Morphological anomalies in Ixodes ricinus and Ixodes inopinatus collected from tick-borne encephalitis natural foci in Central Europe

Study on the Ixodid ticks species diversity (Acari: Ixodidae) on domestic ruminants in different agro-climatic regions of Tamil Nadu

A survey of Ixodid tick species diversity on domestic ruminants was conducted in seven agro-climatic regions of Tamil Nadu State, India. Tick surveys were conducted on domestic ruminants such as cattle, buffalo, sheep, and goat in seven districts of Tamil Nadu. The overall tick infestation was 38.8%, 5.8%, 14.6%, and 40.8% on cattle, buffaloes, sheep, and goats, respectively. A total of 8068 ticks from 18 species belonging to four genera were recorded. Overall, Haemaphysalis intermedia was the predominant (51.38%) tick species which has a wide host range. The most prevalent tick species in cattle and buffalo were Rhipicephalus (B.) microplus (25.41%) and Rhipicephalus haemaphysaloides (56.69%), respectively. Haemaphysalis intermedia was the most prevalent in ticks in sheep (70.35%), goat (70.35%), and dog (55.79%). In the present study, local anomalies such as the ectromely of one leg and the absence of adanal plates were observed in Rh. haemaphysaloides. The study also found that local anomaly such as protuberances in the hind tarsal and atrophy of the adanal plate was observed in Rhipicephalus (Boophilus) microplus. In addition, a general anomaly with three atrophy caudal appendages was also observed in Rhipicephalus (Boophilus) microplus. The overall prevalence of anomalies in Rh. haemaphysaloides and Rh. (B.) microplus was 0.3% (3/971) and 0.4% (3/678), respectively.

Morphological anomalies in hard ticks (Acari: Ixodidae) from Brazil

Tick abnormalities have been unusual in nature, and they can be divided into local and general. In the present study, external morphological anomalies were described in 31 individual adult ticks of 15 different species of Ixodidae, which were collected on wild hosts (20 ticks), domestic hosts (7 ticks), and in the environment (4 ticks) in 11 states of Brazil from 1998 to 2022. Among the 31 tick specimens, 14 (45%) were categorized as local anomalies, and 17 (55%) as general anomalies. The ticks were taxonomically identified into 14 species of Amblyomma, and one species of Rhipicephalus. Local anomalies included malformations of scutum/alloscutum, ectromely, leg atrophy, and a third ectopic spiracular plate. General anomalies included opisthosoma duplication, no expansion of dorsal alloscutum in engorged females, and gynandromorphism; the latter is described for 13 tick specimens. Morphological anomalies in Amblyomma aureolatum, Amblyomma brasiliense, Amblyomma humerale and Amblyomma longirostre are reported for the first time. Although the results herein expand the list of anomalous tick species in the Neotropics, future studies should be conducted to clarify the origin of these anomalies.

Genetic analysis challenges the presence of Ixodes inopinatus in Central Europe: development of a multiplex PCR to distinguish I. inopinatus from I. ricinus

BACKGROUND

Ixodes ricinus is an important vector of several pathogens, primarily in Europe. Recently, Ixodes inopinatus was described from Spain, Portugal, and North Africa and then reported from several European countries. In this study, a multiplex polymerase chain reaction (PCR) was developed to distinguish I. ricinus from I. inopinatus and used in the surveillance of I. inopinatus in Algeria (ALG) and three regions in the Czech Republic (CZ).

METHODS

A multiplex PCR on TROSPA and sequencing of several mitochondrial (16S rDNA, COI) and nuclear markers (TROSPA, ITS2, calreticulin) were used to differentiate these two species and for a subsequent phylogenetic analysis.

RESULTS

Sequencing of TROSPA, COI, and ITS2 separated these two species into two subclades, while 16S rDNA and calreticulin could not distinguish I. ricinus from I. inopinatus. Interestingly, 23 nucleotide positions in the TROSPA gene had consistently double peaks in a subset of ticks from CZ. Cloning of these PCR products led to a clear separation of I. ricinus and I. inopinatus indicating hybridization and introgression between these two tick taxa. Based on a multiplex PCR of TROSPA and analysis of sequences of TROSPA, COI, and ITS2, the majority of ticks in CZ were I. ricinus, no I. inopinatus ticks were found, and 10 specimens showed signs of hybridization. In contrast, most ticks in ALG were I. inopinatus, four ticks were I. ricinus, and no signs of hybridization and introgression were detected.

