Ritva Penttinen

Assessing the abundance, seasonal questing activity, and Borrelia and tick-borne encephalitis virus (TBEV) prevalence of Ixodes ricinus ticks in a Lyme borreliosis endemic area in Southwest Finland

Studies have revealed that Ixodes ricinus (Acari: Ixodidae) have become more abundant and their geographical distribution extended northwards in some Nordic countries during the past few decades. However, ecological data of tick populations in Finland are sparse. In the current study, I. ricinus abundance, seasonal questing activity, and their Borrelia spp. and tick-borne encephalitis virus (TBEV) prevalence were evaluated in a Lyme borreliosis endemic area in Southwest Finland, Seili Island, where a previous study mapping tick densities was conducted 12 years earlier. A total of 1940 ticks were collected from five different biotopes by cloth dragging during May-September 2012. The overall tick density observed was 5.2 ticks/100m(2) for nymphs and adults. Seasonal questing activity of ticks differed between biotopes and life stages: bimodal occurrences were observed especially for nymphal and adult ticks in forested biotopes, while larvae in pastures exhibited mostly unimodal occurrence. Prevalence of Borrelia and TBEV in ticks was evaluated using conventional and real-time PCR. All samples were negative for TBEV. Borrelia prevalence was 25.0% for adults (n=44) and the minimum infection rate (MIR) 5.6% for pooled nymph samples (191 samples, 1-14 individuals per sample; 30/191 positive). No Borrelia were detected in pooled larval samples (63 samples, 1-139 individuals per sample). Five species of Borrelia were identified from the samples: B. afzelii, B. burgdorferi s.s., B. garinii, B. valaisiana and B. miyamotoi. In Finland, B. valaisiana and B. miyamotoi have previously been reported from the Åland Islands but not from the mainland or inner archipelago. The results of the present study suggest an increase in I. ricinus abundance on the island.

Leg deformities of oribatid mites as an indicator of environmental pollution

Oribatid mites have often been used as indicators of the degree of environmental pollution but few studies have assessed the effects of pollution at individual level. One possible indicator of environmental stress at individual level is structural malformations of exoskeleton. We studied whether a number of leg deformities in soil oribatid mites could be used as an indicator of the degree of heavy metal pollution or acidity in nature. For this purpose we collected soil samples in a well known pollution gradient of a Finnish Cu-Ni smelter. Heavy metals are common pollutants in the area. Ten focal oribatid species were inspected under microscope for deformations in their legs (missing, broken or deformed leg). Of the focal species only one (Chamobates cuspidatus) showed an increasing trend along the pollution gradient in the proportion of leg abnormalities but there were clear differences in proportions among species. We consider that leg deformities are not a good indicator of heavy metal exposure in the studied species. Our data suggest, however, that they may indicate spatial variation in soil pH. We also tested for the possible effects of pollution on oribatid species number and abundances. There were pollution-related differences in relative abundances of mites but not in the number of species. We discuss the relationship between soil pH, calcium requirements and skeletal malformations of oribatid mites.

Crowdsourcing-based nationwide tick collection reveals the distribution of Ixodes ricinus and I. persulcatus and associated pathogens in Finland

A national crowdsourcing-based tick collection campaign was organized in 2015 with the objective of producing novel data on tick distribution and tick-borne pathogens in Finland. Nearly 20 000 Ixodes ticks were collected. The collected material revealed the nationwide distribution of I. persulcatus for the first time and a shift northwards in the distribution of I. ricinus in Finland. A subset of 2038 tick samples containing both species was screened for Borrelia burgdorferi sensu lato (the prevalence was 14.2% for I. ricinus and 19.8% for I. persulcatus), B. miyamotoi (0.2% and 0.4%, respectively) and tick-borne encephalitis virus (TBEV; 0.2% and 3.0%, respectively). We also report new risk areas for TBEV in Finland and, for the first time, the presence of B. miyamotoi in ticks from mainland Finland. Most importantly, our study demonstrates the overwhelming power of citizen science in accomplishing a collection effort that would have been impossible with the scientific community alone. Emerging Microbes & Infections (2017) 6, e31; doi:10.1038/emi.2017.17; published online 10 May 2017

