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The zoonotic pathogen Dirofilaria repens, which is transmitted by mosquitos, has been found to date in eastern and southern regions of Europe. It is not considered to be endemic in Germany yet. In recent years, this parasite was found repeatedly in dogs from Brandenburg and Baden-Württemberg as well as in local mosquito species, amongst others in Brandenburg.
This situation was the starting point for the present study with the aim to examine the occurrence of D. repens and other pathogens transmitted by fleas, ticks or mosquitoes in dogs and red foxes from the federal state of Brandenburg. Particularly indications concerning the epidemiological situation and a possible endemisation of D. repens were obtained. During a time period from April 2013 to September 2014, a total of 1023 dog blood samples as well as 195 fox spleen- and 179 fox blood samples were examined. Therefore, DNA isolation was performed for all samples followed by different polymerase chain reactions (PCR) to detect filarial species, Anaplasma phagozytophilum, Candidaus Neoehrlichia mikurensis, Ehrlichia canis, Rickettsia spp. and piroplasms.
Filarial species were detected in six (0.6%) out of 1023 dogs, including two infected with D. repens, two harbouring Dirofilaria immitis and two other with Acanthocheilonema reconditum. One of the two positive D. repens dogs originated from an animal shelter in Brandenburg, but for the other one origin remained unknown.
Interestingly, both ITS-1 D. repens sequences showed a 100% identity to a D. repens sample obtained from a Japanese woman that travelled in Europe. They also showed 97% and 98% identity to a new species Dirofilaria hongkongensis that was so far only described from HongKong, China. An endemic occurence of D. repens in dogs or foxes in the federal state of Brandenburg was not confirmed in this study. Nevertheless, the risk remains high due to previous findings of the pathogen in mosquitoes and dogs. A. phagocytophilum was found in 15 dogs (1.5%), Candidatus N. mikurensis in three dogs (0.3%) and E. canis in one dog (0.1%). The E. canis positive dog (no. 117) also had a co-infection with D. repens. Rickettsia spp. were found with a frequency of 0.8% in dogs, confirming seven samples as Rickettsia raoultii and one as Rickettsia felis.
In 85 (47.5 %) out of 179 fox blood samples piroplasms were found and in 10 of 11 which were furthermore examined by gene sequencing, Theileria annae was identified. Another positive sample showed cross-reactivity to Coccidiae in the PCR and was then confirmed as Sarcocystis arctica. Thus, the red fox was confirmed as a reservoir host for T. annae, but fox
samples were negative for all the other pathogens of interest in the present study. In one dog (0.1 %), Babesia canis was detected but there was no further information about its origin.
A questionnaire for owners of patients should provide information about the origin, past journeys and parasite prevention measures. The evaluation identified a high proportion of 74.2 % (n = 233) of the dogs that were not protected from ectoparasite infestation by using an ectoparasiticide. 21.2 % (n = 236) of the dogs originated from inland or abroad shelters, and therefore might potentially come from endemic areas. 41.6 % of the owners were travelling (also partly) with their dog (n = 245) and 19.2% were travelling outside Germany (within or outside the European Union, n = 245).
An endemisation of D. repens in dogs and foxes from Brandenburg was not confirmed in this study. Nevertheless, the risk of endemisation is high since the pathogen was detected repeatedly in dogs and mosquitoes from this area. In addition, presence of other emerging pathogens as Candidatus N. mikurensis were detected in dogs in this study and must therefore be regarded as a potential risk for dogs and also for people in this region.
An endemisation of D. repens and current prevalences of VBDs should become subject of further investigations in order to assess the risk of infection for humans and animals more closely.
Veterinarians and also doctors of human medicine have a key role in research, prevention, diagnosis and therapy of VBDs. Especially veterinarians are responsible to inform owners about drugs preventing parasite infections in their dogs in a proactive way.