Bacterial communities in Haemaphysalis, Dermacentor and Amblyomma ticks collected from wild boar of an Orang Asli Community in Malaysia

Understanding zoonotic pathogens and risk factors from wildlife in Southeast Asia: a systematic literature review

The COVID-19 pandemic has demonstrated the significance of the human-animal interface in the emergence of zoonotic diseases, with wildlife serving as an important source of infection. A better understanding of the specific pathogens and mechanisms involved is vital to prepare against future outbreaks, especially in Southeast Asia, a hotspot for zoonotic diseases. This paper reviews the published literature on wildlife zoonoses in this region from 2012 to 2022. The results show a diverse range of potential zoonotic pathogens and the widespread occurrence of zoonotic diseases from wildlife. Drivers of zoonotic pathogen spillover include (i) environmental factors (e.g. animal habitat disruption, environmental conditions, exposure to contaminated water/food/soil), (ii) animal factors (e.g. movement patterns, age-related susceptibility), (iii) human factors (e.g. lack of awareness, poor hygiene practices, age, gender and income) and (iv) human-animal-environmental interface factors (e.g. close contact between humans and animals, exposure through visiting animals and presence of vectors). The diverse drivers of zoonoses in Southeast Asia put its communities at risk for infection. To mitigate these risks, global health efforts should consider adopting a One Health approach to foster collaboration across human, animal, and wildlife health sectors. This could involve educating communities on safe animal interactions and improving disease surveillance.

First molecular evidence of Rickettsia conorii subsp. raoultii from Rhipicephalus linnaei (Acari: Ixodidae) infesting pet rabbits (Oryctolagus cuniculus domesticus) (Lagomorpha: Leporidae) in Peninsular Malaysia

A total of 68 adult hard ticks were recovered from 5 cases of infestation involving pet rabbits (Oryctolagus cuniculus domesticus) in Malaysia. The ticks were later identified as the tropical brown dog tick, Rhipicephalus linnaei (Audouin, 1826). Pathogen screening showed 2 out of the 68 Rh. linnaei ticks (2.94% infection rate) were positive for Rickettsia. BLAST analyses revealed that both samples were identical to Rickettsia conorii subsp. raoultii. This paper reports the first detection of R. conorii subsp. raoultii in Rh. linnaei, also highlighting the potential zoonotic threat posed by ticks infesting exotic pets such as rabbits.

Molecular prevalence of Coxiella like endosymbionts and the first record of Coxiella burnetii in hard ticks from Southern Thailand

Eight hard tick species were identified among a total of 466 samples collected from vegetation in southern Thailand: Dermacentor compactus (n = 150), D. steini (n = 100), D. auratus (n = 85), D. tricuspis (n = 41), Haemaphysalis hystricis (n = 69), H. semermis (n = 3), H. shimoga (n = 2) and Amblyomma testudinarium (n = 16). In 93 ticks from these 8 species, Coxiella bacteria were detected via 16 S rRNA, groEL (60-kDa chaperone heat shock protein B) and rpoB (β subunit of bacterial RNA polymerase) genes. Interestingly, Coxiella burnetii was detected for the first time in H. hystricis and D. steini in Songkhla Province. Coxiella-like endosymbionts (CLEs) were also found in 84 ticks from 7 species, namely, D. compactus, D. auratus, D. tricuspis, H. hystricis, H. semermis, H. shimoga and A. testudinarium. Among these, CLEs associated with D. compactus and H. semermis were reported for the first time in Thailand. Phylogenetic analysis and generation of a haplotype network clearly revealed 2 distinct groups of Coxiella bacteria, namely, C. burnetii and CLEs. The nucleotide alignment of Coxiella 16 S rRNA revealed differences in bases at 3 positions between C. burnetii and CLEs. Thus, these differences could be used as liable molecular markers for discriminating these 2 groups in hard ticks.

Egg Protein Compositions over Embryonic Development in Haemaphysalis hystricis Ticks

Tick eggs contain a series of proteins that play important roles in egg development. A thorough characterization of egg protein expression throughout development is essential for understanding tick embryogenesis and for screening candidate molecules to develop novel interventions. In this study, eggs at four developmental stages (0, 7, 14, and 21 incubation days) were collected, and their protein extraction was profiled using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). On the first day of egg protein extraction, protein bands from day-1 eggs were re-collected and subsequently analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The dynamic changes in forty egg proteins during development were further investigated using LC-parallel reaction monitoring (PRM)/MS analysis. A total of 108 transcripts were detected in day-1 eggs. Based on protein functions and families, these transcripts were classified into eight categories: transporters, enzymes, immunity and antimicrobial proteins, proteinase inhibitors, cytoskeletal proteins, heat shock proteins, secreted proteins, and uncharacterized proteins. Identification of the protein bands revealed that nine bands predominantly consisted of vitellogenin and vitellin-A, while other notable proteins included cathepsins and Kunitz domain-containing proteins. LC-PRM/MS analysis indicated that 28 transcripts increased significantly in abundance, including 13/18 enzymes, 1/1 antimicrobial peptide, 2/2 neutrophil elastase inhibitors, 3/4 vitellogenins, 3/3 heat shock proteins, 3/3 cytoskeletal proteins, 1/1 elongation factor-1, and 1/1 uncharacterized protein. Conversely, five transcripts showed a decrease significantly, including 1/1 Kunitz domain-containing protein, 2/6 aspartic proteases, and 2/5 serpins. This research provides a comprehensive overview of egg proteins and highlights the dynamic changes in protein expression during embryonic development, which may be pivotal for understanding protein functions and selecting potential candidates for further study.

