Diagnosis of Imported Canine Filarial Infections in Germany 2008 – 2010

Abstract

Filarial infections of dogs are attracting attention across Europe because of the risk of spread into previously non-endemic areas (e.g. Dirofilaria repens with Culicidae as vectors) and as emerging zoonotic agents. The occurrence of filarial infections in German dogs has been analysed based on 8,545 samples collected either from imported animals or following travel into endemic regions. All samples were tested by means of modified Knott’s test and heartworm antigen assay within the period 2008 – 2010. Heartworm antigen was detected in 127 samples (1.49 %; 95 % CI: 1.25 – 1.77 %), but only 38 dogs also had microfilariae in their blood samples. On the other hand, 125 animals (1.46 %; 95 % CI: 1.23 – 1.74 %) were only positive in the Knott’s test. For discrimination by means of PCR and sequencing a total of 73 blood samples as well as two samples of adult worms were included, which have been sent by veterinarians during 2008 – 2010. A mono-infection caused by D. repens was detected in 35 cases, while D. immitis was proven in 15 samples, with 6 of these showing a combination of D. immitis and D. repens. Imported Dipetalonema dracunculoides (transmitted by Rhipicephalus sanguineus or Hippobosca longipennis) or Acanthocheilonema reconditum (fleas and lice serve as intermediate hosts) infections were diagnosed in 24 cases and in a single sample a co-infection of A. reconditum and D. repens was evident. D. repens was the most common filarial infection imported and it was introduced into Germany from eleven European countries. Slovenia and Hungary are reported for the first time as endemic for D. repens and A. reconditum, respectively. Furthermore this study reports, to the best of our knowledge, for the first time import of D. dracunculoides from the Canary Islands, A. reconditum from Majorca, D. immitis from Corfu and a co-infection of D. repens and A. reconditum from Spain as well as mixed infections of D. repens and D. immitis from Corfu, Sardinia and Bulgaria. Co-infections with other arthropod-borne infections as well as therapeutical follow-up were also considered. Selamectin (as spot-on formulation) was not able to clear microfilaraemia in dogs infected with either D. repens, A. reconditum or D. dracunculoides, whereas a topical moxidectin/imidacloprid formulation was able to eliminate microfilariae in one dog infected with A. reconditum.