OBJECTIVE: This comprehensive global meta-analysis reviews the parasitism levels of tick genera and species, life stages, seasonality, attachment sites, the global mean ranks of tick species parasitism rates and records, and their distribution and role as vectors.
METHODS: From the 418 papers identified, 390 papers were selected to become part of the study.
RESULTS: The genera recorded as infesting domestic ruminants were Rhipicephalus (42 species), Haemaphysalis (32 species), Hyalomma (19 species), Amblyomma (18 species), Ixodes (10 species), Dermacentor (8 species), Margaropus and Nosomma (1 species). Globally, domestic ruminants are more infested by adult females and males than by the nymphal and larval stages of the tick species. The global tick species parasitism levels at the attachment sites of domestic ruminants were, in order, tail and anal region, neck and dewlap, scrotum or udder, ear region, thigh and abdomen, and dorsal surface.
CONCLUSIONS: Among 131 species of eight genera of hard ticks recorded infesting domestic ruminants, 42 species had mean ranks of tick species parasitism rates up to 10%, and 37 species had mean ranks of tick species parasitism up to 10 records. Briefly, the higher the indexes of tick species parasitism rates and records, the more important their role as vectors. In addition, the majority of them are found among tick species-infested humans with nearly high ranks of tick species parasitism rates and records that double their medical, veterinary, and zoonotic importance to be the most common vectors and reservoirs of bacterial, protozoan, and viral pathogenic microorganisms, causing severe infectious diseases, and as a result, can be more dangerous to humans and domestic ruminants.

There are many studies present in literature performed to isolate CCHFV from ticks. However, gaps in knowledge for estimating global annual CCHFV infection rates; global CCHFV infection rates and records; CCHFV infection trend in ticks and ticks infested animals; and lack a decision regarding the role of ticks as CCHFV vectors caused to conduct this review.
From 605 papers identified, 150 papers were selected to become the study meta-analysis (57 papers), detailed CCHFV infected ticks (63 papers), and systematic review (99 papers) parts.
Since there are no significant differences between the annual tick CCHFV infection rates; tick CCHFV infection rates between continents; and CCHFV infection rates between tick species and gender of ticks, and ticks and tick species infested animals. Given that ticks are considered both as CCHFV reservoirs and vectors. It is possible a little burden of CCHFV in infected ticks in natural enzootic cycles to maintain and disseminate CCHFV in humans. The decision regarding the role of ticks as CCHFV vectors administrated based on the study and a separately literature search regarding the role of ticks as CCHFV vectors; CCHFV infection rates and records; and trend of CCHFV infection records in 31 tick species. The trend of CCHFV infection records in 31 tick species exhibited a decreasing trend indicating the degree and importance of their roles as CCHFV vectors.
Among 31 CCHFV infected tick species, 15 species have been enrolled as proven vectors and 16 species are suspected as potential vectors.

Tick-borne illnesses have been on the rise in the United States, with reported cases up sharply in the past two decades. In this literature review, we synthesize the available research on the relationship between vegetation and tick abundance for four tick species in the northeastern United States that are of potential medical importance to humans. The blacklegged tick (Ixodes scapularis) (Say; Acari: Ixodidae) is found to be positively associated with closed canopy forests and dense vegetation thickets, and negatively associated with open canopy environments, such as grasslands or old agricultural fields. The American dog tick (Dermacentor variabilis) (Say; Acari: Ixodidae) has little habitat overlap with I. scapularis, with abundance highest in grasses and open-canopy fields. The lone star tick (Amblyomma americanum) (Linnaeus; Acari: Ixodidae) is a habitat generalist without consistent associations with particular types of vegetation. The habitat associations of the recently introduced Asian longhorned tick (Haemaphysalis longicornis) (Neumann; Acari: Ixodidae) in the northeastern United States, and in other regions where it has invaded, are still unknown, although based on studies in its native range, it is likely to be found in grasslands and open-canopy habitats.

