaria.

In 2016, there were an estimated 216 million cases of Malaria leading to about 445,000 deaths, according to the CDC. Ninety percent of those cases were present in the WHO African Region. Fortunately, from 2010 to 2016 the mortality rate for malaria has been cut by nearly 25%, which is a step in the right direction. The disease continues to prove detrimental to the lives of individuals living in poorer tropical and subtropical areas of the world. In many of these countries, Malaria is the leading cause of death, especially impacting young children, who have weak immune systems, and pregnant women, whose immune systems have been weakened by pregnancy.

Primary transporter of the disease!

The mosquito, Anopheles gambiae complex, is a major transmitter of the disease while the parasite species, Plasmodium falciparum, is the species most likely to cause severe Malaria cases and/or death. The parasites first invade and multiply in the liver followed by the red blood cells. In the red blood cells, broods of parasites destroy the cells and create daughter cells or merozoites which continue the vicious cycle by invading other red blood cells. This is the stage when those who have been invaded begin to feel the effects of the diseases.

Finding a cure for malaria has been a constant struggle for humans for hundreds of years. The first cases of Malaria were reported in the Middle Ages, which was caused by the poor quality of air people lived in during that time. The disease was later brought to America’s by colonizers in the 1600’s. However, colonizers found that the Cinchona tree bark was a cure for the fever caused by Malaria. French scientists later purified a medicine called “Quinine,” in 1821, which came from the tree bark. In 1902, Dr. Ronald Ross proved that malaria was transmitted by a mosquito, which later led to him receiving a Nobel Peace Prize. From there, the spread of Malaria began being controlled from the mid-late 1900s using DDT, dichlorodiphenyltrichloroethane.

The lifecycle of the transmission and infection of the disease.

Unfortunately, even though we have found a way to control the disease, we still do not have an actually licensed vaccine on the market. This is due to two major factors; malaria parasites have very complex life cycles and scientists/doctors still are not completely positive on the immune system response to the malaria parasite. Malaria parasites can produce thousands of antigens which also poses an issue for those striving to create a vaccine for Malaria. Also, unlike most treatable diseases, exposure does not ensure lifelong protection from the disease, only partial protection from the disease.

Currently, there are many studies and experiments taking place to try to find treatments and prophylaxis of malaria. There are multiple drugs currently that are being used to help in the prevention of malaria. But, none of the drugs are 100% preventive, therefore they rely on a person combining the medicine with the use of personal protective measures such as insect repellant, long sleeves, and sleeping in mosquito-free settings.

The most popular malaria preventive drug is Atovaquone/Proguanil, also known as Malarone. This drug is ideal for travelers staying in malaria-prone areas for a short period of time because this drug only must be started two days before possible exposure to malaria. It is taken daily like regular pills, and it only has to be taken seven days after traveling rather than four weeks. Also, this pill has very few side effects and is available to children. Unfortunately, this pill is unavailable to pregnant women or women breastfeeding small children. Additionally, the pill is more expensive than the other options.

Next, we have Doxycycline, the second most popular drug. This another drug good for last-minute travelers because it can start working in just one to two days. It is also less expensive than most drugs and is taken daily like Malarone. Additionally, Doxycycline is used in other drugs for different purposes which provides protection against other infections like Rickettsiae and leptospirosis, infections common in hikers, campers, and swimmers in fresh water. The cons of this drug are that it cannot be used by pregnant women or children, it must be taken four weeks after travel, it will increase a person’s sensitivity to the sun, and it also leads to occasional stomach aches. All in all, this is a very popular drug used by tourists and travelers to malaria transmitted areas.

Another popular dug used is called Mefloquine. This drug is special because it is one of the only preventive drugs that can be used by pregnant women. It also is only taken once a week rather than daily like most of the drugs. Unfortunately, this drug is very particular in who can actually use it; it cannot be used in certain areas when the mosquitos are resistant to the drug, such as people with psychiatric disorders, or those prone to seizures, or by individuals with cardiac conduction abnormalities. In addition to that, it must start being taken at least two weeks before traveling and continued taken four weeks after. In conclusion, this drug is beneficial purely because it is the only drug to treat pregnant women, but the drug is very inefficient and lacking in other areas.

The only other malaria preventive drug that can be used by pregnant women is Chloroquine. This drug is taken weekly and found in drugs that treat chronic for rheumatologic conditions, which provides protection to people who have those conditions. Unluckily, there are areas with Chloroquine or Mefloquine resistance. In addition, the drug must be taken one to two weeks before travel and four weeks after travel. It also may exacerbate psoriasis.

The last two drugs, Tafenoquine (ArakodaTM) and Primaquine, are extremely effective in preventing Plasmodium vivax, a parasite which is one of the top five most dangerous parasites in leading to severe malaria cases and sometimes death. Tafenoquine (ArakodaTM) is also extremely preventive of Plasmodium falciparum, the deadliest parasite associated with malaria. Both drugs must be taken two to three days before traveling and one week after traveling. But neither can be taken by patients with glucose-6-phosphatase dehydrogenase (G6PD) deficiency or who have not been tested for G6PD deficiency. Neither drug can be taken by women who are pregnant or breastfeeding. Tafenoquine (ArakodaTM) cannot be taken by children or people with a psychotic disorder. Primaquine has also been said to cause stomach aches which makes the drug less appealing. Overall, the two drugs are very valuable since they can prevent some of the deadliest parasites but for the drugs to be more used and widely distributed, they will need to vastly increase the number of people who can benefit from the drug.

On the bright side, there is a vaccine that is attempting to be the first medicine that can prevent 100% of malaria. The vaccine has proved to be the most preventive drug ever tested in a lab, and the scientists hope to have similar results when they start field testing in 2020. The field tests will take place off the coast of Equatorial Guinea and will include 2,100 people aged 2-50. The trials are intended to provide the efficacy and safety data needed for regulatory approval of the drug. Hopefully, the test leads to good results so that this drug can start being given to citizens of malaria transmitted countries. Thus, leading to a better and healthier future!

~Tyler D. Wilson

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