Infectious Disease Compendium

Babesia

Microbiology

(2012 Review)

Protozoans that infect red cells of humans and animals. Includes B. microti in the US (the NE), B. divergins (Europe) and B. bovis in Europe. Over 100 others have been reported, especially in animals. Tick spread, after feeding on mice (the ticks, not the patient).

B. microti, B. divergens, B. duncani, and B. venatorum have caused human disease

B. microti also in the Yucatán State of Mexico (PubMed).

There is a B. crassa–like infection in northeastern China (PubMed).

It is not pronounced Babe-si-a, as I have heard, but ba-be-ze-a. Although it was discovered by Victor BabeČ™.

Epidemiologic Risks

Tick bite. Found all over the NE and SE of the US. Cases are increasing in the upper Midwest (PubMed), sometimes with Borrelia or Anaplasma.

Sometimes cases from transfusions (159 reports)(PubMed), and do not assume the blood in your hospital is as locally sourced as the chicken at the restaurant (Portlandia), blood can come from anywhere in the country (PubMed).

It is spreading East; here is hoping it does not reach the Great Pacific NW (PubMed).

Babesia has also been found in France, and I would suspect this is a marker for disease in all of Western Europe (PubMed).

Diagnosis has increased 20 fold this decade in the New York Lower Hudson Valley (PubMed) and it is creeping into Eastern Pennsylvania (PubMed).  Also increasing disease in Maine (PubMed). And "The reported incidence of confirmed babesiosis in Wisconsin increased 26-fold from 2001 to 2015" (PubMed) and there is an increase in cases in SW Pennsylvania (PubMed). As the climate changes so will the range of all environmental infections.

Blood transfusions and screening does decrease disease.

There is one case of transplacental spread and it is the most common transfusion infection in the US and there are a pair of cases from transplanted kidneys.

B. microti: Such cases occur in the Northeast and upper Midwest, primarily from May through October.

B. duncani and B. duncani–type organisms: Pacific Coast from northern California to Washington.

B. divergens–like organisms: Kentucky, Missouri, and Washington.

MO-1, an unnamed strain, has been found in patients in Missouri.

Europe: B. divergens, B. venatorum and B. microti.

Asia: B. microti–like organisms in Japan and Taiwan, and KO1 strain in South Korea.

Sporadic cases of Babesiosis all over the world.

Syndromes

Most infections are subclinical or mild. In the asplenic or immunoincompetent there can be fevers, "flu" like symptoms (no cough so how in hell can you have flu-like symptoms without the main symptom of flu?), hemolytic anemia, thrombocytopenia, and a transaminitis, often severe. It can present as fever, splenomegaly, and splenic infarcts (PubMed) as well as a splenic rupture (PubMed).

Symptoms occur 1 week to 2 months after the bite.

Asplenic, elderly, or immunocompromised have increased risk for symptomatic infection and complications, such as MOSF and death.

It causes a post-infectious warm-antibody autoimmune hemolytic anemia. The alleged mechanism(s) are in the (NEJM) report.

Around 1% will get a splenic rupture, more often in the young and healthy (PubMed).

Diagnosis

Serology PLUS looking for the organisms on the smear. There are some, shall we say, wackaloon labs, often beloved by naturopaths, that diagnosis Babesia (often with Lyme) with a promiscuity and lack of rigor that is most curious. If you are in ID, you probably know who they are.

In endemic areas up to 4% can be seropositive, limiting the utility of serology.

Treatment

Clindamycin 600 mg q 8h PLUS quinine 650 mg q 8h for 7-10 d.

OR

Atovaquone 750 mg every 12 hours plus azithromycin 500 mg on day 1 and 250 mg per day thereafter for 7-10 days (PubMed).

DO NOT give monotherapy as it leads to resistance.

Resistance can occur to azithromycin-atovaquone during the treatment in highly immunocompromised patients (PubMed).

Other drugs to try are doxycycline OR pentamidine. An AIDS patient with refractory disease was treated with atovaquone-proguanil (250 mg/100 mg) for prolonged courses in addition to red cell exchange (PubMed). In patients with poor immune systems, especially lymphoma can be difficult to treat (PubMed).

Smear positivity can persist for three weeks after successful treatment and PCR can persist for at least a month. The PCR should be negative after three months.

If > 10% parasitemia, consider exchange transfusion especially if really sick.

Resistance has occurred on therapy, albeit in a very immunocompromised patient (PubMed).

Notes

Co-infection with Borrelia (Lyme) and/ or Anaplasma occurs but rarely.

There seem to be labs that will diagnose this disease when it really isn't there. Beware. It is often a misdiagnosed infection of those who have "chronic" Lyme.

Curious Cases

Relevant links to my Medscape blog

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Last Update: 01/08/20.