Malaria

Picture of Malaria Precautions by Sleeping Under Mosquito Nets Treated with Insecticide

• More than 215 million cases of malaria occurred worldwide in 2016.
• The World Health Organization estimates that 445,000 people died of malaria in 2016; the vast majority are young children in sub-Saharan Africa.
• Although this is a significant decrease in deaths since 2000 due to increased prevention and control measures, there has been an increase from 2015 to 2016.
• Healthcare professionals diagnose about 1,700 people with malaria in the U.S. annually, usually in travelers returning from endemic areas.
• Malaria was a severe public health threat in the U.S. until disease-control programs eliminated it during the 1920s-1940s. Much of the early work done by the CDC focused on controlling and eliminating malaria in the U.S.

Malaria is a serious, life-threatening, and sometimes fatal, disease spread by mosquitoes and caused by a parasite. Malaria was a significant health risk in the U.S. until multiple disease-control programs in the late 1940s eliminated it. The illness presents with flu-like symptoms that include high fever and chills.

There are three necessary aspects to the malaria life cycle:

1. The Anopheles mosquito carries the parasite and is where the parasite starts its life cycle.
2. The parasite (Plasmodium) has multiple subspecies, each causing different symptoms and responding to other treatments.
3. The parasite first travels to a human's liver to grow and multiply. It then travels into the bloodstream and infects and destroys red blood cells.

Malaria is a mosquito-borne disease that does not spread from person to person (except in pregnancy as noted below) but spreads in particular circumstances without a mosquito. This rarely occurs and is usually found in a transmission from a pregnant woman to an unborn child (congenital malaria), by blood transfusions, or when intravenous-drug users share needles. Malaria is not considered contagious from person to person except for the above conditions.

Following the mosquito bite, there is about a seven- to 30-day period before symptoms appear (incubation period). The incubation period for P. vivax is usually 10-17 days but can be much longer (about one year and rarely, as long as 30 years!). P. falciparum usually has a short incubation period (10-14 days). Other species of Plasmodium that cause malaria have incubation periods similar to P. vivax.

Parasites of the genus Plasmodium cause malaria. Although there are many species of the malaria parasite Plas existmodium, only five infect humans and cause malaria.

• Plasmodium falciparum: found in tropical and subtropical areas; a significant contributor to deaths from severe malaria
• P. vivax: found in Asia and Latin America; has a dormant stage that can cause relapses
• P. ovale: found in Africa and the Pacific islands
• P. malariae: worldwide; can cause a chronic infection
• P. knowlesi: found throughout Southeast Asia; can rapidly progress from an uncomplicated case to a severe malaria infection

Malaria has a wide spectrum of symptoms. After the bite by the infected mosquito occurs, it can take between seven and 30 days (average is seven to 15 days) before symptoms start (incubation period).

Healthcare professionals classify malaria as uncomplicated or complicated (severe).

Uncomplicated malaria

The most common symptoms include:

• fever and chills,
• headaches,
• nausea and vomiting, and
• general weakness and body aches.

The classic description of a malaria attack (rarely observed) would be a six- to 12-hour cold and shivering alternating with fever and headaches and then a stage of sweating and tiredness (sometimes divided into the cold and hot phase).

As these symptoms are very nonspecific, it is essential to evaluate if the patient has risk factors for malaria (usual travel in endemic areas).

Complicated or severe malaria

This occurs when malaria affects different body systems.

• Severe anemia (due to the destruction of red blood cells)
• Kidney failure
• Cerebral malaria -- seizures, unconsciousness, abnormal behavior, or confusion
• Cardiovascular collapse
• Low blood sugar (in pregnant women after treatment with quinine)

Malaria can be treated by your primary care doctor (pediatrician, family medicine, internal medicine), as well as by infectious-disease specialists.

The symptoms of malaria can mimic many other diseases, including influenza or a viral syndrome. It is therefore essential to inquire about a history of recent travel to an endemic area or other possible exposures.

Physicians make a definite diagnosis of malaria by looking at an infected patient's blood under the microscope (blood smear) and identifying the presence of the parasite. The patient's blood is prepared under a slide with a specific stain to help identify the parasite. This is the most widely performed and accepted test.

Rapid diagnostic tests (antigen tests) are available that can give the diagnosis in a few minutes. It is recommended that a blood smear examination follows a positive test.

Besides supportive care, the medical team must choose the appropriate antimalarial drug(s) to treat malaria. The choice will depend on several factors, including:

• the specific species of parasite identified,
• the severity of symptoms, and
• determination of drug resistance based on the geographic area where the patient traveled.

Depending on the above factors, physicians will administer the medication in pill form or as an intravenous antimalarial.

The most commonly used medications include:

• chloroquine (Aralen),
• doxycycline (Vibramycin, Oracea, Adoxa, Atridox),
• quinine (Qualaquin),
• mefloquine (Lariam),
• atovaquone/proguanil (Malarone),
• artemether/lumefantrine (Coartem), and
• primaquine phosphate (Primaquine).

P. vivax and P. ovale can hibernate in the liver and cause relapsing disease weeks or months after the patient is symptom-free.

The FDA approved tafenoquine (Krintafel) as a medication to prevent relapses of Plasmodium vivax in patients 16 years of age and older. According to researchers, it is a single-dose medication that will provide an essential new tool in fighting P. vivax malaria relapse.

If diagnosed early and appropriate antimalarials are available and used, the prognosis of malaria is excellent.

Worldwide, malaria is responsible for over 400,000 deaths per year. The majority of victims are young children from sub-Saharan Africa. Death is usually due to a lack of available treatment or access to treatment.

P. falciparum tends to be the species causing the most complications and has a high mortality if untreated.

Cerebral malaria, a complication of P. falciparum malaria, has a 20% mortality rate even if treated.

There is currently no commercial vaccine available to prevent malaria. Due to the diversity of the Plasmodium species and the P. falciparum species being the deadliest parasite, most efforts are currently directed toward a P. falciparum vaccine. RTS,S/ASO1 is the most advanced candidate as a viable vaccine.

A phase 3 trial of RTS,S/ASO1 was completed and results were published in 2015. The WHO is supporting the pilot implementation in several sub-Saharan countries.

The prevention of malaria includes several steps.

First, evaluate if malaria is a concern in the area of travel (CDC malaria information by country table). This table will also indicate which medication to take as chemo-prophylaxis.

If chemo-prophylaxis is recommended, discuss the recommended medications with a healthcare professional to determine if they are appropriate. Take into consideration any medical conditions, drug interactions with current medication taken continually, as well as side effects of the recommended medications.

No medication is 100% effective, and therefore the prevention of mosquito bites is of paramount importance. These preventive measures should include the following:

• Sleeping under bed nets: These should cover the bed down to the floor. These nets are most effective when treated with an insecticide.
• Clothing: Clothing that covers most of the exposed skin and closed shoes can reduce the risk of bites. Tuck in all clothing, and pants should be tucked into socks to avoid exposure around the ankles. In addition, treating clothes with insecticides can prevent bites even further.
• Apply insect repellent to all exposed skin.