CONCLUSIONS

We developed a multiplex PCR method based on the TROSPA gene to differentiate I. ricinus and I. inopinatus. We demonstrate the lack of evidence for the presence of I. inopinatus in Central Europe and propose that previous studies be re-examined. Mitochondrial markers are not suitable for distinguishing I. inopinatus from I. ricinus. Furthermore, our data indicate that I. inopinatus and I. ricinus can hybridize, and the hybrids can survive in Europe.

Morphological abnormalities in Hyalomma dromedarii and Hyalomma rufipes (Acari: Ixodidae) collected from dromedary camels (Camelus dromedarius) in Aswan, Egypt

The present study reports anomalies in Hyalomma dromedarii and Hyalomma rufipes adults collected from dromedary camels (Camelus dromedarius) in Aswan, Egypt, between January and June 2022. A total of 52 adult ticks displayed one or several local and/or general anomalies. A wide variety of local anomalies was observed including atrophy of one or multiple legs, ectromely, absence of accessory adanal and subanal plates, fusion of adanal and accessory plates, and presence of sclerotized formation in the ventral plate, as well as abnormalities of the spiracle, anal groove, festoon, parma, and posteromedian groove. General anomalies comprised of asymmetries and gynandromorphism. Local anomalies were documented among H. dromedarii and H. rufipes, whereas general anomalies were documented only from H. dromedarii. The present work represents the first report of deuterogynander intrigue gynandromorphism in H. dromedarii, as well as the first report of morphological abnormalities in H. dromedarii and H. rufipes from Egypt.

Decoding the Geography of Natural TBEV Microfoci in Germany: A Geostatistical Approach Based on Land-Use Patterns and Climatological Conditions

Background: Tickborne-encephalitis (TBE) is a potentially life-threating neurological disease that is mainly transmitted by ticks. The goal of the present study is to analyze the potential uniform environmental patterns of the identified TBEV microfoci in Germany. The results are used to calculate probabilities for the present distribution of TBEV microfoci in Germany based on a geostatistical model. Methods: We aim to consider the specification of environmental characteristics of locations of TBEV microfoci detected in Germany using open access epidemiological, geographical and climatological data sources. We use a two-step geostatistical approach, where in a first step, the characteristics of a broad set of environmental variables between the 56 TBEV microfoci and a control or comparator set of 3575 sampling points covering Germany are compared using Fisher's Exact Test. In the second step, we select the most important variables, which are then used in a MaxEnt distribution model to calculate a high resolution (400 × 400 m) probability map for the presence of TBEV covering the entire area of Germany. Results: The findings from the MaxEnt prediction model indicate that multi annual actual evapotranspiration (27.0%) and multi annual hot days (22.5%) have the highest contribution to our model. These two variables are followed by four additional variables with a lower, but still important, explanatory influence: Land cover classes (19.6%), multi annual minimum air temperature (14.9%), multi annual sunshine duration (9.0%), and distance to coniferous and mixed forest border (7.0%). Conclusions: Our findings are based on defined TBEV microfoci with known histories of infection and the repeated confirmation of the virus in the last years, resulting in an in-depth high-resolution model/map of TBEV microfoci in Germany. Multi annual actual evapotranspiration (27%) and multi annual hot days (22.5%) have the most explanatory power in our model. The results may be used to tailor specific regional preventive measures and investigations.

