Babesia divergens–like Infection, Washington State

Abstract

Most reported U.S. zoonotic cases of babesiosis have occurred in the Northeast and been caused by Babesia microti. In Washington State, three cases of babesiosis have been reported previously, which were caused by WA1 (for “Washington 1”)-type parasites. We investigated a case of babesiosis in Washington in an 82–year-old man whose spleen had been removed and whose parasitemia level was 41.4%. The complete 18S ribosomal RNA gene of the parasite was amplified from specimens of his whole blood by polymerase chain reaction. Phylogenetic analysis showed the parasite is most closely related, but not identical, to B. divergens (similarity score, 99.5%), a bovine parasite in Europe. By indirect fluorescent-antibody testing, his serum reacted to B. divergens but not to B. microti or WA1 antigens. This case demonstrates that babesiosis can be caused by novel parasites detectable by manual examination of blood smears but not by serologic or molecular testing for B. microti or WA1-type parasites.

In Vitro Cultivation of a ZoonoticBabesiasp. Isolated from Eastern Cottontail Rabbits (Sylvilagus floridanus) on Nantucket Island, Massachusetts

“…Additionally, an acute case of babesiosis also attributed to a B. divergens-like agent occurred in Washington State (10). The organism in all three cases was described as morphologically and molecularly similar to B. divergens.…”

“…The SSU rRNA gene sequence is nearly identical to that of B. divergens (accession numbers U16370 [11] and AY046576 [12]). A third similar infection was recently reported from Washington State (10).…”

“…3). The sequence shares 99.8% identity, differing in three base positions, with that of B. divergens from cattle (accession numbers U16370 [10] and AY046576 [11]) (Fig. 3).…”

Babesiosis Acquired through Blood Transfusion, California, USA

“…Most human infections reported in the United States are attributed to B. microti and occur most frequently in the Northeast and less commonly in the Midwest (1). Infrequently, babesiosis cases have been documented in California and Washington; however, these cases were caused by local Babesia-like isolates, including B. duncani and a B. divergens-like parasite (1)(2)(3). B. microti infection is often asymptomatic but can potentially be severe and even fatal, especially in the elderly, asplenics, and other immunosuppressed persons.…”

“…The initial examination showed he had hypotension without fever, joint swelling, headaches, or rash. Laboratory evaluation showed a hemoglobin concentration of 8.4 mg/dL, a platelet count of 71,000/mm 3 , and a leukocyte count of 3.5 × 10 3 /mm 3 with 19% bands. Results of liver function tests showed mild elevations in levels of aspartate transaminase (202 mg/dL), alanine transaminase (33 mg/ dL), and total bilirubin (0.7 mg/dL).…”