What is Plasmodium vivax Malaria?
Malaria is a major health issue impacting people globally. According to the World Health Organization’s 2020 Malaria Report, there were roughly 229 million cases of malaria in 2019, leading to about 409,000 deaths. Most of these deaths happened in Africa. Malaria is caused by getting infected with a type of parasite called Plasmodium. There are five types of Plasmodium that can infect humans: P. falciparum, P. vivax, P. ovale, P. malariae, and P. knowlesi.
Out of these, Plasmodium falciparum and Plasmodium vivax cause most of the malaria cases worldwide. Plasmodium falciparum is responsible for more deaths due to malaria, while Plasmodium vivax, although less deadly, is more common. This common type can still lead to serious health issues and is a significant contributor to the overall number of people who get sick or die from malaria around the world.
What Causes Plasmodium vivax Malaria?
Plasmodium vivax is an infection caused by a tiny organism called a protozoa, which is carried and spread by a type of mosquito known as the Anopheles mosquito.
Risk Factors and Frequency for Plasmodium vivax Malaria
P. vivax is a specific type of malaria that is the most widely spread across the globe. Almost 2.5 billion people, or more than a third of the world’s population, are at risk of getting this type of malaria. Due to its ability to stay dormant in the liver, P. vivax can survive in colder weather, which is why it can be found across a wide range of climates including the tropics, subtropics and even moderate climates. It is most widespread in Latin America and Southeast Asia. In 2017, over 74% of malaria cases in the Americas were due to P. vivax according to the World Health Organization’s World Malaria Report.
P. vivax and P. falciparum, another type of malaria, are commonly found in the same locations. However, in some places in Southeast Asia, such as South Korea, only P. vivax is found. A significant feature of P. vivax is that it needs the Duffy antigen, found on cell surfaces, to infect red blood cells. This is why P. vivax is not as common in Africa as most of the population has low levels of the Duffy antigen. However, recent research indicates that P. vivax can infect individuals without the Duffy antigen, even though this is rare. People typically build immunity to P. vivax faster than to P. falciparum, so adults infected with P. vivax often don’t show symptoms. Risk of severe disease in areas with low transmission doesn’t depend on the age of the infected person.
In the United States, the CDC reports about 1,700 malaria cases each year. A study examining malaria deaths between 1963 to 2001 found that the majority were caused by P. falciparum (92.7%). Only 3.3% were due to P. vivax. The study revealed that most malaria deaths could be prevented as the common causes included failure to take preventive medicine, taking incomplete or incorrect medication, and misdiagnosis.
Signs and Symptoms of Plasmodium vivax Malaria
Vivax malaria has an incubation period generally ranging from 12 to 17 days. However, it’s important to note that a relapse can happen up to two years later due to dormant parasites. Common signs and symptoms of this type of malaria include fever, headache, nausea, vomiting, body aches, and yellowing of the skin and eyes (jaundice). Because these symptoms are quite common and can overlap with other illnesses, it can be difficult to diagnose malaria just based on these symptoms.
One unique characteristic of vivax malaria is that patients usually have fevers that come and go every 42 to 56 hours. That’s why it’s sometimes called “tertian fever”. Anemia, or a low level of red blood cells, is often the first symptom seen in adults and children in areas where vivax malaria is common. Unlike another type of malaria, falciparum malaria, vivax malaria less commonly leads to multi-organ failure. But, it’s crucial to remember that there have been cases of severe vivax malaria reported. One potential severe complication is Acute Respiratory Distress Syndrome (ARDS), which may occur due to a strong immune response to the parasites in the body.
Reach out to a health care provider if you experience similar symptoms and suspect you may have contracted malaria.
Testing for Plasmodium vivax Malaria
In 2010, the World Health Organization (WHO) updated their guidelines to say that all suspected malaria cases need to be tested before treatment begins. Two main testing methods for malaria in medical settings are light microscopy and rapid diagnostic tests (RDTs). Polymerase chain reaction (PCR) testing, which is often used for research purposes, can also be helpful to confirm the specific type of malaria after diagnosis.
Blood smears are a traditional method for diagnosing malaria, specifically P. vivax malaria. By using a special stain and a light microscope, doctors can observe the malaria parasites in the blood. A total of three sets of “thick” and “thin” smears are recommended. The thick smears help find the parasites, and thin smears make it easier to see the parasites and count them. The advantage of light microscopy is its good sensitivity and low cost. However, it does require trained lab technicians as well as a microscope and electricity. One thing to keep in mind is that P. vivax malaria usually has fewer parasites in the blood compared to other types, making it harder to find. Also, certain forms of this parasite that stay dormant in the liver can’t be spotted using current diagnostic tools.
Since the 1990s, RDTs have been increasingly used, especially in locations with limited resources. They work by detecting specific antigens, which are substances that trigger an immune response, in the blood. The benefits of these tests are that they are fast, producing results in around 15 to 20 minutes, and don’t require a lab technician skilled at making and reading blood smears. However, they tend to work better when there are more parasites in the blood and may show false negatives when the parasite levels are relatively low.
