The disease is known by different names like deer fly fever, rabbit fever, Ohara’s disease or tularensis. It is an acute, febrile, granulomatous infection, caused by a highly infectious, Gram negative, nonmotile rod shaped bacterium called Francisella tulaernsis. The organisms may infect a wide range of birds and animals including deer, dog, cat, horse, pig, sheep, rabbit, hare, fish, amphibians and rodents. The infectious agent may be transmitted by ingestion of contaminated meat or water, inhalation of contaminated dust, by direct contact through conjunctiva, mucous membrane with the tissues/secretions of infected animals or by infected arthropods like tick or mosquito.
The disease usually develops 2-5 days after infection, but the incubation period can be as short as 1 day or as long as 3 weeks. Clinical symptoms in man may vary depending upon mode of transmission. There is usually development of ulcers at the site of an infected insect bite sometimes on the surface of the eye, fever, sore throat chills, muscle aches, dry cough, headache, pharyngitis or tonsillitis, nausea, vomiting, diarrhoea, erythematous papule, lymphadenitis and bronchopneumonia. The diagnosis can be made on the basis of history of patient and isolation of organisms from clinical case. Guinea pigs are sensitive laboratory animals. Serodiagnosis is done using agglutination test and ELISA. Proper cooking of meat, avoidance of arthropods, use of protective clothing, rodent control and public health education, particularly to the occupationally exposed people reduce the risk of disease.