Shift in the seasonality of ixodid ticks after a warm winter in an urban habitat with notes on morphotypes of Ixodes ricinus and data in support of cryptic species within Ixodes frontalis

This study was initiated to assess the seasonality and to investigate the morphology of questing ixodid ticks in an urban habitat in Central Europe, Hungary. A neglected part of a large cemetery, with sparse tree covering and dense lower vegetation, was sampled monthly from February 2019 to May 2021. All ticks were analyzed morphologically, and selected specimens by amplifying and sequencing two genetic markers. During the study 3818 ticks were collected, including Ixodes ricinus (n = 2772), Ixodes frontalis (n = 350) and Haemaphysalis concinna (n = 696). Ixodes ricinus adults and nymphs showed year-round activity, whereas H. concinna was not active during winter months and early spring. Most I. frontalis nymphs were collected in late winter and early spring, whereas the peak activity of larvae was during late autumn. Interestingly, during the spring, the peak activity of I. ricinus adults and nymphs was later (in May) when preceded by a warm winter in 2020. In contrast, the 2019 and 2021 spring activity peaks occurred in March and April after sharply rising temperatures in February. This shift in the peak activity of I. ricinus coincided with the initiation of questing activity of H. concinna. Three notably different morphotypes and four malformed specimens of I. ricinus were found. However, these were not significantly different in their mitochondrial haplotypes and phylogenetic clustering from typical specimens of this species. On the other hand, I. frontalis was represented by two remarkably different haplogroups, between which in the nymph stage there were no recognizable morphological differences, suggesting the status of these as cryptic species.

Morphological abnormalities and multiple mitochondrial clades of Rhipicephalus haemaphysaloides (Ixodida: Ixodidae)

Rhipicephalus haemaphysaloides is endemic in South and Southeast Asia, and it is known to parasitise domestic animals such as cattle, horses, sheep, and dogs. Despite infestation on multiple hosts, little attention has been paid to its morphological and molecular variation. The present study describes local morphological abnormalities for the first time in R. haemaphysaloides from Malaysia, and highlights the presence of three cytochrome c oxidase subunit I (COI) operational taxonomic units with 0.46-9.81% distances within the so-called R. haemaphysaloides in Malaysia, Thailand, and Pakistan.

Morphological anomalies in Rhipicephalus sanguineus s.s. (Acari: Ixodidae) collected from dogs in steppe and high plateaus regions, Algeria

The present report describes morphological anomalies in Rhipicephalus sanguineus s.s. collected from dogs between February 2017 and May 2019 in the steppic region of Djelfa and high plateau area of Bordj-Bou-Arreridj in Algeria. Out of 1043 ticks from 147 infested dogs, four adult ticks (0.38%), collected from four dogs, exhibited local morphological abnormalities. One male displayed ectromely of leg I left, and the other three specimens exhibited multiple associated anomalies in idiosomas and exoskeletons, festoons, stigmas (spiracles), as well as in adanal and accessory plates. This report provides additional exemplars of morphological abnormalities in tick populations of Africa, particularly North Africa.

The complex interplay of climate, TBEV vector dynamics and TBEV infection rates in ticks-Monitoring a natural TBEV focus in Germany, 2009-2018

BACKGROUND

Tick-borne encephalitis (TBE) is the most important tick-borne viral disease in Eurasia and causes disease in humans and in a number of animals, among them dogs and horses. There is still no good correlation between tick numbers, weather conditions and human cases. There is the hypothesis that co-feeding due to simultaneous occurrence of larvae and nymphs may be a factor for the increased transmission of the virus in nature and for human disease. Based on long-term data from a natural TBEV focus, phylogenetic results and meteorological data we sought to challenge this hypothesis.

METHODS

Ticks from an identified TBE natural focus were sampled monthly from 04/2009 to 12/2018. Ticks were identified and pooled. Pools were tested by RT-qPCR. Positive pools were confirmed by virus isolation and/or sequencing of additional genes (E gene, NS2 gene). Temperature data such as the decadal (10-day) mean daily maximum air temperature (DMDMAT) were obtained from a nearby weather station and statistical correlations between tick occurrence and minimal infection rates (MIR) were calculated.

RESULTS

In the study period from 04/2009 to 12/2018 a total of 15,530 ticks (2,226 females, 2,268 males, 11,036 nymphs) were collected. The overall MIR in nymphs over the whole period was 77/15,530 (0.49%), ranging from 0.09% (2009) to 1.36% (2015). The overall MIR of female ticks was 0.76% (17/2,226 ticks), range 0.14% (2013) to 3.59% (2016). The overall MIR of males was 0.57% (13/2,268 ticks), range from 0.26% (2009) to 0.97% (2015). The number of nymphs was statistically associated with a later start of spring/vegetation period, indicated by the onset of forsythia flowering.

