Keynote Message

Dirofilaria immitis and D. repens are the most important filarial infections of the dog. Dirofilaria immitis is the causative agent of a very severe cardiopulmonary disease (heartworm disease), while D. repens is the agent of the subcutaneous dirofilariasis. Microfilaraemic dogs are the main reservoir (most infected cats are not microfilaraemic), able to infect the mosquito vectors. Both parasites are zoonotic; however, the number of D. repens human infections in Europe is much greater than that caused by D. immitis (more than 3,400 human cases vs. about 25, respectively). Since the last decades, both infections have spread from the endemic areas of southern Europe towards northern and northeastern regions as a consequence of changing climate and the movement of microfilaraemic dogs. This trend is much more noticeable in the case of subcutaneous dirofilariasis, as confirmed by the continuous increase of human infections, in some case causing severe conditions. The only way to decrease the risk for humans is the prevention and the control of the infection in dogs. On the contrary of heartworm infections, quite always symptomatic, D. repens is like a ghost. Most infections are subclinical, no specific signs of infection (sometimes nodules or alopecia) and no serological tests to assess the presence of the parasite. The only way for the diagnosis is the blood examination for circulating microfilariae (Knott test). A further problem is that not all the macrocyclic lactones currently used for the prevention of heartworm are fully effective against D. repens. Until now, only moxidectin has shown a complete efficacy in the prevention of patent infections, full efficacy against circulating microfilariae, and more than 90% of efficacy against the adult worms.

Key References

1.  Albanese F, Abramo F, Braglia C, et al. Nodular lesions due to infestation by Dirofilaria repens in dogs from Italy. Vet Dermatol. 2013;24:255-e56. DOI: 10.1111/vde.12009.

2.  Genchi C, Kramer LH, Rivasi F. Dirofilarial infections in Europe. Vector Borne Zoonotic Dis. 2011;11:1307–1317. DOI: 10.1089/vbz.2010.0247.

3.  Genchi C, Mortarino M, Rinaldi L, et al. Changing climate and changing vector-borne disease distribution: the example of Dirofilaria in Europe. Vet Parasitol. 2011;176:295–299. DOI: 10.1016/j.vetpar.2011.01.012.
http://dx.doi.org/10.1016/j.vetpar.2011.01.012.

4.  Petry G, Genchi M, Schmidt H, Schaper R, et al. Evaluation of the adulticidal efficacy of imidacloprid 10%/moxidectin 2.5 % (w/v) spot-on (Advocate®, Advantage® Multi) against Dirofilaria repens in experimentally infected dogs. Parasitol Res. 2015;114(Suppl 1):S131–44. DOI: 10.1007/s00436-015-4519-7.