Global epidemiology of severe fever with thrombocytopenia syndrome virus in human and animals: a systematic review and meta-analysis

Background

Since the initial identification of the Severe Fever with Thrombocytopenia Syndrome (SFTS) in ticks in rural areas of China in 2009, the virus has been increasingly isolated from a diverse array of hosts globally, exhibiting a rising trend in incidence. This study aims to conduct a systematic analysis of the temporal and spatial distribution of SFTS cases, alongside an examination of the infection rates across various hosts, with the objective of addressing public concerns regarding the spread and impact of the disease.

Methods

In this systematic review and meta-analysis, an exhaustive search was conducted across multiple databases, including PubMed, Web of Science, Embase, and Medline, CNKI, WanFang, and CQVIP. The literature search was confined to publications released between January 1, 2009, and May 29, 2023. The study focused on collating data pertaining to animal infections under natural conditions and human infection cases reported. Additionally, species names were unified using the National Center for Biotechnology Information (NCBI) database. The notification rate, notification death rate, case fatality rate, and infection rates (or MIR) were assessed for each study with available data. The proportions were pooled using a generalized linear mixed-effects model (GLMM). Meta-regressions were conducted for subgroup analysis. This research has been duly registered with PROSPERO, bearing the registration number CRD42023431010.

Findings

We identified 5492 studies from database searches and assessed 238 full-text studies for eligibility, of which 234 studies were included in the meta-analysis. For human infection data, the overall pooled notification rate was 18.93 (95% CI 17.02-21.05) per ten million people, the overall pooled notification deaths rate was 3.49 (95% CI 2.97-4.10) per ten million people, and the overall pooled case fatality rate was 7.80% (95% CI 7.01%-8.69%). There was an increasing trend in notification rate and deaths rate, while the case fatality rate showed a significant decrease globally. Regarding animal infection data, among 94 species tested, 48 species were found to carry positive nucleic acid or antibodies. Out of these, 14 species were classified under Arthropoda, while 34 species fell under Chordata, comprising 27 Mammalia and 7 Aves.

Interpretation

This systematic review and meta-analysis present the latest global report on SFTS. In terms of human infections, notification rates and notification deaths rates are on the rise, while the case fatality rate has significantly decreased. More SFTSV animal hosts have been discovered than before, particularly among birds, indicating a potentially broader transmission range for SFTSV. These findings provide crucial insights for the prevention and control of SFTS on a global scale.

Funding

None.

Unraveling the phylogenetics of genetically closely related species, Haemaphysalis japonica and Haemaphysalis megaspinosa, using entire tick mitogenomes and microbiomes

Ticks have a profound impact on public health. Haemaphysalis is one of the most widespread genera in Asia, including Japan. The taxonomy and genetic differentiation of Haemaphysalis spp. is challenging. For instance, previous studies struggled to distinguish Haemaphysalis japonica and Haemaphysalis megaspinosa due to the dearth of nucleotide sequence polymorphisms in widely used barcoding genes. The classification of H. japonica japonica and its related sub-species Haemaphysalis japonica douglasi or Haemaphysalis jezoensis is also confused due to their high morphological similarity and a lack of molecular data that support the current classification. We used mitogenomes and microbiomes of H. japonica and H. megaspinosa to gain deeper insights into the phylogenetic relationships and genetic divergence between two species. Phylogenetic analyses of concatenated nucleotide sequences of protein-coding genes and ribosomal DNA genes distinguished H. japonica and H. megaspinosa as monophyletic clades, with further subdivision within the H. japonica clade. The 16S rRNA and NAD5 genes were valuable markers for distinguishing H. japonica and H. megaspinosa. Population genetic structure analyses indicated that genetic variation within populations accounted for a large proportion of the total variation compared to variation between populations. Microbiome analyses revealed differences in alpha and beta diversity between H. japonica and H. megaspinosa: H. japonica had the higher diversity. Coxiella sp., a likely endosymbiont, was found in both Haemaphysalis species. The abundance profiles of likely endosymbionts, pathogens, and commensals differed between H. japonica and H. megaspinosa: H. megaspinosa was more diverse.

