Consensus statement ularemia, a bacterial zoono

Natural Occurrences of Inhalational Tularemia

The largest recorded airborne tulare- mia outbreak occurred in 1966-1967 in an extensive farming area of Sweden.43 This outbreak involved more than 600 patients infected with strains of the milder European biovar of F tularensis

(F tularensis biovar palaearctica) [type B]), most of whom acquired infection while doing farm work that created con- taminated aerosols. Case exposures and disease onsets occurred during a period of months but peaked during the win- ter, when rodent-infested hay was being sorted and moved from field stor- age sites to barns. Among 140 serologi- cally confirmed cases thought to have been infected by inhalation, most had typical acute symptoms of fever, fa- tigue, chills, headache, and malaise; only 14 (10%) of confirmed patients had symptoms of pneumonia, such as dys- pnea and chest pains. Patients gener- ally responded well to tetracycline, and no deaths were reported. Inhalational tu- laremia in the United States has in- volved only single cases or small clus- ters of cases, variously resulting from laboratory exposures,18,56,57 disturbance of contaminated animal carcasses,38,39,41 and suspected infective environmental aerosols.41,52 Cases of inhalational tula- remia in the United States are thought to be due mostly to the more virulent F tularensis biovar tularensis (type A) and usually follow an acute and severe course, with prominent pneumonitis. Some cases, however, have radiographic evi- dence of pleuropneumonia with mini- mal or absent respiratory signs on physi- cal examination.39,41,52

Although airborne F tularensis would

be expected to principally cause pri- mary pleuropneumonic infection, some exposures might contaminate the eye, resulting in ocular tularemia; pen- etrate broken skin, resulting in ulcero- glandular or glandular disease; or cause oropharyngeal disease with cervical lymphadenitis. In the aforementioned Swedish outbreak, conjunctivitis was reported in 26% of 140 confirmed cases and an infected ulcer of the skin was reported in nearly 12%; pharyngitis was reported in 31% and oral ulcers in about 9% of the cases; and 32% of these pa- tients had various exanthemas, such as erythema multiforme and erythema no- dosum.43 Tularemia outbreaks arising from similar agricultural exposures have been reported from Finland,53 mostly presenting with general constitutional

symptoms rather than specific mani- festations of pneumonia; enlargement of hilar nodes was the principal radio- graphic finding in these cases.54