What is Plasmodium ovale Malaria?
Plasmodium ovale is one of the types of non-falciparum malaria, a specific kind of malaria that is not caused by the Plasmodium falciparum species. It’s important to note that Plasmodium vivax, Plasmodium malariae, and Plasmodium knowlesi can also cause non-falciparum malaria. Malaria is a disease caused by tiny organisms known as protozoa, which are passed to humans through the bite of infected Anopheles mosquitoes.
This disease is a leading cause of illness from parasites in humans. It’s a problem in 107 countries and affects over 3 billion people, leading to 1 to 3 million deaths each year. Specifically, Plasmodium ovale, contributes to malaria primarily in tropical western Africa. However, unlike some other types of malaria, it seldom leads to severe sickness or death.
To prevent the sickness and death that can come from malaria, it’s important to diagnose and treat it quickly. However, Plasmodium falciparum, a different type of malaria species, often resists common anti-malarial treatments such as chloroquine and can be fatal very quickly. A blood smear that reveals the shape and structure of the species can help differentiate the plasmodium species involved. Plasmodium falciparum, usually presents high parasitemia levels, meaning many parasites in the blood, and it also has distinctive ‘banana-shaped’ reproductive cells known as gametocytes. Interestingly, 5% to 10% of patients with malaria may have more than one species of the parasite at the same time. Each plasmodium species has its own geographic area where it is most commonly found, yet there is often overlap.
What Causes Plasmodium ovale Malaria?
P. ovale malaria, like other types of malaria, starts when a female ‘Anopheles’ mosquito bites a person and transfers parasite cells called ‘sporozoites’ from its salivary gland into the person’s body. P. ovale can exist as either of two species: Plasmodium ovale curtisi or Plasmodium ovale wallikeri.
Malaria is caught after a bite from a mosquito. When the mosquito bites, it injects the malaria parasite into the person’s body through its saliva. The malaria parasites then get into the red blood cells and feed off the hemoglobin, a protein our body uses to carry oxygen. Some parasites will go dormant, or in a state of rest, and others will stay active, which explains the varied symptoms people with malaria might experience. Mosquitos that carry malaria parasites usually only bite between the evening and early morning.
Both P. ovale and P. vivax have a dormant stage that stays in the liver and reawakens later. Therefore, when treating these, it’s necessary to also provide treatment to destroy the dormant parasites. The malaria parasites break down hemoglobin and other proteins, which may lead to an excess of lactic acid (acidosis) and low blood sugar (hypoglycemia). Parasites can also break down both infected and uninfected red blood cells, causing low blood count (anemia) and spleen enlargement (splenomegaly).
The risk of infection can depend on the precautions taken (like using nets or insect repellent) and the intensity of mosquitos in the area. Most healthy individuals can fight off the parasite, but in individuals with weak immune systems, the parasites may continue to reproduce. A few parasites will turn into ‘gametocytes,’ which are believed to be able to reproduce sexually when taken up by a mosquito. These can then develop into infective sporozoites, which will allow the cycle to continue after the mosquito bites a new host.
The time between getting bitten by an infected mosquito and starting to show symptoms of malaria, called the incubation period, is usually 30 days for P. falciparum. This suggests the importance of continuing antimalarial medications for at least four weeks after leaving a place where P. falciparum is common. However, rare cases of P. falciparum taking 12 months to show symptoms have also been noted. The incubation period for P. ovale and P. vivax can range from a few weeks to several months.
People having sickle cell trait, hemoglobin C, thalassemias, and G6PD deficiency are less likely to die from P. falciparum malaria, though the level of protection varies. Some people living in places where malaria is common may develop partial immunity after being bitten by mosquitos several times. This partial immunity may make the infection less severe. But, this immunity will be lost once they move away from the area.
Risk Factors and Frequency for Plasmodium ovale Malaria
Malaria is a disease that occurs mostly in tropical regions all over the world. A particular type of malaria, called P. ovale, is mostly found in Western Africa. It’s seldom seen outside of Africa and makes up less than 1% of identified cases where it’s present. Places like the Philippines, Indonesia, and Papua New Guinea have seen cases of P. ovale, but it’s quite rare.
In a study in Indonesia out of more than 15,000 blood samples, only 34 individuals were infected with P. ovale. Compared to the more common P. falciparum and P. vivax malaria, P. ovale is quite uncommon. Cases of severe P. ovale malaria are also very rare, possibly due to the uncommonness of P. ovale infection.
In various parts of Africa and Asia, malaria is found in individuals who are also infected with HIV; these cases are usually more burdensome than when either infection occurs on its own.
- Malaria can affect any gender equally.
- The P. falciparum type of malaria can lead to serious health problems in pregnant women.
- Complications in the fetus from a mother’s P. falciparum infection can include anemia, low birth weight, death, or premature birth.
Signs and Symptoms of Plasmodium ovale Malaria
Diagnosing P. ovale malaria quickly and accurately is vital to start treatment and decrease the severity of the illness. Initial symptoms are often vague and can include headache, fever, fatigue, muscle aches, sweating, cough, loss of appetite, abdominal pain, diarrhea, joint pain, nausea, vomiting, and lightheadedness when standing up.
If someone has a fever and history of exposure to malaria, such as living in or visiting an area where the disease is common, malaria should be a consideration. Patients with P. ovale malaria often have instances of fever, chills, and shaking that follow a regular pattern.