Characterization of the bacterial microbiota of cattle ticks in northeastern Thailand through 16S rRNA amplicon sequencing

Ticks are vectors of a variety of pathogens that can infect humans and animals. Ticks also harbor non-pathogenic microbiota. This study characterized the microbiota of the ticks infesting beef cattle in Thailand. Two species of ticks; Rhipicephalus microplus (n = 15) and Haemaphysalis bispinosa (n = 5), were collected in seven provinces in northeastern Thailand. Microbial community profile of ticks was examined based on sequences of the V3-V4 region of 16S rRNA gene. Proteobacteria (Pseudomonadota) was the most abundant phylum, followed by Firmicutes (Bacillota), and Actinobacteriota. Coxiella-like endosymbiont was the most abundant bacterial taxon overall (49% of sequence reads), followed by Anaplasma (8.5%), Corynebacterium (5.5%), Ehrlichia (3.9%), and Castellaniella (3.4%). Co-infections of the pathogenic bacteria Ehrlichia and Anaplasma were detected in 19/20 (95%) female ticks. The tick with the lowest number of bacteria had the lowest abundance of the Coxiella-like endosymbiont, and the pathogenic bacteria Anaplasma and Ehrlichia were absent. This study provides baseline information of the microbiota of cattle ticks in northeastern Thailand, suggesting that ticks carry a few dominant bacterial taxa that are primarily non-pathogenic but can co-occur with pathogenic microorganisms. The information obtained is useful for monitoring disease outbreaks in the future and informing prevention and control strategies against cattle tick-borne diseases.

Characterization of bacterial communities in ticks parasitizing cattle in a touristic location in southwestern China

The purpose of this study was to investigate tick species around Mount Fanjing and analyze bacterial communities in two species - Rhipicephalus microplus and Haemaphysalis longicornis - parasitizing cattle in Tongren, Guizhou province, Southwest China, using high-throughput sequencing methods. In April 2019, ticks were collected from five sites in Jiangkou County, Yinjiang County, and Songtao County. In total, 296 ticks were collected, comprising two genera and three species: H. longicornis, Haemaphysalis flava, and R. microplus. Rhipicephalus microplus was the most representative species (57.4%) within the collected group, being the dominant species in Tongren City, followed by H. longicornis (39.5%) and H. flava (3.0%). Beta-diversity analysis revealed differences in bacterial community composition among the tick species. The bacterial community structure of R. microplus collected in the three counties was highly similar. Chlorella and Bacillus were highly abundant in H. longicornis. Rickettsia was detected at high relative abundance in R. microplus but in low relative abundance in H. longicornis, suggesting that Rickettsia is more associated with R. microplus than with H. longicornis. More in-depth investigations are needed to determine the pathogenic risk of Rickettsia and its relationship with the host. This is the first survey on tick-borne bacterial communities in this area, which is of great significance for the prevention and control of tick-borne diseases locally.

Metagenomic profile of the bacterial communities associated with Ixodes granulatus (Acari: Ixodidae): a potential vector of tick-borne diseases

Ixodes granulatus Supino, 1897 (Acari: Ixodida) is one of Malaysia's most common hard ticks and is a potential vector for tick-borne diseases (TBDs). Despite its great public health importance, research on I. granulatus microbial communities remains largely unexplored. Therefore, this study aimed to investigate the bacterial communities of on-host I. granulatus collected from three different recreational areas on the East Coast of Peninsular Malaysia using high throughput Next Generation Sequencing (NGS). A total of 9 females on-host I. granulatus were subjected to metabarcoding analysis targeting V3-V4 regions of 16S ribosomal RNA (rRNA) using the Illumina MiSeq platform. This study identified 15 bacterial phyla corresponding to 19 classes, 54 orders, and 90 families from 435 amplicon sequence variants (ASVs), revealing a diverse bacterial community profile. Together with 130 genera assigned, local I. granulatus harbored 4 genera of pathogens, i.e., Rickettsia da Rocha Lima, 1916 (Rickettsiales: Rickettsiaceae) (58.6%), Borrelia Swellengrebel 1907 (Spirochaetales: Borreliaceae) (31.6%), Borreliella Adeolu and Gupta 2015 (Spirochaetales: Borreliaceae) (0.6%), and Ehrlichia Cowdria Moshkovski 1947 (Rickettsiales: Ehrlichiaceae) (39.9%). Some endosymbiont bacteria, such as Coxiella (Philip, 1943) (Legionellales: Coxiellaceae), Wolbachia Hertig 1936 (Rickettsiales: Ehrlichiaceae), and Rickettsiella Philip, 1956 (Legionellales: Coxiellaceae), were also detected at very low abundance. Interestingly, this study reported the co-infection of Borrelia and Ehrlichia for the first time, instilling potential health concerns in the context of co-transmission to humans, especially in areas with a high population of I. granulatus. This study successfully characterized the tick microbiome and provided the first baseline data of I. granulatus bacterial communities in Malaysia. These results support the need for way-forward research on tick-associated bacteria using NGS, focusing on medically important species toward TBD prevention.

