Cross-reactions may occur between Brucella and Francisella species. Positive test indicates current infection; low titers may indicate a previous exposure to Francisella or a related organism.
Tularemia in humans is incidental and is usually the result of interaction with wild animals and their environs. The organism penetrates the skin and an ulcer forms at the site of penetration which may persist for several months.
Positive: > or = to 1:160 on a single serum (or 4-fold increase in titer between acute and convalescent paired sera)