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Babesia microti:an unusual travel-related disease
© Poisnel et al.; licensee BioMed Central Ltd. 2013
Received: 22 June 2012
Accepted: 18 February 2013
Published: 22 February 2013
Human babesiosis is a rare tick-borne infectious disease. The clinical presentation ranges from an asymptomatic form to a life threatening infection with severe hemolysis. Human babesiosis due to Babesia microti is the most common and is endemic in North America.
We report a European patient with severe pancytopenia and reactive hemophagocytosis related to a Babesia microti infection. Babesia infection was acquired during a travel in the USA.
Babesiosis should be considered in patients who traveled in endemic areas, especially North America for the most common agent Babesia microti.
Human babesiosis is a tick-borne infectious disease caused by intraerythrocytic protozoan species of the genus Babesia transmitted by Ixodes. Babesia microti is the most common cause of human babesiosis endemic in USA on the northeastern seabord and the upper midwest. The first confirmed case was a normosplenic individual on Nantucket Island published in 1970 . After additional cases the disease became known as Nantucket fever. The incubation period may last from 1 to 9 weeks and clinical features are similar to those of malaria. The severity is variable depending on the immune status of the host, ranging from an asymptomatic infection to a severe life threatening disease . Severe disease generally occurs in patients over the age of 50 years or with splenectomy, malignancy, HIV, or immunosuppressive medication. B. microti infections can also rarely be acquired by transfusion of blood products from asymptomatic donors . In Europe few isolated cases have been reported related to other Babesia species: B. divergens and B. venatorum. Most of European cases are observed in splenectomized patients .
The clinical symptoms and the biological abnormalities observed during babesiosis are very similar to Plasmodium infection. Thus malaria is often evoked even in travelers who have never visited a malarious area because of the rare “airport malaria” . This case underline that the diagnosis of babesiosis should be considered in patients who traveled in endemic areas, especially North America, for the most common agent Babesia microti. Babesia microti infection cannot be ruled out in patients with intact spleen in contrary to the European Babesia species (Babesia divergens and Babesia venatorum). Moreover in some rare cases spontaneous splenic rupture secondary to babesia microti infection have been reported . Babesiosis has been reported to be associated to reactive hemophagocytosis in few cases [7, 8] however regenerative hemolytic anemia is the most usual presentation . In the present case the unusual severe neutropenia and non-regenerative anemia led to the bone marrow aspiration analysis. Typical hemophagocytosis was seen however without evidence of phagocytosis of babesia infected red blood cells.
Diagnosis of babesia is usually strongly evoked by the blood smear analysis and can be confirmed by specific PCR, allowing to identify Babesia species and to exclude plasmodium infection. Despite some similarities with plasmodium, babesiosis does not respond to chloroquine. The use of clindamycin with quinine have been shown to be effective as the combination of atovaquone and azithromycin [2, 9]. Because Borrelia burgdorferi, the agent of Lyme disease, is transmitted by the same tick and is endemic in North America it should systematically be screened by serology in these patients.
The diagnosis of babesiosis should be considered in patients who traveled in endemic areas especially North America for the most common agent Babesia microti. Blood analyses usually show regenerative hemolytic anemia, thrombocytopenia, and elevated liver enzymes. In case of pancytopenia associated with non-regenerative anemia reactive hemophagocytosis should be evoked. Diagnosis of babesiosis can be made on blood smear analysis but needs usually more specific tests, as PCR, to be confirmed.
The patient has given his consent for the publication of this case report.
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