Babesia Mistaken for Malaria: Two Travelers, One Fatal Outcome
Babesia infection is sometimes mistaken for malaria because both parasites appear inside red blood cells on blood smear. This diagnostic confusion can delay treatment and, in severe cases, lead to fatal outcomes.
International travel can further complicate diagnosis when patients develop tick-borne infections outside the regions where they were originally exposed.
In this Inside Lyme podcast, I discuss the Babesia treatment of two travelers from the United States who became ill after returning to South Korea—where physicians initially suspected malaria instead.
Kwon and colleagues described these cases in the Korean Journal of Parasitology in 2018.
Case 1: Babesia Misdiagnosed as Malaria — Patient Survives
The first patient was a 50-year-old woman admitted to a hospital in South Korea with fever, abdominal pain, and nausea.
Four weeks earlier she had visited a forested area in New Jersey. She recalled a reddish skin lesion on her right calf that was suspicious for a tick bite. Two days later she developed headache, muscle soreness, fever, and chills.
Had she remained in the United States, physicians might have suspected Lyme disease and possible tick-borne coinfections.
However, after traveling to South Korea—where malaria is more common—doctors initially suspected malaria. Her blood smear appeared suspicious for Plasmodium species and imaging revealed a splenic infarction. She was treated with hydroxychloroquine for presumed malaria.
Subsequent testing did not confirm malaria.
Physicians reviewed the blood smear again and identified a Maltese cross pattern characteristic of Babesia—a tetrad formation of parasites within red blood cells.
A PCR test confirmed Babesia infection.
After treatment for babesiosis was started, her fever, abdominal pain, and abnormal laboratory findings resolved within a day.
Case 2: Babesia Misdiagnosed as Malaria — Patient Dies
The second patient was a 72-year-old woman who presented to the same hospital with a fever of 99.9°F.
Laboratory testing revealed moderate anemia with hemoglobin of 10.8 g/dL and thrombocytopenia. Her C-reactive protein and erythrocyte sedimentation rate were elevated.
Malaria-like organisms were seen on the blood smear, although malaria antigen testing was negative.
When physicians reexamined the smear, they observed Maltese cross forms within the red blood cells—the same finding seen in the first patient.
She was started on atovaquone 250 mg/proguanil 100 mg and azithromycin 500 mg, medications marketed in the United States as Malarone and Zithromax.
Despite treatment, her condition worsened. She developed fever and pulmonary congestion.
Her therapy was changed to quinine and clindamycin, a regimen sometimes used in severe babesiosis.
She also underwent a red blood cell exchange transfusion, a procedure that removes infected red blood cells and replaces them with healthy donor cells.
Her condition deteriorated and she required intubation for respiratory failure.
Physicians added doxycycline to treat possible coinfection with Lyme disease or anaplasmosis.
Subsequent testing confirmed concurrent Lyme disease. Both IgM and IgG Western blot tests were positive.
Despite aggressive treatment, she died 31 days after hospital admission—an outcome similar to other fatal Babesia cases in which delayed diagnosis played a role.
Why Babesia Is Mistaken for Malaria
Only eight cases of babesiosis have been reported in South Korea, seven of which were imported cases.
Both Babesia and malaria parasites infect red blood cells and can appear similar on blood smear. In areas where malaria is endemic, physicians naturally suspect malaria first.
However, when malaria testing is negative, Babesia should be considered—particularly in travelers returning from the Northeastern United States, where babesiosis is more common.
Kwon cautions both clinicians and travelers:
“As the population traveling abroad increases each year, both physicians and travelers must be familiar not only with endemic diseases in their own regions but also with those from other parts of the world.”
Similar diagnostic confusion has also been reported in other travel-related Babesia cases from Singapore and Spain.
Babesia infection is also one of the most important Lyme disease coinfections and may complicate both diagnosis and treatment.
Key Differences Between Babesia and Malaria
Although Babesia and malaria can appear similar on blood smear, several features help distinguish them.
- Babesia may show a characteristic Maltese cross tetrad pattern
- Malaria antigen tests may be negative in Babesia infection
- Babesia exposure often occurs after tick bites in the Northeastern United States
- Malaria medications are not effective for babesiosis
What Clinicians Can Learn from These Cases
- Babesia infection can mimic malaria on blood smear.
- Symptoms of babesiosis may appear weeks after tick exposure.
- International travel increases the risk of diagnostic confusion.
- Older adults and delayed diagnosis increase the risk of severe disease.
- Earlier recognition of Babesia and Lyme disease may improve outcomes.
References
- Kwon HY, Im JH, Park YK, Durey A, Lee JS, Baek JH. Two Imported Cases of Babesiosis with Complication or Co-Infection with Lyme Disease in Republic of Korea. Korean Journal of Parasitology. 2018;56(6):609-613.
Related Reading
- Babesia and Lyme: What Patients Need to Know
- Babesia Travel: How Infections Cross Borders
- Fatal Babesia: A Family’s Story of Delayed Diagnosis
Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
Is there any cure for Babesia?
I start with Malarone and Zithromax I have more recently prescribed tafenoquine https://danielcameronmd.com/treatment-relapsing-babesia/ I have patients do well. Some relapse
I have found Malarone and Zithromax helpful I sometimes have to add other medications ie tafenoquine https://danielcameronmd.com/treatment-relapsing-babesia/. Some relapse