The diversity and prevalence of hard ticks attacking human hosts in Eastern Siberia (Russian Federation) with first description of invasion of non-endemic tick species

The structure and behavioral patterns of the human population affected by ixodid tick bites in Irkutsk Region, Eastern Siberia, Russia

The bites of hard ticks are the major route of transmission of tick-borne infections to humans, causing thousands of cases of diseases worldwide. However, the characteristics of the human population that is exposed to tick bites are still understudied. This work is aimed at characterizing both the structure of the population directly contacting ticks and the human behavioral features associated with tick bites. We studied 25,970 individuals who sought medical help after a tick bite at the Centre for Diagnostics and Prevention of Tick-borne Infections (CDPTBI) in Irkutsk City (Russian Federation). The demographic and behavioral characteristics of the human population were analyzed using z-tests for proportions, the Mann-Whitney U test, and the Spearman rank correlation coefficient. The majority of bitten people were urban residents (70 %), and most of them were either of active ages between 30 and 74 years old (62 %), or children between 0 and 9 years old (approximately 20%). Tick bites occurred mostly in the range of 150 km around the location of the diagnostic facility (83 %). In comparison to the general population, significant differences were revealed in the representation of different age groups among bitten people. The population affected by tick bites included fewer men and women in the ages of 10-29 and over 75 years old than would be predicted based on the demographics of the general population. Vice versa, the proportions of people in the ages of 5-9 and 60-74 increased among bitten people. Among men, such activities (in order of occurrence) as "leisure and recreation", "visiting allotments", "foraging for forest food", and "fulfilling work duties" tend to be more associated with tick bites. Among women, tick bites occurred mainly during "visiting allotments", "leisure and recreation", "visiting cemeteries" and "contact with pets and plants at home". The overall vaccination rate was 12 %; however, significantly more men than women were vaccinated against tick-borne encephalitis (up to 20 % vs. approximately 7 % respectively). The structure of the tick bite - affected population suggests that it is age-specific human behavior that mainly determines the frequency of contact between people and ticks. However, in several age groups, especially among children from 5 to 9 and people aged 30-39 years old, gender-related factors could significantly change the exposure of people to tick bites.

Ticks and tick-borne microbes identified through passive and active surveillance in Alaska

Rapid environmental change in Alaska and other regions of the Arctic and sub-Arctic has raised concerns about increasing human exposure to ticks and the pathogens they carry. We tested a sample of ticks collected through a combination of passive and active surveillance from humans, domestic animals, and wildlife hosts in Alaska for a panel of the most common tick-borne pathogens in the contiguous United States to characterize the diversity of microbes present in this region. We tested 189 pooled tick samples collected in 2019-2020 for Borrelia spp., Anaplasma spp., Ehrlichia spp., and Babesia spp. using a multiplex PCR amplicon sequencing assay. We found established populations of Ixodes angustus Neumann (Acari: Ixodidae), Ixodes uriae White (Acari: Ixodidae), and Haemaphysalis leporispalustris Packard (Acari: Ixodidae) in Alaska, with I. angustus found on a variety of hosts including domestic companion animals (dogs and cats), small wild mammals, and humans. Ixodes angustus were active from April through October with peaks in adult and nymphal activity observed in summer months (mainly July). Although no known human pathogens were detected, Babesia microti-like parasites and candidatus Ehrlichia khabarensis were identified in ticks and small mammals. The only human pathogen detected (B. burgdorferi s.s.) was found in a tick associated with a dog that had recently traveled to New York, where Lyme disease is endemic. This study highlights the value of a combined passive and active tick surveillance system to detect introduced tick species and pathogens and to assess which tick species and microbes are locally established.

The life cycle of Dermacentor nuttalli from the Qinghai-Tibetan Plateau under laboratory conditions and detection of spotted fever group Rickettsia spp

