Coinfection Fails to Affect Babesia Outcomes

Adults with Babesia who were coinfected with tick-borne zoonoses showed no increased risk for mortality or disease severity than those with Babesia alone, based on data from more than 3500 individuals.

Conducting the study was essential because of the rise in tick-borne infections, said lead author Paddy Ssentongo, MD, of the Division of Infectious Diseases and Epidemiology, Penn State Health Milton S. Hershey Medical Center, Hershey, Pennsylvania.

“If not promptly treated, the consequences are dire, which include severe disease, ICU admissions, and even death,” he said. The researchers hypothesized that coinfection with Babesia and other tick-borne pathogens would be associated with greater disease severity and mortality.

In a study published in Open Forum Infectious Diseases, the researchers reviewed data from 3521 patients with Babesia across the United States. The data came from the TriNetX database for the time between January 1, 1980, and July 24, 2023. The mean age of the patients was 56 years; 51% were men, and 78% were White. The primary outcome was 90-day mortality following a diagnosis of Babesia.

Overall, 42% of the patients had one or more coinfections. Of these, 41% were coinfected with Borrelia burgdorferi, 3.7% with ehrlichiosis, and 0.3% with anaplasmosis. Patients with coinfections were significantly more likely to receive doxycycline than those with Babesia only (25% vs 18%; P 

In an adjusted analysis, the odds of 90-day mortality were lower in coinfected patients, but the difference was not significant (adjusted odds ratio [aOR], 0.43). Secondary outcomes included acute respiratory distress syndrome, multiorgan failure, and disseminated intravascular coagulopathy. No significant differences in any of these outcomes appeared between the Babesia-only and coinfection groups (aOR, 1.56; aOR, 0.82; and aOR, 0.99, respectively).

Overall, the most common comorbidities were hypertension (42%), chronic obstructive pulmonary disease (18%), and diabetes (14%). The overall malignancy rate was 19%.

Ssentongo said he was somewhat surprised by the increase in new babesiosis cases per year and by the high rate of coinfections with other tick-borne illnesses, including Lyme disease and anaplasmosis.

The Babesia infection rate in the United States has been rising over the past decade at a rate of at least 9%, Ssentongo told Medscape Medical News. “Importantly, Babesia infection does not travel alone,” and clinicians should be aware that 4 in 10 patients are coinfected with other tick-borne diseases, each requiring a different treatment, he said.

“Healthcare providers should have a high index of suspicion of the disease in patients presenting with typical symptoms, even if these individuals do not remember a tick bite,” Ssentongo emphasized.

The study’s major limitation was the inability to analyze the data separately by state or county, which could have shown hot spots for infection, Ssentongo said. “Another limitation is the lack of blood parasitemia (the percentage of red blood cells infected), which could have been used to determine the severity of the disease,” he noted.

Looking ahead, more research is needed to determine whether red cell exchange improved mortality and outcomes among patients with higher parasite burdens or severe organ dysfunction, Ssentongo told Medscape Medical News. Also, “little is known regarding the long-term sequelae of the disease; many unanswered questions exist, such as the long-term effects on the brain,” he noted.

Outcomes Data Inform Care as Infection Rates Rise

“Cases of human babesiosis are increasing in the United States, and this study helped to characterize the mortality risk of babesiosis along with tick-borne co-infections,” said Shirin Mazumder, MD, associate professor and infectious disease specialist at the University of Tennessee Health Science Center, Memphis, Tennessee, in an interview.

“Since more of the population is experiencing tick-borne infections, it is important to be aware of the outcomes when tick-borne coinfections are involved,” said Mazumder, who was not involved in the current study.

“The results of this study were surprising to me, since I assumed that patients with Babesia infections who were coinfected with another tick-borne infection would have both higher mortality and disease severity,” Mazumder told Medscape Medical News.

The current study showed that patients with Babesia infections who were coinfected with B burgdorferi, anaplasmosis, and ehrlichiosis did not have a higher mortality rate or more severe disease, Mazumder noted. “Clinicians should have a low threshold to look for other tick-borne coinfections among patients with babesiosis, and presumptive treatment with doxycycline should be considered,” she said.

This study had a low number of coinfections with anaplasmosis and ehrlichiosis, Mazumder said. Asplenia and the elderly are known risk factors for more severe disease; the mean age in the current study was 56 years, and the rate of asplenia was 2%, she said. “It would be interesting to see if conducting a similar study including a more advanced age group and higher rates of asplenia would produce different results,” she noted.

Another limitation of the study was the inability to include parasitemia in the statistical analysis because of the lack of data from the database used in the study, Mazumder told Medscape Medical News. “Further research looking at parasitemia analysis may be beneficial,” she said. “Looking at complications, such as chronic fatigue, renal failure, and congestive heart disease, among patients with tick-borne coinfections may be a useful future study as well,” she said.

The study was supported by start-up funds from the Department of Public Health Sciences, College of Medicine, Penn State, part of a tenure-track professorship package for Ssentongo. The researchers had no financial conflicts to disclose. Mazumder had no financial conflicts to disclose.