Tick-Borne Pathogens and Diseases in Greece

A systematic review and meta-analysis of the prevalence of tick-borne SFGR in China from 2000 to 2022

BACKGROUND

Ticks carry and transmit a wide range of pathogens (bacteria, viruses, and protozoa) that pose significant threats to human and animal health worldwide. Only few meta-analyses have been conducted on the distribution of ticks and tick-borne spotted fever group rickettsia (SFGR). Therefore, this study aims to examine the tick species and SFGR positivity in China in order to provide support for further research and improvements in the prevention and control of tick-borne diseases.

METHODOLOGY

This systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Relevant Chinese and English studies were retrieved from PubMed, Embase, Cochrane Library, Web of Science, China National Knowledge Infrastructure (CNKI), VIP database, Chinese Biomedical literature database (CBM) and Wanfang database from inception to January 9, 2023. Pooled SFGR positive rate was meta-analyzed using a random effects model and heterogeneity was assessed by the I2 index. Publication bias was also evaluated by funnel plot and Egger's test. The meta-analysis was performed on R studio 4.0.4.

PRINCIPAL FINDINGS

Meta-analysis of 57 studies published between 2000 and 2022 involving 39,380 ticks revealed a pooled SFGR positive rate of 21.4% (Q = 6423.74, I2 = 99%, Q-p<0.001, 95% CI: 15.0-29.6). Most studies of tick-borne SFGR infection rate were conducted in forest areas and developed animal husbandry areas in the northern region. There were slightly more tick species in the southern region, but the differences in tick species (Feeding tick 31.5%, 95%CI: 15.7-53.2, Questing tick 11.5%, 95%CI: 4.4-26.7, Q = 3.29, Q-p = 0.19) between areas (Northern area 20.4%, 95%CI: 14.1-28.7, Southern area 25.5%, 95%CI: 15.0-29.6, Q = 0.21, Q-p = 0.64) were not statistically significant. The most common tick species were Dermacentor silvarum (13%), Ixodes persulcatus (11%) and Haemaphysalis Iongicornis (10%), and the most prevalent SFGR species were Rickettsia raoultii (20%), Rickettsia heilongjiangiensis (11%), and some uncultured species (18%).

CONCLUSIONS

This study examined the distribution of tick-borne SFGR in China. Our findings revealed that the main tick species were D. silvarum, I. persulcatus and H. iongicornis, and the common SFGR species were R. raoultii, R. heilongjiangiensis, and some uncultured species. Further studies are warranted to identify the potential vectors of SFGR and to better understand the epidemiology and pathogenesis of tick-borne diseases in China.

Bacterial community of ticks (Acari: Ixodidae) and mammals from Arauca, Colombian Orinoquia

Ticks are obligate hematophagous ectoparasites of vertebrates and are relevant worldwide due to the number of bacterial and other pathogens they can transmit. To date, the knowledge about the microorganisms that ticks harbor and transmit to their hosts is incipient. In this study, 24 samples of mammals belonging to four taxonomic orders and ticks of the genera Amblyomma and Rhipicephalus from the Orinoco region of Colombia were analyzed to described and compare the bacterial microbiome. Genetic extraction was performed, and the V3-V4 region of the 16S rRNA gene was amplified by PCR. Libraries were created, and those samples with adequate quality indices were sequenced using Illumina MiSeq technology. Bacterial taxonomic assignment analyses were conducted through Amplicon Sequence Variants (ASVs) and Operational Taxonomic Units (OTUs). The results correspond to 16 samples that passed the quality filters, with 3218 OTUs (415 families). Although a considerable number of unknown bacteria was found, Enterobacteriaceae, Beijerinckiaceae, Moraxellaceae, and Burkholderiaceae are the most prevalent families, and the presence of the genera Coxiella, Escherichia-Shigella, Enterobacter, which can harbor pathogenic species was confirmed. In individuals of Amblyomma mixtum found actively feeding on Hydrochoerus hydrochaeris, bacteria of the genera Escherichia-Shigella and Enterobacter were documented. Similarly, Rhipicephalus microplus found actively feeding on Odocoileus virginianus cariacou shared Escherichia-Shigella. Ralstonia was shared among the blood samples of H. hydrochaeris, while Anaplasma and Eubacterium were shared in blood and liver samples of O. v. cariacou. Shared bacteria between A. mixtum and R. microplus included Bacillus, Coxiella, and Escherichia-Shigella. The results highlight the need of additional studies in other natural regions of Colombia and other American countries where tick-borne diseases have been detected. Likewise, the recorded data are the first at the level of bacterial communities in ticks of the family Ixodidae and provide valuable knowledge for the understanding host-tick and pathogen interactions.

