Plasmodium ovale malaria is a less common type of malaria that usually causes cycles of fever, chills, headache, and fatigue, often starting weeks after a mosquito bite and sometimes much later. Many people first hear about Plasmodium ovale malaria when a fever starts after travel to West or Central Africa or certain Pacific islands. Illness can be mild to moderate compared with other malaria types, but without treatment it can return because the parasite can “sleep” in the liver and reactivate months later. Most healthy adults recover with prompt treatment that combines a standard antimalarial for the blood-stage infection and a second medicine (such as primaquine or tafenoquine) to clear the liver stage; doctors screen for G6PD deficiency before those liver-clearing drugs. Severe complications are less common than with falciparum malaria, but anyone with symptoms after travel should seek urgent care, as early treatment greatly lowers the risk of serious illness.
How many people live with Plasmodium ovale malaria?
Worldwide, the WHO estimated about 249 million malaria cases in 2022; Plasmodium ovale malaria is a small share—often cited at roughly 0.5% to 1%—which suggests around 1.2 million to 2.5 million P. ovale cases globally that year (an estimate rather than a direct count). In the United States, CDC surveillance recorded about 2,000 malaria cases in 2021; with P. ovale typically making up about 2% to 4% of U.S. cases, that implies roughly 40 to 80 P. ovale cases in that year, again an estimate.
Overview
Plasmodium ovale malariaSymptoms
Plasmodium ovale malaria usually brings cyclic fevers with chills and sweats, headache, tiredness, and body aches. Early symptoms can mimic flu, with nausea. Some develop jaundice, anemia, or an enlarged spleen, and relapses can recur weeks to months later.
Outlook and prognosis
Most people with Plasmodium ovale malaria recover fully when treated promptly, though fatigue can linger for weeks. Because this parasite can “sleep” in the liver, relapses may occur months later without preventive medication. With early care and follow-up, long-term complications are uncommon.
Causes and risk factors
Plasmodium ovale malaria results from bites by infected Anopheles mosquitoes. Risk rises with travel or residence in endemic tropical regions, dusk-to-dawn exposure, limited bed-net or repellent use, no chemoprophylaxis, pregnancy, young age, immunosuppression, splenectomy, and rarely transfusion exposure.
Genetic influences
Genetics matters for Plasmodium ovale malaria, but less than for some other malarias. Variants like sickle cell trait and G6PD deficiency can influence severity and drug safety. Parasite genetic differences may affect relapse patterns and resistance surveillance.
Diagnosis
Clinicians diagnose Plasmodium ovale malaria with microscopy of thick and thin blood smears during fever, often repeated. Rapid tests support diagnosis but may miss P. ovale; PCR confirms species. Travel history and fever pattern guide diagnosis of Plasmodium ovale malaria.
Treatment and drugs
Plasmodium ovale malaria is treated with prescription antimalarial medicines to clear parasites from the blood and relieve fever and chills. Doctors also give a short course of primaquine or tafenoquine to target dormant liver forms and prevent relapse. Treatment choice depends on local resistance patterns, G6PD testing, severity, age, and pregnancy status.
Symptoms
Fevers that come and go, chills, sweats, and feeling wiped out can upend sleep, work, and plans. In Plasmodium ovale malaria, symptoms may start weeks after a mosquito bite and can return months later when dormant parasites wake up. Early symptoms of Plasmodium ovale malaria often look like a flu-like illness—headache, body aches, and tiredness—so it’s easy to miss at first. Symptoms vary from person to person and can change over time.
Fevers often rise to 38.5–40°C (101–104°F) and may come every 48 hours, though timing can be irregular. With Plasmodium ovale malaria, a fever episode can begin suddenly and leave you drained when it breaks.
Intense shivering can build before the fever, followed by drenching sweats as the temperature falls. Sheets or clothes may get soaked, and you may feel very weak afterward.
Energy can drop sharply, making routine chores or a short walk feel unusually hard. Fatigue often lingers between fevers in Plasmodium ovale malaria.
A throbbing or pressure-like headache is common and may worsen during fevers. Light sensitivity or pain behind the eyes can happen for some.
How people usually first notice Plasmodium ovale malaria?