A comparative study of oribatid mite communities in red wood ant Formica polyctena nests and surrounding soil in a Finnish oak forest

Ant nests are also inhabited by other invertebrates, ant associates. The oribatid mite (Acari: Oribatida) fauna of nests is poorly known, both in terms of abundance and diversity. We compared the oribatid assemblages within and outside red wood ant Formica polyctena nests in a Finnish oak forest. Altogether ten mounds were investigated and comparable samples were collected from adjacent soil 4 m from each mound. A total of 10 529 specimens were recovered, 4959 of them in mounds and 5633 in soil. The specimens represented 74 species (and two higher taxa) belonging to 60 genera and 39 families. Significant differences in abundance or diversity were not observed between nests and soil habitats. For nest samples the abundance of specimens significantly correlated with diversity indicating that mounds form rich habitat patches with a diverse set of niches. Mound size had no effect on community composition. The nest and soil habitats were predominantly occupied by different species resulting in dissimilarities in community composition; 34% of the species showed a preference for nest habitat and 50% for soil habitats, whereas16% were indifferent with equal abundances in both habitats. Nonetheless, most of the species with a preference for nests are frequently found in various habitats in nature, and may be classified as facultative myrmecophiles that maintain populations also in ant nests. Ant nests host abundant and diverse oribatid assemblages, which differ from the fauna in adjacent soil, and wood ants are therefore important factors in maintaining biodiversity.

Two zoogeographically remarkable mite species from Finland (Acari, Oribatida, Oribotritiidae)

Diagnosis of Maerkelotritia cryptopa (Banks, 1904) and description of a new species Austrotritia finlandica sp. nov. are given. The first‐mentioned species, previously recorded from the Nearctic Region, can now be considered as a holarctic species. The second species belongs to the genus Austrotritia Sellnick, 1959 from the southern hemisphere. Thus, it is highly unexpected to find it in Finland.

Tick-borne pathogens in Finland: comparison of Ixodes ricinus and I. persulcatus in sympatric and parapatric areas

BackgroundAlmost 3500 tick samples, originally collected via a nationwide citizen science campaign in 2015, were screened to reveal the prevalence and distribution of a wide spectrum of established and putative tick-borne pathogens vectored by Ixodes ricinus and I. persulcatus in Finland. The unique geographical distribution of these two tick species in Finland allowed us to compare pathogen occurrence between an I. ricinus-dominated area (southern Finland), an I. persulcatus-dominated area (northern Finland), and a sympatric area (central Finland).ResultsOf the analysed ticks, almost 30% carried at least one pathogen and 2% carried more than one pathogen. A higher overall prevalence of tick-borne pathogens was observed in I. ricinus than in I. persulcatus: 30.0% (604/2014) versus 24.0% (348/1451), respectively. In addition, I. ricinus were more frequently co-infected than I. persulcatus: 2.4% (49/2014) versus 0.8% (12/1451), respectively. Causative agents of Lyme borreliosis, i.e. bacterial genospecies in Borrelia burgdorferi (sensu lato) group, were the most prevalent pathogens (overall 17%). “Candidatus Rickettsia tarasevichiae” was found for the first time in I. ricinus ticks and in Finnish ticks in general. Moreover, Babesia divergens, B. venatorum and “Candidatus Neoehrlichia mikurensis” were reported for the first time from the Finnish mainland.ConclusionsThe present study provides valuable information on the prevalence and geographical distribution of various tick-borne pathogens in I. ricinus and I. persulcatus ticks in Finland. Moreover, this comprehensive subset of ticks revealed the presence of rare and potentially dangerous pathogens. The highest prevalence of infected ticks was in the I. ricinus-dominated area in southern Finland, while the prevalence was essentially equal in sympatric and I. persulcatus-dominated areas. However, the highest infection rates for both species were in areas of their dominance, either in south or north Finland.