Behavioral characteristics and endosymbionts of two potential tularemia and Rocky Mountain spotted fever tick vectors

Environmental sampling for Dermacentor species (Acari: Ixodidae) in southern British Columbia, Canada in May, 2022

Traditionally, the most commonly encountered Dermacentor spp. (Acari: Ixodidae) in southern British Columbia, Canada has been Dermacentor andersoni Stiles. However, with the novel detection of Dermacentor similis Lado in southern British Columbia, environmental sampling for Dermacentor spp. is needed to provide up-to-date information on which ticks are present in this area. Drag sampling was conducted at 33 sites across southern British Columbia, covering 2000 m2 per site. Environmental and weather data were recorded at the time of sampling. The only Dermacentor spp. collected was D. andersoni, with these ticks found at 10 sites. Univariable mixed-effect Poisson regression models with a random effect for site were used to investigate the relationship between transect-level environmental variables and the number of D. andersoni collected within a transect. As soil moisture decreased, the number of D. andersoni collected increased. No other relationships were detected. This study suggests that D. andersoni remains present in southern British Columbia and may be affected by the environmental variable of soil moisture. It also provides evidence that coupling different tick collection methods, for example, environmental and host sampling, has benefit in providing a more complete picture of the tick species present in an area.

Francisella tularensis in Wild Lagomorphs in Southern Spain's Mediterranean Ecosystems

Francisella tularensis is a vector-borne zoonotic bacterium that causes tularemia, a disease of great importance for animal and public health. Although wild lagomorphs are considered one of the major reservoirs of this bacterium, information about the circulation of F. tularensis in European wild rabbit (Oryctolagus cuniculus) and Iberian hare (Lepus granatensis) populations in Europe is still very limited. In Spain, F. tularensis is present in northern central regions, with recurrent outbreaks occurring annually. However, southern Spain has been neglected in terms of monitoring and research. Thus, the aim of this study was to investigate the occurrence of F. tularensis in wild lagomorphs in the Mediterranean ecosystems of southern Spain through using molecular techniques. Spleen samples from 774 European wild rabbits and 178 Iberian hares were collected on 135 hunting grounds between the 2017/2018 and 2022/2023 hunting seasons. A primer set targeting the 16S rRNA gene was used for the detection of F. tularensis DNA. None of the 952 (0.0%; 95%CI: 0.0-0.4) wild lagomorphs sampled showed presence of F. tularensis DNA. Our finding indicates the absence or very low circulation of the bacterium in wild rabbit and Iberian hare populations in the Mediterranean ecosystems of southern Spain, denoting a limited risk of transmission of this pathogen from wild lagomorphs to other sympatric species, including human beings, in this Iberian region.

Assessing the Influence of Climate Change and Environmental Factors on the Top Tick-Borne Diseases in the United States: A Systematic Review

In the United States (US), tick-borne diseases (TBDs) have more than doubled in the past fifteen years and are a major contributor to the overall burden of vector-borne diseases. The most common TBDs in the US-Lyme disease, rickettsioses (including Rocky Mountain spotted fever), and anaplasmosis-have gradually shifted in recent years, resulting in increased morbidity and mortality. In this systematic review, we examined climate change and other environmental factors that have influenced the epidemiology of these TBDs in the US while highlighting the opportunities for a One Health approach to mitigating their impact. We searched Medline Plus, PUBMED, and Google Scholar for studies focused on these three TBDs in the US from January 2018 to August 2023. Data selection and extraction were completed using Covidence, and the risk of bias was assessed with the ROBINS-I tool. The review included 84 papers covering multiple states across the US. We found that climate, seasonality and temporality, and land use are important environmental factors that impact the epidemiology and patterns of TBDs. The emerging trends, influenced by environmental factors, emphasize the need for region-specific research to aid in the prediction and prevention of TBDs.

Do ticks exhibit repeatable individual behaviors?