CONCLUSION

There was no particular correlation between DMDMAT dynamics in spring and/or autumn and the MIR of nymphs or adult ticks detected. However, there was a positive correlation between the number of nymphs and the number of reported human TBE cases in the following months, but not in the following year. The hypothesis of the importance of co-feeding of larvae and nymphs for the maintenance of transmission cycle of TBEV in nature is not supported by our findings.

Morphological abnormalities in ticks (Acari: Ixodidae) collected from domestic animal species in Sudan

Morphological abnormalities in ticks have rarely been reported in nature. The existing knowledge about anomalies in ticks collected in Africa is very sparse. In this paper, we describe abnormalities in Amblyomma, Hyalomma, and Rhipicephalus ticks collected from cattle, sheep, goats, camels, and horses in Kassala and North Kordofan states, Sudan, between January and August 2017. A number of 15 adult ticks displayed one or several local anomalies, such as ectromely, abnormalities of the ventral plates, and body deformities, besides newly described multiple cuticula scars. This study presents the first report of local anomalies in ticks belonging to three genera in Sudan and highlights the need to investigate the association between such morphological abnormalities and tick biology.

A case of morphological anomalies in Amblyomma americanum (Acari: Ixodidae) collected from nature

We describe a case of morphological anomalies in Amblyomma americanum, a medically important species associated with several human diseases and medical conditions. Based on morphological characters using dichotomous morphological keys, high-resolution light microscopy, and scanning electron microscopy imaging, the tick was identified as Am. americanum nymph exhibiting various morphological anomalies including ectromely associate with asymmetry, olygomely (lack) of the fourth left leg, and schizomely (bifurcation of palpus) on the right side. We believe this is the first report of the presence of several spontaneous anomalies in one Am. americanum specimen. Morphological identity of the specimen was corroborated by DNA sequencing of the mitochondrial 16S region. We discuss recent reports of morphological anomalies in ixodid ticks and emphasize the significance of additional studies of teratology in medically important tick species and its potential implications.

A seven-legged tick: Report of a morphological anomaly in Ixodes scapularis (Acari: Ixodidae) biting a human host from the Northeastern United States

Cases of morphological anomalies in the blacklegged tick, Ixodes scapularis (Acari: Ixodidae), have recently been reported from the Northeastern and upper Midwestern United States, potentially complicating identification of this important vector of human disease-causing pathogens. We hereby report a case of a morphological anomaly in I. scapularis, biting a human host residing in Norwich, Connecticut. Using a dichotomous morphological key, high-resolution and scanning electron microscopy images, as well as DNA sequencing, the tick was identified as an adult female I. scapularis with three legs on the left side of the abdomen versus four on the right side, which we believe is the first case of ectromely in an adult I. scapularis. Using diagnostic genes in polymerase chain reaction, the specimen tested positive for Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum, the causative agents for Lyme disease and anaplasmosis, respectively, and also showed evidence of a rickettsial endosymbiont. Here we discuss recent reports of morphological anomalies in I. scapularis, and emphasize the significance of additional studies of teratology in this important tick species and its potential implications.

Abnormal Development of Hyalomma Marginatum Ticks (Acari: Ixodidae) Induced by Plant Cytotoxic Substances

The increasing application of toxic plant substances to deter and fight ticks proves the need for investigations focused on the elucidation of their impact on the developmental stages and populations of these arthropods. We examined the course of embryogenesis and egg hatch in Hyalomma marginatum ticks under the effect of cytotoxic plant substances. The investigations demonstrated that the length of embryonic development of egg batches treated with 20 μL of a 0.1875% colchicine solution did not differ significantly from that in the control group. Colchicine caused the high mortality of eggs (16.3%) and embryos (9.7%), disturbances in larval hatch (8.1%), and lower numbers of normal larval hatches (65.6%). In 0.2% of the larvae, colchicine induced anomalies in the idiosoma (67.6%) and gnathosoma (22.5%) as well as composite anomalies (8.5%). The study demonstrates that cytotoxic compounds with an effect similar to that of colchicine can reduce tick populations and cause teratological changes, which were observed in the specimens found during field studies. Since there are no data on the toxic effects of active plant substances on other organisms and the risk of development of tick resistance, a strategy for the use of such compounds in tick control and the management of plant products should be developed.

