Transovarial and transstadial transmission of Borrelia valaisiana, the pathogen of Lyme borreliosis, in the sheep tick, Ixodes ricinus L.

In this study, molecular analysis was used to show the possibility of transovarial and transstadial transmission of Borrelia valaisiana in Ixodes ricinus ticks in the natural biotopes of North-Western Russia. Female ticks collected in nature were fed on rabbits; larvae obtained from these females were fed on white mice. Eggs, female ticks after the egg deposition, larvae and nymphs of ticks after overwintering were studied for Borrelia burgdorferi s.l. within the natural inserts. The identification of Borrelia burgdorferi in ticks was carried out using the PCR method with real-time hybridization-fluorescence detection. The genotyping was performed by sequencing fragments of the intergenic region rrf-rrl. Spirochetes of only one genospecies B. valaisiana, previously not detected in North-Western Russia, were identified in ticks I. ricinus. The isolates of B. burgdorferi were obtained by inoculation of the gut contents of ticks into a prepared nutrient medium BSK-H with 6% rabbit serum (Sigma, USA). The positive reaction for B. valaisiana was observed in six out of 13 I. ricinus females (46.2%), which were successfully fed and laid eggs. Of the six infected female ticks, four (66.7%) (30.8% of the total four out of 13) were able to transmit B. valaisiana to eggs and then to larvae. 50.0% of the infected female ticks (23.1% of the total number) could transmit B. valaisiana to nymphs. In addition, the overwintered larvae and nymphs did not retain B. valaisiana. The subsequent transmission can occur as a result of feeding the overwintered larvae and nymphs on the infected overwintered hosts.

Grigoryeva LA ，Miteva OA ，Kustova DV ，Shatrov AB ... -  《-》

Adaptive immunity in Mus musculus influences the acquisition and abundance of Borrelia burgdorferi in Ixodes scapularis ticks.

Koloski CW ，Adam H ，Hurry G ，Foley-Eby A ，Zinck CB ，Wei H ，Hansra S ，Wachter J ，Voordouw MJ ... -  《-》

The role of southern red-backed voles, Myodes gapperi, and Peromyscus mice in the enzootic maintenance of Lyme disease spirochetes in North Dakota, USA.

Lyme disease has expanded into the Great Plains of the USA. To investigate local enzootic transmission, small mammals were trapped in two forested tracts in northeastern North Dakota during 2012 and 2013. Peromyscus mice and southern red-backed voles, Myodes gapperi, comprised over 90% of all mammals captured. One site was dominated by Peromyscus (79% of 100 mammals captured). At the other site, M. gapperi (59% of 107 mammals captured) was more abundant than Peromyscus (36%). Immature stages of two tick species parasitized small mammals: Dermacentor variabilis and Ixodes scapularis. Larval I. scapularis ectoparasitism was significantly higher on Peromyscus (81% infested; 3.7 larvae per infested mouse) than M. gapperi (47% infested; 2.6 larvae per infested vole) whereas larval and nymphal D. variabilis ectoparasitism were highest on M. gapperi. Over 45% of infested rodents were concurrently infested with both tick species. Testing engorged I. scapularis larvae from Peromyscus (n = 66) and M. gapperi (n = 20) yielded xenopositivity prevalence for Borrelia burgdorferi sensu lato (s.l.) in these rodents of 6% and 5%, respectively. Progeny of field collected M. gapperi were used to determine host infectivity for a local isolate of B. burgdorferi sensu stricto (s.s.). Five M. gapperi were injected with spirochetes, infested with pathogen-free I. scapularis larvae on days 10, 20, and 40 after infection, and engorged larvae molted to nymphs. Subsamples of nymphs were tested by PCR for B. burgdorferi s. s. DNA and yielded infection rates of 56% (n = 100 nymphs tested), 75% (n = 8) and 64% (n = 31), respectively. The remaining infected nymphs were fed on BALB/c Mus musculus mice and 7 d later, mice were euthanized, and tissues were cultured for B. burgdorferi s.s. Nymphs successfully transmitted spirochetes to 13 of 18 (72%) mice that were exposed to 1-5 infected ticks. Theoretical reservoir potentials - i.e., ability to generate B. burgdorferi infected nymphs - were compared between Peromyscus and M. gapperi. At one site, Peromyscus accounted for nearly all Borrelia-infected nymphs produced (reservoir potential value of 0.935). At the other site, the reservoir potentials for Peromyscus (0.566) and M. gapperi (0.434) were comparable. The difference was attributed to differences in the relative abundance of voles versus mice between sites and the higher level of ectoparasitism by larval I. scapularis on Peromyscus versus M. gapperi at both sites. The southern red-backed vole, M. gapperi, contributes to the enzootic maintenance of Lyme disease spirochetes in North Dakota and possibly other areas where this rodent species is abundant.

