Babesia Travel Cases: Symptoms, Diagnosis, and Missed Infections
MISSED INFECTIONS?
WHY BABESIA IS OFTEN
OVERLOOKED IN TRAVELERS
Babesia travel cases are often missed because symptoms resemble malaria or flu-like illness, particularly in patients returning from endemic regions.
Babesia infections are increasingly identified in travelers returning from endemic regions such as the Northeastern United States.
Unlike Lyme disease, Babesia infection does not typically cause an erythema migrans rash, which can make diagnosis more difficult.
Because Babesia is not expected outside endemic regions, diagnosis is often delayed in travelers.
Babesia is transmitted by the same ticks that spread Lyme disease, which is why patients with persistent symptoms are often evaluated for Lyme disease coinfections including Babesia infection.
“Recently, sporadic cases of human babesiosis caused by several species of Babesia have been reported in other countries,” write the authors of “Imported Human Babesiosis, Singapore, 2018.”
Early Babesia Travel Cases
In 2003, Nohýnková and colleagues reported what was believed to be the first case of symptomatic Babesia microti infection imported into the Czech Republic from the United States.
In 2013, investigators described the first human case imported to Denmark in a 64-year-old patient with fever of unknown origin.
These early reports highlight how easily Babesia infections can be overlooked when travel exposure is not considered.
Case 1: Babesia Travel from US to Singapore
A 37-year-old man traveled to multiple countries in the year before his illness, including the United States.
After visiting the Northeastern USA, he noted a right ankle papule lasting 3 weeks, followed by high fever (104°F), rigors, and headaches that worsened over 18 days.
Initial treatment with amoxicillin did not improve symptoms.
Laboratory results showed thrombocytopenia and anemia, while blood smear revealed parasites within red blood cells suggestive of Babesia.
This combination—fever, anemia, and parasites on blood smear with negative malaria testing—is a key diagnostic clue.
The diagnosis of Babesia microti was confirmed with additional testing, and he was successfully treated with quinine and clindamycin.
Case 2: Babesia Travel from US to Spain
A 72-year-old man presented in Spain with a 15-day history of fever, arthralgia, fatigue, and decreased appetite after visiting Westchester County, New York.
Malaria was initially suspected because parasites were seen inside red blood cells, but testing was negative.
Babesia microti infection was presumed with a parasitemia of 0.5%.
After treatment with atovaquone and azithromycin, his infection resolved.
Why Imported Babesia Cases Are Missed
Babesiosis may present with fever, anemia, thrombocytopenia, fatigue, and flu-like symptoms that overlap with other infections.
Because Babesia parasites appear inside red blood cells, the infection can resemble malaria—especially in regions where Babesia is not endemic.
When malaria tests are negative, the diagnosis of babesiosis may be delayed.
A thorough travel history is essential. Patients who have visited endemic regions of the United States—particularly Massachusetts, Rhode Island, Connecticut, New York, and New Jersey—should be evaluated if they present with:
- Unexplained fever
- Thrombocytopenia
- Anemia
- Negative malaria tests despite parasites on blood smear
This pattern also applies to tourists visiting the United States who develop symptoms after returning home.
Editor’s Note
It is encouraging to see Babesia being recognized and treated appropriately—even in countries where the infection is not endemic.
As Babesia travel cases increase, awareness and careful history-taking will be critical for timely diagnosis.
Clinical Takeaway
Babesia should be considered in any patient with unexplained fever, anemia, and thrombocytopenia following travel to endemic regions.
A careful travel history remains one of the most important tools for diagnosis.
References
- Lim PL, et al. Imported Human Babesiosis, Singapore, 2018. Emerg Infect Dis. 2020.
- Nohýnková E, et al. First case of symptomatic Babesia microti infection imported into the Czech Republic from the United States. Emerg Infect Dis. 2003.
- Hildebrandt A, et al. First confirmed autochthonous case of human Babesia microti infection in Europe. Eur J Clin Microbiol Infect Dis. 2007.
- Guirao-Arrabal E, et al. Imported babesiosis caused by Babesia microti—A case report. Travel Med Infect Dis. 2020.
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
