The distribution of lagomorph syphilis caused by Treponema paraluisleporidarum in Europe

Treponema paraluisleporidarum infects both rabbits (ecovar Cuniculus) and hares (ecovar Lepus). While the occurrence of the bacterium has previously been reported for European brown hares (Lepus europaeus) and domestic rabbits (Oryctolagus cuniculus f. domestica), there are no data available that report infection in the European context. We tested a total of 1,995 serum samples and 287 genital swabs from opportunistically sampled European brown hares (Lepus europaeus; n = 2135), Mountain hares (Lepus timidus; n = 4), European rabbits (Oryctolagus cuniculus; n = 138), and pet rabbits (O. cuniculus f. domestica; n = 5). The samples originated from eight European countries. In case only serum was available, we tested the samples for the presence of anti-treponemal antibodies. For this, we utilized the Treponema pallidum-particle agglutination test (TP-PA), which is suited for the use in lagomorphs due to the antigenic cross-reactivity of anti-T. pallidum and anti-T. paraluisleporidarum antibodies. In addition, the results of 380 sera were confirmed using the fluorescent-Treponema antibody absorption test (FTA-ABS). In all cases where swab samples were available, DNA was extracted and tested using quantitative PCR to test for the presence of the lagomorph syphilis-bacterium. We were able to detect antibodies in 825 of 1,995 lagomorph sera (41.4%; brown hare: 825/1,868; rabbit: 0/127) and obtained positive qPCR results from 182 of 287 swab samples (63.4%; European brown hare: 167/267; mountain hare: 4/4; rabbit: 11/16). While all rabbit sera (n = 127) tested negative for anti-treponemal antibodies, the presence of the bacterium was confirmed in eight wild (n = 8/11) and three domestic rabbits (n = 3/5) from Germany using qPCR.