Many people first notice Plasmodium ovale malaria after travel or living in a malaria area when a “flu-like” illness starts days to weeks later, with fever that comes and goes, chills, sweats, headache, and feeling wiped out. Because P. ovale can lie dormant in the liver and relapse months after leaving an endemic region, the first signs of Plasmodium ovale malaria may appear long after the trip, which can make it easy to miss the travel link. Doctors often suspect it when someone has intermittent fevers and a recent or remote history of travel to West or Central Africa or certain Pacific islands, confirmed by a blood test.
Types of Plasmodium ovale malaria
Plasmodium ovale malaria has two closely related variants that behave very similarly in daily life but differ slightly in their genetics and geographic spread. Both can cause fever episodes that come and go, tiredness that lingers, and a return of symptoms months after travel due to dormant liver forms. People may notice different sets of symptoms depending on their situation. When reading about types of Plasmodium ovale malaria, you’ll often see two names that reflect these variants rather than different severities of illness.
P. ovale curtisi
This variant is one branch of P. ovale that infects humans, with a genetic makeup distinct from wallikeri. Symptoms generally include cycles of fever, chills, fatigue, and headache that can resemble the flu. Relapses can occur due to dormant liver stages called hypnozoites.
P. ovale wallikeri
This sister variant differs mainly in its genetic fingerprint and some patterns seen in lab studies and outbreaks. Illness looks much like curtisi, with intermittent fevers and fatigue, and can also relapse after a quiet period. Some reports suggest wallikeri may relapse sooner, but both variants are managed the same way.
Can I slow down the onset of symptoms?
There isn’t a reliable way to slow when symptoms start once you’re infected, but you can lower your chances of ever developing them by preventing infection in the first place. Research and travel-health guidelines support using mosquito-avoidance steps (repellent, long sleeves, bed nets) and taking preventive antimalarial tablets in risk areas; in some situations, a short medicine course after travel may be advised to reduce the chance of a late relapse. These steps reduce risk rather than guarantee prevention, but planning ahead with a travel clinic can make illness much less likely.
What genetics can tell you about symptoms
Certain human gene variants, like G6PD deficiency and sickle cell trait, can change how Plasmodium ovale malaria shows up, sometimes causing milder fevers or altered blood test findings. People with Duffy-negative blood groups may have lower risk, but infection can still occur.
Causes and risk factors
Infection happens after a bite from an infected Anopheles mosquito in regions where the parasite circulates—mainly parts of sub-Saharan Africa and some Pacific areas—and Plasmodium ovale can lie dormant in the liver, triggering relapses months or even years later. The causes and risk factors of Plasmodium ovale malaria include living in or traveling to these regions, evening and nighttime mosquito exposure, missing or stopping malaria prevention medicine, and limited use of repellents, long sleeves, or bed nets. Young children, people who are pregnant, newcomers without prior exposure, and those with weaker immune systems (such as after spleen removal or with HIV) face higher chances of illness and complications, and the risk can persist after returning home because dormant liver forms may reactivate. Doctors distinguish between risk factors you can change and those you can’t. Genetics seems to play a smaller role here: unlike some other malaria types, common inherited blood traits don’t reliably protect against Plasmodium ovale malaria, so prevention focuses mainly on avoiding bites and using the right preventive medicine for your trip.
What are the most common causes or risk factors?
Plasmodium ovale malaria is caused by a tiny parasite spread by the bite of an infected Anopheles mosquito, mostly in West and Central Africa and a few Western Pacific islands. The biggest risk is living in or traveling to these areas—especially staying in rural places, being outdoors at dusk or night, not using repellent, bed nets, or long sleeves, and not taking preventive malaria medicine. Pregnancy, very young children, older adults, and people with weakened immunity face higher risk of severe illness, and because this parasite can “sleep” in the liver, illness can return months later if the liver stage isn’t treated.
Environmental and biological risk factors
Where you live, travel, and the state of your immune system all shape your chance of encountering Plasmodium ovale malaria. Doctors often group risks into internal (biological) and external (environmental). Because this species can rest quietly in the liver, early symptoms of Plasmodium ovale malaria may appear weeks or even months after exposure. Below are common environmental exposures and body-based factors that can raise risk.
Sub-Saharan and West Africa have widespread transmission by malaria-carrying mosquitoes. Travel or residence in these areas raises the chance of Plasmodium ovale malaria.