The dynamics of the microbiome in Ixodidae are shaped by tick ontogeny and pathogens in Sarawak, Malaysian Borneo

Tick-borne diseases have recently been considered a potential emerging public health threat in Malaysia; however, fundamental studies into tick-borne pathogens and microbiome appear limited. In this study, six tick species (Ixodes granulatus, Haemaphysalis hystricis, Haemaphysalis shimoga, Dermacentor compactus, Dermacentor steini and Dermacentor atrosignatus) collected from two primary forests and an oil palm plantation in Sarawak, Malaysian Borneo, were used for microbiome analysis targeting bacterial 16S rDNA using next-generation sequencing (NGS). In addition, bacterial species were further characterized in conventional PCRs to identify potential pathogens. Sequences generated from NGS were first filtered with the Decontam package in R before subsequent microbial diversity analyses. Alpha and beta analyses revealed that the genus Dermacentor had the highest microbial diversity, and H. shimoga significantly differed in microbial composition from other tick species. Alpha and beta diversities were also significantly different between developmental stages of H. shimoga. Furthermore, we observed that some bacterial groups were significantly more abundant in certain tick species and developmental stages of H. shimoga. We tested the relative abundances using pairwise linear discriminant analysis effect size (LEfSe), which also revealed significant microbial composition differences between Borrelia-positive and Borrelia-negative I. granulatus ticks. Finally, pathogenic and potentially pathogenic bacteria circulating in different tick species, such as Rickettsia heilongjiangensis, Ehrlichia sp., Anaplasma sp. and Bartonella spp. were characterized by PCR and sequencing. Moreover, Coxiella and Francisella-like potential symbionts were identified from H. shimoga and D. steini, respectively. More studies are required to unravel the factors associated with the variations observed in this study.

Comparative analysis of the mitochondrial genome of Dermacentor steini from different regions in China

Ticks are a group of blood-sucking ectoparasites that play an important role in human health and livestock production development as vectors of zoonotic diseases. The phylogenetic tree of single genes cannot accurately reflect the true kinship between species. Based on the complete mitochondrial genome analysis one can help to elucidate the phylogenetic relationships among species. In this study, the complete mitochondrial genome of Dermacentor steini (isolate Longyan) was sequenced and compared with the mitochondrial genes of 3 other Chinese isolates (Nanchang, Jinhua and Yingtan). In Dermacentor steini 4 isolates had identical or similar mitochondrial genome lengths and an overall variation of 0.76% between sequences. All nucleotide compositions showed a distinct AT preference. The most common initiation and stop codons were ATG and TAA, respectively. Fewer base mismatches were found in the tRNA gene of D. steini (isolate Longyan), and the vicinity of the control region and tRNA gene was a hot rearrangement region of the genus Dermacentor. Maximum likelihood trees and Bayesian trees indicate that D. steini is most closely related to Dermacentor auratus. The results enrich the mitochondrial genomic data of species in the genus Dermacentor and provide novel insights for further studies on the phylogeographic classification and molecular evolution of ticks.

Identification of Bacterial Communities and Tick-Borne Pathogens in Haemaphysalis spp. Collected from Shanghai, China

Ticks can carry and transmit a large number of pathogens, including bacteria, viruses and protozoa, posing a huge threat to human health and animal husbandry. Previous investigations have shown that the dominant species of ticks in Shanghai are Haemaphysalis flava and Haemaphysalis longicornis. However, no relevant investigations and research have been carried out in recent decades. Therefore, we investigated the bacterial communities and tick-borne pathogens (TBPs) in Haemaphysalis spp. from Shanghai, China. Ixodid ticks were collected from 18 sites in Shanghai, China, and identified using morphological and molecular methods. The V3-V4 hypervariable regions of the bacterial 16S rRNA gene were amplified from the pooled tick DNA samples and subject to metagenomic analysis. The microbial diversity in the tick samples was estimated using the alpha diversity that includes the observed species index and Shannon index. The Unifrac distance matrix as determined using the QIIME software was used for unweighted Unifrac Principal coordinates analysis (PCoA). Individual tick DNA samples were screened with genus-specific or group-specific nested polymerase chain reaction (PCR) for these TBPs and combined with a sequencing assay to confirm the results of the V3-V4 hypervariable regions of the bacterial 16S rRNA gene. We found H. flava and H. longicornis to be the dominant species of ticks in Shanghai in this study. Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria are the main bacterial communities of Haemaphysalis spp. The total species abundances of Proteobacteria, Firmicutes and Bacteroidetes, are 48.8%, 20.8% and 18.1%, respectively. At the level of genus analysis, H. longicornis and H. flava carried at least 946 genera of bacteria. The bacteria with high abundance include Lactobacillus, Coxiella, Rickettsia and Muribaculaceae. Additionally, Rickettsia rickettsii, Rickettsia japonica, Candidatus Rickettsia jingxinensis, Anaplasma bovis, Ehrlichia ewingii, Ehrlichia chaffeensis, Coxiella spp. and Coxiella-like endosymbiont were detected in Haemaphysalis spp. from Shanghai, China. This study is the first report of bacterial communities and the prevalence of some main pathogens in Haemaphysalis spp. from Shanghai, China, and may provide insights and evidence for bacterial communities and the prevalence of the main pathogen in ticks. This study also indicates that people and other animals in Shanghai, China, are exposed to several TBPs.

