Published Date: 1997-07-22 23:50:00
Subject: PRO/AH> Murine typhus - California, USA (Pasadena)
Archive Number: 19970722.1526

MURINE TYPHUS - CALIFORNIA, USA (PASADENA)
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Date: Tue, 22 Jul 1997 17:14:17 -0700
From: Steve Berger <mberger@post.tau.ac.il>
[see
Murine typhus - California, USA (Pasadena) 970721142519]
In fact, "endemic typhus" in California may actually represent _Rickettsia
felis_ infection. The following summary on typhus-group rickettsiae in the
U.S. is extracted from The GIDEON software.
Endemic typhus is caused by _Rickettsia typhi_ (formerly _R. mooseri_) and
transmitted by the rat flea (_Xenopsylla_ or _Nosopsyllus_ spp.). Following
an incubation period of 10 to 20 days (range 4 to 18), the patient develops
fever, headache and myalgia. A truncal maculopapular rash (present in 60%)
appears on days 3 to 5 and persists for 4 to 8 days. The fever resolves after
12 to 16 days; and the case fatality rate (untreated cases) is 2%.
Diagnosis is based on serology; however, identification of rickettsiae in
smear or culture of skin lesions may be performed by specialized
laboratories.
Thge typical adult therapy consists of doxycycline 100 mg BID forX 3 to 5d;
however, some would prefer chloramphenicol (12.5 mg/kg QID X 3 to 5d) for
children.
High activity exists in the Rio Grande valley (southern Texas) and Los Angeles
area.
19,663 cases were reported during 1944 to 1953 (5,401 in 1944); 812 during
1954 to 1963; 315 during 1964 to 1973; 588 during 1974 to 1983. 33 cases were
reported from Los Angeles during 1984 to 1988 (cats and opossums implicated
as reservoirs); 50 cases nationwide in 1990; 43 in 1991 (22 in Texas); 28 in
1992 (18 in Texas); 25 in 1993. As of 1994, the disease was no longer
nationally notifiable.
Two deaths were ascribed to endemic typhus during 1982 to 1991.
The cat flea (_Ctenocephalides felis_) is an important vector in Texas and
California.
Another rickettsial disease (_Rickettsia felis_ infection) with similar
clinical features and cross-reactive serology is described in Texas and
California. Infested fleas are identified in Texas, California, Louisiana
and New York State.
_Rickettsia felis_ aquired from fleas (_Ctenocephalides felis_) of the
opossoum (_Didelphis marsupialis_). The incubation period is not known.
Signs include fever, headache and myalgia. A macular rash is present in only
20% of patients. Serological tests (IFA) and nucleic acid amplification have
been used; however, the `classic' serological response seen in endemic typhus
(Weil-Felix OX-19) may be positive in this disease as well. Therapy is not
established; however, drugs and dosages used in endemic typhus appear to be
appropriate for this disease as well.

Endemic typhus must not be confused with the more severe disease, epidemic or
louse-borne typhus. Epidemic typhus is caused by _Rickettsia prowazekii_ and
transmitted man-to-man by the body louse (_Pediculus_). A putative reservoir
has been suggested in the American flying squirrel (_Glaucomys volans_), with
enzootic transmission by squirrel fleas.
Following and incubation period of 10 to - 14 days (range 5 to 23), the
patient develops headache and myalgia. A truncal maculopapular rash appears
on days 4 to 7; and encephalopathy or myocarditis may ensue. Although fever
resolving after 2 weeks, convalescence is prolonged. The case-fatality rate
for untreated cases is 10% to 20%.
Diagnostic Tests and therapy are as for endemic typus
The last outbreak of epidemic typhus in the United States was reported in
1922. 15 cases of sylvatic typhus (with reservoir in the flying squirrel)
were reported in North Carolina, Virginia, West Virginia, Georgia, Tennessee,
Massachusetts and Pennsylvania. Highest rates are anticipated in rural areas
and during winter.
Other rickettsial infections of the United States include Rocky Mountain
spotted fever, Rickettsialpox and Q-fever. At least two species of the
closely related genus _Ehrlichia_ are also active.
---
Stephen A. Berger, M.D.
Tel Aviv Medical Center
e-mail: <mberger@post.tau.ac.il>
..........................................................................chc
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