Impact of abiotic factors, habitat type and urban wildlife on the ecology of hard ticks (Acari: Ixodidae) in urban and peri-urban habitats

Abstract

Background Ticks are increasingly acknowledged as significant vectors for a wide array of pathogens in urban environments with reports of abundant tick populations in recreational areas. The study aims to contribute to a better knowledge of the abiotic and biotic factors which impact the ecology of hard ticks in urban and peri-urban habitats in Romania. Methods Questing ticks were collected by flagging in seven recreational locations, from four types of habitats in Cluj-Napoca, Romania: parks; gardens; a cemetery; and peri-urban forests. Hedgehogs, birds and micromammals were also sampled and searched for ticks, using standard methods (i.e. torch-based searches, ornithological mist nets, snap-traps, etc.), while vegetation was evaluated on surveyed areas. Data on questing ticks were converted to abundance indices. Moodʼs median tests were used to assess the relationship between the abiotic and biotic factors and the abundance of questing ticks. Results Two species of questing ticks were found: Ixodes ricinus (96.8%) and Haemaphysalis punctata (3.2%). Ixodes ricinus was also the predominant engorged tick collected from urban wildlife. For I. ricinus the highest mean total abundance index/location (total no. of ticks/100 m2) was recorded in the urban gardens (3.79, 95% CI: ± 1.59) and parks (2.68, 95% CI: ± 0.75), whereas the lowest mean total abundance index was noted in the peri-urban forests (0.06, 95% CI: ± 0.03) and the urban cemetery (0.04, 95% CI: ± 0.02). The adults and nymphs of I. ricinus displayed a bimodal activity pattern, while the larvae showed a unimodal questing behaviour with an autumnal peak. Positive correlations were found between the mean total abundance index and the rise in the daily mean temperature and relative humidity, and between the global abundance of questing ticks and the presence of hedgehogs in the respective locations (P < 0.01). Conclusions Ticks were collected in all the recreational sites surveyed in Cluj-Napoca. Ixodes ricinus was the dominant questing and engorged tick species. Several abiotic and biotic factors shape the ecology of ticks in Cluj-Napoca city, with climate and the local presence of suitable hosts being the most important.

High Diversity, Prevalence, and Co-infection Rates of Tick-Borne Pathogens in Ticks and Wildlife Hosts in an Urban Area in Romania

“…This was not related to bias in the selection algorithm but because of the availability and abundance of wildlife hosts and questing ticks when the collection was performed. A previous study we conducted in these seven recreational locations in Cluj-Napoca showed a higher abundance of ticks in the urban versus the peri-urban locations, linked to the abundance and diversity of local wildlife species, particularly hedgehogs (E. roumanicus) (Borşan et al, 2020). These findings may explain the more diverse TBPs community we detected in urban sites, further highlighting the importance of urban dwellers such as hedgehogs, rodents, and birds in the ecology of tick-borne diseases.…”

“…During the necropsy, the heart, liver tissue, and two skin biopsies (one from the interscapular region and the second from the ear pavilion that were pooled together for DNA isolation) were collected from each animal. All the tissue samples were labeled accordingly and stored at −20 • C. During the anesthesia -protocol described in Borşan et al (2020), 0.5 ml of blood were collected from the jugular or saphenous vein of eight hedgehogs. Blood sampling was unsuccessful in the case of three hedgehogs.…”

“…Blood sampling was unsuccessful in the case of three hedgehogs. Regarding the birds (Borşan et al, 2020), a 150 µl blood sample was collected from the brachial vein using a microcapillary tube. All blood samples were stored in a 3.2% citrate tube at −20 • C. Overall, DNA was individually isolated from the heart, liver, and skin biopsy tissues from 29 mammal hosts, 33 blood samples from birds, and eight blood samples from hedgehogs ( Supplementary File 1).…”

“…Ixodes ricinus is the predominant tick species reported in Europe ( Rizzoli et al, 2014 ) and the most widespread questing tick species collected in Romania’s natural ( Mihalca et al, 2012a ) and urban habitats ( Borşan et al, 2020 ). Moreover, it is also the most prevalent tick species reported to bite humans in Romania ( Briciu et al, 2014 ; Andersson et al, 2018 ).…”

Tick hazard in the South Downs National Park (UK): species, distribution, key locations for future interventions, site density, habitats

“…In contrast, H.punctata can likely survive better in short grass, its traditional range includes deserts (Nosek, 1973). Outside the UK H.punctata is also found in forest (Borşan et al, 2020). Whilst its established foci in the eastern Downs is relatively unwooded, if allowed to expand its range westward along the downland ridge (which was not certified by peer review) is the author/funder.…”