Frequent rains and warm temperatures expand mosquito breeding sites. Risk is higher during and soon after the rainy season.
The main mosquitoes that spread this parasite bite from dusk through dawn. Nighttime exposure increases the likelihood of Plasmodium ovale malaria.
Puddles, rice fields, and water-filled containers create breeding spots near homes and workplaces. Staying close to standing water increases mosquito contact.
Genetic risk factors
Certain inherited traits can influence how easily this parasite infects red blood cells, how severe the illness becomes, and how safely the dormant liver stage can be cleared. Some risk factors are inherited through our genes. Below are the main genetic risk factors for Plasmodium ovale malaria described in current research. Effects can differ between individuals and populations.
Duffy-negative status: Unlike Plasmodium vivax, Plasmodium ovale can invade red blood cells that lack the Duffy antigen. Being Duffy-negative does not lower your risk of Plasmodium ovale malaria.
Sickle cell trait: This trait lowers the risk of severe falciparum malaria but does not reliably prevent infection by this malaria species. People with sickle cell trait can still be infected and become unwell.
Sickle cell disease: Having sickle cell disease increases the risk of severe anemia and complications during any malaria episode. If Plasmodium ovale malaria occurs, illness may be more severe and recovery slower.
Thalassemia traits: Alpha or beta thalassemia can blunt severe falciparum malaria, but they do not prevent infection by this parasite. People with these traits can still develop fever, chills, and other symptoms.
G6PD deficiency: This inherited enzyme condition does not raise infection risk, but it affects safe use of anti-relapse medicines. Because drugs such as primaquine or tafenoquine can trigger dangerous breakdown of red blood cells, limited treatment options can raise relapse risk in Plasmodium ovale malaria.
Immune gene differences: Variants in immune system genes can influence how well the body controls malaria parasites. For this species, these effects are less clearly defined than for falciparum, but they may shift the odds of severe illness.
Lifestyle risk factors
Day-to-day habits can raise or lower your chance of Plasmodium ovale malaria because they affect how often mosquitoes can bite. For most travelers and outdoor workers, it comes down to where you spend evenings and nights, and how consistently you use prevention. Risk is more of a probability than a promise. When people ask about lifestyle risk factors for Plasmodium ovale malaria, they’re usually asking which choices increase exposure from dusk to dawn.
Trips to regions where Plasmodium ovale malaria circulates increase exposure, especially during rainy seasons and rural stays. Planning stopovers, side trips, or extended stays outside cities can add risk.
Spending time outdoors from dusk to dawn increases bites, when malaria‑carrying mosquitoes are most active. Scheduling exercise, dining, or socializing indoors during these hours can reduce exposure.
Sleeping without an insecticide‑treated bed net raises the chance of overnight bites. Making a net part of your routine, even for naps, lowers risk.
Not using or reapplying repellent on skin and clothing leaves more skin exposed to bites. Packing enough repellent and reapplying as directed helps protect against Plasmodium ovale malaria.
Risk prevention
You can lower your risk of Plasmodium ovale malaria by avoiding mosquito bites, using the right preventive medicines, and acting quickly if you get a fever after travel. People visiting or living in areas where malaria is common benefit most from a layered approach. Alongside medical care, everyday habits also matter. Knowing the early symptoms of Plasmodium ovale malaria—such as fever, chills, sweats, headache, and feeling wiped out—helps you seek testing fast.
See a travel health clinic 4–6 weeks before departure. Ask about your destination’s malaria risk and the best prevention plan for Plasmodium ovale malaria.
Sleep under a long-lasting insecticide-treated bed net. Tuck the net under the mattress and repair any holes.
Use an EPA- or EU-approved repellent with DEET, picaridin, or IR3535 on exposed skin. Reapply as directed, especially after sweating or swimming.
Wear long sleeves, long trousers, and socks in the evening and at night. Treat clothing and gear with permethrin, or buy pre-treated items.
Can you prevent Plasmodium ovale malaria?
You can’t prevent Plasmodium ovale malaria completely, and there’s no vaccine for this type, but you can greatly lower your risk. Use measures that stop mosquito bites (repellent, long sleeves, insecticide-treated bed nets, staying in screened or air-conditioned rooms) and take the right antimalarial tablets before, during, and after travel as recommended for your destination. Because this parasite can stay in the liver and cause illness months later, a follow-up medicine after you leave an area may be advised to prevent relapses.
