Long term study of ixodid ticks feeding on red deer (Cervus elaphus) in a meso-Mediterranean climate

Emerging Hyalomma lusitanicum: From identification to vectorial role and integrated control

In the Mediterranean basin, the tick species Hyalomma lusitanicum Koch stands out among other species of the Hyalomma genus due to its wide distribution, and there is great concern about its potential role as a vector and/or reservoir and its continuous expansion to new areas because of climate warming and human and other animal movements. This review aims to consolidate all the information on H. lusitanicum, including taxonomy and evolution, morphological and molecular identification, life cycle, sampling methods, rearing under laboratory conditions, ecology, hosts, geographical distribution, seasonality, vector role and control methods. The availability of adequate data is extremely relevant to the development of appropriate control strategies in areas where this tick is currently distributed as well as in new areas where it could become established in the near future.

The Impact of Host Abundance on the Epidemiology of Tick-Borne Infection

Tick-borne diseases are an increasing global public health concern due to an expanding geographical range and increase in abundance of tick-borne infectious agents. A potential explanation for the rising impact of tick-borne diseases is an increase in tick abundance which may be linked to an increase in density of the hosts on which they feed. In this study, we develop a model framework to understand the link between host density, tick demography and tick-borne pathogen epidemiology. Our model links the development of specific tick stages to the specific hosts on which they feed. We show that host community composition and host density have an impact on tick population dynamics and that this has a consequent impact on host and tick epidemiological dynamics. A key result is that our model framework can exhibit variation in host infection prevalence for a fixed density of one host type due to changes in density of other host types that support different tick life stages. Our findings suggest that host community composition may play a crucial role in explaining the variation in prevalence of tick-borne infections in hosts observed in the field.

Modelling the current and future temperature suitability of the UK for the vector Hyalomma marginatum (Acari: Ixodidae)

Hyalomma marginatum is the main vector of Crimean-Congo haemorrhagic fever virus (CCHFV) and spotted fever rickettsiae in Europe. The distribution of H. marginatum is currently restricted to parts of southern Europe, northern Africa and Asia, and one of the drivers limiting distribution is climate, particularly temperature. As temperatures rise with climate change, parts of northern Europe currently considered too cold for H. marginatum to be able to survive may become suitable, including the United Kingdom (UK), presenting a potential public health concern. Here we use a series of modelling methodologies to understand whether mean air temperatures across the UK during 2000-2019 were sufficient for H. marginatum nymphs to moult into adult stages and be able to overwinter in the UK if they were introduced on migratory birds. We then used UK-specific climate projections (UKCP18) to determine whether predicted temperatures would be sufficient to allow survival in future. We found that spring temperatures in parts of the UK during 2000-2019 were warm enough for predicted moulting to occur, but in all years except 2006, temperatures during September to December were too cold for overwintering to occur. Our analysis of the projections data suggests that whilst temperatures in the UK during September to December will increase in future, they are likely to remain below the threshold required for H. marginatum populations to become established.

One Health Approach to Tick and Tick-Borne Disease Surveillance in the United Kingdom

Where ticks are found, tick-borne diseases can present a threat to human and animal health. The aetiology of many of these important diseases, including Lyme disease, bovine babesiosis, tick-borne fever and louping ill, have been known for decades whilst others have only recently been documented in the United Kingdom (UK). Further threats such as the importation of exotic ticks through human activity or bird migration, combined with changes to either the habitat or climate could increase the risk of tick-borne disease persistence and transmission. Prevention of tick-borne diseases for the human population and animals (both livestock and companion) is dependent on a thorough understanding of where and when pathogen transmission occurs. This information can only be gained through surveillance that seeks to identify where tick populations are distributed, which pathogens are present within those populations, and the periods of the year when ticks are active. To achieve this, a variety of approaches can be applied to enhance knowledge utilising a diverse range of stakeholders (public health professionals and veterinarians through to citizen scientists). Without this information, the application of mitigation strategies to reduce pathogen transmission and impact is compromised and the ability to monitor the effects of climate change or landscape modification on the risk of tick-borne disease is more challenging. However, as with many public and animal health interventions, there needs to be a cost-benefit assessment on the most appropriate intervention applied. This review will assess the challenges of tick-borne diseases in the UK and argue for a cross-disciplinary approach to their surveillance and control.

