An integrated database on ticks and tick-borne zoonoses in the tropics and subtropics with special reference to developing and emerging countries

Molecular characterisation of Amblyomma integrum circulating in southern India

Amblyomma integrum is a large gooseberry sized longirostrate tick (when fully repleted) found in India and Sri Lanka. In Kerala (India), this tick is commonly found in the forest and its fringe areas frequently infesting deer and hence it is locally known as "maan chellu / maanunny" (deer tick). In the present study, molecular characterisation and phylogenetic analysis of A. integrum collected from the area grazed by the sambar deer (Rusa unicolor) of Kerala, south India was performed using three molecular markers viz., the mitochondrial cytochrome c oxidase subunit 1 (COI), mitochondrial 16S ribosomal RNA, and nuclear 18S ribosomal RNA genes. Cytochrome c oxidase subunit 1 (COI) gene showed better resolving ability for elucidating the evolutionary relationship of A. integrum and identified two distinct clades, viz., A and B. The Tamil Nadu isolates of south India and Marayoor isolate 1 (from Idukki district of Kerala bordering with Tamil Nadu) belonged to clade A. Majority of Wayanad isolates from Kerala, occupied clade B. The intraspecific genetic distance among the A. integrum species ranged from 0.00 to 13.34%. Between clades A and B, the genetic distance observed was 11.49%. The clade B isolates were genetically close to A. geoemydae (GD: 1.22%). Morphological variations between the clades included darker exoskeletal coloration in clade A and distinct differences in the shape of basis capitulum. Further analysis using Assemble Species by Automatic Partitioning (ASAP) and Generalized Mixed Yule Coalescent (GMYC) provided additional insights. Assemble Species by Automatic Partitioning (ASAP) identified 26 Molecular Operational Taxonomic Units (MOTUs) at a threshold distance of 5.38%, supporting the species partition of A. integrum clade B. Generalized Mixed Yule Coalescent (GMYC) analysis retained the same species complex (A. integrum-geoemydae Complex) inferred from the ASAP analyses. It could be inferred from the present study that the A. integrum clades A and B could be two different putative pseudocryptic species.

Risk factors affecting the feeding site predilection of ticks on cattle in Ghana

Ticks are important disease vectors affecting animal health and causing substantial economic loss, especially in the tropics and subtropics. To examine the tick burden of cattle and associated risk factors for tick infestation, ticks were collected from 388 cattle within five regions in Ghana. Most of the cattle were males (50.3%) and generally older than 3 years (65%). Of the animals sampled, 2187 ticks were collected with a mean tick burden of 5.6 ticks per cattle, and the average tick burden on the udder/scrotum being significantly higher than in the anal region (Generalized Linear Mix Model [GLMM], p = 0.01197). The tick species identified were predominantly Amblyomma variegatum (42.6%) and Hyalomma rufipes (26.2%). High proportions of cattle examined were found to have A. variegatum infesting the udder/scrotum. Furthermore, H. rufipes infested mostly the anal region compared to other examined body parts (OR 14.8, 95% CI 8.6-25.4, p < 0.001). Using the GLMM, tick abundance was found to be significantly higher in cattle older than 3 years. The tick burden in the udder/scrotum was higher than that from the chest and leg/thigh of the cattle (GLMM, p < 0.05). The tick burden at the anal region was also significantly higher than the leg/thigh and chest. This study indicates that the preferred attachment sites of ticks on cattle are species-dependent and effective treatment with acaricides should take into consideration the udder/scrotum and anal regions as well as prioritizing older cattle.

Ticks and prevalence of tick-borne pathogens from domestic animals in Ghana

Background

Ticks are important vectors of various pathogenic protozoa, bacteria and viruses that cause serious and life-threatening illnesses in humans and animals worldwide. Estimating tick-borne pathogen prevalence in tick populations is necessary to delineate how geographical differences, environmental variability and host factors influence pathogen prevalence and transmission. This study identified ticks and tick-borne pathogens in samples collected from June 2016 to December 2017 at seven sites within the Coastal, Sudan and Guinea savanna ecological zones of Ghana.

Methods

A total of 2016 ticks were collected from domestic animals including cattle, goats and dogs. Ticks were morphologically identified and analysed for pathogens such as Crimean-Congo haemorrhagic fever virus (CCHFV), Alkhurma haemorrhagic fever virus (AHFV), Rickettsia spp. and Coxiella burnetii using polymerase chain reaction assays (PCR) and sequence analysis.

