Tick-borne encephalitis virus (TBEV) (Flaviviridae, Flavivirus) is an arthropod-borne virus, an etiologic agent of tick-borne encephalitis (TBE), a human infection involving the central nervous system. The disease is endemic in a large region in Eurasia, where it is transmitted mainly by Ixodes ricinus and Ixodes persulcatus ticks. It is known that also Dermacentor reticulatus is involved in circulation of TBEV. However, the current knowledge of D. reticulatus importance in TBE epidemiology is still insufficient. A total of 471 adult D. reticulatus ticks were collected by flagging vegetation in the Białowieża Primeval Forest, Biebrza National Park, Masurian Landscape Park (North-Eastern Poland) and in the city of Warsaw in the years 2007–2010. All collected ticks were examined individually for the presence of RNA of TBEV using nested RT-PCR assay. Positive results were noted in all investigated localities with the infection rate ranging from 0.99 to 12.5 % with a total mean of 2.12 %. The difference in the percentage of infective males and females was not statistically significant.

During the current century, 88 species of parasites have been recorded in Bison bonasus. These are 22 species of protozoa (Trypanosoma wrublewskii, T. theileri, Giardia sp., Sarcocystis cruzi, S. hirsuta, S. hominis, S. fusiformis, Neospora caninum, Toxoplasma gondii, Cryptosporidium sp., Eimeria cylindrica, E. subspherica, E. bovis, E. zuernii, E. canadensis, E. ellipsoidalis, E. alabamensis, E. bukidnonensis, E. auburnensis, E. pellita, E. brasiliensis, Babesia divergens), 4 trematodes species (Dicrocoelium dendriticum, Fasciola hepatica, Parafasciolopsis fasciolaemorpha, Paramphistomum cervi), 4 cestodes species (Taenia hydatigena larvae, Moniezia benedeni, M. expansa, Moniezia sp.), 43 nematodes species (Bunostomum trigonocephalum, B. phlebotomum, Chabertia ovina, Oesophagostomum radiatum, O. venulosum, Dictyocaulus filaria, D.viviparus, Nematodirella alcidis, Nematodirus europaeus, N. helvetianus, N. roscidus, N. filicollis, N. spathiger, Cooperia oncophora, C. pectinata, C. punctata, C. surnabada, Haemonchus contortus, Mazamastrongylus dagestanicus, Ostertagia lyrata, O. ostertagi, O. antipini, O. leptospicularis, O. kolchida, O. circumcincta, O. trifurcata, Spiculopteragia boehmi, S. mathevossiani, S. asymmetrica, Trichostrongylus axei, T. askivali, T. capricola, T. vitrinus, Ashworthius sidemi, Onchocerca lienalis, O. gutturosa, Setaria labiatopapillosa, Gongylonema pulchrum, Thelazia gulosa, T. skrjabini, T. rhodesi, Aonchotheca bilobata, Trichuris ovis), 7 mites (Demodex bisonianus, D. bovis, Demodex sp., Chorioptes bovis, Psoroptes equi, P. ovis, Sarcoptes scabiei), 4 Ixodidae ticks (Ixodes ricinus, I. persulcatus, I. hexagonus, Dermacentor reticulatus), 1 Mallophaga species (Bisonicola sedecimdecembrii), 1 Anoplura (Haematopinus eurysternus), and 2 Hippoboscidae flies (Lipoptena cervi, Melophagus ovinus). There are few monoxenous parasites, many typical for cattle and many newly acquired from Cervidae.