Most RDTs check for an antigen found on the P. falciparum malaria parasite, with sensitivity rates as high as 93-99 percent. Tests specifically for P. vivax look for either a P. vivax-specific antigen or antigens common to all types of malaria parasites. These tests have shown lower sensitivities when used to detect P. vivax.
In a review of 47 studies involving 22,862 participants, RDTs that detect either pan-pLDH or aldolase had sensitivities for non-falciparum malaria that ranged from 78% to 89%. However, RDTs that specifically looked for a P. vivax antibody showed better results with a pooled sensitivity of 95% and specificity of 99%. It’s worth noting that RDTs can remain positive up to a month after successful malaria treatment. In the US, it’s standard practice to confirm all RDT results with light microscopy.
Treatment Options for Plasmodium vivax Malaria
Chloroquine is a drug that is primarily used to treat vivax malaria, a type of malaria caused by the Plasmodium vivax parasite. However, in areas, such as Papua New Guinea and Indonesia, where this parasite has developed resistance to Chloroquine, it may not work as effectively.
The Centers for Disease Control and Prevention (CDC) advises using either Chloroquine phosphate, hydroxychloroquine, or primaquine to treat uncomplicated vivax malaria that is susceptible to Chloroquine. The doses of these drugs will be decided by the healthcare professional.
If you’ve contracted P. vivax in an area where it’s Chloroquine-resistant, the CDC suggests alternative treatment options. These may include combining primaquine with either atovaquone-proguanil, quinine plus either tetracycline or doxycycline, or mefloquine. The healthcare professional will select the most appropriate treatment option for you.
Given that the P. vivax parasite has a dormant liver phase, primaquine is used along with other drugs to treat this phase. However, primaquine cannot be used in all cases. For instance, people with Glucose-6-phosphate dehydrogenase(G6PD) deficiency, an inherited condition causing red blood cells to break down prematurely, and pregnant women can’t take primaquine. G6PD deficiency may cause severe anemia, and in pregnant women, the drug may cause harm to the unborn baby. Therefore, health professionals will consider these factors before prescribing primaquine.
For cases of severe malaria around the globe, the World Health Organization (WHO) recommends the use of intravenous artesunate. It has shown good results in multiple studies and is safer when compared to the older drug, intravenous quinidine. However, the Food and Drug Administration in the United States has not yet approved it.
If you’re in the United States and have severe malaria, the CDC suggests using intravenous quinidine along with tetracycline, doxycycline, or clindamycin. However, while quinidine is being administered, the patient’s heart must be continuously monitored because of the potential risk of irregular heartbeats. In cases where malaria doesn’t respond to other treatments or when IV quinidine is unavailable, intravenous artesunate may be sourced via the CDC.
What else can Plasmodium vivax Malaria be?
These are some illnesses that might have similar symptoms to certain diseases. They include:
- Dengue fever
- Chikungunya
- Typhoid Fever
- Sepsis from bacteremia
- Viral hemorrhagic fever
- Leptospirosis
- Rickettsial infections
- Brucellosis
- Influenza
- Viral hepatitis
What to expect with Plasmodium vivax Malaria
If identified and treated correctly, Plasmodium vivax malaria— a type of malaria— has a good chance of recovery and generally leads to fewer complications than another type, called falciparum malaria. However, it’s important to note that more severe complications can still occur. (More details about these complications are mentioned below.)
Possible Complications When Diagnosed with Plasmodium vivax Malaria
Traditionally, P. vivax was thought to cause a milder disease and lower parasite count in the blood in comparison to P. falciparum. But recent findings suggest that P. vivax might be culpable for more severe diseases than previously thought. There have been instances of P. vivax leading to cerebral malaria, kidney failure, severe lung conditions, and shock.
Another rare but severe complication is the rupture of the spleen, which has a mortality rate as high as 80%.
Pregnant women are more susceptible to severe outcomes from all forms of malaria, including P. vivax. Malaria during pregnancy is linked to higher parasite count in the blood and can also increase the risk of preterm delivery, miscarriage, low birth weight, as well as neonatal or maternal death.
Common Complications:
- Cerebral malaria
- Kidney failure
- Severe lung conditions
- Shock
- Rupture of the spleen
- Preterm delivery
- Miscarriage
- Low birth weight
- Neonatal or maternal death
Preventing Plasmodium vivax Malaria
Preventing malaria involves a mix of strategies. For people travelling to areas where malaria is present, regularly taking prescribed malaria prevention medicines is crucial. Wearing the right clothing, like long-sleeve shirts and pants, and using insect repellents such as DEET or permethrin can reduce the chance of getting infected significantly. In addition, awareness that the Anopheles mosquitos, which carry the malaria parasite, generally bite around sunrise and sunset, can help people adopt behaviors that avoid these peak biting times and reduce their risk of getting infected.
For people who live or are visiting in places where malaria is prevalent, using mosquito nets treated with insecticide can decrease the chance of infection. These nets are especially effective because they create a protective barrier that helps keep mosquitoes away while you sleep, a time when you can’t defend yourself from mosquito bites.