Results

Seven species were identified, with Amblyomma variegatum (60%) most frequently found, followed by Rhipicephalus sanguineus sensu lato (21%), Rhipicephalus spp. (9%), Hyalomma truncatum (6%), Hyalomma rufipes (3%), Rhipicephalus evertsi (1%) and Rhipicephalus (Boophilus) sp. (0.1%). Out of 912 pools of ticks tested, Rickettsia spp. and Coxiella burnetii DNA was found in 45.6% and 16.7% of pools, respectively, whereas no CCHFV or AHFV RNA were detected. Co-infection of bacterial DNA was identified in 9.6% of tick pools, with no statistical difference among the ecozones studied.

Conclusions

Based on these data, humans and animals in these ecological zones are likely at the highest risk of exposure to rickettsiosis, since ticks infected with Rickettsia spp. displayed the highest rates of infection and co-infection with C. burnetii, compared to other tick-borne pathogens in Ghana.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05208-8.

Emergence of Theileria species in ticks from free-ranging domestic animals in Raymond Mhlaba Local Municipality, South Africa

Ticks infestation and diseases associated with it, are becoming a major life threatening concern to wildlife, domesticated animals and human health in general. Besides causing skin damage, ticks infestations have become a growing burden in food security and transmission of multiple pathogens. There is paucity of data on the occurrence of etiologic agents of tick-borne diseases in the Eastern Cape Province South Africa. We therefore carried out a molecular surveillance on Babesia and Theileria species in ticks obtained from livestock in Raymond Mhlaba District Municipality of the Province. A total of 962 ticks were collected and were morphologically identified and processed for DNA extraction using commercial DNA extraction kit. The extracted DNA samples were used to molecular identification of the ticks, and also to assess the occurrence of the Babesia and Theileria spp by PCR using genus specific primers. Positive amplicons obtained were sequenced, processed and characterised using appropriate bioinformatics tools. The molecular and morphological identifications of ticks obtained from the domestic animals in the study areas revealed that they belong to three different genera namely: Haemophalis, Rhipicephalus, and Amblyomma in ascending order of their abundance. Furthermore, the DNA of Theileria spp. was detected from 10 out of 962 ticks screened, with an overall infection of about 1% for Rhipicephalus spp., while none of the ticks was positive for Babesia spp. The phylogenetic analysis of the 10 theilerial sequences showed that nine (9) clustered distinctly within the T. orientalis complex clade, while only one (1) sequence formed a cluster with reference sequences of T. velifera. The findings from this study therefore expand the knowledge on recent emergence of Theileria spp. in livestock reared in the study area. This calls for an urgent effort in curbing the further spread of the pathogens in the area and beyond.

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Distribution of ticks' species in domestic animals was described.

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Emergence of theilerial parasites in ticks from free-ranging domestic animals was observed

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Rhipicephalus spp. of ticks serve as the major transmission vector for Theileria spp. in the Eastern Cape Province, South Africa

Metagenomics of the midgut microbiome of Rhipicephalus microplus from China

Background

Ticks, which are ectoparasites of animals, may carry multiple pathogens. The cattle tick Rhipicephalus microplus is an important bovine parasite in China. However, the midgut microbiome of R. microplus from China has not been characterized via metagenomic methods.

Methods

Rhipicephalus microplus were collected from cattle in the city of Changsha in Hunan province, China. The DNA of the midgut contents was extracted from fully engorged adult female R. microplus. A DNA library was constructed and sequenced using an Illumina HiSeq sequencing platform. SOAPdenovo software was used to assemble and analyze the clean data. The latent class analysis algorithm applied to system classification by MEGAN software was used to annotate the information on the species’ sequences. DIAMOND software was used to compare unigenes with the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, and functional annotation was carried out based on the results of the comparison.