Dermacentor nuttalli has been a focus of study because tick-borne pathogens have been widely identified in this tick from northern and southwestern China. The aim of this study was to characterize the life cycle of D. nuttalli under laboratory conditions and to detect spotted fever group (SFG) Rickettsia in the midgut and salivary glands of both field-collected and first laboratory generation adults. D. nuttalli ticks were collected in the field on the Qinghai-Tibetan Plateau from March to April 2021 and their life cycle was studied under laboratory conditions. Tick identify was molecularly confirmed, and SFG Rickettsia were detected in the midgut and salivary glands of males and females by PCR targeting different rickettsial genes. The results showed that the life cycle of D. nuttalli under laboratory conditions was completed in an average of 86.1 days. High positivity of Rickettsia spp. was detected in the midgut and salivary glands of both males (92.0%) and females (93.0%) of field-collected D. nuttalli ticks. However, a relatively lower positivity (4.0-6.0%) was detected in first laboratory generation adults. Furthermore, sequencing analysis showed that the Rickettsia sequences obtained in this study shared 98.6 to 100% nucleotide identity with Rickettsia slovaca and Rickettsia raoultii isolated from Dermacentor spp. in China. Phylogenetic analysis of Rickettsia spp. based on the gltA, ompA, ompB and sca4 genes revealed that the Rickettsia sequences obtained could be classified as belonging to R. slovaca and R. raoultii clades. This study described for the first time the life cycle of D. nuttalli from the Qinghai-Tibetan Plateau under laboratory conditions. Two species of SFG Rickettsia were detected in the midgut and salivary glands of males and females in both field-collected and first laboratory-generation adults of D. nuttalli. Our study provides new insights into pathogen detection in ticks in the Qinghai-Tibet Plateau, and the relationships among hosts, ticks, and pathogens.

Prevalence and clinical manifestation of Borrelia miyamotoi in Ixodes ticks and humans in the northern hemisphere: a systematic review and meta-analysis

BACKGROUND

Various studies have evaluated the infection of Ixodes ticks and humans with the relapsing fever spirochaete Borrelia miyamotoi. However, to our knowledge, the prevalence of infection and disease has not been assessed systematically. We aimed to examine the prevalence of B miyamotoi in Ixodes ticks and humans, and the disease it can cause, in the northern hemisphere.

METHODS

For this systematic review and meta-analysis, we searched PubMed and Web of Science up to March 1, 2021. Studies assessing Ixodes tick infection published since Jan 1, 2011 were eligible, whereas no time limitation was placed on reports of human infection and disease. We extracted B miyamotoi test positivity ratios and used a random-effects model to calculate estimated proportions of infected ticks, infected humans, and human disease with 95% CI. This study was registered with PROSPERO, CRD42021268996.

FINDINGS

We identified 730 studies through database searches and 316 additional studies that referenced two seminal articles on B miyamotoi. Of these 1046 studies, 157 were included in the review, reporting on 165 637 questing ticks, 45 608 unique individuals, and 504 well described cases of B miyamotoi disease in humans. In ticks, the highest prevalence of B miyamotoi was observed in Ixodes persulcatus (2·8%, 95% CI 2·4-3·1) and the lowest in Ixodes pacificus (0·7%, 0·6-0·8). The overall seroprevalence in humans was 4·4% (2·8-6·3), with significantly (p<0·0001) higher seroprevalences in the high-risk group (4·6%, 2·6-7·1), participants with confirmed or suspected Lyme borreliosis (4·8%, 1·8-8·8), and individuals suspected of having a different tick-borne disease (11·9%, 5·6-19·9) than in healthy controls (1·3%, 0·4-2·8). Participants suspected of having a different tick-borne disease tested positive for B miyamotoi by PCR significantly more often than did the high-risk group (p=0·025), with individuals in Asia more likely to test positive than those in the USA (odds ratio 14·63 [95% CI 2·80-76·41]).

INTERPRETATION

B miyamotoi disease should be considered an emerging infectious disease, especially in North America and Asia. Prospective studies and increased awareness are required to obtain further insights into the burden of disease.

FUNDING

ZonMW and the European Regional Development Fund (Interreg).

Detailed Infestation Spectrums About Biological Stages of Hard Ticks (Acari: Ixodida: Ixodidae) in Humans: A Systematic Review and Meta-Analysis

PURPOSE

A comprehensive systematic meta-analysis review which deals with the degrees and trends of human infestation by biological stages of ticks, the degrees and trends of human infestation by biological stages of ticks in rural and urban areas, the infestation scale of tick attachment sites in body parts of humans, and the degrees of tick infestation in human age groups is critical. Therefore, this systematic meta-analysis review summarizes the above-detailed human infestation spectrums about biological stages of hard ticks.

METHODS

After a preliminary review from 605 papers representing areas of the study objectives, 96 were selected for detailed human infestation spectrums of biological stages of hard ticks.

RESULTS

In general, the results suggest that the adult ticks, and mostly females attack humans more than larval and nymphalid ones, and adult males, respectively. Unlike the trends of human infestation by larval and nymphalid stages of ticks, and the adult, male and female ticks which exhibited approximately a sharply decreasing trend, the global trend of human infestation by hard ticks exhibited approximately a sharply increasing trend over time. Ticks attack humans more in rural area than urban area. Also, the trends of human tick infestation in rural and urban areas exhibit, respectively, a sharp increase and decrease trends over time.

