The respiratory capillariid nematode Eucoleus aerophilus (Creplin, 1839) infects wild and domestic carnivores and, occasionally, humans. Thus far, a dozen of human infections have been published in the literature but it cannot be ruled out that lung capillariosis is underdiagnosed in human medicine. Also, the apparent spreading of E. aerophilus in different geographic areas spurs new studies on the epidemiology of this nematode. After the recognition of the first human case of E. aerophilus infection in Serbia, there is a significant merit in enhancing knowledge on the distribution of the nematode. In the present work the infection rate of pulmonary capillariosis was investigated in 70 red foxes (Vulpes vulpes) from the northern part of Serbia by autopsy. The estimated infection rate with Eucoleus aerophilus was 84%. In contrast, by copromicroscopic examination only 38% of foxes were positive. In addition, 10 foxes were investigated for the closely related species in nasal cavity, Eucoleus boehmi, and nine were positive. Our study demonstrates one of the highest infection rates of pulmonary capillariosis in foxes over the world.

In the present study, 223 foxes were collected from various localities in the northern part of the Republic of Serbia (Vojvodina province) and examined for intestinal helminths. Among the examined foxes 178 (79.8%) were infected. The most frequently identified parasites were Mesocestoides spp. (49.3%) and Toxascaris leonina (36.3%). The parasite with the lowest prevalence was Pterygodermatites affinis (0.9%), and this is the first confirmed finding in Serbia. The other recovered species were Alaria alata (25.6%), Taenia spp. (6.3%), Echinococcus multilocularis (13%), Toxocara canis (16.6%) and Uncinaria stenocephala (14.8%). The highest number of foxes infected with E. multilocularis were in the Srem area. The results of this study indicate the presence of helminth species in red foxes in Vojvodina which may also infect humans.

Lyme borreliosis (LB) and tick-borne encephalitis (TBE) are important tick-borne diseases in Europe. This study aimed to investigate the seroreactivity against Borrelia burgdorferi and TBE virus (TBEV) in tick-infested individuals in North Macedonia and Serbia. Serum samples were collected from tick-infested individuals and from healthy individuals in the same regions. Samples were tested for anti-Borrelia IgG reactivity and TBEV-neutralizing antibodies. Results showed higher seroreactivity against Borrelia antigens in patients and healthy donors from Novi Sad compared to those from the Skopje region. However, there was no statistically significant difference between tick-infested patients and healthy donors within each region. No TBEV-neutralizing antibodies were detected in participants from Novi Sad or in the control groups, except for one person from North Macedonia who had a moderate TBEV-neutralizing reaction. The study highlights the need for improved surveillance and diagnostic capabilities for LB and TBE in these regions. It also suggests the potential existence of TBEV foci in North Macedonia. The findings provide a complementary understanding of the LB and TBE epidemiology in the studied regions; however, further research is needed to investigate the presence and distribution of Borrelia spp. and TBEV in ticks to assess the significance of detected seroreactivity.

Summary: As part of routine monitoring of foxes ( Vulpes vulpes ) and jackals ( Canis aureus ) on the territory of Vojvodina province (northern Serbia), an analysis of respiratory and cardiopulmonary parasitic nematodes was conducted. Both host species harbored Eucoleus aerophilus , E. boehmi and Crenosoma vulpis , whereas Angiostrongylus vasorum was found only in foxes. A high prevalence of infection (72.6 %) was noted for E. aerophilus in foxes. The remaining parasite species occurred less frequently in both host species. In all species where it could be quantified, a high degree of parasite aggregation within host individuals was noted. Single species infections were most common, whereas two and three species infections occurred less frequently in both host species. The distribution of abundance of E. aerophilus was affected by host sex, with abundances higher in male foxes. Sampling site and year influenced abundance variation in E. boehmi.