Dougherty MW ，Russart NM ，Gaultney RA ，Gisi EM ，Cooper HM ，Kallis LR ，Brissette CA ，Vaughan JA ... -  《-》

Two decades of research on Borrelia burgdorferi sensu lato in questing Ixodes ricinus ticks in Slovakia.

In Europe, Borrelia burgdorferi sensu lato (s.l.), the causative agent of Lyme borreliosis is transmitted by the castor bean tick, Ixodes ricinus. In the last decades, global changes affect the spread of ticks and also their bionomics. The aim of this study was summarization of a large dataset obtained during 20 years of research. The research was carried out in 1999-2019 at 16 localities in Slovakia that were continuously monitored. In total, 17,249 questing I. ricinus ticks were tested for the presence of B. burgdorferi s.l. The total prevalence of infected ticks was 18.8% (3,248/17,249), with 15.1% (1,557/10,302) infected nymphs and 24.3% (1,691/6,947) infected adults. Nine species of B. burgdorferi s.l. were identified. Borrelia afzelii (37.1%), B. garinii/bavariensis (24.7%), and B. valaisiana (15.4%) were the most frequent and were present at all study sites, followed by B. lusitaniae (12.6%), B. burgdorferi sensu stricto (4.1%) and B. spielmanii (1.6%). Borrelia bavariensis was confirmed only in four samples (0.1%), however, detection of this species has been performed only since 2017. Borrelia bissettii and B. kurtenbachii were both recorded in one case. The total prevalence differed significantly among four habitat types (urban, suburban, natural, agricultural). The highest infection prevalence was confirmed in natural habitat (22.0%), the lowest in urban habitat (13.2%). In addition, molecular analysis was carried out on part of the collected ticks previously morphologically identified as I. ricinus. The analysis did not confirm the occurrence of Ixodes inopinatus in Slovakia. Long-term monitoring of the abundance and spread of ticks as well as the prevalence and genetic variability of tick-borne pathogens can reveal the impact of global climatic and socio-economic changes on different habitats, including natural foci of tick-borne pathogens.

Rusňáková Tarageľová V ，Derdáková M ，Selyemová D ，Chvostáč M ，Mangová B ，Didyk YM ，Koči J ，Kolenčík S ，Víchová B ，Peťko B ，Stanko M ，Kazimírová M ... -  《Frontiers in Cellular and Infection Microbiology》

Assessment of occupational exposure of soldiers to Lyme disease and Borrelia miyamotoi disease in selected military training areas from northern Poland.

Ixodes ricinus tick is a vector of bacteria of Borreliella genus and Borrelia miyamotoi. Exposure to ticks constitutes occupational risk to soldiers, but the current knowledge on this subject is still limited. Therefore, the aim of this study was to evaluate tick abundance and prevalence of infection with Borreliella spp. and/or B. miyamotoi. Ticks were collected from vegetation on Drawsko, Ustka and Orzysz military training areas. Additionally, ticks infesting soldiers were also obtained. Ticks were examined by nested PCR and sequencing of flaB gene fragment. General Linear Models of One Variable was used for analysis of mean tick abundance and Maximum Likelihood technique based on log-linear analysis of contingency tables was used for analysis of prevalence of pathogens in ticks. Molecular phylogenetic analyses were also performed. 852 I. ricinus were collected from vegetation from three military areas. The overall mean abundance of ticks was almost 4 ticks/100 m2. Season of study had a significant effect on density of total ticks, infected nymphs and females and infected nymphs, which were higher in spring-early summer. Total prevalence of pathogens was 25.7% in 711 questing ticks, and 16.0% in 282 I. ricinus collected from soldiers. Six species of Borreliella and Borrelia were identified with predominance of B. afzelii. It should be assumed that there is a risk for soldiers of acquiring infection after tick bite. The awareness of presence of pathogens in ticks should be raised in military.

Gajda-Sawicka E ，Kowalec M ，Sieńko A ，Ochab A ，Żuk M ，Bielat U ，Krzowski Ł ，Dwużnik-Szarek D ，Bajer A ... -  《-》