This study aimed to consolidate current knowledge of wildlife brucellosis in Africa and to analyse available predictors of infection. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Information on species, test used, test results, area, rainfall, livestock and wildlife contact and year of study were extracted. This systematic review revealed 42 prevalence studies, nine disease control articles and six articles on epidemiology. Brucella abortus, Brucella melitensis, Brucella inopinata and Brucella suis were reported in wildlife. The prevalence studies revealed serological evidence of brucellosis in buffalo, antelope (positive in 14/28 species), carnivores (4/12) and other species (7/20) over the last five decades. Buffalo populations were more likely to be infected and had a higher seroprevalence than other species; the pooled seroprevalence was 13.7% (95% CI 10.3-17.3%) in buffalo, 7.1% (95% CI 1.1-15.5%) in carnivores and 2.1% (95% CI 0.1-4.9%) in antelope. Wildlife in high rainfall areas (≥ 800 mm) were more likely to be infected, and infected populations showed higher seroprevalence in high rainfall areas and in studies published after 2000. Domestic animal contact was associated with increased seroprevalence in antelope and carnivore species, but not in buffalo, supporting the hypothesis that buffalo may be a reservoir species.

Tick-borne diseases (TBDs), in particular Crimean-Congo hemorrhagic fever (CCHF) and tick-borne encephalitis (TBE), have been found to be expanding beyond their traditional geographic locations in Kazakhstan, which led to increased awareness and concern against TBDs in recent years. The tick fauna of Kazakhstan includes more than 30 species of human-biting ixodid ticks, recognized as carriers of a number of dangerous infectious pathogens that cause CCHF, TBE, tularemia, tick-borne rickettsioses and Lyme borreliosis. This paper presents the current knowledge of the main vectors of tick-borne pathogens (TBP) occurring in Kazakhstan, as well as a review of recent studies of ticks performed with the use of molecular methods being currently developed and widely utilized by Kazakh epidemiologists.

Tropical theileriosis caused by the apicomplexan hemoparasite Theileria annulata is a tick-borne disease that constraints livestock production in parts of Europe, Asia and Africa. Four Hyalomma tick species transmit T. annulata in at least eight Africa countries (Mauritania, Morocco, Algeria, Tunisia, Egypt, Sudan, South Sudan and Ethiopia). The two dominant T. annulata vector ticks present in Africa, H. scupense and H. anatolicum, underlie two different patterns of transmission, which in turn greatly influence the epidemiology of tropical theileriosis. H. dromedarii and H. lusitanicum are also capable of transmitting T. annulata in North Africa, but their roles are associated with specific production systems and agro-ecological contexts. The emergence of resistance to the most widely used theilericidal compound, buparvaquone, continues to limit the effectiveness of chemotherapy. In addition, acaricide use is increasingly becoming unsustainable. Deployable T. annulata attenuated live vaccines established from local strains in Tunisia, Sudan and Egypt are available, and recent work has indicated that these vaccines can be protective under conditions of natural transmission. However, vaccination programmes may vary over space and time due to differences in the prevalence of disease amongst cattle populations, as well seasonal variation in vector activity. We review recent descriptive and analytical surveys on the epidemiology of T. annulata infection with reference to (a) demographic aspects such as breeds and ages of cattle herds previously exposed to distinct T. annulata infection pressures and (b) seasonal dynamics of tick activity and disease transmission. We then discuss how the wider endemic patterns that we delineate can underpin the development and execution of future vaccination programmes. We also outline options for integrated control measures targeting tick vectors and husbandry practices.

Use of emerging technology allowing for identification of genetic material from pathogens and endosymbionts in ticks collected from humans, domestic animals, wildlife, or the environment has resulted in an avalanche of new data on tick-microorganism associations. This rapidly growing stream of new information is a tremendous resource but also presents challenges, including how detection of pathogen genetic material in ticks should best be interpreted. There is a tendency in the more recent published literature to incorrectly use the term \"vector\" based on detection of pathogen genetic material from tick species not experimentally confirmed to serve as vectors of the pathogen in question. To serve as a vector of a horizontally maintained pathogen, such as a Borrelia burgdorferi sensu lato (s.l.) Lyme borreliosis spirochete, the tick species in question must be capable of acquiring the pathogen while feeding in the larval or nymphal stage on an infectious host, maintaining it transstadially through the molt, and then transmitting the pathogen to a naïve host while feeding in the subsequent nymphal or adult stage. This review examines the experimental evidence for and against species of hard (ixodid) ticks from different genera to serve as vectors of B. burgdorferi s.l. spirochetes. Of the 18 Ixodes species ticks evaluated to date, 13 were experimentally confirmed as vectors of B. burgdorferi s.l. spirochetes. These studies focused primarily on the three major Lyme borreliosis agents: Borrelia burgdorferi sensu stricto, Borrelia afzelii, and Borrelia garinii. In striking contrast, none of 8 tick species from other genera (1 Amblyomma species, 5 Dermacentor species, and 2 Haemaphysalis species) evaluated to date were unequivocally experimentally confirmed as vectors of B. burgdorferi s.l. spirochetes. The strength of the evidence for or against each tick species to serve as a vector of B. burgdorferi s.l. spirochetes is discussed together with key knowledge gaps and research challenges.