CONCLUSIONS

The majority of ticks mostly attach to human body trunk and extremity than head and neck, and genital area. Ticks attack human age groups of 0-9, 20-39, and 40-59 years more than those aged between 10 and 19 or older than 60 years.

New insights about human tick infestation features: a systematic review and meta-analysis

There are many studies that provide information regarding ticks infesting humans. However, there is no a meta-analysis about the global ranks of tick infestation rates and records, global monthly tick bites and annually and periodically trends of tick infestation rates, and the global tick infestation rates among years, mounts, regions, and countries. The study provides new insights about the above objectives in a global context and therefore performed. After a preliminary review of the 610 papers representing objective areas, 241 were selected for detailed meta-analysis. In general, the global ranks of tick species were, respectively, between 0.01-85.4% and 1-53 for human infestation rates and records. Twenty-six and sixteen tick species have more than 10% and 10 records of human tick infestation rates and records, respectively. It seems these tick species tend to be more blood-feeding on humans and as a result can be more dangerous to humans. The outcome of study demonstrated that there is no difference between seasonal human tick infestation patterns in the northern and southern hemispheres. The most global monthly mean tick bites in humans were observed in June then followed in July, August, May, and September. The global annually and periodically trends of tick infestation rates in humans exhibited decreasing trends over the past decades suggesting the preventive measure to prohibit human tick infestation have been successful. It seems that the ranks of tick infestation rates and records in humans may be as two indexes to illustrate the degree of importance of tick infesting humans.

Vectors of disease at the northern distribution limit of the genus Dermacentor in Eurasia: D. reticulatus and D. silvarum

The two ixodid tick species Dermacentor reticulatus (Fabricius) and Dermacentor silvarum Olenev occur at the northern distribution limit of the genus Dermacentor in Eurasia, within the belt of [Formula: see text] latitude. Whilst the distribution area of D. reticulatus extends from the Atlantic coast of Portugal to Western Siberia, that of D. silvarum extends from Western Siberia to the Pacific coast. In Western Siberia, the distribution areas of the two Dermacentor species overlap. Although the two tick species are important vectors of disease, detailed information concerning the entire distribution area, climate adaptation, and proven vector competence is still missing. A dataset was compiled, resulting in 2188 georeferenced D. reticulatus and 522 D. silvarum locations. Up-to-date maps depicting the geographical distribution and climate adaptation of the two Dermacentor species are presented. To investigate the climate adaptation of the two tick species, the georeferenced locations were superimposed on a high-resolution map of the Köppen-Geiger climate classification. The frequency distribution of D. reticulatus under different climates shows two major peaks related to the following climates: warm temperate with precipitation all year round (57%) and boreal with precipitation all year round (40%). The frequency distribution of D. silvarum shows also two major peaks related to boreal climates with precipitation all year round (30%) and boreal winter dry climates (60%). Dermacentor silvarum seems to be rather flexible concerning summer temperatures, which can range from cool to hot. In climates with cool summers D. reticulatus does not occur, it prefers warm and to a lesser extent hot summers. Lists are given in this paper for cases of proven vector competence for various agents of both Dermacentor species. For the first time, the entire distribution areas of D. reticulatus and D. silvarum were mapped using georeferenced data. Their climate adaptations were quantified by Köppen profiles.

Microbiome analysis of the saliva and midgut from partially or fully engorged female adult Dermacentor silvarum ticks in China

Dermacentor silvarum is widely distributed in northern China and transmits several pathogens that cause diseases in humans and domestic animals. We analysed the comprehensive bacterial community of the saliva and midgut from partially and fully engorged female adult D. silvarum. Dermacentor silvarum samples were collected from Guyuan, China. Bacterial DNA was extracted from the saliva and midgut contents of partially or fully engorged female adult D. silvarum. Sequencing of the V3-V4 hypervariable regions of the 16S rRNA genes was performed using the IonS5^TMXL platform. The bacterial diversity in saliva was higher than in the midgut. The bacterial diversity of saliva from fully engorged ticks was greater than in partially engorged tick saliva. The bacterial diversity in midguts from partially engorged ticks was greater than in fully engorged tick midguts. Proteobacteria was the most dominant bacterial phylum in all of the samples. Twenty-nine bacterial genera were detected in all of the samples. Rickettsia, Anaplasma, and Stenotrophomonas were the main genera. The symbionts Coxiella, Arsenophonus, and Wolbachia were also detected in all of the samples. Eight bacterial species were identified in all of the experimental samples. Anaplasma marginale was reported for the first time in D. silvarum.