Results

The dominant phyla in the five samples were Firmicutes, Proteobacteria, and Actinobacteria. Streptococcus, Mycobacterium, Anaplasma, Enterococcus, Shigella, Lactobacillus, Brachyspira, Pseudomonas, Enterobacter, Bacillus, and Lactococcus were the dominant genera in the five samples. The endosymbiotic bacterium Wolbachia was also detected in all of the samples. Mycobacterium malmesburyense, Streptococcus pneumoniae, Anaplasma phagocytophilum, Enterococcus faecium, Shigella sonnei, Enterococcus faecalis, Lactobacillus casei, Brachyspira hampsonii, Pseudomonas syringae, Enterobacter cloacae, and Lactococcus garvieae were the dominant species in the five samples. In addition to these bacterial species, we also detected some eukaryotes, such as Rhizophagus irregularis, Enterospora canceri, Smittium culicis, Zancudomyces culisetae, Trachipleistophora hominis, and viruses such as orf virus, human endogenous retrovirus type W, enzootic nasal tumor virus of goats, bovine retrovirus CH15, and galidia endogenous retrovirus in all of the samples at the species level. The results of the annotated KEGG pathway predictions for the gene functions of the midgut microflora of R. microplus indicated genes involved in lipid and amino acid metabolism, infectious diseases (e.g., Streptococcuspneumonia infection, human granulocytic anaplasmosis, Shigellasonnei infection, Salmonella enterica infection, and pathogenic Escherichia coli infection), and cancer.

Conclusions

Our study revealed that the midgut microbiome of R. microplus is not only composed of a large number of bacteria, but that a portion also comprises eukaryotes and viruses. The data presented here enhance our understanding of this tick’s midgut microbiome and provide fundamental information for the control of ticks and tick-borne diseases.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05161-6.

Molecular screening of ticks of the genus Amblyomma (Acari: Ixodidae) infesting South African reptiles with comments on their potential to act as vectors for Hepatozoon fitzsimonsi (Dias, 1953) (Adeleorina: Hepatozoidae)

In South Africa, the role of reptilian ticks in the transmission of haemoparasites is lacking, in part, due to limited information on tick diversity and their associated haemoparasites. The aim of this research was to identify tick species parasitizing reptiles and to molecularly screen these ectoparasites for species of the blood apicomplexan genus Hepatozoon. Samples were collected from Ndumo Game Reserve, KwaZulu-Natal, and the Cape Columbine region, Western Cape. Reptiles collected included 2 snakes, 2 monitor lizards of a single species respectively, as well as 17 tortoises of four species. Ticks collected from these were morphologically identified as Amblyomma latum (n = 2) and Amblyomma marmoreum (n = 98), this identification was molecularly confirmed using 16S rRNA and CO1 genes. Screening for Hepatozoon was done by amplifying the 18S rRNA gene. A species of Hepatozoon, Hepatozoon fitzsimonsi, was identified from A. marmoreum ticks, with an overall prevalence of 10%. This Hepatozoon species, has been described parasitizing tortoises from southern Africa, and has been reported from ticks infesting tortoises from Kenya, East Africa. Even though ticks have been suggested to be the likely vector of this Hepatozoon species, with this supported by the findings of Hepatozoon-like developmental stages in ticks collected off of infected tortoises, a recent systematic revision placed this species in a newly erected genus Bartazoon, a genus vectorised by biting insects. The present study thus provides further support for ticks acting as the potential vectors of H. fitzsimonsi.

Molecular Detection and Characterization of Rickettsia Species in Ixodid Ticks Collected From Cattle in Southern Zambia

Tick-borne zoonotic pathogens are increasingly becoming important across the world. In sub-Saharan Africa, tick-borne pathogens identified include viruses, bacteria and protozoa, with Rickettsia being the most frequently reported. This study was conducted to screen and identify Rickettsia species in ticks (Family Ixodidae) infesting livestock in selected districts of southern Zambia. A total of 236 ticks from three different genera (Amblyomma, Hyalomma, and Rhipicephalus) were collected over 14 months (May 2018-July 2019) and were subsequently screened for the presence of Rickettsia pathogens based on PCR amplification targeting the outer membrane protein B (ompB). An overall Rickettsia prevalence of 18.6% (44/236) was recorded. Multi-locus sequencing and phylogenetic characterization based on the ompB, ompA, 16S rRNA and citrate synthase (gltA) genes revealed the presence of Rickettsia africae (R. africae), R. aeschlimannii-like species and unidentified Rickettsia species. While R. aeschlimannii-like species are being reported for the first time in Zambia, R. africae has been reported previously, with our results showing a wider distribution of the bacteria in the country. Our study reveals the potential risk of human infection by zoonotic Rickettsia species and highlights the need for increased awareness of these infections in Zambia's public health systems.

