Rabbits, hares, and rodents: Clinical signs are not well described, as affected animals are most often found dead. Experimentally infected animals exhibit weakness, fever, ulcers, swollen lymph nodes, and abscesses. Death usually occurs in 8–14 d.

Sheep: Tularemia is typically a seasonal disease in sheep, coinciding with tick infestations. Clinical signs include fever, a stiff gait, diarrhea, frequent urination, weight loss, and difficulty breathing. Affected sheep may isolate themselves from the remainder of the flock. Death is most common in young animals, and pregnant ewes may abort.

Horses: Fever, breathing difficulty, incoordination, and depression have been described, and affected horses have had extensive tick infestation.

Cats: Signs may include fever, depression, swollen lymph nodes, abscesses, ulceration of mouth or tongue, gastroenteritis, enlarged liver or spleen, icterus, anorexia, weight loss, pneumonia, shock and death.

Dogs: Natural infection occurs, but clinical illness is inapparent or mild. Signs include fever, depression, mucopurulent discharge from nose and/or eyes, pustules at sites of contact, swollen lymph nodes, and loss of appetite. Puppies are more likely than adult dogs to develop disease.

Nonhuman primates: Signs include depression, lethargy, anorexia, dehydration, vomiting, diarrhea, swollen lymph nodes, petechiae, and sudden death.

Humans: Incubation period is typically 3–5 d, but can be 1–21 d, and exhibits fever, chills, headache, muscle soreness, and vomiting, followed by more specific signs depending on route of entry. All forms of tularemia can progress to pleuropneumonia, meningitis, shock and death. Immunocompromised patients and those with underlying diseases are at increased risk of severe, prolonged infection and death. Ulceroglandular tularemia is the most common form (75–85% of reported cases). An ulcer is evident at the site of entry, usually the fingers or hands in cases associated with exposure to rabbits, hares, or rodents. Swollen lymph nodes are observed; the lymph nodes may open, drain pus, and scar. Signs of glandular tularemia are similar, but no skin ulcer is evident. In the United States, the overall case fatality rate is < 2%.

ELISA, hemagglutination, microagglutination, and tube agglutination are used to identify agglutinating antibodies in serum. Fluorescent antibody assays and polymerase chain reaction (PCR) may also be useful. A minimum of biological safety level II (BSL-2) protocol is recommended when handling suspected or confirmed F. tularensis samples. In nonendemic areas, a single serum titer of +/> 1:160 is considered diagnostic. In endemic areas, a 4-fold increase in antibody levels between samples obtained 2–4 wk apart is considered diagnostic.

Tularemia is a reportable disease in the United States.

Tick control is an important preventive measure. The use of insect repellants containing DEET is recommended. Contact with untreated water should be avoided when contamination with F. tularensis is suspected, and wild game should be thoroughly cooked before consumption. In endemic areas, handling of dead and dying animals should be avoided, and gloves should be worn when handling wild game, their skins, and carcasses. As landscapers in endemic areas may be at higher risk of respiratory exposure and pulmonary tularemia, use of respiratory protection is recommended in endemic areas.

There is no vaccine available, although one is under evaluation by the FDA.

Streptomycin and tetracyclines (especially doxycycline) are the antibiotics of choice for treating wild and domestic animals. For humans, streptomycin has been preferred, with doxycycline, gentamicin, and chloramphenicol as alternatives. Fluoroquinolones, such as gatifloxacin and moxifloxacin, may also be useful.

Reference: AVMA Backgrounder, November 27, 2006.