The bacteria of the genus Bartonella are obligate parasites of vertebrates. Their distribution range covers almost the entire world from America, Europe, Asia to Africa and Australia. Some species of Bartonella are pathogenic for humans. Their main vectors are blood-sucking arthropods such as fleas, ticks and blood-feeding flies. One such dipteran able to transfer vector-borne pathogens is the deer ked (Lipoptena cervi) of the family Hippoboscidae. This species acts as a transmitter of Bartonella spp. in cervid hosts in Europe. In the present study, 217 specimens of deer ked (Lipoptena cervi) were collected from 26 red deer (Cervus elaphus) hunted in January 2014. A short fragment (333 bp) of the rpoB gene was used as a marker to identify Bartonella spp. in deer ked tissue by PCR test. A longer fragment (850 bp) of the rpoB gene was amplified from 21 of the positive samples, sequenced and used for phylogenetic analysis. The overall prevalence of Lipoptena cervi infection with Bartonella spp. was 75.12% (163/217); 86.67% (104/120) of females and 60.82% (59/97) of males collected from red deer hunted in the Strzałowo Forest District in Poland (53°45′57.03″N, 21°25′17.79″E) were infected. The nucleotide sequences from 14 isolates (Bartonella sp. 1) showed close similarity to Bartonella schoenbuchensis isolated from moose blood from Sweden (GenBank: KB915628) and human blood from France (GenBank: HG977196); Bartonella sp. 2 (5 isolates) and Bartonella sp. 3 (one isolate) were similar to Bartonella sp. from Japanese sika deer (GenBank: AB703149), and Bartonella sp. 4 (one isolate) was almost identical to Bartonella sp. isolated from Japanese sika deer from Japan (GenBank: AB703146). To the best of our knowledge, this is the first report to confirm the presence of Bartonella spp. in deer keds (Lipoptena cervi) in Poland by molecular methods. Bartonella sp. 1 isolates were most closely related to B. schoenbuchensis isolated from moose from Sweden and human blood from France. The rest of our isolates (Bartonella spp. 2–4) were similar to Bartonella spp. isolated from Japanese sika deer from Japan.

Wild species are essential hosts for maintaining Ixodes ticks and the tick-borne diseases. The aim of our study was to estimate the prevalence, the rate of co-infection with Babesia, Bartonella , and Anaplasma phagocytophilum , and the molecular diversity of tick-borne pathogens in roe deer in Poland. Almost half of the tested samples provided evidence of infection with at least 1 species. A. phagocytophilum (37.3%) was the most common and Bartonella (13.4%) the rarest infection. A total of 18.3% of all positive samples from roe deer were infected with at least 2 pathogens, and one-third of those were co-infected with A. phagocytophilum , Bartonella , and Babesia species. On the basis of multilocus molecular studies we conclude that: (1) Two different genetic variants of A. phagocytophilum , zoonotic and nonzoonotic, are widely distributed in Polish roe deer population; (2) the roe deer is the host for zoonotic Babesia ( Bab. venatorum , Bab. divergens ), closely related or identical with strains/species found in humans; (3) our Bab. capreoli and Bab. divergens isolates differed from reported genotypes at 2 conserved base positions, i.e ., positions 631 and 663; and (4) this is the first description of Bart. schoenbuchensis infections in roe deer in Poland. We present 1 of the first complex epidemiological studies on the prevalence of Babesia, Bartonella , and A. phagocytophilum in naturally infected populations of roe deer. These game animals clearly have an important role as reservoir hosts of tick-borne pathogens, but the pathogenicity and zoonotic potential of the parasite genotypes hosted by roe deer requires further detailed investigation.

The family Hippoboscidae is a less known group of blood-sucking flies. Deer ked are particularly important for animal health; they may act as potential vectors of disease to ungulates, and may transmit pathogens to animals and humans. The aim of this study was to investigate the presence of Trypanosoma (Megatrypanum) DNA in deer keds using molecular methods. Results prove the presence of Megatrypanum trypanosome DNA in the studied winged adult deer keds and this is the first detection of this pathogen in Lipoptena fortisetosa. In addition, this paper evidences the occurrence of L. fortisetosa in two new locations: one in the Białowieża Primeval Forest, and another in the Strzałowo Forest Inspectorate (Piska Forest), both in north-eastern Poland.