A checklist of the ticks of Malaysia (Acari: Argasidae, Ixodidae), with lists of known associated hosts, geographical distribution, type localities, human infestations and pathogens

Studies of ticks in Malaysia from past articles were reviewed, resulting in a list of 47 species belonging to seven genera (Argas, Ornithodoros, Amblyomma, Dermacentor, Haemaphysalis, Ixodes, and Rhipicephalus). The most prevalent genus in Malaysia is Haemaphysalis (20 species), followed by Amblyomma (eight species) and Dermacentor (seven species). Out of 47 species, only 28 have bitten humans, mostly belonging to Haemaphysalis. The most researched tick-borne pathogens in Malaysia are Rickettsia and Anaplasma, and most research was focused on the tropical-lineage brown dog ticks, R. sanguineus sensu lato, and the cattle ticks, Haemaphysalis bispinosa and Rhipicephalus microplus. 18 species were excluded from the list due to lack of definite records or dubious findings: Ornithodoros mimon, O. turicata, Amblyomma breviscutatum, A. clypeolatum, A. integrum, A. maculatum, Dermacentor marginatum, D. taiwanensis, Haemaphysalis birmaniae, H. flava, H. humerosa, H. longicornis, H. punctata, H. sulcata, Ixodes holocyclus, Rhipicephalus appendiculatus, R. annulatus and R. bursa. This paper presents the first complete and updated list for Dermacentor and Ixodes tick species in Malaysia since Kohls (1957).  

Molecular detection of vector-borne agents in wild boars (Sus scrofa) and associated ticks from Brazil, with evidence of putative new genotypes of Ehrlichia, Anaplasma and hemoplasmas

The present study aimed to investigate, by molecular techniques, the occurrence of Anaplasmataceae, Bartonellaceae, Rickettsiaceae, Mycoplasmataceae, Coxiellaceae e Babesiidae/Theileriidae agents in blood samples of free-living wild boars (Sus scrofa) and associated ticks in southeastern Brazil. For this purpose, 67 blood samples and 265 ticks (264 Amblyomma sculptum and one A. ovale) were analyzed. In the screening for Anaplasmataceae agents by a PCR assay based on the 16S rRNA gene, 5.97% blood samples and 50.54% ticks were positive. In the PCR assay for Ehrlichia spp. based on the dsb gene, 9.24% of ticks were positive. Despite the low occurrence, a possible new 16S rRNA genotype of Anaplasma sp. was detected in a wild boar's blood sample. According to phylogenetic analyses based on the groEL, gltA, sodB genes and ITS (23S-5S rRNA) intergenic region, it was found that A. sculptum and A. ovale ticks collected from wild boars carry Ehrlichia genotypes phylogenetically associated with E. ewingii, E. ruminantium, and new Ehrlichia genotypes previously detected in horses, peccaries, and ticks collected from jaguars. In the screening for hemoplasmas by a qPCR based on the 16S rRNA gene, 88.06% of blood samples and 8.69% of ticks were positive. Mycoplasma suis, M. parvum and a possible new hemoplasma genotype were detected in wild boars in southeastern Brazil. In the screening for Bartonella spp. using a nuoG-based qPCR assay, 3.8% of tick samples were positive. Phylogenetic inferences positioned four nuoG and one r gltA Bartonella sequences into the same clade as Bartonella machadoae. No blood or tick samples from wild boars showed to be positive in the qPCR for Coxiella burnetii based on the IS1111 gene. On the other hand, only 1.6% of ticks was positive in the nested PCR assay for piroplasmids based on the 18S rRNA gene. A 18S rRNA sequence detected in a pool of A. sculptum nymphs was phylogenetically close to Cytauxzoon felis sequences previously detected in cats from the United States. Rickettsia sp. closely related to R. bellii was detected in a pool of A. sculptum nymphs. This is the first report of hemoplasmas, B. machadoae and Cytauxzoon spp. in A. sculptum. Wild boars and associated ticks do not seem to participate in the epidemiological cycle of C. burnetii in the region studied. This invasive mammal species may act as a potential disperser of ticks infected with Ehrlichia spp., Bartonella spp., hemotropic mycoplasmas, and Cytauxzoon, and may bring important epidemiological implications in the transmission of bartonelosis, ehrlichiosis, hemoplasmosis, and cytauxzoonosis to humans and animals, more specifically to horses, rodents, pigs, and cats. This article is protected by copyright. All rights reserved.

