The Central Upper-Rhine (Baden-Württemberg, Germany) is one of the warmest regions in Germany and also harbours abundant numbers of mosquitoes. Case reports on presumably autochthonous occurrence of Dirofilaria spp. were reported previously and were a reason for a further investigation into the occurrence of vector-borne pathogens. For this purpose, 44 hunting dogs from the Central Upper-Rhine region were tested between 4(th) and 29(th) June 2007. The blood samples were tested using the Knott's test and IDEXX SNAP 4Dx test. The Knott's test revealed unsheathed microfilaria identified as Dirofilaria repens by PCR in 3 dogs with no history of travelling (6.8%; 95% CI: 2.4-18.2%). The seroprevalence for Anaplasma phagocytophilum was 43.2% (95% CI: 29.7-57.8%), but only 4.5% (95% CI: 1.3-15.1%) for antibodies to Borrelia C6 peptide. Dirofilaria immitis antigen was not detected in any of the samples. A further 288 blood samples from non-hunting companion dogs of the Central Upper-Rhine region were tested negative for heartworm antigen between February and August 2007.