General and Local Morphological Anomalies in Amblyomma lepidum (Acari: Ixodidae) and Rhipicephalus decoloratus Infesting Cattle in Uganda

Morphological abnormalities in ticks seem to be rare phenomena in nature, and are underreported in Africa. In this article, we describe general and local anomalies in two Amblyomma lepidum females and one Rhipicephalus decoloratus female collected from cattle in Moroto and Kasese districts, Uganda. One A. lepidum specimen displayed metagynander gynandromorphism with the presence of both male and female features in the same organism. The second A. lepidum female showed slight asymmetry and lacked a genital aperture. The R. decoloratus displayed multiple anomalies that included asymmetry on the right side in association with ectromely, chitinous formations and constrictions on the left side. This article presents the first report of metagynander gynandromorphism, as well as genital aperture absence which is not linked to gynandromorphism, in A. lepidum collected from cattle.

Phylogenetic characterization of tick-borne encephalitis virus from Bornholm, Denmark

The Danish island of Bornholm in the Baltic Sea has been known as a tick-borne encephalitis (TBE) natural focus for more than 60 years. TBE in humans is diagnosed on a regular basis either in inhabitants or tourists of the island. Other areas in Denmark have been suggested as possible risk areas of TBE. Despite the long-known endemicity on Bornholm and the possibility of the virus circulating in other areas, no data on the prevalences of TBE virus (TBEV) in ticks, or adequate molecular characterization and phylogenetic studies are available for the circulating TBEV strains. This study aimed to detect TBEV in ticks collected on the island of Bornholm and other possible risk areas, with the attempt to isolate the circulating viruses for molecular and phylogenetic analysis and confirm the presence of virus in the predicted risk areas. From 2014 to 2016, 9321 I. ricinus (nymphs, females, and males) were collected by flagging 31 locations in Denmark. The ticks were pooled and tested for TBEV by qPCR. The envelope gene of the detected TBE virus strains was amplified and sequenced by RT-PCR. After successful virus isolation, whole genome sequencing was performed. Phylogenetic analysis of the obtained sequences was done by the Maximum Likelihood method. One pool of 11 females and one pool of eight males from a total of 34 tick pools collected from the northwestern shore of lake Rubinsøen on Bornholm tested positive, resulting in a local estimated point prevalence of 0.6% [CI95% 0,1-1.85%] in this microfocus. We were not successful in confirming any other of the predicted TBEV-endemic areas. Alignment of the two complete E genes from Bornholm revealed identical sequences. Virus isolation and whole genome sequencing were succeeded from one of the positive samples. Phylogenetic analysis showed that the isolated virus had the closest phylogenetic relationship to TBEV sequences detected in Eastern and Central Europe.

Report of the 20th annual meeting of the International Scientific Working Group on Tick-Borne Encephalitis (ISW-TBE): ISW-TBE: 20 years of commitment and still challenges ahead

The 20th Meeting of the International Scientific Working Group on Tick-Borne Encephalitis (ISW-TBE) - a group of neurologists, general practitioners, clinicians, travel physicians, virologists, pediatricians, ecologists, and epidemiologists - was held under the theme "ISW-TBE: 20 years of commitment & still challenges ahead". On the occasion of the 20^th anniversary of the ISW-TBE several key topics in TBE were extensively discussed, among them current epidemiological developments and investigations, expansion of risk areas, clinical aspects and cases, traveling and mobility, and latest news on TBE vaccination. The main goals that have been achieved by the ISW-TBE so far are, among others, an increased awareness in endemic and non-endemic countries, an increase of vaccination rates in various countries, getting TBE acknowledged and established as a travel-related risk, and building contact with the European Centre for Disease Prevention and Control.