Seasonality of Coxiella burnetii among Wild Rabbits (Oryctolagus cuniculus) and the Hyalomma lusitanicum (Acari: Ixodidae) in a Meso-Mediterranean Ecosystem

(1) Background: Q fever is a worldwide zoonosis caused by Coxiella burnetii that have cases reported in humans and animals almost everywhere. The aim of this study was to describe the seasonality of Coxiella burnetii in the wild rabbit (Oryctolagus cuniculus) and the tick Hyalomma lusitanicum in a meso-Mediterranean ecosystem. (2) Methods: two populations of wild rabbits that differ in whether or not they share habitat with ungulates, mainly red deer (Cervus elaphus) were sampled for a year to collect ticks, blood and vaginal or anal swabs. Presence of C. burnetii DNA in swabs and the tick H. lusitanicum was determined by PCR and serum antibodies by ELISA. (3) Results: C. burnetii DNA was detected in 47.2% of 583 rabbits, in 65.5% of sera, and in more than half of the H. lusitanicum. There were small variations according to sex and age of the rabbits but significant according to the habitat (4) Conclusions: The results indicate that C. burnetii circulates freely between wild rabbits and H. lusitanicum and the sylvatic cycle in meso-Mediterranean environments relies in the presence of wild rabbits and H. lusitanicum above all if sharing habitat with red deer.

Red deer reveal spatial risks of Crimean-Congo haemorrhagic fever virus infection

Crimean-Congo haemorrhagic fever virus (CCHFV) continues to cause new human cases in Iberia while its spatial distribution and ecological determinants remain unknown. The virus remains active in a silent tick-animal cycle to which animals contribute maintaining the tick populations and the virus itself. Wild ungulates, in particular red deer, are essential hosts for Hyalomma ticks in Iberia, which are the principal competent vector of CCHFV. Red deer could be an excellent model to understand the ecological determinants of CCHFV as well as to predict infection risks for humans because it is large, gregarious, abundant and the principal host for Hyalomma lusitanicum. We designed a cross-sectional study, analysed the presence of CCHFV antibodies in 1444 deer from 82 populations, and statistically modelled exposure risk with host and environmental predictors. The best-fitted statistical model was projected for peninsular Spain to map infection risks. Fifty out of 82 deer populations were seropositive, with individual population prevalence as high as 88%. The highest prevalence of exposure to CCHFV occurred in the southwest of the Iberian Peninsula. Climate and ungulate abundance were the most influential predictors of the risk of exposure to the virus. The highest risk regions were those where H. lusitanicum is most abundant. Eight of the nine primary human cases occurred in or bordering these regions, demonstrating that the model predicts human infection risk accurately. A recent human case of CCHF occurred in northwestern Spain, a region that the model predicted as low risk, pointing out that it needs improvement to capture all determinants of the CCHFV infection risk. In this study, we have been able to identify the main ecological determinants of CCHFV, and we have also managed to create an accurate model to assess the risk of CCHFV infection.

Antiparasitic Effects of Potentially Toxic Beetles (Tenebrionidae and Meloidae) from Steppe Zones

Arthropods and specifically beetles can synthesize and/or sequester metabolites from dietary sources. In beetle families such as Tenebrionidae and Meloidae, a few studies have reported species with toxic defensive substances and antiparasitic properties that are consumed by birds. Here we have studied the antiparasitic activity of extracts from beetle species present in the habitat of the Great Bustard (Otis tarda) against four pathogen models (Aspergillus niger, Meloidogyne javanica, Hyalomma lusitanicum, and Trichomonas gallinae). The insect species extracted were Tentyria peiroleri, Scaurus uncinus, Blaps lethifera (Tenebrionidae), and Mylabris quadripunctata (Meloidae). M. quadripunctata exhibited potent activity against M. javanica and T. gallinae, while T. peiroleri exhibited moderate antiprotozoal activity. The chemical composition of the insect extracts was studied by gas chromatography coupled with mass spectrometry (GC-MS) analysis. The most abundant compounds in the four beetle extracts were hydrocarbons and fatty acids such as palmitic acid, myristic acid and methyl linoleate, which are characteristic of insect cuticles. The presence of cantharidin (CTD) in the M. quadripunctata meloid and ethyl oleate (EO) in T. peiroleri accounted for the bioactivity of their extracts.

Comparative Ecology of Hyalomma lusitanicum and Hyalomma marginatum Koch, 1844 (Acarina: Ixodidae)

The genus Hyalomma belongs to the Ixodidae family and includes many tick species. Most species in this genus are African species, but two of them, Hyalomma lusitanicum and Hyalomma marginatum, are also found in Europe and, owing to their morphological similarity, it is very difficult to tell them apart. This is a major concern because their phenology and vector capacities are quite different. Moreover, they share many habitats and both are currently spreading to new areas, probably due to climate change and animal/human movements. In this study, we review the described ecology of the two species and provide further interesting data on H. lusitanicum based on the authors' experience, which could be useful in assessing the risk they pose to humans and animals.

