Bandouchova et al. Acta Veterinaria Scandinavica 2011, 53:2 http://www.actavetscand.com/content/53/1/2 susceptibility to tularemia were obtained in a study when three European brown hares survived intramuscu- lar or intraperitoneal inoculation of 1.0 × 109 bacteria of F. tularensis biovar palaearctica [24]. Authors of the study discussed these unexpected results by the possibi- lity of lower virulence of the bacteria due to decapsula- tion of F. tularensis by solution of sodium chloride. Attenuation of the F. tularensis strain by in vitro passage could be another reason for the survival of experimental hares after an enormous infectious dose. It was, how- ever, improbable because virulence of the experimental F. tularensis strain was tested by inoculation of BALB/c mice and provided results standard for this highly sus- ceptible laboratory species [19]. Our results of low sus- ceptibility of European brown hares to tularemia contrast with some other reports classifying hares as highly susceptible [26,31]. Experimental hares were infected by the subcutaneous route, which is clinically relevant because it imitates one of the natural routes of tularemia transmission via ticks that carry the agent. It was demonstrated that the numbers of F. tularensis cells fluctuate from 40 to 69 300 in infected ticks such as Page 4 of 13 Dermacentor reticulatus, D. marginatus and Ixodes rici- nus from natural foci of tularemia [7]. In light of this, however, fatal infection due to transmission of tularemia in this way would require a really heavy tick infestation. In terms of the development profile of the plasma bio- chemistry parameters in the control and F. tularensis- inoculated groups, no significant differences were found in total cholesterol, triglycerides and creatine kinase. Figures 1 and 2 demonstrate differences in the develop- ment profile of total protein and albumin. As shown, the levels of total protein were higher from day 2 to 35 post-infection by up to 120% when compared to the normal levels in healthy hares. On the other hand, albu- min levels showed a decreasing trend, falling to as low as 60% of the normal levels from day 2 to 12 post-infec- tion, and the reversal of the trend from day 14 to 35 was not sufficient enough to normalize the levels. It is known that sepsis initiates a cascade of changes associated with substrate metabolism and a reprioritiza- tion of the normal catabolic and anabolic processes [32]. Increased levels of total protein are due to the produc- tion of the acute phase proteins such as a1-acid Figure 1 Total plasma protein in European brown hares on individual days post-inoculation with F. tularensis. Group 0 represents the range of values obtained when measuring control hares throughout days 0 to 35 of the experiment plus healthy hares sampled prior to inoculation (n = 60); 2 to 35 represent groups of animals sampled on days 2 to 35 post-infection (n = 5 until day 4, n = 4 on days 6 and 8, and n = 3 from day 10 to 35); * = p < 0.05, ** = p < 0.01 when compared against control group 0.