Development of an all-in-one real-time PCR assay for simultaneous detection of spotted fever group rickettsiae, severe fever with thrombocytopenia syndrome virus and hantaan virus prevalent in central China

Central China has been reported to be one of the most important endemic areas of zoonotic infection by spotted fever group rickettsiae (SFGR), severe fever with thrombocytopenia syndrome virus (SFTSV) and hantaan virus (HTNV). Due to similar clinical symptoms, it is challenging to make a definite diagnosis rapidly and accurately in the absence of microbiological tests. In the present study, an all-in-one real-time PCR assay was developed for the simultaneous detection of nucleic acids from SFGR, SFTSV and HTNV. Three linear standard curves for determining SFGR-ompA, SFTSV-L and HTNV-L were obtained within the range of 101-106 copies/μL, with the PCR amplification efficiencies ranging from 93.46% to 96.88% and the regression coefficients R2 of >0.99. The detection limit was 1.108 copies/μL for SFGR-ompA, 1.075 copies/μL for SFTSV-L and 1.006 copies/μL for HTNV-L, respectively. Both the within-run and within-laboratory coefficients of variation on the cycle threshold (Ct) values were within the range of 0.53%-2.15%. It was also found there was no statistical difference in the Ct values between single template and multiple templates (PSFGR-ompA = 0.186, PSFTSV-L = 0.612, PHTNV-L = 0.298). The sensitivity, specificity, positive and negative predictive value were all 100% for determining SFGR-ompA and SFTSV-L, 97%, 100%, 100% and 99.6% for HTNV-L, respectively. Therefore, the all-in-one real-time PCR assay appears to be a reliable, sensitive, rapid, high-throughput and low cost-effective method to diagnose the zoonotic infection by SFGR, SFTSV and HTNV.

A global systematic review and meta-analysis on the babesiosis in dogs with special reference to Babesia canis

BACKGROUND

Canine babesiosis is a clinically significant tick-transmitted disease caused by several species of the intraerythrocytic protozoan parasite Babesia, which result in a wide range of clinical manifestations, from mild, transient infection to serious disease and even death.

OBJECTIVES

The current study aimed to estimate the global prevalence and associated risk factors of Babesia in dogs.

METHODS

Multiple databases (PubMed, Scopus, ProQuest, Web of Science and Google Scholar) were searched for relevant literature published from January 2000 up to December 2022. The statistical analyses were performed based on the R software (version 3.6) meta-package.

RESULTS

Out of 23,864 publications, 229 studies met the inclusion criteria. The pooled prevalence of canine babesiosis was 0.120 (95% CI; 0.097-0.146). The highest pooled prevalence was found in Europe (0.207, 95% CI; 0.097-0.344). Among several species, Babesia canis was the most prevalent parasite (0.216, 95% CI; 0.056-0.441). The highest pooled prevalence of Babesia in dogs was observed in the summer season (0.097, 95% CI; 0.040-0.174).

CONCLUSIONS

Regular screening and appropriate control strategies are recommended for the prevention of transmission of tick-borne disease transmission among dogs.

First clinical case of tick-borne encephalitis (TBE) in a dog in Greece

Tick-borne encephalitis virus (TBEV) causes tick-borne encephalitis (TBE), affecting human health in Europe and Asia. Reports on canine clinical cases of TBE are rare, although dogs are used as sentinels for assessing human health risks. The first canine clinical TBE case in Greece is reported in this case report. The dog had a history of tick infestation and displayed neurological symptoms, particularly tetraparesis, neck hyperalgesia, and a sudden behavior change. Serum samples were obtained and examined in a commercial ELISA to detect anti-TBEV specific IgG and IgM antibodies. The dog tested seropositive for both IgG and IgM, and based on its history and compatible clinical signs, the diagnosis of TBE infection was reached. The prognosis was initially poor, and treatment included the administration of fluids, corticosteroids, and antibiotics, followed by physical therapy. After a 10-day hospitalization, the dog had a much better prognosis. This case highlights that TBEV does emerge in new locations, increasing human and animal infection risk. Veterinarians should include TBE in their differential diagnosis of canine patients with a history of tick infestations, progressive neurological symptoms, and abnormal behavior.

