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BackgroundVertical transmission is one of the transmission routes for Babesia microti, the causative agent of the zoonotic disease, babesiosis. Congenital Babesia invasions have been recorded in laboratory mice, dogs and humans. The aim of our study was to determine if vertical transmission of B. microti occurs in naturally-infected reservoir hosts of the genus Microtus.MethodsWe sampled 124 common voles, Microtus arvalis; 76 root voles, M. oeconomus and 17 field voles, M. agrestis. In total, 113 embryos were isolated from 20 pregnant females. Another 11 pregnant females were kept in the animal house at the field station in Urwitałt until they had given birth and weaned their pups (n = 62). Blood smears and/or PCR targeting the 550 bp 18S rRNA gene fragment were used for the detection of B. microti. Selected PCR products, including isolates from females/dams and their embryos/pups, were sequenced.ResultsPositive PCR reactions were obtained for 41% (89/217) of the wild-caught voles. The highest prevalence of B. microti was recorded in M. arvalis (56/124; 45.2%), then in M. oeconomus (30/76; 39.5%) and the lowest in M. agrestis (3/17; 17.7%). Babesia microti DNA was detected in 61.4% (27/44) of pregnant females. Vertical transmission was confirmed in 81% (61/75) of the embryos recovered from Babesia-positive wild-caught pregnant females. The DNA of B. microti was detected in the hearts, lungs and livers of embryos from 98% of M. arvalis, 46% of M. oeconomus and 0% of M. agrestis embryos from Babesia-positive females. Of the pups born in captivity, 90% were born to Babesia-positive dams. Babesia microti DNA was detected in 70% (35/50) of M. arvalis and 83% (5/6) of M. oeconomus pups. Congenitally acquired infections had no impact on the survival of pups over a 3-week period post partum. Among 97 B. microti sequences, two genotypes were found. The IRU1 genotype (Jena-like) was dominant in wild-caught voles (49/53; 92%), pregnant females (9/11; 82%) and dams (3/5; 60%). The IRU2 genotype (Munich-like) was dominant among B. microti positive embryos (20/27; 74%) and pups (12/17; 71%).ConclusionA high rate of vertical transmission of the two main rodent genotypes of B. microti was confirmed in two species of naturally infected voles, M. arvalis and M. oeconomus.

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Long-term field studies on parasite communities are rare but provide a powerful insight into the ecological and evolutionary processes shaping host–parasite interactions. The aim of our study was to identify the principal factors regulating long-term trends in the haemoparasite communities of bank voles, and to this end, we sampled three semi-isolated populations of bank voles (n = 880) in 1999, 2002, 2006 and 2010 in the Mazury lake district region of NE Poland. Overall, 90.8 % of the bank voles harboured at least one of the species of haemoparasites studied. Whilst overall prevalence (all species combined) did not vary significantly between the surveys, different temporal changes were detected among voles in each of the three sites. In voles from Urwitałt, prevalence increased consistently with successive surveys, whereas in Tałty, the peak years were 2002 and 2006, and in Pilchy, prevalence oscillated without a clear pattern. Across the study, bank voles harboured a mean of 1.75 ± 0.034 haemoparasite species, and species richness remained stable with no significant between-year fluctuations or trends. However, each of the five constituent species/genera showed a different pattern of spatio-temporal changes. The overall prevalence of Babesia microti was 4.9 %, but this varied significantly between years peaking in 2006 and declining again by 2010. For Bartonella spp., overall prevalence was 38.7 %, and this varied with year of study, but the temporal pattern of changes differed among the three sites. The overall prevalence of Haemobartonella (Mycoplasma) was 68.3 % with an increase in prevalence with year of study in all three sites. Hepatozoon erhardovae had an overall prevalence of 46.8 % but showed a marked reduction with each successive year of the study, and this was consistent in all three sites. The overall prevalence of Trypanosoma evotomys was 15.4 % varying significantly between sites, but showing temporal stability. While overall prevalence of all haemoparasites combined and species richness remained stable over the period of study, among the five haemoparasites, the pattern of spatiotemporal changes in prevalence and abundance of infections differed depending on parasite species. For some genera, host age was shown to play an important role, but a significant effect of host sex was found only for Haemobartonella spp.

