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Letter
Babesiosis in Fairfield County,
Connecticut
John F. Anderson* and Louis A. Magnarelli*
*Connecticut Agricultural Experiment Station, New Haven, Connecticut,
USA
Suggested citation
for this article:
Anderson JF, Magnarelli LA. Babesiosis in Fairfield County, Connecticut.
Emerg Infect Dis [serial online] 2004 Mar [date cited]. Available
from: http://www.cdc.gov/ncidod/EID/vol10no3/03-0561.htm
To the Editor: Human babesiosis, caused by Babesia microti,
was initially described in the eastern United States in 1970 in a woman
vacationing on Nantucket Island, Massachusetts (1). With
few exceptions, almost all subsequent cases were recorded from islands
in the northeastern United States and Cape Cod, Massachusetts (2),
until this illness was diagnosed in 13 patients living in New London County
in southeastern Connecticut (3,4). B. microti
was isolated from white-footed mice, Peromyscus leucopus, captured
from 1988 to 1990 in the yards of patients. Babesiosis also was diagnosed
in persons living in Wisconsin (5) and in New Jersey
(6) who acquired the organism locally. The number of
cases of babesiosis reported by health departments on their Web sites
and by personal communication in Massachusetts, Rhode Island, and New
York State, was 330 from 1988 to 2002, 121 from 1994 to 2002, and 542
from 1986 to 2001, respectively. The number of cases reported by the
New York City Health Department from 1991 to 2000 was 75.
From 1991 to 2000, babesiosis was diagnosed in 230 persons residing in
New London County and adjacent Middlesex County, Connecticut (7).
Fifty-three additional cases were reported in five other counties in Connecticut,
but epidemiologic data did not indicate that these infections likely were
acquired within Connecticut. We now note a new and distinct geographic
focus by reporting the isolation of B. microti from rodents captured
in the yards of two patients in whom babesiosis was diagnosed at Greenwich
Hospital in 2002. These patients lived in Greenwich, Connecticut, which
is located in Fairfield County in the extreme southwestern part of the
state. Neither patient had traveled outside of the immediate area of Greenwich,
Connecticut, before onset of illness. We also trapped rodents in the yards
of two additional patients in whom babesiosis was diagnosed. These two
patients had traveled to Rhode Island shortly before becoming ill. Patients
became ill from June 23 to July 7, 2002, and none reported a tick bite.
Attempts to trap small mammals on the properties of the four patients
were made on July 22, 23, and 29, 2002. Rodents were captured in Sherman
box traps baited with peanut butter and apple. Approximately 0.3 mL of
blood was drawn from the heart of each animal into a syringe coated with
heparin or uncoated. Blood was kept on ice in the field and then returned
to the laboratory. A 3- to 5-week-old male Syrian hamster was injected
intraperitoneally with 0.1 mL of each blood sample.
Blood smears were obtained from a drop of blood taken from the tail of
each hamster on weeks 3 to 6 after injection. Blood cells were stained
with Giemsa and examined for B. microti at a magnification of 1,008x.
Hamsters were considered uninfected when no parasites were found in 75
fields of stained erythrocytes.
B. microti was isolated from rodents captured at the residences
of two of the patients who did not travel outside of the Greenwich area
6 weeks before onset of illness. Blood from two of three white-footed
mice and from the two eastern chipmunks, Tamias striatus, captured
in the yards of the patients, produced infections in injected hamsters.
Infections did not develop in hamsters injected with blood from 10 white-footed
mice captured at the residences of two patients who visited Wakefield
and Charlestown, Rhode Island, shortly before becoming ill.
B. microti is prevalent in rodent populations in Greenwich, Connecticut,
and causes human disease. Establishing evidence of B. microti in
rodents and documenting this protozoan parasite as the cause of human
disease in Greenwich are important. Relatively high populations of the
vector tick, Ixodes scapularis, are present in Greenwich and nearby
towns. In 2002, the health departments of Greenwich, Stamford, New Canaan,
and Darien submitted 1,671 I. scapularis ticks removed from persons
to the Connecticut Agricultural Experiment Station for identification
and testing for Borrelia burgdorferi. Two hundred and thirty cases
of Lyme disease were reported from these four towns in 2002 (Connecticut
Department of Public Health, unpub. data). With such extensive human exposure
to ticks and a relatively large number of Lyme disease cases in these
four towns and elsewhere in Fairfield County, the number of cases of babesiosis
is likely to increase appreciably in the future.
B. microti has been transmitted through blood transfusion in Connecticut
(8). Blood collection agencies in southwestern Connecticut
and adjacent Westchester County, New York, should be aware of the possibility
that blood donors could be infected with this pathogen. Physicians should
also be alert to the possibility that patients could be coinfected with
the etiologic agents of Lyme disease or human granulocytic ehrlichiosis.
Some patients in whom Lyme disease was diagnosed have been simultaneously
infected with B. microti (9,10).
Acknowledgments
We thank Michael
Vasil and Bonnie Hamid for their technical assistance; the staff of
Greenwich Hospital for assistance; Caroline Baisley and Doug Serafin
for helping coordinate the trapping of rodents in Greenwich; and Michael
Gosciminski, Palma Caron, and Dennis White for providing documentation
of several cases of babesiosis from the states of Rhode Island, Massachusetts,
and New York, respectively.
This study was supported
in part by Hatch funds administered by the U.S. Department of Agriculture.
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