Tick-Borne
Diseases of Massachusetts, 2000
Tick-Borne
Diseases Of Massachusetts, 2000
An
Update For Health Care Providers
Massachusetts Department of Public Health
Division of Epidemiology and Immunization
February 2000
I. Four tick-borne diseases endemic to coastal Massachusetts:
Human Granulocytic Ehrlichiosis (HGE), Rocky Mountain Spotted
Fever (RMSF), Babesiosis, Tularemia
-
All of
these diseases are of low frequency; all can cause life-threatening
illness.
-
HGE and
babesiosis are transmitted primarily by the tiny deer tick,
Ixodes scapularis.
RMSF is transmitted by the common dog tick, Dermacentor
variabilis. Tularemia is transmitted by both.
-
Coinfection
of Ixodes scapularis
with two or more of these human pathogens has been reported
and may be responsible for more severe variants of these tick-borne
diseases.
-
Since
residents from all areas of Massachusetts travel to coastal
Massachusetts, and infected individuals may not show clinical
signs until they have returned to their homes in other parts
of the state, taking a complete travel history is essential
when considering many infectious diseases.
-
The tick
vectors of these infectious agents are widely distributed
throughout the state, and the infections may spread to central
and western parts of Massachusetts, as has happened with Lyme
disease. (Lyme disease is covered under a separate update.)
-
The greatest
risk of infection with any of these agents is from April through
August, when ticks are most active.
II.
Reporting
- Rocky Mountain
spotted fever, babesiosis, and tularemia are reportable by law
to the local board of health or the Massachusetts Department
of Public Health (MDPH).
- Although
human granulocytic ehrlichiosis (HGE) is not yet reportable
by law, to assist us in accurately estimating the prevalence
of this disease, the MDPH encourages direct reporting of this
disease to the MDPH Division of Epidemiology and Immunization
at (617) 983-6800. It is believed that cases of HGE are
currently significantly underestimated.
III.
Summary of clinical symptoms, incidence, and etiology
-
Human
Granulocytic Ehrlichiosis (HGE)
HGE, an
acute febrile illness caused by an agent similar or identical
to the veterinary pathogens Ehrilichia
equi and Ehrilichia
phagocytophila, can be mistaken for a rashless Lyme disease
or babesiosis, especially when associated with a history of
tick attachment. Since its discovery in 1993, over 449 cases
of HGE have been collected by the Centers for Disease Control
and Prevention (CDC). To date, 10 confirmed cases of
HGE have been identified in Massachusetts; the majority of
cases occurred in tick-exposed residents of Cape Cod and the
surrounding islands. Clinical features of HGE include
fever, headache, malaise, myalgia, chills, sweats, nausea,
and vomiting. Cough, arthralgia, confusion, and a macular
or papular rash at any site on the body occur, but are less
common. Laboratory findings commonly include leukopenia,
thrombocytopenia, and elevated liver function tests.
HGE is treatable with doxycycline and other tetracyclines.
The effectiveness of chloramphenicol, preferred by many physicians
for use in younger children, remains controversial.
As HGE may progress swiftly to become life-threatening, it
is critical to begin treatment for HGE as soon as the diagnosis
is strongly suspected (even prior to laboratory confirmation).
-
Rocky
Mountain spotted fever (RMSF)
RMSF, caused
by the bacterium Rickettsia
rickettsii, is a systemic, febrile illness with a characteristic
rash that usually occurs before the sixth day of illness.
Frequently described clinical features include fever, headache,
myalgia, toxicity, malaise, and nausea or vomiting, with abdominal
pain and cough being noted less frequently. The rash
first appears more than 48 hours after the onset of illness
on the extremities and then spreads proximally to the trunk;
there is often involvement of the palms and soles. However,
the rash is not a universal feature of the illness.
