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Letter
Rickettsia felis
in the United Kingdom
Martin J. Kenny,* Richard J. Birtles,† Michael J. Day,* and Susan
E. Shaw*
*University of Bristol, Langford, Somerset, United Kingdom; and †University
of Liverpool, Leahurst, Neston, Cheshire, United Kingdom
Suggested citation for this article: Kenny MJ,
Birtles RJ, Day MJ, Shaw SE. Rickettsia felis in the United Kingdom.
Emerg Infect Dis [serial online] 2003 Aug [date cited]. Available
from: URL: http://www.cdc.gov/ncidod/EID/vol9no8/03-0314.htm
To the Editor: Rickettsia felis is a bacterium transmitted
by the cat flea (Ctenocephalides felis), which also acts as a reservoir
by means of transovarial transmission (1–3). The distribution
of R. felis is potentially as wide as that of its insect host,
and to date, its presence has been confirmed in cat flea populations in
North and South America and southern Europe (4,5). R.
felis was first identified as a human pathogen in 1994 (6),
and cases of “flea-borne spotted fever,” which have signs and symptoms
of febrile exanthema, have now been reported in the United States, Mexico,
Brazil, France, and Germany (7,8). To our knowledge,
reports on the presence of R. felis, or indeed any other spotted
fever group rickettsia, in the United Kingdom have not been published.
To determine whether R. felis is present in the United Kingdom,
we surveyed cat fleas collected from dogs and cats seen at veterinary
practices in southern England and Northern Ireland. A total of 31 dogs
and 79 cats from veterinary practices in Bristol, Dorset, London, Devon,
Gloucestershire, Hampshire, and Antrim were included in our study. Fleas
were collected by combing these animals for 10 minutes. All fleas from
each animal were pooled in 70% ethanol. A total of 316 Ct. felis
(Bouché, 1835), identified by using accepted morphologic criteria, were
obtained, with each animal yielding one to five fleas. DNA was extracted
from each of the 110 flea pools by using a standard silica cartridge method
(QiaAmp DNA mini kit, QIAGEN Ltd., Crawley, West Sussex, U.K.) using the
manufacturer’s instructions for tissue DNA extraction. The presence of
rickettsial DNA was determined by using the polymerase chain reaction
(PCR) with oligonucleotide primers that target rickettesial ompB
(5) or gltA (2) genes. Positive
control material was cultured R. felis. Rigorous controls to limit
contamination were carried out, including the use of separate, dedicated
rooms for DNA extraction, PCR setup, and gel analysis. Amplification products
obtained from ompB and gltA PCRs were analyzed by using
DNA sequencing. Sequences obtained were edited by using BioEdit (available
from: URL: http://www.mbio.ncsu.edu/BioEdit/bioedit.html).
Similarity to published sequences was determined with the BLAST program
(available from: URL: http://www.ncbi.nlm.nih.gov)
hosted by the National Centre for Biotechnology Information.
Eighteen flea DNA pools were positive for spotted fever group rickettsia.
All 18 yielded PCR products with both ompB and gltA-targeting
PCRs. The ompB and gltA DNA sequences of all PCR products
were 100% identical to those published for R. felis, thereby providing
evidence for the presence of R. felis in fleas collected from >16%
of the animals surveyed. PCR-positive fleas were collected from 4 dogs
and 14 cats from Bristol, Hampshire, Dorset, and Northern Ireland. Taking
into account the number of fleas in each pool, we estimate that 6% to
12% of the fleas collected were infected with R. felis.
This study represents the first description of a spotted fever group
rickettsia endemic to the United Kingdom. The species detected, R.
felis, has clear public health implications. The bacterium appears
to be widely distributed within the country, infecting a geographically
dispersed population of Ct. felis. Up to 12% of Ct. felis
may be infected with R. felis, a flea that is by far the most common
species of ectoparasite encountered on cats and dogs in the U.K. mainland.
Furthermore, Ct. felis often feeds on humans.
Clinicians encountering patients with fever or rash (or both) and a history
of cat contact or flea bites should consider a diagnosis of R. felis.
Laboratory confirmation of infection is not easy, but in vitro culture
of R. felis, and hence material for a serologic assay for the diagnosis
of human R. felis infections, has recently been described, and
serology appears to be an accurate indicator of exposure (9).
As with other spotted fever group rickettsial infections, molecular diagnostics
may provide a useful alternative approach to detecting and identifying
R. felis in infected tissues. In culture, R. felis has been
shown to be resistant to erythromycin (unlike other rickettsia), gentamicin,
amoxicillin, and trimethoprim-sulfamethoxazole. Thus, infection with this
bacterium should be considered in cases of antibiotic-insensitive fever
with a rash, especially in young, old, and immunosuppressed persons. The
organism is sensitive to doxycycline, rifampicin, thiamphenicol, and fluoroquinolones
(10)
Acknowledgments
We thank Alex Davies
and Anne Seabright for assistance with collecting and processing the
fleas and D. Raoult for providing Rickettsia felis.
Novartis UK provided
financial assistance with this project.
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