Identification of Amblyomma javanense and detection of tick-borne Ehrlichia spp. in confiscated Malayan Pangolins

Due to habitat destruction and illegal hunting and trade, the number of pangolins has been sharply reduced. To protect pangolins from extinction, relevant departments are combined and active action have been taken. A total of 21 confiscated Malayan pangolins were rescued in 2019, but died continuously for unknown reasons. This study aimed to investigate the reasons for the death of these pangolin and rescue them. 19 of the 21 confiscated pangolins had ticks on their body integument. A total of 303 ticks were collected and identified as Amblyomma javanense (A. javanense) according to their morphology and the sequences of 16S rRNA and internal transcribed spacer 2 (ITS2). There were multi-organ damages in the dead pangolins, especially congestion and hemorrhage in lung, heart and kidney and inflammation of which were observed using HE staining. Pathogens' nucleic acid detection showed ticks were only positive for Ehrlichia spp, with 56.7% positive rate of collected ticks (127/224), which was further confirmed in tissues from dead pangolins. Our findings confirm that ehrlichiosis caused by Ehrlichia spp. from A. javanense might accelerate the confiscated pangolin's death. More attention should be payed to tick-elimination work and the diagnoses and treatment of tick-borne diseases in the follow-up rescue operation.

Tick-, Flea-, and Louse-Borne Diseases of Public Health and Veterinary Significance in Nigeria

Mosquito-borne diseases are common high-impact diseases in tropical and subtropical areas. However, other non-mosquito vector-borne pathogens (VBPs) may share their geographic distribution, seasonality, and clinical manifestations, thereby contributing their share to the morbidity and mortality caused by febrile illnesses in these regions. The purpose of this work was to collect and review existing information and identify knowledge gaps about tick, flea-, and louse-borne diseases of veterinary and public health significance in Nigeria. Full-length articles about VBPs were reviewed and relevant information about the vectors, their hosts, geographic distribution, seasonality, and association(s) with human or veterinary diseases was extracted. Specific laboratory tools used for detection and identification of VBPs in Nigeria were also identified. A total of 62 original publications were examined. Substantial information about the prevalence and impacts of ticks and fleas on pet and service dogs (18 articles), and livestock animals (23 articles) were available; however, information about their association with and potential for causing human illnesses was largely absent despite the zoonotic nature of many of these peri-domestic veterinary diseases. Recent publications that employed molecular methods of detection demonstrated the occurrence of several classic (Ehrlichia canis, Rickettsia africae, Bartonella sp.) and emerging human pathogens (R. aeschlimannii, Neoehrlichia mikurensis) in ticks and fleas. However, information about other pathogens often found in association with ticks (R. conorii) and fleas (R. typhi, R. felis) across the African continent was lacking. Records of louse-borne epidemic typhus in Nigeria date to 1947; however, its current status is not known. This review provides an essential baseline summary of the current knowledge in Nigeria of non-mosquito VBPs, and should stimulate improvements in the surveillance of the veterinary and human diseases they cause in Nigeria. Due to increasing recognition of these diseases in other African countries, veterinary and public health professionals in Nigeria should expand the list of possible diseases considered in patients presenting with fever of unknown etiology.

Tick microbiome: the force within

Ticks are obligate blood-feeders and serve as vectors of human and livestock pathogens worldwide. Defining the tick microbiome and deciphering the interactions between the tick and its symbiotic bacteria in the context of tick development and pathogen transmission will likely reveal new insights and spawn new paradigms to control tick-borne diseases. Descriptive observations on the tick microbiome that began almost a century ago serve as forerunners to the gathering momentum to define the tick microbiome in greater detail. This review will focus on the current efforts to address the microbiomes of diverse ticks, and the evolving understanding of tick microbiomes. There is hope that these efforts will bring a holistic understanding of pathogen transmission by ticks.

Ixodid tick infestation in cattle and wild animals in Maswa and Iringa, Tanzania

Ticks and tick-borne diseases are important in human and livestock health worldwide. In November 2012, ixodid ticks were collected and identified morphologically from cattle and wild animals in the Maswa district and Iringa urban, Tanzania. Amblyomma gemma, A. lepidum, and A. variegatum were identified from Maswa cattle, and A. variegatum was the predominant species. A. marmoreum, Hyalomma impeltatum, and Rhipicephalus pulchellus were identified from Iringa cattle in addition to the above 3 Amblyomma species, and A. gemma was the most abundant species. Total 4 Amblyomma and 6 Rhipicephalus species were identified from wild animals of the 2 areas. A. lepidum was predominant in Maswa buffaloes, whereas A. gemma was predominant in Iringa buffaloes. Overall, A. variegatum in cattle was predominant in the Maswa district and A. gemma was predominant in Iringa, Tanzania.

