Why Babesiosis Can Be More Severe in Older Adults

Babesiosis cases are increasing in several endemic states
Older adults may face greater risk of severe illness and complications
Some patients may require longer treatment and closer monitoring

Babesiosis in older adults is more likely to cause severe illness, hospitalization, prolonged recovery, and occasionally life-threatening complications than in younger, otherwise healthy patients. Age, immune function, coexisting medical conditions, anemia, thrombocytopenia, delayed diagnosis, and tick-borne co-infections can all influence the course of illness.

Overall, the number of individuals contracting Babesia is rising. The annual number of reported cases increased from 4 per 100,000 to 9 per 100,000 in the United States between 2006 and 2017. Among adults over age 85, the annual incidence was 4 per 100,000. In comparison, the annual incidence of Lyme disease among adults over age 65 was 15.98 per 100,000. Cases of babesiosis in older adults are also increasing and may require longer treatment.

Most cases of Babesia occurred in the Lyme-endemic states of Massachusetts, Rhode Island, Connecticut, New York, and New Jersey, according to the authors. Other states reporting Babesia cases included Florida, Pennsylvania, California, Maryland, and Virginia. Cases were also reported in New Hampshire, Maine, Vermont, Minnesota, Wisconsin, Texas, North Carolina, and Illinois.

Why Babesiosis Can Be More Severe in Older Adults

Babesiosis has become an increasing concern in the Northeast and upper Midwest. CDC surveillance found rising reported babesiosis incidence in several northeastern states, including Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, and Vermont.

The expanding geographic distribution of Babesia means clinicians should consider the diagnosis even outside traditionally recognized endemic areas.

This matters for older adults because severe babesiosis is more likely when patients have advanced age, immune compromise, asplenia, cancer, congestive heart failure, or other comorbidities.

How Babesiosis Is Diagnosed

The most common test used to diagnose Babesia in clinical settings was a peripheral blood smear, wrote Menis and colleagues in a related paper. [2] Because parasitemia may decline after several days, Babesia can become more difficult to detect on a peripheral blood smear, making PCR or antibody testing increasingly helpful. In physician offices, antibody and PCR testing were the most commonly used diagnostic methods. [2]

Diagnosis may be delayed when patients do not recall a tick bite, do not have a rash, or present with nonspecific symptoms such as weakness, fever, sweats, jaundice, anemia, low platelets, or worsening fatigue.

Co-infections Can Be Deadly

A Babesia infection can be serious. “Patients co-infected with Lyme disease experienced more symptoms and a more persistent episode of illness than did those (n=10) experiencing babesial infection alone,” wrote Krause and colleagues. [3]

In another paper, the authors explain, “Immunocompromised people who are infected by B. microti are at risk of persistent relapsing illness.” [4]

For some patients, particularly older adults, babesiosis can be more serious. “Babesiosis can be life threatening, particularly for persons who are asplenic, immunocompromised, or elderly,” wrote Krause and colleagues. [4]

An 85-Year-Old Man Died From Babesiosis and Ehrlichiosis

The following case illustrates how rapidly severe babesiosis can progress in an older adult when co-infections and organ dysfunction are present.

Javed and colleagues describe the case of an 85-year-old man who died from concurrent babesiosis and ehrlichiosis. [5]

He was an avid gardener and golfer who was in good health except for hypertension. He did not recall a tick bite or rash. The man was hospitalized with weakness and jaundice. Laboratory testing revealed mild anemia, severe thrombocytopenia, mildly elevated bilirubin, and mildly impaired renal function.

The physicians diagnosed babesiosis after a bone marrow biopsy revealed intraerythrocytic inclusions, or tetrads, characteristic of Babesia infection. In retrospect, his admission blood smear demonstrated parasitemia involving 8% of red blood cells. Both Babesia IgM and IgG antibody tests were positive.

Read more: Older adults with Lyme disease more likely to have unfavorable treatment outcomes

The older patient was treated with intravenous clindamycin and quinine. His anemia worsened despite transfusion of two units of blood, and he was transferred to a tertiary care center for possible exchange transfusion. Azithromycin was added, but atovaquone was not.

His condition continued to deteriorate. His oxygen saturation fell to 84%, and he subsequently developed bilateral pneumonia, renal failure, hepatic failure, and coma. He became too ill to undergo exchange transfusion.