Transmission
Plasmodium ovale malaria spreads to people through the bite of an infected female Anopheles mosquito. It is not contagious from person to person, so you can’t catch it from casual contact, coughing, or sex; how Plasmodium ovale malaria is transmitted depends on mosquito exposure in areas where the parasite is present. Rarely, it can be passed through blood—such as a transfusion, organ transplant, shared needles—or from a pregnant parent to a baby before or during birth. People with Plasmodium ovale malaria can infect mosquitoes if bitten while parasites are in their blood, but they do not directly give it to others. Risk is highest in regions where these mosquitoes are common; for travelers, repellents, treated bed nets, and preventive medicines lower the chance of infection.
When to test your genes
Test your genes if you’ve had repeated or severe malaria, unusual reactions to antimalarial drugs, or plan to take primaquine/tafenoquine, which require G6PD testing to prevent dangerous anemia. People from regions where malaria is common may also benefit from testing for traits like sickle cell that change risk. Discuss results with your clinician to tailor prevention and treatment.
Diagnosis
Fever that comes and goes, chills that leave you shivering, and feeling wiped out after recent travel can point doctors toward malaria. Doctors usually begin with your story—where you’ve been, when symptoms started, and how they’ve changed—then move quickly to blood tests. Because parasite levels can be low, especially early on, the diagnosis of Plasmodium ovale malaria sometimes takes more than one test. Getting prompt, accurate results helps guide the right treatment and prevents complications.
Your clinician asks about recent or past travel to malaria regions and timing of fevers, chills, and sweats. Relapses months after travel can occur with Plasmodium ovale malaria, so older trips matter. Any malaria prevention you used is also noted.
The exam focuses on fever, pulse, blood pressure, and breathing. Doctors look for signs such as an enlarged spleen, jaundice, or dehydration. These features help assess how sick you are right now.
A lab specialist examines stained blood drops under a microscope to find malaria parasites and estimate how many are present. Thin smears help identify the species, including Plasmodium ovale malaria. Multiple smears improve the chances of catching low-level infection.
Fingerstick or blood tests that detect malaria proteins can give quick answers. Sensitivity is lower for Plasmodium ovale malaria, so a negative rapid test does not rule it out. Microscopy is still needed to confirm and to gauge parasite levels.
How is Plasmodium ovale malaria diagnosed?
Doctors diagnose Plasmodium ovale malaria by considering recent travel and symptoms and, most importantly, testing your blood. The key test is looking at a drop of blood under a microscope to see malaria parasites and work out the type; a rapid finger-prick test can help, but it may miss P. ovale, so microscope testing and sometimes repeat samples are needed. When results are unclear, some labs use a special test that looks for the parasite’s genetic material (DNA) to confirm the type.
Stages of Plasmodium ovale malaria
Plasmodium ovale malaria often follows a predictable pattern rather than a numbered staging system. Early symptoms of Plasmodium ovale malaria can be mild and easy to mistake for a common viral illness. Different tests may be suggested to help confirm the diagnosis and check for complications.
Incubation period
After an infected mosquito bite, there may be no symptoms for about 10–24 days. During this time the parasite grows quietly in the liver.
Liver dormant phase
Some parasites go to sleep in the liver as “hypnozoites.” These sleeping forms can wake up months or even years later and cause a relapse.
Early uncomplicated phase
Tiredness, headache, body aches, and sometimes nausea may appear. Fevers can be irregular at first.
Paroxysm cold stage
An attack can start with sudden chills and shivering. People may feel very cold and shaky.
Paroxysm hot stage
Fever rises quickly, often to 39–41°C (102–106°F). Skin may feel hot and flushed with pounding headache and rapid pulse.
Paroxysm sweating stage
Heavy sweating follows as the fever drops. Many feel drained and weak afterward.
Between attacks
With Plasmodium ovale malaria, fevers often return about every 48 hours. Some feel relatively well between these episodes.
Severe disease rare
Serious complications are uncommon with Plasmodium ovale malaria. Get urgent care for confusion, trouble breathing, severe weakness, or dehydration.
Recovery and relapse
Symptoms usually improve with the right treatment. Relapse can occur if the dormant liver forms are not cleared with anti‑relapse medication.