Prompt recognition and treatment of RMSF are important as
the disease can be fatal. RMSF is most often reported
from Cape Cod and the surrounding islands, although some cases
have occurred in central Massachusetts. One confirmed
case of RMSF was reported in 1999, with no cases in 1998 or
1997, two cases in 1996, one in 1995, four cases in each of
1994 and 1993, three cases in 1992, 4 cases in 1991 and 15
in 1990.
-
Babesiosis
Babesiosis,
caused by the parasite Babesia
microti, resembles malaria. Persons who are asplenic
are particularly susceptible to symptomatic babesiosis and
more severe disease. It is typically characterized by
a gradual onset of malaise, anorexia and fatigue, followed
by intermittent fever (as high as 104oF) and one
or more of the following: chills, sweats, myalgia, arthralgia,
nausea or vomiting. There were 41 confirmed cases of
babesiosis reported in Massachusetts in 1999, 65 cases in
1998, 20 cases in 1997, 20 cases in 1996, 13 cases in 1995,
15 cases in 1994, 6 in 1993, 14 in 1992, 9 in 1991 and 3 in
1990. Babesiosis is diagnosed by observing the parasite
in red blood cells on thick and thin blood smears with Giemsa
solution. A serologic antibody test is now available
at the Centers for Disease Control and Prevention (See Section
IV).
- Tularemia
Tularemia,
caused by the bacterium Francisella
tularensis, is usually characterized by high fever and severe,
influenza-like constitutional symptoms of chills, myalgia, and
headache. The incubation period averages 3 to 5 days,
but can be as long as 21 days. Although the infection
is commonly acquired from ticks, it can be acquired by inhalation,
ingestion of contaminated water or undercooked meat, or direct
contact with infected animals. Depending on the mode of
transmission, the patient may have one of several tularemic
syndromes, including the ulceroglandular, oculoglandular, oropharyngeal,
glandular, typhoidal, or pneumonic syndromes. Over 100
species of wild and domestic animals are susceptible, including
rabbits, squirrels, deer, cats, and cattle. In Massachusetts,
major reservoirs of tularemia include ticks and rabbits. There
were 5 confirmed cases of tularemia reported in Massachusetts
in 1999, 3 cases in 1998, 1 case each in 1996, 1994, and 1992,
5 cases in 1991, 4 cases in 1990 and no cases in 1993, 1995,
and 1997. Streptomycin for 6 to 10 days is the usual therapy
for infected persons, and gentamicin also appears effective.
Bacteriostatic antibiotics, such as tetracyclines and chloramphenicol,
have been associated with treatment failure and relapse.
A fourfold or greater rise in the serum F.
tularensis agglutinin titer frequently is evident after
the second week of illness and is considered diagnostic.
A single convalescent titer of 1:160 or greater is consistent
with recent or past infection.
In rare cases of acute illness where the patient may not
yet have developed antibodies, physicians may want to culture
specimens (biopsy, aspirate, bone marrow) for F.
tularensis.
IV.
Testing
The
Viral Serology Laboratory at the State Laboratory Institute (SLI),
Massachusetts Department of Public Health (MDPH), 305 South Street,
Jamaica Plain, MA 02130, provides free serologic testing for RMSF
(R. ricketsii). Samples for serology should be sent to the above
address. For HGE and babesiosis, sera should be sent to
the MDPH Viral Serology Laboratory, which will then forward it
to the CDC for testing. For tularemia, the MDPH Enterics
Laboratory provides free serologic testing. Samples should
be sent to Room 406 or 407, MDPH, 305 South Street, Jamaica Plain,
MA 02130. Physicians wishing to have specimens cultured
for F. tularensis should
call the MDPH Reference Laboratory at 617-983-6607.
For
additional information about prevention and epidemiology, contact:
Division
of Epidemiology and Immunization, MDPH
617-983-6800
For
information about submitting specimens to the SLI, contact:
Viral
Serology Laboratory, MDPH
Enterics Laboratory, MDPH
Reference Laboratory, MDPH |
617-983-6396
617-983-6609
617-983-6607 |
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