Francisella tularensis is a Gram-negative bacillus thatinfects a wide range of wild animals; humans are occasionallyinfected in rural areas of the northern hemisphere(North America, Sweden, Norway, northern Europe,Russia and Japan). Infection occurs by the bite of aninfected deerfly or tick, by mucosal or skin contact with aninfected animal, by inhalation, and by eating inadequatelycooked meat.The effects in humans may be localized cutaneouspustular disease with regional adenopathy, a pneumonicillness, or a systemic illness sometimes with diarrhoea.Inapparent (subclinical) infections occur.The North American rabbit strain produces severedisease, with a mortality of up to 10% without treatment.Mortality is negligible (except for the American rabbitstrain) even without treatment.The diagnosis is made by finding the organisms in materialfrom infected tissues. Direct immunofluorescence maybe used. Serological tests may also be used to detect antibodiesto the organism by ELISA and agglutination techniques.Great caution is needed in handling specimens toavoid the risk of laboratory infection.Streptomycin (lOmg/kg twice daily for 14 days) is veryeffective. Tetracycline and chloramphenicol are effective.Patients need to be isolated until they have been on treatmentfor 48 hours to minimize the risk of cross-infection.

Clinical featuresMost cases occur in children or young adults. There is grossenlargement of a single group of lymph nodes, which areusually tender. Lymphadenopathy develops about 2 weeksafter the scratch and usually lasts for 2-4 months, but itmay persist for up to a year. A papule may occur at the siteof the scratch; it appears about a week after the scratch andpersists for 1-3 weeks. Although most patients remainwell, one-third have a low-grade fever for a few daysand may experience malaise, headache and sore throat.Rare manifestations are conjunctivitis and preauricularlymphadenopathy (oculoglandular syndrome), encephalopathy,thrombocytopenic purpura, osteomyelitis andpneumonia.DiagnosisThe diagnosis is usually based on the histology ofexcised lymph node with negative cultures for bacteria andmycobacteria. The Warthin-Starry silver impregnationstain may reveal the CSD bacilli but they are present insmall numbers.There may be a mild neutrophil leukocytosis, butother tests are unhelpful. Antibody tests are being developed.ManagementBecause the disease resolves spontaneously the only treatmentusually required is analgesia if the lymph nodes arepainful, and reassurance. Antibiotics do not help.