Seroprevalence of dirofilarioses in Serbia

In 2009 canine and human dirofilarioses were investigated in Serbia by means of home-made immunoassays to detect antibodies to D. repens and D. immitis somatic/metabolic polyproteins and, in dogs, to the recombinant Wolbachia surface protein (rWSP) (Marcos-Axutegi et al., 2005, Proc EMOP IX, 2: 297-302). A total of 122 dogs (56 males and 66 females; mean age = 4.15 years) were checked, coming from two northern areas of Serbia (Pančevo and Veliko Gradište). Considering their shelter, nutrition, care, training, working, health protection, sanitary controls, 38 of them were dogs bred in partially controlled life conditions and the remaining 84 subjects lived in uncontrolled life conditions. Human sera were taken from 298 people (109 males, 189 females) living in different areas of Serbia (Pančevo, Novi Sad, Zaječar, Leskovac, Vranje, Niš, Pirot). Antibodies to D. immitis were detected in 28 dogs, indicating an overall heartworm disease seroprevalence of 22.9%, whereas IgG antibodies to D.repens and to rWSP were evidenced in 42.6% and 5.7% of the subjects, respectively. As for the two different areas, antibodies to Dirofilaria were detected in 72.9% of dogs living in Pančevo, therefore more than living in Veliko Gradište (57.1%). No risk factors were evidenced, confirming data on the uselessness of prophylactic drugs at least against D. repens, and suggesting the presence, in these areas, of by day, sunrise or sunset biting mosquitoes as important vectors. As previously evidenced, the low antibody production to rWSP depends on the parasitic burden and on the larval/adult stage of the worms and to the cytokine synthesis patterns activated by this endosymbiont which is different from that activated by D. repens and D. immitis (Simon et al., 2009, Trends in Parasitology, 25 (9): 404-409). As for humans, 46 people (14 men and 32 women) had antibodies to dirofilarial nematodes, accounting for an overall seroprevalence of 15.4%. Particularly, antibodies to D. repens were found in 29 (9.7%) subjects, and that to D. immitis in 24 (8.1%) individuals; seven of them had specific antibodies to both species. No differences were evidenced by people sex (p=0.347), by dirofilarial species (p=0.551) and by area (p=0.056). However the highest seroprevalence were found in Pančevo (27,1%), one of area where we proved very high seroprevalence (72.9%) in dogs. In Serbia diriofilarioses represent an emerging disease of interest for both human and veterinary health. Infections are mainly due to D. repens, even if an active transmission level of both species has been evidenced. Our findings indicates that also D. immitis is transmitted to humans, although all the cases by now reported in the country have been attributed to D. repens. More widespread and detailed investigations are needed to better define the impact of this neglected disease on humans. Finally, entomological investigations are needed to identify the mosquito species actually involved in the parasites transmission and the vector efficiency of each of them, which are data essential to start appropriate control programs.