Babesia Travel Cases: How Tick-Borne Infections Cross Borders
Babesia travel cases are increasingly reported as international travelers carry tick-borne infections across borders. Several countries have documented imported babesiosis in travelers returning from endemic areas such as the Northeastern United States.
Babesia is frequently 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.”
These imported cases include:
- Babesia microti (Germany, Australia, South Korea)
- Babesia microti-like (Japan, Taiwan, China)
- Babesia duncani (United States, Canada)
- Babesia divergens (Europe)
- Babesia venatorum (Europe, China)
- Babesia crassa-like (China)
- Babesia motasi-like (South Korea)
Although babesiosis is traditionally associated with the Northeastern United States, international travel has revealed how tick-borne infections can spread beyond endemic regions.
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 of Babesia microti infection imported to Denmark from the United States by a 64-year-old female traveler with fever of unknown origin.”
According to the authors, “The case raises the possibility that Babesia infections may be under-diagnosed, [and] illustrates the importance of a thorough travel history.”
As international travel increases, clinicians worldwide are more likely to encounter patients who acquired tick-borne infections abroad.
Case 1: Babesia Travel from US to Singapore
A 37-year-old man traveled to multiple countries in the year before his illness, including Vietnam, Thailand, Indonesia, Cambodia, and the United States.
On June 17, 2018, after visiting the Northeastern USA, he noted a right ankle papule that lasted 3 weeks.
“He sought consultation at a travel clinic [in Singapore] because of high fever (104°F), rigors, and headaches, which had persisted and worsened over 18 days,” writes Lim and colleagues.
Doctors initially prescribed amoxicillin, but the symptoms persisted.
Laboratory results revealed moderate thrombocytopenia and anemia, and malaria blood films showed trophozoites within erythrocytes suggestive of Babesia.
The doctors confirmed the diagnosis of Babesia microti with additional testing. He was successfully treated with quinine and clindamycin.
Case 2: Babesia Travel from US to Spain
“A 72-year-old man with a 15-day history of fever, generalized arthralgia, asthenia, and decreased appetite was admitted to Hospital Universitario San Cecilio, Granada, Spain,” write Guirao-Arrabal and colleagues.
The patient had a history of night sweats and elevated inflammatory markers. He also had type 2 diabetes.
His travel history included a visit to a park in Westchester County, New York, an area considered endemic for babesiosis.
Malaria was initially suspected because parasites were seen inside red blood cells. However, malaria antigen and PCR tests were negative.
Babesia microti infection was presumed with a parasitemia of 0.5%. After treatment with atovaquone and azithromycin, his parasitemia resolved.
Why Imported Babesia Cases Are Missed
Babesiosis may present with fever, anemia, thrombocytopenia, fatigue, and flu-like symptoms that overlap with other infections.
Babesia parasites appear inside red blood cells on blood smear, a pattern that can resemble malaria. Clinicians outside endemic areas may therefore assume malaria first.
When malaria tests return 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 for Babesia if they present with:
- Unexplained fever
- Thrombocytopenia
- Anemia
- Negative malaria tests despite parasites on blood smear
This pattern also applies to tourists visiting the US 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 continue to rise, awareness will be critical for timely diagnosis.
Frequently Asked Questions
Can you get Babesia while traveling internationally?
Yes. Babesia travel cases occur when people visit endemic areas such as the Northeastern United States and bring the infection home. Symptoms may appear weeks after travel.
Why is Babesia confused with malaria?
Both infections show parasites inside red blood cells on blood smear. Clinicians in non-endemic areas may assume malaria first—but when malaria tests are negative, Babesia should be considered.
Which countries have reported imported Babesia cases?
Cases have been reported in Singapore, Spain, Denmark, Czech Republic, Germany, Australia, South Korea, and other countries.
What should doctors ask about travel history?
Doctors should ask whether patients visited the Northeastern United States, spent time outdoors in wooded areas, or noticed tick bites or unexplained rashes before symptoms began.
How is Babesia treated in travelers?
Standard treatment is atovaquone and azithromycin or quinine and clindamycin. Both cases described here resolved after appropriate therapy.
Clinical Takeaway
As international travel increases, babesiosis should be considered in patients with unexplained fever, anemia, and thrombocytopenia after visiting endemic regions. A careful travel history remains essential 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.