Pathogenic and Endosymbiotic Bacteria and Their Associated Antibiotic Resistance Biomarkers in Amblyomma and Hyalomma Ticks Infesting Nguni Cattle (Bos spp.)

Deciphering the interactions between ticks and their microbiome is key to revealing new insights on tick biology and pathogen transmission. However, knowledge on tick-borne microbiome diversity and their contribution to drug resistance is scarce in sub–Saharan Africa (SSA), despite endemism of ticks. In this study, high-throughput 16S rRNA amplicon sequencing and PICRUSt predictive function profiling were used to characterize the bacterial community structure and associated antibiotic resistance markers in Amblyomma variegatum, A. hebraeum, and Hyalomma truncatum ticks infesting Nguni cattle (Bos spp.). Twenty-one (seven families and fourteen genera) potentially pathogenic and endosymbiotic bacterial taxa were differentially enriched in two tick genera. In H. truncatum ticks, a higher abundance of Corynebacterium (35.6%), Porphyromonas (14.4%), Anaerococcus (11.1%), Trueperella (3.7%), and Helcococcus (4.7%) was detected. However, Rickettsia (38.6%), Escherichia (7%), and Coxiellaceae (2%) were the major differentially abundant taxa in A. variegatum and A. hebraeum. Further, an abundance of 50 distinct antibiotic resistance biomarkers relating to multidrug resistance (MDR) efflux pumps, drug detoxification enzymes, ribosomal protection proteins, and secretion systems, were inferred in the microbiome. This study provides theoretical insights on the microbiome and associated antibiotic resistance markers, important for the design of effective therapeutic and control decisions for tick-borne diseases in the SSA region.

Current debates and advances in tick microbiome research

The main importance of ticks resides in their ability to harbor pathogens that can be transmitted to terrestrial vertebrates including humans. Recently, studies have focused on the taxonomic and functional composition of the tick microbiome, its microbial diversity and variation under different factors including tick species, sex, and environment among others. Of special interest are the interactions between the tick, the microbiome and pathogens since tick microbiome can influence pathogen colonization within the tick vector, and potentially, transmission to the vertebrate host. In this review, we tackled a synthesis on the growing field of tick microbiomes. We focus on the current state of tick microbiome research, addressing controversial and hotly debated topics and advances in the precise manipulation of tick microbiome. Furthermore, we discuss the innovative anti-tick microbiota vaccines as a possible tool for microbiome modulation and thus, control of tick-borne diseases. Deciphering tick-microbiome pathogen interactions can spur new strategies to control tick-borne diseases via modulation of tick microbiome.

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Whether the diversity observed in tick microbiomes concerns the biology or the methodology remains an open question.

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Tick immunity must play a major role in selecting ‘who stays and who leaves’ the microbiome.

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Anti-tick microbiota vaccines can target specific bacteria and subsequently modulate tick microbiome.

Molecular Survey and Spatial Distribution of Rickettsia spp. in Ticks Infesting Free-Ranging Wild Animals in Pakistan (2017-2021)

Rickettsia spp. associated with ticks infesting wild animals have been mostly neglected in several countries, including Pakistan. To address this knowledge gap, ticks were collected during 2017 to 2021 from wild animals including cats (Felis chaus), Indian hedgehogs (Paraechinus micropus), and wild boars (Sus scrofa). The collected ticks were morpho-molecularly identified and screened for the detection of Rickettsia spp. Morphologically identified ticks were categorized into four species of the genus Rhipicephalus: Rhipicephalus haemaphysaloides, Rh. turanicus, Rh. sanguineus sensu lato (s.l), and Rh. microplus. Among 53 wild animals examined, 31 were infested by 531 ticks, an overall prevalence of 58.4%. Adult female ticks were predominant (242 out of 513 ticks collected, corresponding to 46%) in comparison with males (172, 32%), nymphs (80, 15%) and larvae (37, 7%). The most prevalent tick species was Rh. turanicus (266, 50%), followed by Rh. microplus (123, 23%), Rh. sanguineus (106, 20%), and Rh. haemaphysaloides (36, 7%). Among the screened wild animals, wild boars were the most highly infested, with 268 ticks being collected from these animals (50.4%), followed by cats (145, 27.3%) and hedgehogs (118, 22.3%). Tick species Rh. haemaphysaloides, Rh. turanicus, and Rh. sanguineus were found on wild boars, Rh. haemaphysaloides, and Rh. microplus on cats, and Rh. turanicus on hedgehogs. In a phylogenetic analysis, mitochondrial cytochrome C oxidase 1 (cox1) sequences obtained from a subsample (120) of the collected ticks clustered with sequences from Bangladesh, China, India, Iran, Myanmar, and Pakistan, while 16S ribosomal DNA (16S rDNA) sequences clustered with sequences reported from Afghanistan, Egypt, India, Pakistan, Romania, Serbia, and Taiwan. Among Rickettsia infected ticks (10/120, 8.3%), Rh. turanicus (7/10, 70%), and Rh. haemaphysaloides (3/10, 30%) were found infesting wild boars in the districts Mardan and Charsadda. The obtained rickettsial gltA gene sequences showed 99% and ompA gene sequences showed 100% identity with Rickettsia massiliae, and the phylogenetic tree shows ompA clustered with the same species reported from France, Greece, Spain, and USA. This study emphasizes the need for effective surveillance and control programs in the region to prevent health risks due to tick-borne pathogens, and that healthy infested wild animals may play a role in the spread of these parasites.