Outlook and prognosis
Looking ahead can feel daunting, but most people with Plasmodium ovale malaria recover well with prompt treatment. This parasite tends to cause milder illness than some other malaria types, though fever, chills, and fatigue can come in cycles. Relapses can happen weeks to months later because dormant liver forms can “wake up,” so medicines that target both the bloodstream infection and the liver stage are important. Doctors call this the prognosis—a medical word for likely outcomes.
For otherwise healthy adults and children who receive the right medicines quickly, the outlook for Plasmodium ovale malaria is very good, and death is uncommon. Severe complications are rare compared with falciparum malaria, but dehydration, anemia, and in pregnant people, risks to the baby can occur if care is delayed. People living with Plasmodium ovale malaria who have other health conditions—such as chronic illness, very young age, or pregnancy—may face a higher chance of complications and may need closer follow-up. Early symptoms of Plasmodium ovale malaria that return after feeling better often signal a relapse rather than a new infection.
With ongoing care, many people maintain full, active lives after treatment and have no long-term problems. Preventing relapse usually requires confirming enzyme safety (G6PD testing) before prescribing the liver‑targeting medicine; once completed, the chance of future episodes drops sharply. Talk with your doctor about what your personal outlook might look like, including relapse risk and how to spot warning signs early. Understanding the prognosis can guide planning and help you return to normal routines with confidence.
Long-term effects
Plasmodium ovale malaria can come back months or even years after the first illness if the liver form isn’t cleared. Long-term effects vary widely, and many people recover fully once relapses are prevented and anemia is treated. When infections do recur, ongoing tiredness or spleen swelling can linger between bouts. During pregnancy and in young children, repeated episodes can have broader health impacts.
Dormant liver stages can trigger new attacks long after the first episode. Relapses often start with the same early symptoms of Plasmodium ovale malaria—fever, chills, and sweats. These recurrences may happen several times over months to years.
Repeated infections can lower red blood cell levels and lead to persistent anemia. People may feel tired, look pale, or get short of breath with routine activity. Anemia usually improves once relapses stop.
The spleen may stay enlarged after repeated bouts, causing a feeling of fullness or discomfort under the left ribs. This can take weeks to settle even after symptoms improve. Very rarely, a suddenly painful, tender spleen can signal a rupture and needs urgent care.
Some people feel weak, low on energy, or less able to exercise for weeks after an acute episode. Concentration and sleep can be off for a while. Gradual recovery is common once infections are fully controlled.
How is it to live with Plasmodium ovale malaria?
Living with Plasmodium ovale malaria often means feeling well for stretches of time and then being hit by waves of fever, chills, headaches, and deep fatigue that can return weeks or even months later due to the parasite’s dormant liver stage. Daily life can be disrupted by these relapses, with missed work or school, careful planning around travel and access to care, and the need to complete specific medications that clear both bloodstream and liver forms. People around you may worry during febrile episodes and may need to help with childcare, errands, or transportation, but clear communication and a plan for prompt evaluation and treatment usually ease that burden. With preventive measures, adherence to prescribed therapy, and follow-up to confirm cure, many regain routine and confidence even in areas where malaria is a risk.
Treatment and drugs
Treatment for Plasmodium ovale malaria focuses on clearing the active infection and preventing relapse from dormant liver forms called hypnozoites. Most people receive an antimalarial to clear parasites in the blood, often artemisinin-based combination therapy or chloroquine where sensitivity remains, followed by primaquine or tafenoquine to target the liver stage and reduce the chance of the malaria returning. Before primaquine or tafenoquine, doctors usually test for G6PD deficiency to avoid serious hemolysis, and pregnant or breastfeeding people generally need alternative plans. Treatment often looks different for each person, with dosing and drug choice adjusted for age, pregnancy, other illnesses, and local resistance patterns. Alongside medical treatment, lifestyle choices play a role, including rest, fluids, fever control with acetaminophen/paracetamol, and prompt medical care if symptoms worsen or return.
Can you cure Plasmodium ovale malaria?
Yes—Plasmodium ovale malaria is usually curable with prompt antimalarial treatment. Doctors use medicines to clear the parasites from your blood, and a second medicine is often needed to kill “sleeping” forms in the liver so it doesn’t come back. Your care team will make sure the plan is safe for you—for example during pregnancy or if you have certain blood conditions—and will guide you on follow-up to confirm you’re fully cleared.