Evidence of Horse Exposure to Anaplasma phagocytophilum, Borrelia burgdorferi, and Leishmania infantum in Greece through the Detection of IgG Antibodies in Serum and in an Alternative Diagnostic Sample-The Saliva

Among the various zoonotic pathogens that infect horses, Anaplasma phagocytophilum, Borrelia spp. and Leishmania spp. have gained scientific interest, and relevant molecular and serological studies in horses have been conducted worldwide. Moreover, human and veterinary medicine have extensively applied alternatives to serum diagnostic samples-such as saliva-for detecting pathogens or antibodies. In this study, we investigated the exposure of horses in Greece to A. phagocytophilum, B. burgdorferi, and L. infantum, and we assessed the diagnostic accuracy of saliva compared to serum in detecting IgG antibodies against the abovementioned pathogens. Paired saliva and serum samples were collected from 317 horses from different regions in Greece. The paired samples were examined using the indirect fluorescent antibody test (IFAT) for detecting IgG antibodies against A. phagocytophilum, B. burgdorferi, and L. infantum. Sensitivity, specificity, positive likelihood ratio (PLR), and negative likelihood ratio (NLR) were determined to assess the validity of saliva as an alternative to serum. The receiver operating characteristic (ROC) curve revealed that the optimal cut-off value for detecting antibodies against all the examined pathogens in saliva was 1/10. Higher seropositivity rates were found for B. burgdorferi (15.14%) and A. phagocytophilum (14.19%) compared to L. infantum (1.26%). The detection of IgG antibodies using IFAT in saliva samples had a good test performance compared to serum. The two sample types had a substantial to almost perfect agreement. Although the sensitivity was moderate (70.83-75.56%) in all cases, the specificity was almost perfect to perfect (99.63-100%). This study provides the first evidence that horses in Greece are exposed to A. phagocytophilum and B. burgdorferi and confirms that the seroprevalence of L. infantum in horses in Greece remains low. Our findings suggest that saliva sampling coupled with IFAT could be successfully applied for detecting IgG antibodies against these important zoonotic pathogens in large-scale epidemiological studies in horses, at the population level, as an alternative to serum.

Exploration of Multi-Gene DNA Barcode Markers to Reveal the Broad Genetic Diversity of Field Ticks (Acari: Ixodidae) in a Tropical Environment of Hainan Island, China

Ticks are hematophagous arthropods and obligate ectoparasites of humans and other animals. This study focused on the molecular discrimination of ticks in the tropical environment of Hainan according to multi-gene DNA barcode markers with the expectation of accurately distinguishing species. A total of 420 ticks, including 49 adult ticks, 203 nymphal ticks, and 168 larval ticks, were collected in the field, and the 49 adult ticks were identified as Rhipicephalus turanicus, Dermacentor marginatus, and Haemaphysalis longicornis. The mitochondrial 16S rRNA, ribosomal 28S rRNA D2, and ribosomal internal transcribed spacer 2 (ITS2) regions were used as DNA barcode markers to discriminate species. According to basic local alignment search tool analysis against the GenBank database, 16S rRNA positively identified ticks in the Rhipicephalus, Dermacentor, and Haemaphysalis genera; the 28S rRNA D2 region identified ticks in the Rhipicephalus and Dermacentor genera; and ITS2 identified ticks as D. marginatus. Pairwise sequence comparisons based on these three regions were visualized with a Sequence Demarcation Tool matrix. Substitution saturation tests using data analysis and molecular biology and evolution revealed little substitution saturation (Iss < Iss.c, p < 0.05) in the 16S rRNA region for the Haemaphysalis genus; 28S rRNA D2 region for the Rhipicephalus, Dermacentor, and Haemaphysalis genera; and ITS2 region for the Rhipicephalus and Dermacentor genera. Distinctive sequences for which it is difficult to obtain good matches with the sequences available in GenBank exist in the ticks of Hainan. Future studies should obtain complementary sequences to refine and update the database for the molecular characterization of ticks.