Morphological and molecular identification of medically important questing Dermacentor species collected from some recreational areas of Peninsular Malaysia

Questing is a situation when a tick is seeking to get closer or ambush its potential host. However, information on questing tick species in Malaysia is still lacking, thus the association with tick-borne diseases (TBD) is not completely understood. The aim of this study was to investigate the tick species from five most frequently visited recreational areas in Pahang and Terengganu states, which were recorded to have high potential of TBD cases. By implementing handpick method, a total of 18 males and 15 females belonging to five Dermacentor Koch, 1844 species, were collected, namely D. compactus Neumann 1901, D. tricuspis (Schulze, 1933), D. auratus Supino 1897, D. steini (Schulze, 1933), and D. falsosteini Apanaskevich, Apanaskevich & Nooma respectively. The specimens were collected and identified based on morphological characters prior to obtaining the molecular data of COI and 16S rDNA. The D. compactus was the most abundant species collected in this study, while D. falsosteini was the least. All species were distinctly separated on the Neighbor Joining and Maximum Parsimony tree topologies and supported with high bootstrap values. Furthermore, a low intraspecific variation (0.00 - 0.01) was observed amongst the individuals of the same species in both genes. Meanwhile, each Dermacentor species was genetically different, with interspecific values ranging from 0.13-0.19 and 0.11-0.20 for COI and 16S rDNA. These findings had successfully recorded the tick species that were potentially associated with TBD, and which might be circulated among humans and animals. This study also has some implications on the diversity and geographical extension of Dermacentor ticks, thus should warrant further investigation as a potential vector of tick-borne diseases and public health importance.

Francisella philomiragia bacteremia in an immunocompromised patient: a rare case report

Background

Francisella philomiragia is a very rare opportunistic pathogen of humans which causes protean diseases such as pneumonia and other systemic infections. Subsequent failure of prompt treatment may result in poor prognosis with mortality among infected patients.

Case presentation

The present report describes a case of F. philomiragia bacteraemia first reported in Malaysia and Asian in a 60-year-old patient with underlying end-stage renal disease (ESRF) and diabetes mellitus. He presented with Acute Pulmonary Oedema with Non-ST-Elevation Myocardial Infarction (NSTEMI) in our hospital. He was intubated in view of persistent type I respiratory failure and persistent desaturation despite post haemodialysis. Blood investigation indicated the presence of ongoing infection and inflammation. The aerobic blood culture growth of F. philomiragia was identified using the matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (Score value: 2.16) and confirmed by 16S Ribosomal DNA (16S rDNA) sequencing. He was discharged well on day 26 of admission, after completing one week of piperacillin/tazobactam and two weeks of doxycycline.

Conclusion

Clinical suspicion should be raised if patients with known risk factors are presenting with pneumonia or pulmonary nodules especially as these are the most common manifestations of F. philomiragia infection. Early diagnosis via accurate laboratory identification of the organism through MALDI-TOF mass spectrometry and molecular technique such as 16S rDNA sequencing are vital for prompt treatment that results in better outcomes for the afflicted patients.

Replication Kinetics of Rickettsia raoultii in Tick Cell Lines

Rickettsia raoultii is one of the causative agents of tick-borne lymphadenopathy in humans. This bacterium was previously isolated and propagated in tick cell lines; however, the growth characteristics have not been investigated. Here, we present the replication kinetics of R. raoultii in cell lines derived from different tick genera (BME/CTVM23, RSE/PILS35, and IDE8). Tick cell cultures were infected in duplicate with cryopreserved R. raoultii prepared from homologous cell lines. By 12–14 days post infection, 100% of the cells were infected, as visualized in Giemsa-stained cytocentrifuge smears. R. raoultii growth curves, determined by rickettsiae-specific gltA qPCR, exhibited lag, exponential, stationary and death phases. Exponential phases of 4–12 days and generation times of 0.9–2.6 days were observed. R. raoultii in BME/CTVM23 and RSE/PILS35 cultures showed, respectively, 39.5- and 37.1-fold increases compared to the inoculum. In contrast, multiplication of R. raoultii in the IDE8 cultures was 110.1-fold greater than the inoculum with a 7-day stationary phase. These findings suggest variation in the growth kinetics of R. raoultii in the different tick cell lines tested, amongst which IDE8 cells could tolerate the highest levels of R. raoultii replication. Further studies of R. raoultii are needed for a better understanding of its persistence within tick populations.