Diseases caused by ticks are often addressed as a traditional epidemiological mathematical puzzle, i.e., how many identical infected vectors, how many uniform potential hosts, and a dependable rate of transmission, etc. Although often useful at the population level, at the individual level disease transmission occurs when one tick bites one person. Just as we assign agency to people in their outdoor behavior and use of prophylactics against arthropods, perhaps we should also see ticks as individual actors? Are all ticks automatons that just quest and attach, or do they exhibit repeatable individual behaviors that affect transmission? We wanted to determine whether Dermacentor andersoni and D. variabilis adult ticks exhibited repeatable behaviors in four experiments. The experiments focused on left/right movement, attraction to CO2, photophilic tendencies, and avoidance of a repellant. We hypothesized that over two seasons we would find repeatable behavior patterns. In 2021, but not 2022, we found that within an experiment, individuals exhibited repeatable behaviors between trials and between experiments, i.e., if an animal showed repeatable 'adventurous' behavior in one experiment, this predicted adventurous behavior in a separate experiment. This strong evidence of predictable trait-like behavior was present in 2021 but was absent when we repeated the same experiments, with the same collection site, in 2022. This illustrates the importance of multiyear experimentation when testing for repeatable individual behaviors. Incidental to the study, we also observed that a major heat wave in 2021 altered the tick species composition (toward a more dry-adapted population) at our study site.

Effect of Eucalyptus globulus oil and Ricinus communis methanolic extract as potential natural molluscicides on the reproductive biology and some antioxidant enzymes of the land snail, Theba pisana

This study was conducted to investigate the effects of Eucalyptus globulus oil and methanolic extract of Ricinus communis seeds on the reproductive biology of the land snail Theba pisana. For this purpose, the snails were exposed to different concentrations of these plant extracts for six weeks. Rates of oviposition, hatching percentages, reproductive hormones and the histological structures of the hermaphrodite gland were estimated. Antioxidant enzymes were also estimated. The obtained results revealed that all tested concentrations of both tested natural products exerted hazardous effects on exposed snails. The mean egg number/snail treated with 2% E. globulus and R. communis were significantly decreased to 22 and 14 eggs respectively compared to 79 eggs for control. The hatching rates were dramatically decreased with increasing concentrations of both products. 2% of R. communis extract caused highly significant decrease in the activities of CAT, SOD, GST and MDA antioxidant enzymes while the same concentration of Eucalyptus oil resulted in elevations of CAT and SOD activities and significantly decreased GST and MDA activities. Levels of reproductive hormones were greatly disrupted and the histological structures of hermaphrodite acini as well as various developmental stages of spermatogenesis and oogenesis of treated snails were strictly spoiled.

Identification of Rickettsia spp. and Babesia conradae in Dermacentor spp. Collected from Dogs and Cats Across the United States

In the United States, Dermacentor variabilis and Dermacentor andersoni are considered key vectors for Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever. Through regional surveillance, a wide diversity of Rickettsia spp. have been documented in D. variabilis, and Dermacentor spp. has been suggested as potential vectors for various other pathogens, including Babesia spp. and Ehrlichia canis. To better define the prevalence and diversity of pathogens in Dermacentor spp. across the United States, 848 ticks collected from dogs and cats in 44/50 states in 2018–2019 were tested by PCR for Rickettsia spp.-specific 17 kDa and ompA gene fragments; a subset of Dermacentor spp. was also tested with PCR, targeting fragments of the 18S and large subunit region rRNA genes of Babesia spp. and 16S rRNA genes of E. canis. Rickettsia spp. was identified in 12.5% (106/848) of ticks. Species detected include Rickettsia montanensis (n = 64 ticks), Rickettsia bellii (n = 15 ticks), Rickettsia rhipicephali (n = 13 ticks), Rickettsia peacockii (n = 8 ticks), Rickettsia amblyommatis (n = 3 ticks), Rickettsia cooleyi (n = 1 tick), and unclassified Rickettsia spp. (n = 2 ticks). Ticks with R. montanensis and R. bellii were submitted from every U.S. region; R. rhipicephali was predominantly detected in ticks from the southern half of the United States, and all R. peacockii-positive ticks were D. andersoni that originated from the Rocky Mountain states. Ehrlichia canis was not detected in any Dermacentor spp., and Babesia conradae was detected in two Dermacentor albipictus. Because most ticks had fed on dogs or cats before submission, these findings do not implicate a given Dermacentor sp. as a primary vector of these agents, but in regard to Rickettsia spp., the data do support other published work showing D. variabilis harbors a diversity of Rickettsia species with unknown implications for animal and human health.