The effect of excluding ungulates on the abundance of ixodid ticks on wild rabbit (Oryctolagus cuniculus)

Tick abundance depends heavily on host density, so reducing access to the host should reduce tick populations in a determined area. In this study we compared the Parasitic Index (PI = average number of ticks per rabbit) of two wild rabbit populations separated 16 years ago by a fence keeping ungulates from moving freely. Two areas were selected (closed and open) wherein 50 wild rabbits per area were sampled for ticks. The PI in the open area (PI = 989.62) was significantly higher than in the closed area (PI = 515.40). Hyalomma lusitanicum Koch was globally the most abundant species, followed by Rhipicephalus pusillus Gil Collado, Rhipicephalus bursa Canestrini and Fanzago, Haemaphysalis hispanica Gil Collado, Rhipicephalus sanguineus s.l. Latreille and Ixodes ventalloi Gil Collado. Differences between areas varied depending on the species. The number of H. hispanica, R. bursa and R. pusillus were significantly more abundant on rabbits in the closed area, whereas H. lusitanicum predominated in the open area. Ungulates in the open area may have played an important role as the main or alternative host for ticks and/or drawing some tick species away from rabbits. In the closed area other reasons such as inter-specific competition could have influenced the tick abundance. These results show a clear reduction in tick abundance for at least 16 years as well as influenced species distribution.

In vitro feeding of Hyalomma lusitanicum ticks on artificial membranes

In vitro feeding of ticks (Acari: Ixodidae) is an important means to study the biology of ticks and their vectorial capacity. Here, we have adapted the tick Hyalomma lusitanicum Koch to previously published silicone-based membranes for in vitro feeding. For comparison purposes data on pre-oviposition, oviposition and hatching from females engorged on animals were used. A total of 68 engorged females out of 169 were obtained; feeding duration and feeding behaviour were similar to that of ticks on live host animals, although the final weight achieved for membrane-fed ticks was lower than that of their animal-fed counterparts. Comparison of the time taken for egg production and hatching showed that pre-oviposition was faster for membrane-fed ticks (16 days) than for animal-fed ticks (36 days), whereas the duration of oviposition-hatching was the same for the two feeding methods (34 days). We also observed that seasonality has an influence on tick feeding success: the conditions in Spring/Summer accelerated the tick life cycle. It is concluded that relatively large numbers of homogeneous laboratory-raised Hyalomma ticks can be produced without feeding them on experimental animals.

Control of Hyalomma lusitanicum (Acari: Ixodidade) Ticks Infesting Oryctolagus cuniculus (Lagomorpha: Leporidae) Using the Entomopathogenic Fungus Beauveria bassiana (Hyocreales: Clavicipitaceae) in Field Conditions

Entomopathogenic fungi are widely used to control arthropods not just in agricultural settings but also in Veterinary Medicine and Public Health. These products have been employed to control tick populations and tick-borne diseases. The effectiveness of these control measures not only depends on the fungi, but also on the tick species and environmental conditions. In Mesomediterranean areas, tick species are adapted to extreme climatic conditions and it is therefore especially important to develop suitable tick control strategies. The aim of this study was to evaluate the effectiveness of a new method of tick control which entails the application of a commercial strain of Beauveria bassiana (Balsamo, Vuillemin) on wild rabbit burrows under field conditions. Aqueous solutions of the product were applied using a mist blower sprayer into 1,717 burrows. Two trials were performed, one in spring and the other in summer. The parasitic index (PI) was calculated for 10 rabbits per treatment per time point on day +30, +60, and +90 posttreatment and efficiency was calculated by comparing the PI for ticks in treated and untreated rabbits. A total of 20,234 ixodid ticks were collected. Hyalomma lusitanicum Koch, 1844 was the most abundant tick feeding on rabbits. Treatment significantly reduced the PI in spring (by 78.63% and 63.28% on day +30 and +60, respectively; P < 0.05), but appeared to be less effective in summer, with a marginally significant tick reduction of 35.72% on day +30 (P = 0.05). Results suggest that the efficacy of applications inside burrows could be temperature-dependent and that such applications could be an economic alternative to rabbit tick control during at least two months using a diluted solution of B. bassiana conidia.