Non-drug treatment
Alongside medicines, non-drug therapies can ease symptoms, prevent dehydration, and lower the risk of complications from Plasmodium ovale malaria. These approaches focus on comfort, safety, and stopping mosquito bites to protect you and those around you. They’re supportive—helpful while you’re getting the medication that clears the infection and prevents relapse.
Frequent sips of water or oral rehydration solution replace fluids lost with fever and sweating. Aim for steady intake even if appetite is low. Clear broths and diluted juices can help if plain water is hard to tolerate.
Lukewarm sponging, light clothing, and a fan can make fevers more bearable. Avoid ice-cold baths, which can cause shivering and discomfort. Rest in a cool, well-ventilated room if possible.
Plan short rest periods and gentle activity as energy returns. Overexertion can worsen fatigue during recovery from Plasmodium ovale malaria. Gradually increase daily tasks as symptoms improve.
Small, frequent meals can help when nausea dulls appetite. Choose easy-to-digest foods with some protein and complex carbohydrates. Try soups, yogurt, eggs, rice, or bananas.
Your genes may have an impact on how drugs work for you
Genes can affect how your body processes antimalarial drugs for Plasmodium ovale, changing how well they work and whether side effects appear. For example, G6PD deficiency raises the risk of hemolysis with primaquine, and CYP2D6 variants can reduce its activation.
Pharmacological treatments
Most people with Plasmodium ovale malaria are treated with a medicine that clears the parasites from the blood, then another drug to prevent relapses from dormant liver forms. Chloroquine is commonly used for the blood stage where this parasite remains sensitive, and a second medicine like primaquine or tafenoquine is added later to stop it coming back. Severe illness is uncommon with P. ovale, but if it occurs, hospital treatment with IV artesunate is used. Not everyone responds to the same medication in the same way.
Clears the parasites from the blood and is the usual first choice when available. It’s generally well tolerated and considered safe in pregnancy.
Used when chloroquine isn’t available, as it works in a similar way against blood-stage parasites. It is not used for severe malaria.
Artemisinin-based combination therapy (such as artemether–lumefantrine) can be used if chloroquine isn’t an option or if mixed infection is suspected. This treats the blood stage of Plasmodium ovale malaria but does not prevent relapse from dormant liver forms.
This targets the dormant liver stage to prevent relapses after the blood-stage treatment. A G6PD blood test is needed first to avoid serious side effects, and it is not used during pregnancy or while breastfeeding unless the infant’s G6PD status is known. Many consider it the best medication for Plasmodium ovale malaria relapse prevention when G6PD is normal.
Genetic influences
Your genes don’t cause Plasmodium ovale malaria, but they can shape how your body responds and which medicines are safest. It’s natural to ask whether family history plays a role. A blood‑type variation called Duffy‑negative, common in parts of Africa and known to protect against P. vivax malaria, does not block P. ovale, so having this trait doesn’t prevent infection. Inherited enzyme differences such as G6PD deficiency don’t change your chance of catching the parasite, but they do matter for treatment because medicines used to clear dormant liver forms can trigger dangerous breakdown of red blood cells in people with this trait. Doctors generally check G6PD status before prescribing primaquine or tafenoquine to prevent relapse. Genetic factors in Plasmodium ovale malaria also include the parasite’s own types—two closely related forms—that may differ in how often illness comes back and how well some tests pick them up. Overall, exposure to infected mosquitoes drives risk, while genetics mainly guides testing, medication choices, and safety.
Is Plasmodium ovale malaria genetic?
Genetics matters for Plasmodium ovale malaria, but less than for some other malarias. Variants like sickle cell trait and G6PD deficiency can influence severity and drug safety. Parasite genetic differences may affect relapse patterns and resistance surveillance.
Having a genetic risk is not necessarily a diagnosis
Genetic variants are a routine feature of human biology and occur frequently across the population. The majority do not affect health and instead reflect ordinary human diversity. With many genes, having a variant that’s been associated with a condition points to a potential link, not a certain diagnosis—particularly when more than one gene and the environment play a role. That said, there are situations where one well-studied variant in a specific gene is enough to confirm a diagnosis.