BackgroundBartonella spp. cause persistent bacterial infections in mammals. Although these bacteria are transmitted by blood-feeding arthropods, there is also evidence for vertical transmission in their mammalian hosts. We aimed to determine: (i) the prevalence and diversity of Bartonella spp. in a Microtus spp. community; (ii) whether vertical transmission occurs from infected female voles to their offspring; (iii) the effect of concurrent Babesia microti infection on the success of vertical transmission of Bartonella; and (iv) the impact of congenital infection on pup survival.ResultsWe sampled 124 Microtus arvalis, 76 Microtus oeconomus and 17 Microtus agrestis. In total, 115 embryos were isolated from 21 pregnant females. In the following year 11 pregnant females were kept until they had given birth and weaned their pups (n = 62). Blood smears and PCR targeting the Bartonella-specific rpoB gene fragment (333bp) were used for the detection of Bartonella. Bartonella DNA was detected in 66.8% (145/217) of the wild-caught voles. Bartonella infection was detected in 81.8% (36/44) of pregnant female voles. Bartonella-positive individuals were identified among the embryos (47.1%; 40/85) and in 54.8% (34/62) of pups. Congenitally acquired Bartonella infections and co-infection with B. microti had no impact on the survival of pups over a 3-week period post partum. Among 113 Bartonella sequences, four species were detected: Bartonella taylorii, Bartonella grahamii, Bartonella doshiae and a Bartonella rochalimae-like genotype. Bartonella taylorii clade B was the dominant species in wild-caught voles (49%), pregnant females (47%), their embryos (85%), dams (75%) and pups (95%).ConclusionsHigh prevalence of Bartonella spp. infection maintained in Microtus spp. community is followed by a high rate of vertical transmission of several rodent species of Bartonella in three species of naturally infected voles, M. arvalis, M. oeconomus and M. agrestis. Congenitally acquired Bartonella infection does not affect the survival of pups. Co-infection with B. microti does not affect the effectiveness of the vertical transmission of Bartonella in voles. Bartonella taylorii clade B was found to be the dominant species in wild-caught voles, including pregnant females and dams, and in their offspring, and was also found to be the most successful in vertical transmission.Electronic supplementary materialThe online version of this article (10.1186/s13071-018-3047-6) contains supplementary material, which is available to authorized users.

Abundance and prevalence of helminth infections often differ between host sexes, and are usually biased in favor of males. Relatively few cases of female-biased parasitism have been reported. We sampled bank voles in three woodland sites in N.E. Poland over 11 years at 3-4-year intervals, and assessed their parasite burdens. Prevalence and abundance of the stomach nematode Mastophorus muris were consistently higher among females. Among adult female bank voles from the two sites that showed the highest prevalence with M. muris, both prevalence and abundance were significantly higher in lactating bank voles, but not pregnant animals, and the effect of lactation was evident in both sites, in all four surveys, and in both age classes. Although the magnitude of the effect of lactation varied between years, it was not confounded by any significant interactions with other factors. We hypothesize that mature and reproductively active female bank voles are subject to higher exposure compared with males of similar age, as a consequence of the increased content of invertebrates in their diet, including the intermediate hosts of M. muris, required to meet the higher increased energy and protein demands of nursing litters throughout the summer months.

Rodents are known to play a significant role as reservoir hosts for TBEV. During three sequential expeditions at 4-year intervals to three ecologically similar study sites in NE Poland, we trapped bank voles (Myodes glareolus) and then tested their blood for the presence of specific antiviral antibodies to TBEV. The strongest effects on seroprevalence were the extrinsic factors, site of capture of voles and year of sampling. Seroprevalence increased markedly with increasing host age, and our analysis revealed significant interactions among these three factors. Seroprevalence did not differ between the sexes. Therefore, based on the seroprevalence results, the dynamics of TBEV infection differ significantly in time, between local sub-populations of bank voles and with increasing host age. To fully understand the circulation of the virus among these reservoir hosts and in the environment, long-term monitoring is required and should employ a multi-site approach, such as the one adopted in the current study.

Dirofilariasis is a fast-spreading disease of dogs and humans in Europe. We investigated whether Dirofilaria spp. have spread northwards in Europe, invading the Baltic countries. Altogether, 424 blood samples were collected from eight countries in the period 2017–2019, including 227 samples from sled dogs and 197 samples from other dogs. PCR amplification and sequencing were conducted employing three genetic markers (mitochondrial [mt] 12S rDNA, mt cytochrome c oxidase subunit I [COI] gene and mt dehydrogenase subunit I [NAD1] gene). The SNAP test (IDEXX) for detection of D. immitis infections was also implemented. The DNA of D. repens was detected in 59 of 424 dogs (prevalence 13.9%). D. repens was found in sled dogs from Lithuania, Latvia, Poland and Belarus. Only one dog from Estonia was infected, apparently an imported case. The highest prevalence was recorded in Lithuania (38%). Among pet dogs from the Ukraine, six dogs tested positive (3.8%). Our study has revealed a high prevalence of D. repens infections in Lithuania and Latvia, but no evidence for spread of the heartworm D. immitis. We conclude that sled dog kennels constitute hot spots for D. repens transmission.