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TULARAEMIA
("RABBIT FEVER") Note for Pet Owners:
This information is provided by
Provet for educational purposes only.
You should seek the advice of
your veterinarian if your pet is ill as only he or she can correctly advise
on the diagnosis and recommend the treatment that is most appropriate for
your pet.
Tularaemia
is a zoonosis and so precautions including the wearing of gloves and
masks should be taken when handling suspected infected
animals or materials from such animals
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Description
Tularaemia is a bacterial infection which causes acute illness in many species
including birds and mammals - including humans.. The disease occurs in the
Northern Hemisphere.
Also known as Rabbit Fever
Cause
Th e cause of Tularaemia is a small gram-negative rod-shaped bacterium called
Francisella tularensis which occurs in two variants - A and B. Type A
only occurs in the USA and is very virulent for rabbits, Type B occurs
throughout the Northern Hemisphere and is not virulent for rabbits and
rarely causes disease in its main hosts eg rodents . The organism can survive
for long periods of time in carcases, mud or water but it is susceptible to heat
and disinfectants.Ectoparasites (ticks and mosquitoes) provide a reservoir of
infection and act as vectors for the disease, transmitting it to rabbits,
rodents and other hosts. Cats and dogs become infected through tick bites or
when they hunt or eat infected rabbits, hares or rodents. In the USA the
majority of human cases are thought to be contracted from tick bites or
contact with the infected tissue of wild animals, especially rabbits. Some
cases (1.6%) are associated with cat bites or scratches and only a few cases
are associated with dogs. The disease can be transmitted by :
- Aerosol spread
- Inoculation - bites, scratches, wounds, open skin sores
- Through the conjunctiva of the eye
Exposure to very few organisms is necessary to cause disease , and in
humans less than 100 organisms are needed and humans are most often infected
through one of the following routes :
- Direct contact with blood, body secretions or tissues of an infected
animal
- Bite from an infected parasite (eg fleas, lice or ticks)
Breed Occurrence
There is no breed predisposition, but dogs and cats that hunt rabbits are at
greater risk
Humans most often contract the disease from :
Human workers most at risk to contract the disease include :
- Abattoir workers
- Agricultural workers
- Forestry workers
- Hunters
- Veterinarians
Signs
Various signs have been described in this
disease, including the following : In cats
:
- Some cats are unaffected
- Kittens are more susceptible than adults
- Anorexia
- Depression
- Multiple abscesses in organs eg liver and spleen
- Hepatomegaly - occasionally jaundice
- Splenomegaly
- Oral ulcers
- Respiratory signs eg pneumonia
- Panleukopenia
- Weight loss
- Death
In dogs :
- Clinical cases in dogs are rare
- Puppies are more susceptible than adults
- Anorexia
- Ocular-nasal discharge may occur
- A high body temperature (fever) occurs
Signs start about 2 days after ingesting infected material.
Lymphadenopathy
Skin rash
Uveitis
Conjunctivitis
Septicaemia may occur
Multiple abscesses in internal organs
Weight loss
Sudden death
In humans the signs of tularemia depend
upon the route of infection :
- The incubation period is 2-10 days
- Fever
- A local reaction (skin ulcer) occurs at the site of inoculation (eg
scratch or bite)
- Enlargement of local and regional lymph nodes (lymphadenopathy)
- Splenomegaly
- Spread via the bloodstream to multiple organs.
- In one form of the disease an atypical pneumonia occurs - mortality may be over 30%
Diagnosis
Diagnosis can be made by several methods :
- Finding antibodies in blood samples - ELISA and FA tests
- Isolation of the bacterium F.tularensis from fluids or tissue
samples
Because so few organisms (<100) are necessary to cause disease in humans
safety precautions (eg use of a biohazard cabinet) should be taken to ensure
that staff are not contaminated during sampling, testing or post-mortem
examination.
Treatment
Antibiotics that are reported to be effective against F.tularensis
include :
- Aminoglycosides - used to treat human cases of tularemia (eg
gentamicin and streptomycin).
- Chloramphenicol
- Fluorquinolones
- Tetracycline
No vaccine is available.
Routine ectoparasite treatment for ticks may be important to minimise
transmission to domestic animals living in endemic areas. Direct contact with
rabbits and rodents should be avoided in endemic areas.
Prognosis
Poor if untreated and once the disease has become disseminated throughout the
body. Mortality can be high in certain forms of the disease - eg pneumonic form
in humans.
Updated October 2013
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