Determination of the effect of collars containing 10% w/w imidacloprid and 4.5% w/w flumethrin (Seresto®) on the incidence of Leishmania and other canine vector-borne pathogen infections in Greece

BACKGROUND

The objective of this field study was to assess the effect of treating a considerable portion of a dog population naturally exposed to canine vector-borne pathogens (CVBPs) in endemic areas with a 10% w/w imidacloprid/4.5% w/w flumethrin collar (Seresto®) on the transmission of CVBPs and the resulting incidence of infection.

METHODS

A total of 479 dogs from two sites were enrolled in the study. Collars were placed on all dogs continuously for 21 months, with replacement of the collar every 7 months. All dogs were examined, including body weight and blood/conjunctival swab collections, every 7 months. Serum samples were analysed for the presence of antibodies against Leishmania infantum, Ehrlichia canis and Anaplasma phagocytophilum. PCR assays were also performed on blood samples and conjunctival swab collected from the dogs for the presence of L. infantum, and on blood samples only for the presence of Ehrlichia spp. and Anaplasma spp. Sand flies were collected, identified to species level and molecularly tested for L. infantum throughout two vector activity seasons.

RESULTS

The results showed that the Seresto collar was safe with continuous use. At study inclusion, 419, 370 and 453 dogs tested negative for L. infantum, Ehrlichia spp. and Anaplasma spp., respectively (353 dogs tested negative for any pathogen). Overall, 90.2% of the dogs were protected from L. infantum infection on both sites combined. The entomological survey confirmed the presence of competent vectors of L. infantum at all monitored locations, namely the sand flies Phlebotomus neglectus and Phlebotomus tobbi, both of which are regarded as the most important competent vectors in the Mediterranean basin. All captured sand flies tested negative for L. infantum. Protection against ticks and fleas was high, with only two dogs showing a low number of ticks and seven dogs having low numbers of fleas at single evaluation time points. Across the entire study population, a number of dogs became infected with tick-transmitted pathogens, but prevention of transmission was 93% for E. canis and 87.2% for Anaplasma spp. when all cases from both sites were combined.

CONCLUSIONS

The Seresto® (10% w/w imidacloprid/4.5% w/w flumethrin) collar significantly reduced the risk of CVBP transmission when compared to previously observed incidences of CVBP infections in two highly endemic areas under field conditions.

Natural Co-Exposure to Borrelia burgdorferi s.l. and Anaplasma phagocytophilum: Unraveling the Hematological Profile in Sheep

The occurrence of co-infected hosts and questing ticks with more than one tick-borne pathogen-as in the case of Anaplasma phagocytophilum and Borrelia burgdorferi sensu lato-is expected in endemic regions. Their synergy-in terms of pathogenesis and disease severity-has been suggested previously in humans. Limited data exist on the clinicopathological alterations in co-infected sheep. In this study, we investigated the impact of A. phagocytophilum and B. burgdorferi s.l. seropositivity, alone and in combination, on the hematological parameters of naturally infected sheep. A complete blood count was performed, and indirect immunofluorescence assays were used to detect IgG antibodies against A. phagocytophilum and IgG and IgM antibodies against B. burgdorferi s.l. Single natural exposure to B. burgdorferi s.l. was characterized by low Packed Cell Volume (PCV) values and platelet (PLT) counts, while single exposure to A. phagocytophilum was characterized by low PCV values, low white blood cell (WBC) counts, and an increased risk for leukopenia and neutropenia. Co-exposure resulted in the most severe blood abnormalities; all the blood parameters decreased, and the sheep presented an increased risk for anemia. Our study showed that natural co-exposure to A. phagocytophilum and B. burgdorferi s.l. in sheep leads to more severe blood abnormalities and enhances the pathogenic processes. More studies are needed to clarify the possible background mechanisms.

Mediterranean spotted fever-like illness caused by Rickettsia sibirica mongolitimonae, North Macedonia, June 2022

Mediterranean spotted fever-like illness (MSF-like illness) is a tick-borne disease caused by Rickettsia sibirica mongolitimonae first reported in France more than 25 years ago. Until today, more than 50 cases of MSF-like illness have been reported in different regions of Europe and Africa, highlighting variable clinical manifestation. Here we report a case of MSF-like illness following a bite from a Hyalomma tick in the Skopje region of North Macedonia.

