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The objective of the present study was to determine the reference ranges of hematological parameters in pet rabbits (Oryctolagus cuniculus) on the one hand. We especially looked at the automatically measured hematocrit and the absolute reticulocyte count. On the other hand the causes and the severity of anemia in pet rabbits were studied.
The reference range for the automatically measured hematocrit of 68 healthy pet rabbits was between 0,33 and 0,45 l/l. The reference range for reticulocytes ranged from 57.623 to 407.384 reticulocytes/μl (0,91–7,75 %). All pet rabbits with a hematocrit below 0,33 l/l were considered as anemic. We conducted a retro- and prospective study of 223 pet rabbits with an anemia over a timeperiod of eleven years (2000–2011). The anemia was classified by cause and severity. Anemia was considered to be mild at hematocrit values between 0,32 and 0,26 l/l. Moderate anemia was classified with a hematocrit from 0,25 to 0,19 l/l and at a hematocrit below 0,19 l/l the anemia was called severe. Anemia was mostly caused by inflammation (65/223, 29 %) and bleeding (54/223, 24 %). 7 % (15/223) of the rabbits suffered from renal diseases and one rabbit got diagnosed with hemolysis caused by liver lobe torsion. In 14 % (32/223) of rabbits more than one underlying disease, like inflammation and bleeding, was diagnosed as possible cause for anemia. In 25 % (56/223) of the anemic rabbits no cause was found. The classification of hemolytic anemia was found to be difficult because of missing criteria. Evidence for an immune-mediated hemolytic anemia could not be found in any rabbits. Most anemias were mild (156/223, 70 %). Moderate (43/223, 19 %) and severe (24/223, 11 %) anemia was diagnosed more rarely. A significant difference of the severity related to the cause (either inflammation, bleeding or renal disease) of the anemia could not be found (p = 0,08). A differentiation between regenerative and non-regenerative anemia, as found in dogs and cats, was difficult due to the high amount of reticulocytes in the peripheral blood of healthy rabbits. In comparison to the healthy rabbits the reticulocyte counts of anemic rabbits (15.360–536.500 /μl) differed only slightly. Considering this, the devolution of reticulocyte counts for every single patient during anemia should be taken as a more proper parameter to differentiate between regenerative and non-regenerative anemia. The blood chemistry revealed a significant lower total protein in rabbits with bleeding anemia to those with anemia caused by inflammatory disease (p < 0,001) although the median was within the reference range.
Consequently it can be said, that anemia in rabbits as well as in dogs and cats can commonly be found, even though it was often an incidental finding.