Another Reason to Avoid Ticks: Babesiosis

The incidence of babesiosis, a tick-bourne infection, in the Lower Hudson Valley (LHV), New York, increased 20 fold between 2001 and 2008. The rate increased from six cases per year to 119. The increased incidence was lower in the rest of New York: 1.6 fold. The infection can be acquired through blood transfusions, tick bites or prenatal exposure to the infectious agent, a microbe called Babesia microti. Clinicians should examine patients with hemolytic anemia and fever for the possibility of babesiosis, especially if they have had blood transfusions or have received tick bites.

Babesiosis, an infection of red blood cells, occurs in North America. The cause, Babesia microti, is transmitted by ticks (Ixodes scapularis), the same bloodsucker that carries the organism responsible for causing Lyme disease and Human Granulocytic Anaplasmosis (HGA). Unlike Lyme disease, babesiosis surfaced only recently, in 2001, in the LHV in New York. This study evaluates the emergence of babesiosis between 2001 and 2008, in seven counties that constitute the LHV.

* All reported instances of babesiosis, Lyme disease and HGA in the seven counties of the LHV were collected for this study. All cases were confirmed by blood smear tests for the disease-causing microbe.
* Complete hospital reports of diagnosis, confirmation and medical care were collected for the period between 2002 and 2009.
* Risk estimates were calculated within and across counties for characterization and prediction.

* Babesiosis cases increased 48.7 percent per year between 2001 and 2008 in the seven-county region of the LHV.
* Tick bites accounted for 15 hospitalized cases, blood transfusion for two and prenatal transmission for one.
* B. microti DNA was found in eight blood smears.
* Nearly 63 percent of patients were prone to infection because their immune systems were compromised by a preexisting state or condition such as age, cancer, removal of spleen or AIDS.
* Patients were hospitalized between three and 73 days.
* In most cases, a single course of antimicrobial therapy successfully treated the disease. In a few cases, more prolonged therapy was required. Only one death occurred: that of a 95-year old person with respiratory failure.

Next steps/Shortcomings
There may have been false positive results in the tests for the microbe due to the presence of closely related, non-infectious species of Babesia. This study failed to identify how the microbe spread to other areas from the locales in which it was originally endemic. These issues should be addressed in future studies.

The present status of babesiosis in the LHV region raises concern because it accounts for 45.6 percent of all cases reported in New York. This study showed that contaminated blood used in blood transfusions can be a source of the disease. There is therefore a need to ensure that blood products are free of the organism that causes babesiosis. A large population of ticks infected by the Babesia spp. also carries B. burgdorferi, the micorbe that causes Lyme disease. This points out the need to look for these co-existing diseases in patients. Both diseases can lead to severe illnesses that may even be fatal in some cases, specifically in people with cancer or AIDS. Physicians should be sure to check for babesiosis in patients having fever and hemolytic anemia.

For More Information:
Babesiosis in Lower Hudson Valley, New York, USA
Emerging Infectious Diseases, May 2011
By Julie T. Joseph; Sumith S. Roy, et al., The New York Medical College, New York, USA

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