Mosquito Maladies – 2. Malaria
This Mosquito Maladies Post Series breaks down some of the most common dangerous diseases that can be transmitted by mosquitos. In this blog, we breakdown: Malaria.
**PLEASE NOTE: This blog is intended for informational purposes only and should not be taken as medical advice. Always seek the advice of a doctor and/or medical treatment if necessary**
Malaria is arguably the most infamous mosquito-borne disease. It is known for being carried in Anopheles, one of the most common mosquitos in United States along with Aedes, Coquillettidia, Culex, Culiseta, Ochlerotatus, and Psorophora.
The root of the disease are Plasmodium parasites that utilize two hosts: mosquitos and humans; and go through three stages: sporozoite, gametocyte, and merozoite. Infected mosquitos are full of gametocytes that mate in their gut, morphing into their sporozoite form. When a mosquito bites, they insert their sharp, needle-like appendage known as a proboscis into their victims’ skin. Immediately, they inject their saliva into the wound which creates a numbing sensation to mask their presence and provides anticoagulant enzymes so that the blood they’re sucking doesn’t clot. Along with the enzymes, an infected mosquito’s saliva contains the sporozoites which migrate into the victim’s liver once after they’re bitten. Once in the liver, the merozoites (the “daughter parasite”) are released. These eventually mature into adult gametocytes that can then be transferred into any other mosquitos that bite the new host, completing the cycle of transmission.
Environmental factors can greatly affect the likelihood of outbreaks of malaria. This is due to the necessity of the Anopheles in the parasite’s life cycle. The successful development of gametocytes to sporozoites hinges on several environmental factors including elevated temperatures and humidity. The formation and growth of the parasite is accelerated by heat and humidity, and are also beneficial to the Anopheles, which has to remain alive and feeding long enough for the sporozoites to fully form and leave the mosquito, which can take roughly 18 days.
The only other known methods of transmission are congenital (mother to child during pregnancy) or transfusion related (where an infected persons blood is utilized in a blood transplant for a patient). Both of these occurrences are rather rare in the United States, even with there being a lack in screening for malaria in donated blood. Only about one case of transfusion-transmission is reported every 2 years and congenital transmission is even rarer due to typically careful observation of pregnant mothers.
Prior to symptoms appearing, an infected victim will go through an incubation period that can last between 7-30 days depending on the specific species of Plasmodium parasite that they’re contaminated with. Classically, malaria presents in three stages, a cold/shivering stage, a hot/fever stage, and lastly a sweating stage. Overall however, a combination of the following symptoms may occur:
- Body Aches
- Seizures (in young children with elevated temperatures)
- Nausea and/or Vomiting
Unfortunately, due to the commonality of many of the symptoms with the common flu, malaria is sometimes misdiagnosed initially in countries where the disease is not prevalent (such as the United States). Other physical findings that can indicate malaria include:
- An Enlarged Spleen
- Mild Jaundice
- An Enlarged Liver
- Increased Respiratory Rates
In some cases, malaria can become very severe and can even be fatal. In this case, it is considered a medical emergency and needs to be treated both aggressively and quickly to avoid permanent damage and/or death. Symptoms of a serious case include:
- Severe Anemia
- Neurologic Abnormalities (ie. abnormal behavior, periods of loss of consciousness, seizures, or even coma)
- Hemoglobin in Urine
- Acute Respiratory Distress Syndrome (ARDS)
- Cardiovascular Collapse
- Severely Low Blood Pressure
- Acute Kidney Failure
- Metabolic Acidosis (tissues and blood are oversaturated with acidity)
- Hypoglycemia (common in pregnant women with malaria)
- Hyperparasitemia (the parasite has multiplied to the point where it is infecting over 5% of the body’s red blood cells)
Official diagnosis of the disease requires diagnostic confirmation in which indications of the parasite are recognized in the patient’s blood. Once it is confirmed as the cause, those infected can be properly treated.
As discussed in the Overview, areas with high temperatures and humid climates provide the ideal environment for the growth and spread of the malaria parasite. Some people are naturally immune to malaria due to genetics, however, in the absence of protective genetics malaria can be prevented with antimalarial drugs and other mosquito-based precautions.
Unlike some mosquito-transmitted diseases, malaria can be prevented, treated, and cured. Treatments for malaria can depend on several factors including, but not limited to, age, weight, pregnancy status, drug allergies, and what species of Plasmodium parasites the victim is infected with. However, no matter the treatment method, care should be initiated urgently because the longer malaria is left to fester, the more serious the condition of the patient may become and possibly lead to death. With proper treatment, malaria can be cured over the span of roughly two weeks. In some more rare cases where malaria is both minor and left untreated, the cold, hot, and sweating episodes can periodically occur over the years.
After being exposed to malaria, those cured are partially immune and, if re-infected, will experience milder cases than before. Thankfully, the creation of a vaccine is in the works and, once proven effective, will be a game changer in the prevention of the disease worldwide.
Malaria (2019) Harvard Health Publishing. Harvard University. Available at: https://www.health.harvard.edu/a_to_z/malaria-a-to-z (Accessed: July 2020).
Malaria (2020) Centers for Disease Control and Prevention. U.S. Department of Health and Human Services. Available at: https://www.cdc.gov/parasites/malaria/index.html (Accessed: July 2020).
Malaria (2020) World Health Organization. Available at: https://www.who.int/news-room/fact-sheets/detail/malaria (Accessed: July 2020).