Severe malaria can lead to a variety of serious symptoms, such as unstable blood pressure, fluid accumulation in the lungs, red blood cell breakdown, severe anemia, blood clotting disorders, low blood sugar, metabolic acidosis, kidney failure, liver problems, altered mental state, neurological problems, and seizures. Physical signs may include paleness, small red or purple spots on the skin, yellow skin and eyes, enlarged liver, and enlarged spleen. Blood tests may show high levels of the parasite in the blood, anemia, low platelets, problems with blood clotting, increased liver enzymes, increased BUN/creatinine, metabolic acidosis, and low blood sugar.
Severe P. ovale malaria is rare but can cause complications like the rupture of the spleen, low platelets, and widespread intravascular clotting.
Given the potential complexity of the symptoms, the following are things to look out for if P. ovale malaria is suspected:
- Headache
- Fever
- Fatigue
- Muscle aches
- Sweating
- Cough
- Loss of appetite
- Abdominal pain
- Diarrhea
- Joint pain
- Nausea
- Vomiting
- Lightheadedness when standing up
- Regular intervals of fever, chills, and shaking
Testing for Plasmodium ovale Malaria
If your doctor thinks that you may be infected with P. ovale, a type of parasite that causes a kind of malaria, they will likely want to confirm this with a test. The best way to check for this infection is with a blood test called a blood smear microscopy. This process involves taking a sample of your blood, staining it with a special dye, and then looking at it under a microscope to try to spot the parasites.
There is a certain way the test needs to be done to make sure the results are as accurate as possible. Ideally, at least two blood smears should be taken as soon as the blood sample is collected. If this doesn’t happen quickly, the parasites can change shape and become harder to identify. The special stain used in the test, called Giemsa stain, can highlight important features of the parasites, like Schuffner dots, which can help to identify the species of Plasmodium.
It’s important to note that P. ovale only infects young red blood cells, so the number of parasites in your blood (parasitemia) is usually lower than with other species of Plasmodium. A very high parasitemia is more indicative of a different type of malaria infection, caused by P. falciparum.
There’s another test that can be done if the blood smear microscopy testing is not available. This is called a Rapid Diagnostic Test (RDT). RDTs are very useful, especially in places where resources are limited, because they don’t require electricity or a laboratory, and can provide results within 15 to 20 minutes. One downside is that they cannot tell the doctor how many parasites are in your blood. Also, there are no RDTs that can specifically diagnose a P. ovale infection.
There’s yet another test that can also be used, called a polymerase chain reaction (PCR) test. This test is great at detecting a low number of parasites, even as few as one per microliter of blood. However, PCR tests are mainly used for research purposes. But if an RDT comes back negative and microscopy isn’t an option, a PCR test can be useful for diagnosing a malaria infection.
Treatment Options for Plasmodium ovale Malaria
Treating non-falciparum malaria primarily involves dealing with the forms of the disease that affect red blood cells. When it comes to Plasmodium ovale infections, which is a type of non-falciparum malaria, it’s important to wipe out a specific stage of the parasite’s life cycle, called ‘hypnozoites’, that hide in the liver to prevent the infection from coming back.
Patients with an uncomplicated Plasmodium ovale infection, meaning they’re experiencing symptoms of malaria but have no other health problems, can usually be treated outside the hospital. To check how well the treatment is working, it’s important to monitor the number of parasites in the patient’s blood during the treatment. This can be done by taking a blood sample every day until either no more parasites are detected in the blood or a full seven days of treatment have passed. If a patient who’s been taking medicines to prevent malaria still gets infected, they should be treated with a different drug.
Most non-falciparum malaria, including Plasmodium ovale infections, can be treated with a drug called chloroquine or a combination of drugs known as ‘artemisinin combination therapy’ (ACT). If the disease isn’t widespread and resistance to chloroquine is low, chloroquine alone could work, but the patient must be closely monitored. However, if there’s a high rate of chloroquine treatment failure, meaning more than 1 out of 10 patients don’t get better after 28 days of treatment, ACT should be used instead.
A specific stage of the Plasmodium ovale life cycle, known as ‘gametocytes’, is susceptible to chloroquine, making the drug highly effective against the forms of the parasite that affect red blood cells. If a patient has multiple types of malaria infections including the more severe Plasmodium falciparum, they should receive treatment that specifically targets Plasmodium falciparum.
Getting rid of the Plasmodium ovale parasites that are hiding in the liver (the ‘hypnozoites’) requires a different drug, primaquine. This should be started after the patient’s fever has subsided and once tests have confirmed their body can safely process the drug (they must have normal glucose-6-phosphate dehydrogenase status).
What else can Plasmodium ovale Malaria be?
The following conditions may present symptoms similar to each other:
- Dengue fever
- Chikungunya
- Meningitis
- Pneumonia
- Sepsis due to bacteremia (bacterial infection in the blood)
- Typhoid fever
- Leptospirosis (an infection caused by corkscrew-shaped bacteria called Leptospira)
- Viral hemorrhagic fever (a severe multisystem syndrome)
What to expect with Plasmodium ovale Malaria
Generally, healthy individuals who contract uncomplicated malaria are likely to fully recover within 3 to 7 days. However, a type of malaria caused by a microorganism called P. falciparum is quite serious, and can be fatal if not treated promptly.
Possible Complications When Diagnosed with Plasmodium ovale Malaria
Most complications are related to P. falciparum, a type of malaria parasite. These might include:
- Fluid build-up in the lungs
- Malaria that affects the brain
- Problems with kidney function
- Low red blood cell count (anemia)
- Death
- Seizures
- Low blood sugar (hypoglycemia)
- Presence of hemoglobin in urine
- Build-up of lactic acid in the body
- Low platelet count in the blood
- Breakage of the spleen
It’s important to note that most deaths from these complications occur in children who are under five years old.
