Heartworm on the rise—new insights into Dirofilaria immitis epidemiology

Abstract

Until recently Dirofilaria immitis, the causative agent of serious canine heartworm disease, has been detected relatively infrequently in Central Europe in comparison with the predominant D. repens species. In the present study, the elevated number of heartworm cases among dogs from a breeding establishment in south-western Slovakia is described. Out of 25 dogs examined, dirofilariasis was detected by single or several diagnostic approaches in 18 animals, which represents a mean prevalence of 72.0%. D. immitis was confirmed in 16 (64.0%) of the infected dogs and D. repens in 8 dogs (32.0%). All cases of D. immitis infection were detected in areas regarded as D. repens-endemic to date. Following the presented results and discussed circumstances, the question of whether the real prevalence of canine heartworm disease in Slovakia, or even in Central Europe as a whole, has been underestimated, or if D. immitis is currently becoming endemic in this area.

Comparison of Diagnostic Tools for the Detection of Dirofilaria immitis Infection in Dogs

“…In the last two decades, reports of clinical cases of heartworm (HW) infection in dogs have increased even in non-endemic areas with new endemic foci detected in the Mediterranean region [ 8 , 9 , 10 ]. However, several studies have recorded a large variability in prevalence data [ 11 , 12 , 13 ], which depends on epidemiological factors (e.g., presence and abundance of competent vectors and absence of chemoprophylaxis treatments) as well as on the diagnostic methods employed. Indeed, the frequency of Dirofilaria spp.…”

“…Indeed, the frequency of Dirofilaria spp. infections in dogs may differ according to the diagnostic method used, as demonstrated in Slovakia, where 36% and 64% of the dogs were found positive using the modified Knott’s method and heartworm (HW) antigen test, respectively [ 12 ]. In fact, HW antigen tests are also able to detect occult infections characterized by amicrofilaremia.…”

“…Serological tests (i.e., enzyme-linked immunosorbent assay (ELISA) and immunochromatographic tests (ICT)) for the detection of somatic and female antigens of D. immitis adults are available for point-of care (POC) testing or for reference diagnostic laboratories [ 1 , 12 , 17 , 18 ]. The antigen tests are highly specific to D. immitis .…”

The fatal case of an autochthonous heartworm disease in a dog from a non-endemic region of south-eastern Slovakia

“…Any way, in recent years, localities with increased occurrences of D. immitis were identified in Slovakia. Interestingly, these areas have been regarded as endemic for D. repens until now (Miterpáková et al, 2018). In this regard, the competent authorities, including veterinary practitioners in affected regions should take note.…”

“…This situation has been altered during the last fi ve years and D. immitis has increased its prevalence. Only recently, have heartworm cases been detected in a breeding establishment in south-western Slovakia (Miterpáková et al, 2018) and new autochthonous infections have been recorded regularly during routine diagnostic procedures at the Institute of Parasitology SAS (IP SAS). The clinical presentation of heartworm disease is very heterogeneous; from no symptoms (for several months, even years) up to a serious "caval syndrome" leading to the displacement of worms from the pulmonary arteries into the right cardiac chambers.…”