Molecular investigation of tick-borne pathogens in ticks from grazing cattle in Korea

This study was carried out to identify the tick species that infest grazing cattle and to determine the presence of tick-borne pathogens transmitted by these ticks in Korea. A total of 903 ticks (categorized into 566 tick pools) were collected from five provinces during 2010-2011. The most prevalent tick species was Haemaphysalis longicornis, followed by three Ixodes spp. ticks. The collected ticks were infected with both rickettsial and protozoan pathogens. In all, 469 (82.9%) tick pools tested positive for the Anaplasma/Ehrlichia 16S rRNA gene, whereas 67 (11.8%) were positive for the Babesia/Theileria 18S rRNA gene. Among the rickettsial pathogens, E. canis was detected with the highest rate (22.3%), followed by A. platys (20%), E. chaffeensis (19.4%), E. ewingii (19.3%), Rickettsia sp. (12.4%), A. phagocytophilum (5.5%) and E. muris (0.5%). Among the protozoan pathogens, T. equi was detected with the highest rate (7.2%), followed by T. sergenti/T. buffeli (3.7%) and B. caballi (0.35%). Simultaneous infections with up to seven pathogens were also identified. In particular, ticks infected with rickettsial pathogens were also infected with protozoan pathogens (22 samples). All five provinces investigated infected with tick-borne pathogens.

Integrated Strategy for Sustainable Cattle Fever Tick Eradication in USA is Required to Mitigate the Impact of Global Change

The ticks Rhipicephalus (Boophilus) annulatus and R. (B.) microplus, commonly known as cattle and southern cattle tick, respectively, impede the development and sustainability of livestock industries throughout tropical and other world regions. They affect animal productivity and wellbeing directly through their obligate blood-feeding habit and indirectly by serving as vectors of the infectious agents causing bovine babesiosis and anaplasmosis. The monumental scientific discovery of certain arthropod species as vectors of infectious agents is associated with the history of research on bovine babesiosis and R. annulatus. Together, R. microplus and R. annulatus are referred to as cattle fever ticks (CFT). Bovine babesiosis became a regulated foreign animal disease in the United States of America (U.S.) through efforts of the Cattle Fever Tick Eradication Program (CFTEP) established in 1906. The U.S. was declared free of CFT in 1943, with the exception of a permanent quarantine zone in south Texas along the border with Mexico. This achievement contributed greatly to the development and productivity of animal agriculture in the U.S. The permanent quarantine zone buffers CFT incursions from Mexico where both ticks and babesiosis are endemic. Until recently, the elimination of CFT outbreaks relied solely on the use of coumaphos, an organophosphate acaricide, in dipping vats or as a spray to treat livestock, or the vacation of pastures. However, ecological, societal, and economical changes are shifting the paradigm of systematically treating livestock to eradicate CFT. Keeping the U.S. CFT-free is a critical animal health issue affecting the economic stability of livestock and wildlife enterprises. Here, we describe vulnerabilities associated with global change forces challenging the CFTEP. The concept of integrated CFT eradication is discussed in reference to global change.

Pathogen prevalence in ticks collected from the vegetation and livestock in Nigeria

Ticks are important disease vectors that can cause considerable economic losses by affecting animal health and productivity, especially in tropical and subtropical regions. In this study, we investigated the prevalence and diversity of bacterial and protozoan tick-borne pathogens in ticks collected from the vegetation and cattle in Nigeria by PCR. The infection rates of questing ticks were 3.1% for Rickettsia species, 0.1% for Coxiella burnetii and 0.4% for Borrelia species. Other pathogens, such as Babesia, Theileria, Anaplasma, and Ehrlichia species, were not detected in ticks from the vegetation. Feeding ticks collected from cattle displayed infection rates of 12.5% for Rickettsia species, 14% for Coxiella burnetii, 5.9% for Anaplasma species, 5.1% for Ehrlichia species, and 2.9% for Theileria mutans. Babesia and Borrelia species were not detected in ticks collected from cattle. Mixed infections were found only in feeding ticks and mainly Rickettsia species and Coxiella burnetii were involved. The diversity of tick-borne pathogens in Nigeria was higher in feeding than in questing ticks, suggesting that cattle serve as reservoirs for at least some of the pathogens studied, in particular C. burnetii. The total estimated herd infection rates of 20.6% for a Rickettsia africae-like species, 27% for Coxiella burnetii, and 8.5% for Anaplasma marginale/centrale suggest that these pathogens may have considerable implications for human and animal health.