Extensive sex-specific and regional variations observed in the microbiome of Dermacentor reticulatus

Recent progress in DNA sequencing technologies and advanced bioinformatic tools have enabled researchers to rapidly decipher the tick microbiome. To date, however, a number of microbiome studies performed on Dermacentor reticulatus ticks is still quite limited. Despite the importance of this ixodid tick for veterinary and human medicine, only two investigations have examined its microbiome. Moreover, these studies analyzed only a limited number of ticks/tick pools. Given the scarcity of microbiome data for D. reticulatus in general and the lack of microbiome studies on tick species from Eastern Europe in particular, the objective of the current investigation was to analyze the microbiome of D. reticulatus ticks collected from three geographical regions of Ukraine. A total of 88 individual tick microbiomes were analyzed by sequencing the V6 region of 16S rRNA. As a result, numerous significant differences in the bacterial relative abundance were detected between males and females of D. reticulatus for each region. The alpha diversity measures indicate that microbiomes were significantly different between females of D. reticulatus inter-regionally. In contrast, the collective results for male ticks are more suggestive of inter-regional microbiome homogeneity. The overall findings indicate that the composition and diversity of the D. reticulatus microbiome can be impacted by geographical and sex-related factors.

Current tools for the diagnosis and detection of spotted fever group Rickettsia

Spotted fever group (SFG) rickettsiae causes a number of diseases in humans worldwide, which can range from mild to highly lethal. Since the clinical presentations of rickettsioses caused by SFG rickettsiae are variable and may be similar to the diseases caused by other rickettsiae, such as Orientia tsutsugamushi (agent for scrub typhus), Coxiella burnetii (agent for Q fever) and the typhus group rickettsiae (agents for epidemic and murine typhus), the accurate diagnosis of infections caused by SFG Rickettsia remains challenging especially in resource-poor settings in developing countries. This review summarizes the various diagnostic and detection tools that are currently available for the confirmation of infections by SFG rickettsiae. The advantages and challenges pertaining to the different serological and molecular detections methods, as well as new assays in development, are discussed. The utility of the detection tools contributing to the surveillance of SFG rickettsiae in arthropods and animals are reviewed.

Identification and molecular analysis of Ixodid ticks (Acari: Ixodidae) infesting wild boars (Sus scrofa) and tick-borne pathogens at the Meihua mountain of southwestern Fujian, China

Wildlife is essential to the biodiversity of the Meihua mountain, southwestern Fujian province, China. However, there have been few surveys of the distribution of ixodid ticks (Acari: Ixodidae) and tick-borne pathogens affecting wild animals at these locations. In this study, 1197 adult ixodid ticks infesting wild boars were collected from 10 sampling sites during 2019. Ticks were identified to species based on morphology, and the identification was confirmed based on mitochondrial 16S, ITS1 and ITS2 rRNA sequences. Eight tick species belonging to 2 genera were identified, including H. longicornis (n = 373, 31.1%), H. flava (n = 265, 22.1%), D. auratus (n = 153, 12.8%), H. hystricis (n = 119, 9.9%), D. silvarum (n = 116, 9.7%), H. bispinosa (n = 114, 9.5%), D. atrosignatus (n = 33, 2.8%), and D. taiwanensis (n = 24, 2.0%). DNA sequences of Rickettsia spp. (spotted fever group) and Babesia spp. were detected in these ticks. Phylogenetic analyses revealed the possible existence of Candidatus Rickettsia laoensis and Rickettsia raoultii. This study illustrates the potential threat to wild animals and humans from tick-borne pathogens.

Ticks and tick-borne pathogens in animals and humans in the island nations of Southeast Asia: A review

Ticks are blood-feeding ectoparasites and major vectors of pathogens that cause infectious diseases in humans and animals worldwide including mammals, birds and reptiles. Despite the growing scientific effort in the 20th century, there is still limited information on ticks and tick-borne pathogens in Southeast Asia, especially concerning medical, veterinary, socioeconomic and agricultural aspects in the island nations. This review provides an overview of the current state of knowledge of ticks and their pathogens in the island nations of Southeast Asia and peninsular Malaysia. We aim to stimulate further research studies on ticks and tick-borne pathogens of human and veterinary importance in this geographical region.