Cytokine Profiling of Subclinical Tick-Borne Infections in Humans

Over many years, tick-borne infections remain one of the most serious threats to human health worldwide. The immune response to these infections in a human after confirmed bite by an infected carrier at the early stages of infection in the absence of clinical symptoms can be the first indicator of the presence of the infectious agent in the body. During viral infection, the concentration of IL-1α, IL-8, IL-10, IL-17A, and IFNγ increases; superoxide dismutase also increases, in contrast to bacterial infections. A slight decrease in the concentration is observed only for receptor antagonist IL-1Ra. During the infection caused by bacterial pathogens, very similar profiles of the innate human immune response are observed: activation of IL-1α, IL-8, and IFNα and suppression of superoxide dismutase, IL-1Ra, and IL-17A production. It has been demonstrated, that the immune response is triggered immediately after infection, and changes in the concentration of the main cytokines in the blood plasma can be detected as early as on days 2-5 after tick bite. These results can be useful in developing new methods of emergency diagnosis and prevention of tick-borne infections.

Dog survey in Russian veterinary hospitals: tick identification and molecular detection of tick-borne pathogens

Background

Species of Canidae in Russia can be infested with up to 24 different tick species; however, the frequency of different tick species infesting domestic dogs across Russia is not known. In addition, tick-borne disease risks for domestic dogs in Russia are not well quantified. The goal of this study was to conduct a nationwide survey of ticks collected from infested dogs admitted to veterinary clinics in Russian cities and to identify pathogens found in these ticks.

Methods

Ticks feeding on dogs admitted to 32 veterinary clinics in 27 major cities across Russia were preserved in ethanol and submitted to a central facility for examination. After identification, each tick was evaluated for infection with known tick-borne pathogens using PCR.

Results

There were 990 individual ticks collected from 636 dogs. All collected ticks belonged to the Ixodidae (hard ticks) and represented 11 species of four genera, Dermacentor, Ixodes, Rhipicephalus and Haemaphysalis. Four most common tick species were D. reticulatus, followed by I. persulcatus, I. ricinus and R. sanguineus. Ixodes persulcatus ticks were found to be infected with 10 different pathogens, and ticks of this species were more frequently infected than either D. reticulatus or I. ricinus. Ixodes persulcatus females were also more frequently co-infected with two or more pathogens than any other tick. Pathogenic species of five genera were detected in ticks: Anaplasma centrale, A. phagocytophilum and A. marginale; Babesia canis, B. microti, B. venatorum, B. divergens, B. crassa and B. vogeli; Borrelia miyamotoi, B. afzelii and B. garinii; Ehrlichia muris, E. canis and E. ruminantum; and Theileria cervi. Anaplasma marginale, E. canis, B. crassa, B. vogeli and T. cervi were detected in I. persulcatus, and Babesia canis in D. marginatum, for the first time in Russia.

Conclusions

Multiple ticks from four genera and 11 species of the family Ixodidae were collected from domestic dogs across Russia. These ticks commonly carry pathogens and act as disease vectors. Ixodes persulcatus ticks present the greatest risk for transmission of multiple arthropod-borne pathogens.

NECESSITY TO IMPROVE THE EMERGENCY DIAGNOSTICS OF TICK-BORNE INFECTIONS IN PEOPLE BITTEN BY IXODID TICKS ABROAD OF THE RUSSIAN FEDERATION

Introduction. Annually, there are several patients attended the Center for Diagnosis and Prevention of Tick-borne Infections in  Irkutsk after bites of ticks that happened outside the Pribaikalye  region or abroad. In such cases, the attacking ticks do not belong to  convenient species that are usual for Eastern Siberia. Consequently,  the spectrum of pathogenic microorganisms transmitted by these  ticks may significantly differ from those that are detected by usual  laboratory tests. Thus, both physicians and laboratory personnel may  have difficulties in proper detection and identification of pathogens as well as in diagnosing and treating of such patients.

The purpose of the study was the analysis of potential risks of human infection with the pathogens that are common in foreign countries outside the Russian Federation.

Material and methods. The article uses information from electronic databases created by the authors during 2007-2017.