The Scenario of Ticks and Tick-Borne Pathogens of Sheep on a Mediterranean Island

Ticks and transmitted pathogens constitute a major concern for livestock health/welfare and productivity for the Mediterranean region, often posing an important zoonotic threat. The aim of this study was to investigate the presence, infection intensity, and seasonality of ticks and tick-borne pathogens on the island of Lesvos in Greece, which was selected as a potential hotspot for their circulation. To this end, 101 sheep farms were visited over a tick activity season, and ticks, blood samples, and questionnaire data were collected. Ticks were identified by species, and DNA from both ticks and blood samples was further investigated using the polymerase chain reaction–reverse line blot (PCR–RLB) technique. In 72.3% of the farms, sheep were found to be infected by 9 ixodid species, with Rhipicephalus turanicus being the most common during the spring/early summer period. As regards tick-borne pathogens (TBPs), 84.9% of the animals were found to be infected with at least one pathogen, the most common being genera of Anaplasma and Theileria, alone or in co-infections. To further characterize the Anaplasma species found, selected samples were sequenced, revealing isolates of A. ovis, A. capra, A. marginale, and A. phagocytophilum. Of the 169 female R. turanicus ticks analyzed by PCR–RLB, 89.9% were harboring at least one TBP belonging to the genera Anaplasma, Ehrlichia, Babesia, Theileria, or Rickettsia. Overall, the data presented in this study revealed a high burden of ticks and TBPs in sheep, including zoonotic species, stressing the need for applying effective monitoring and control programs using a more holistic One Health approach.

Climate Changes Exacerbate the Spread of Ixodes ricinus and the Occurrence of Lyme Borreliosis and Tick-Borne Encephalitis in Europe-How Climate Models Are Used as a Risk Assessment Approach for Tick-Borne Diseases

Climate change has influenced the transmission of a wide range of vector-borne diseases in Europe, which is a pressing public health challenge for the coming decades. Numerous theories have been developed in order to explain how tick-borne diseases are associated with climate change. These theories include higher proliferation rates, extended transmission season, changes in ecological balances, and climate-related migration of vectors, reservoir hosts, or human populations. Changes of the epidemiological pattern have potentially catastrophic consequences, resulting in increasing prevalence of tick-borne diseases. Thus, investigation of the relationship between climate change and tick-borne diseases is critical. In this regard, climate models that predict the ticks’ geographical distribution changes can be used as a predicting tool. The aim of this review is to provide the current evidence regarding the contribution of the climatic changes to Lyme borreliosis (LB) disease and tick-borne encephalitis (TBE) and to present how computational models will advance our understanding of the relationship between climate change and tick-borne diseases in Europe.

Knowledge, Attitudes, and Practices on Tick-Borne Encephalitis Virus and Tick-Borne Diseases within Professionally Tick-Exposed Persons, Health Care Workers, and General Population in Serbia: A Questionnaire-Based Study

This study assessed the level of knowledge, attitudes, and practices (KAP) regarding tick-borne encephalitis virus (TBEV) and tick-borne diseases (TBDs) among different groups of people in Serbia. Professionally tick-exposed persons (PTEPs), health care workers (HCWs), and the general population (GP) were subjected to an anonymous, voluntary, online questionnaire using Microsoft Forms. A total of 663 questionnaire responses were collected (February–March 2021), while 642 were included in the analysis. The significant difference in knowledge in TBDs existed between GP and PTEPs, and HCWs (p < 0.001). The perception of risk-to-tick exposure and TBDs was generally high (42.4 (95% CI: 33.6–51.2) within GP, 44.9 (95% CI: 35.8–53.9) within PTEPs and 46.2 (95% CI: 38.0–54.5) within HCWs), while fear was low (13.7 (95% CI: 7.9–19.5) within GP, 12.6 (95% CI: 7.3–19.9) within PTEPs, and 13.5 (95% CI: 7.4–19.5) within HCWs). Protective practices differed across groups (F (2639) = 12.920, p < 0.001, η² = 0.039), with both PTEPs (t = 3.621, Cohen d = 0.332, p < 0.001) and HCWs (t = 4.644, Cohen d = 0.468, p < 0.001) adhering to more protective practices than the GP, without differences between PTEPs and HCWs (t = 1.256, Cohen d = 0.137, p = 0.421). Further education about TBDs in Serbia is required and critical points were identified in this study.