He died within 60 hours of admission to the tertiary care center.

Postmortem testing was positive for Human Monocytic Ehrlichiosis. He never received doxycycline, the standard treatment for ehrlichiosis.

This case illustrates how delayed recognition of tick-borne co-infections can rapidly lead to life-threatening complications in vulnerable older patients.

Treatment of Babesiosis in Older Adults

Krause and colleagues reported that a 10-day course of Mepron (atovaquone) plus Zithromax (azithromycin) was as effective as clindamycin plus quinine while causing fewer adverse effects. [3] Medicare beneficiaries were far more likely to receive Mepron with Zithromax than clindamycin with quinine. [1]

Some older patients with babesiosis require longer treatment. Krause and colleagues reported that immunocompromised patients and older adults were more likely to require prolonged therapy. [4]

“Cases of babesiosis among older adults are increasing, and studies report these patients are more likely to require longer treatment.”

In another paper, the authors point out that, “Such patients generally require antibabesial treatment for >or=6 weeks to achieve cure, including 2 weeks after parasites are no longer detected on blood smear.” [4]

More than one-third of older adults with babesiosis did not receive anti-Babesia therapy during their initial evaluation. The study was not designed to determine whether these patients were treated later.

IDSA Position on Severe Babesiosis

The 2020 Infectious Diseases Society of America (IDSA) guidelines highlighted concerns regarding severe babesiosis in older adults. “Numerous immunodeficiencies and comorbidities have been associated with severe babesiosis, including asplenia and hyposplenism, cancer, congestive heart failure, HIV infection, immunosuppressive drugs, and advanced age.” [6]

For immunocompromised patients, the IDSA recommends monitoring Babesia parasitemia using peripheral blood smears even after patients become asymptomatic and until blood smears are negative. PCR testing should be considered if blood smears become negative but symptoms persist (weak recommendation, moderate-quality evidence).

The IDSA guidelines also recommend longer treatment for highly immunocompromised patients. “A subgroup of highly immunocompromised patients reported in a case control study required at least 6 consecutive weeks of antibiotic therapy, including 2 final weeks during which parasites were no longer detected on peripheral blood smear.” [6]

However, relapse can still occur. “A few cases of relapse despite at least 6 consecutive weeks of atovaquone plus azithromycin demonstrate that resistance to atovaquone and/or azithromycin can emerge in highly immunocompromised patients during an extended course of this antibiotic combination,” wrote Krause and colleagues. [6]

Editor’s note: I share the same concerns regarding babesiosis in older adults and base the duration of antibiotic therapy on each patient’s clinical response to treatment.

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Frequently Asked Questions

Why can babesiosis be more severe in older adults?

Babesiosis can be more severe in older adults because advanced age, immune compromise, asplenia, heart disease, cancer, and other comorbidities increase the risk of anemia, thrombocytopenia, organ complications, relapse, and prolonged illness.

Can older adults need longer treatment for babesiosis?

Yes. Some older adults, especially those who are immunocompromised or have persistent parasitemia, may require longer treatment and closer monitoring than otherwise healthy patients.

What tests are used to diagnose babesiosis?

Babesiosis may be diagnosed with a peripheral blood smear, PCR testing, and antibody testing. Blood smear testing is often most useful early in infection, while PCR may help when parasitemia is low or symptoms persist.

Can babesiosis occur with Lyme disease?

Yes. Babesiosis and Lyme disease are both transmitted by Ixodes ticks in many endemic regions. Patients with both infections may experience more severe or prolonged illness than those with babesiosis alone.

What symptoms may suggest severe babesiosis?

Severe babesiosis may cause high fever, drenching sweats, profound fatigue, anemia, jaundice, thrombocytopenia, shortness of breath, kidney injury, liver abnormalities, or worsening illness in an older or immunocompromised patient.

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Clinical Takeaway

Babesiosis can be more severe in older adults, especially when diagnosis is delayed or when patients have immune compromise, asplenia, anemia, organ dysfunction, or tick-borne co-infections.

Prompt recognition of babesiosis, evaluation for Lyme disease and other tick-borne co-infections, and individualized treatment are especially important for older adults and immunocompromised patients, who face the greatest risk of severe disease.

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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