|
Health Advisory for Veterinarians
Tularemia in Western Washington,
2005
Seven human cases of tularemia in Cowlitz (2),
Clark (2) and Thurston (2), and King(1) County residents have been
reported between May 28, 2005 and August 15, 2005. This compares to a
statewide average of 1-4 cases annually. Also, seven dogs and cats
(1.9%) showed serological evidence of exposure to tularemia in a recent
veterinary serosurvey involving 370 cats and dogs in 18 counties
statewide.
In the subset of samples from Pierce, Lewis,
Clark and Cowlitz counties, 4.4% of 90 pet dogs and cats showed evidence
of exposure to tularemia. In Washington, there are natural foci of
tularemia cycling in wild rodents. Veterinarians should be aware of the
potential for an infected pet to be seen at your clinic.
Tularemia causes die-offs or illness in rabbits,
squirrels, voles, muskrats, beaver and rodents. Infected small mammals
may be obviously ill (depressed, anorexic, ataxic, inactive, have a
roughened coat) or may be found dead. Sick rabbits and rodents are
easily caught and eaten by outdoor pets; ticks and deer flies also
transmit the infection. Cats and dogs that are infected with tularemia
can transmit infection to people.
Tularemia, also known as “rabbit fever” is a
bacterial zoonosis caused by the Gram negative pathogen Francisella
tularensis. Humans and animals can become infected by:
1) inoculation (e.g. animal bite, arthropod bite, handling infected
animals, etc.)
2) inhalation (e.g. aerosolization of bacteria occurs during landscaping
activities such as lawnmowing and disturbing dust or hay in barns), or
3) ingestion of contaminated food or water (e.g. eating uncooked or
undercooked rabbit, small mammals, drinking contaminated water).
Tularemia is not spread directly from person to person.
Clinical forms of Tularemia:
The incubation period for tularemia is usually
3-5 days (range1-14 days). Some species are more susceptible to disease
after infection than others; the spectrum of clinical signs in each
species varies. Signs of septicemia can be seen in sheep and other
mammals; common symptoms may include fever, lethargy, anorexia, stiff
gait, increased pulse and respiration, coughing, vomiting, diarrhea and
pollakiuria.
Pet dogs and cats are also susceptible. If you
see a pet with a fever of unknown origin that has not responded to
routine antibiotics, ask if it has recently been exposed to rabbits,
squirrels, or other rodents. Tularemia can be transmitted to pets when
they sniff, lick or eat infected rabbits or rodents, or by tick and deer
fly bites.
There are various clinical forms of infection
that manifest according to the route of exposure. Humans most often
present with ulceroglandular tularemia (an ulcerative skin lesion with
lymphadenopathy of the regional lymph nodes). Humans and pets also can
manifest tularemia as one of these syndromes: fever, inappetance, muscle
aches and lethargy combined with:
-
Pharyngeal (via ingestion) infection:
cervical, submandibular, mediastinal lymphadenitis; exudative
pharyngitis, oral ulcers
-
Septicemia (typhoidal): hepatomegaly,
splenomegaly
-
Pneumonic (via inhalation): radiographic and
clinical evidence of pneumonia, plueritis
Humans can contract ulceroglandular tularemia
from animals by direct inoculation (animal bites, ungloved veterinary
procedures, insect bites, direct contact with exudates or infected
tissues, skinning or preparing meat for cooking).
Prevention
If tularemia is suspected in a cat or dog it is
important to prevent zoonotic infection. Veterinarians, pet owners and
veterinary clinic staff can be exposed when handling infected animals.
Use barrier protection including disposable gloves; wear a mask if you
suspect a pneumonic infection. Wash hands thoroughly after handling the
animal. Disinfect surfaces that have had contact with the animal or its
tissues. Should a wound occur, clean it well and monitor for fever for
14 days or see a health care provider.
Laboratory Diagnosis
Confirm the diagnosis by PCR, serology, time
resolved fluorescence, direct fluorescent antibody (DFA), PCR, and/or
culture. Specimen collection includes:
1) The most rapid preliminary diagnosis is made
by PCR, TRF, or DFA testing on lymph node aspirate/biopsy; throat swab;
whole blood; exudate from an abscess; pleural fluid, or carcass for
necropsy. Culture is also done to confirm.
2) Serology: If tissues are not available, an
acute serum sample followed if possible by convalescent sample > 10 days
later. [A very high single titer strongly indicates acute infection; a
rise in titer confirms acute infection.]
Treatment
Aminoglycosides or doxycyline |
