Francisella tularensis subspecies holarctica Biovar II (erythromycin resistant) is endemically widespread in the east of Austria. In western Austria Biovar I (erythromycin sensitive) of the subspecies holarctica is found in addition to Biovar II. The different distribution areas of biovars I and II in Western and Eastern Europe overlap in Western Austria, where rabbits and rodents (Lagomorpha and Rodentia) are considered reservoir animals of tularemia.
Ectoparasites, especially ticks, play an important role as vectors in maintaining the natural occurance. Francisella tularensis subspecies holarctica, which occurs in Europe, North America and Japan, and subspecies mediaasiatica, which occurs in Central Asia, usually cause less severe, localised diseases in humans. Life-threatening, generalised forms of the disease are possible when infected with the highly virulent subspecies tularensis, which occurs predominantly in North America.
Transmission occurs through contact and smear infection or splashes of pathogen-containing fluids (especially while handling raw meat from field hares), but also through tick bites or insect bites. Dust or droplet infection can also occur during skinning or cutting of infected field hares and during work with agricultural products such as hay, straw, grain or sugar beet if they are contaminated with excrements or carcasses of mice.
The clinical picture is very diverse, depending on the transmission route and the point of entry of the pathogen. While in the case of an infection by field hares the ulceroglandular or glandular form with inflammation of the lymph nodes of the upper extremities is usually observed, the entry site of the pathogen in the case of transmission by arthropods is more likely to be in the area of the lower extremities. Diseased brown hares can show unusual movements and a lack of escape behaviour.
Prevention and control
Sick, killed or dead hares as well as hunted hares with pathological changes in the internal organs must never be thrown away or buried, but should be sent to the IVET in Mödling for examination or disposed in a way to prevent spreading of the disease. Since hares with chronic renal entularaemia excrete the bacteria with urine over a long period of time, hunters in endemic areas should pay more attention to killing sick animals with unusual behaviour to prevent further spread of the pathogen. Sick, killed or dead field hares must not be skinned, but should only be touched with gloves and securely packed immediately to prevent infection of humans through inhalation of pathogen-containing dust or contact with fur, blood or excrements.