Results and discussion. During 11 years of observations, 52 tick bites were registered in 20 countries, with 48 of them in the Eastern  Hemisphere (92.3 %), three (5.8 %) in the United States and one  (1.9 %) in the Republic of Cuba. The results indicate a real danger of infection by tick-borne pathogens of people traveling as the tourists  and with business purposes to the countries of Europe, Asia and America.

 

Conclusion. It is necessary to improve the existing algorithm for diagnosis, prevention and treatment for people bitten by ixodid ticks  outside the Russian Federation, taking into account the possibility of  infection by inconvenient imported infections.

Dermacentor reticulatus: a vector on the rise

Dermacentor reticulatus is a hard tick species with extraordinary biological features. It has a high reproduction rate, a rapid developmental cycle, and is also able to overcome years of unfavourable conditions. Dermacentor reticulatus can survive under water for several months and is cold-hardy even compared to other tick species. It has a wide host range: over 60 different wild and domesticated hosts are known for the three active developmental stages. Its high adaptiveness gives an edge to this tick species as shown by new data on the emergence and establishment of D. reticulatus populations throughout Europe. The tick has been the research focus of a growing number of scientists, physicians and veterinarians. Within the Web of Science database, more than a fifth of the over 700 items published on this species between 1897 and 2015 appeared in the last three years (2013–2015). Here we attempt to synthesize current knowledge on the systematics, ecology, geographical distribution and recent spread of the species and to highlight the great spectrum of possible veterinary and public health threats it poses. Canine babesiosis caused by Babesia canis is a severe leading canine vector-borne disease in many endemic areas. Although less frequently than Ixodes ricinus, D. reticulatus adults bite humans and transmit several Rickettsia spp., Omsk haemorrhagic fever virus or Tick-borne encephalitis virus. We have not solely collected and reviewed the latest and fundamental scientific papers available in primary databases but also widened our scope to books, theses, conference papers and specialists colleagues’ experience where needed. Besides the dominant literature available in English, we also tried to access scientific literature in German, Russian and eastern European languages as well. We hope to inspire future research projects that are necessary to understand the basic life-cycle and ecology of this vector in order to understand and prevent disease threats. We conclude that although great strides have been made in our knowledge of the eco-epidemiology of this species, several gaps still need to be filled with basic research, targeting possible reservoir and vector roles and the key factors resulting in the observed geographical spread of D. reticulatus.

Bird ticks in Hungary reflect western, southern, eastern flyway connections and two genetic lineages of Ixodes frontalis and Haemaphysalis concinna

BACKGROUND

Birds play an important role in short- and long-distance transportation of ticks and tick-borne pathogens. The aim of the present study was to provide comprehensive information on the species and genetic diversity of ixodid ticks transported by migratory and non-migratory bird species in Central Europe, and to evaluate relevant data in a geographical, as well as in an ecological context.

METHODS

During a three year period (2012-2014), altogether 3339 ixodid ticks were collected from 1167 passerine birds (representatives of 47 species) at ringing stations in Hungary. These ticks were identified, and the tick-infestations of bird species were compared according to various traits. In addition, PCR and sequencing of part of the cytochrome oxidase subunit-I (COI) and 16S rDNA genes were performed from representatives of five tick species.

RESULTS

The most abundant tick species found were Ixodes ricinus and Haemaphysalis concinna (with 2296 and 989 immature stages, respectively). In addition, 48 I. frontalis (all stages), three Hyalomma rufipes nymphs, one I. lividus and two I. festai females were collected. The majority of I. ricinus and I. frontalis specimens occurred on ground-feeding bird species, as contrasted to Ha. concinna. Hy. rufipes showed the highest degree of sequence identity to an Ethiopian hybrid of the same tick species. Based on both COI and 16S rDNA gene analyses, two genetic lineages of I. frontalis were recognized (with only 91.4 % identity in their partial COI gene). These were highly similar to South-Western European isolates of the same tick species. Phylogenetic analysis of Ha. concinna specimens collected from birds in Hungary also revealed two genetic lineages, one of which showed high (≥99 %) degree of 16S rDNA sequence identity to conspecific East Asian isolates.

CONCLUSIONS

Two genetic lineages of I. frontalis and Ha. concinna are transported by birds in Central Europe, which reflect a high degree of sequence identity to South-Western European and East Asian isolates of the same tick species, respectively. In addition, I. festai was collected for the first time in Hungary. These findings highlight the importance of western and eastern migratory connections by birds (in addition to the southern direction), which are also relevant to the epidemiology of tick-borne diseases.