Pharmacogenetics—how genetics influence drug effects
For Plasmodium ovale malaria, treatment uses one medicine to clear parasites in the blood and another to wipe out the dormant forms in the liver. Before taking primaquine or tafenoquine—the drugs that target the liver stage—doctors check for G6PD deficiency, an inherited enzyme difference that can cause dangerous breakdown of red blood cells with these medicines. If G6PD levels are low, your team will avoid these drugs or use a safer plan, and will treat the blood-stage illness with other medicines. Variants in a liver enzyme gene called CYP2D6 may affect how well primaquine works, and people with very low activity may be more likely to relapse, so your clinician may consider this if symptoms return. Genetics is only one factor, and other things—such as other medications you take, liver or kidney health, and pregnancy—also shape which drug and dose are safest. In practice, testing for G6PD is standard before primaquine or tafenoquine for Plasmodium ovale malaria, while pharmacogenetic testing for CYP2D6 is not routine but may be discussed if relapses occur.
Interactions with other conditions
Living with HIV, being pregnant, or having a weakened immune system can make Plasmodium ovale malaria harder to clear and more likely to relapse from its sleeping liver forms. Early symptoms of Plasmodium ovale malaria can overlap with other infections, and mixed infections with other malaria species sometimes occur, which can blur the pattern of fevers and deepen anemia. Long-term illnesses like chronic liver or kidney disease can complicate treatment choices and how your body handles antimalarial medicines. Inherited blood conditions matter too: people with G6PD deficiency can have dangerous breakdown of red blood cells with primaquine, the medicine used to target the liver forms, while sickle cell disease can add to anemia and hospital risk during an episode. For those without a working spleen, malaria may run a rougher course because the spleen helps clear infected red cells. Talk with your doctor about how your conditions may influence each other.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
What other conditions can cause similar symptoms to Plasmodium ovale malaria?
Other types of malaria can look the same, especially falciparum malaria (often more severe) and vivax malaria (which can flare up again weeks or months later). Among travel-related illnesses, dengue and typhoid fever often cause similar high fevers, headaches, and body aches. Early flu or COVID-19 can resemble malaria, and babesiosis—a tick-borne parasite infection of red blood cells—can mimic it closely.
History
Throughout history, people have described cycles of fever and chills that came and went with striking regularity, sometimes after travel or a stay near forests or farms. In parts of West and Central Africa, island regions of the western Pacific, and pockets of Southeast Asia, families noted a “milder” malaria that still left people worn down for days. The pattern—fever that spiked, eased, then returned weeks or even months later—set it apart in community stories and clinic notes.
First described in the medical literature as a distinct malaria in the early 20th century, Plasmodium ovale malaria was long overshadowed by the deadlier P. falciparum. Early doctors grouped many relapsing fevers together, not realizing different malaria parasites were involved. As microscope methods improved, clinicians began to see features in blood smears that suggested a separate species. Even then, reports were inconsistent because cases were scattered, often mild, and easily missed when people took antimalarials before a diagnosis was confirmed.
Over time, descriptions became more precise. Researchers recognized that P. ovale can form a dormant liver stage, which helps explain late relapses after someone feels well again. This was a turning point for understanding patterns seen by families and field workers: a child who seemed recovered could develop fever again after moving to a different town, or a traveler could fall ill months after returning home. These clinical clues matched what laboratory studies later confirmed.
In recent decades, awareness has grown that there are at least two closely related types—often called curtisi and wallikeri—circulating in overlapping areas. This helped explain why some people had shorter incubation times while others relapsed later than expected. Molecular testing clarified where P. ovale malaria persists and showed it is more widespread than older maps suggested, including in regions where routine testing was limited.
Despite evolving definitions, one theme has stayed constant: P. ovale malaria is usually less severe than falciparum malaria but can still cause significant illness, especially in young children, people who are pregnant, and those with limited access to care. Historical differences highlight why some health systems undercounted cases, focusing resources on the most lethal species while missing this relapsing form.
Advances in genetics and modern diagnostics now allow more reliable identification, guiding treatment that targets both the bloodstream infection and the dormant liver stage. Looking back helps explain why people experienced relapses that puzzled clinicians a century ago, and it underscores today’s emphasis on complete treatment to prevent those late returns of fever.