Scrub typhus, caused by Orientia tsutsugamushi, is an important and neglected vector-borne zoonotic disease with an expanding known distribution. The ecology of the disease is complex and poorly understood, impairing discussion of public health interventions. To highlight what we know and the themes of our ignorance, we conducted a systematic review of all studies investigating the pathogen in vectors and non-human hosts. A total of 276 articles in 7 languages were included, with 793 study sites across 30 countries. There was no time restriction for article inclusion, with the oldest published in 1924. Seventy-six potential vector species and 234 vertebrate host species were tested, accounting for over one million trombiculid mites (\'chiggers\') and 83,000 vertebrates. The proportion of O. tsutsugamushi positivity was recorded for different categories of laboratory test and host species. Vector and host collection sites were geocoded and mapped. Ecological data associated with these sites were summarised. A further 145 articles encompassing general themes of scrub typhus ecology were reviewed. These topics range from the life-cycle to transmission, habitats, seasonality and human risks. Important gaps in our understanding are highlighted together with possible tools to begin to unravel these. Many of the data reported are highly variable and inconsistent and minimum data reporting standards are proposed. With more recent reports of human Orientia sp. infection in the Middle East and South America and enormous advances in research technology over recent decades, this comprehensive review provides a detailed summary of work investigating this pathogen in vectors and non-human hosts and updates current understanding of the complex ecology of scrub typhus. A better understanding of scrub typhus ecology has important relevance to ongoing research into improving diagnostics, developing vaccines and identifying useful public health interventions to reduce the burden of the disease.

Crimean-Congo hemorrhagic fever (CCHF) is one of the severe forms of high-fatality hemorrhagic fever transmitted by bite of infected ticks or body fluids of infected individuals. Lack of sufficient research and endemic potential of the disease is posing serious threats to public health. The aim of this review was to explore the current status of Crimean-Congo hemorrhagic fever virus (CCHFV) related research and to identify knowledge gaps and the areas that are yet to be explored. An interpretative scoping review methodology was followed to systematically characterize the most recent literature. Literature survey was conducted using electronic databases: PubMed, Scopus, ScienceDirect and Google Scholar. This comprehensive research yielded more than 300 records, but we excluded 100 articles based on our inclusion criteria and duplicates removal. All articles (n=85) that have been published currently were discussed in this scoping review. From a total of 303 documents retrieved, 85 met the criteria. All the documents (case studies, review articles, systematic reviews, meta-analysis, case control studies, cohort studies, randomised control trials, and longitudinal studies) were included in the study. The articles mainly cover different areas such as epidemiology, prevalence, diagnosis, pathogenesis, clinical outcomes, molecular basis, phylogenetics, transmission and treatment of CCHF. Treatment and prevention related knowledge is limited; therefore, future research should focus the development of therapeutics to mitigate the increasing risk of CCHF. Priority future goal should be studies on the molecular basis and treatment of CCHFV infection because several knowledge gaps have been identified in these areas.

Ticks (Acari:Ixodoidea) are important ectoparasites infesting livestock and human populations around the globe. Ticks can cause damage directly by affecting the site of infestation, or indirectly as vectors of a wide range of protozoa, bacteria and viruses which ultimately lead to lowered productivity of livestock populations. Hyalomma is a genus of hard ticks, having more than 30 species well-adapted to hot, humid and cold climates. Habitat diversity, vector ability, and emerging problem of acaricidal resistance in enzootic regions typify this genus in various countries around the world. This paper reviews the epidemiology, associated risk factors (temperature, climate, age, sex, breed etc.), vector role, vector-pathogen association, and reported control strategies of genus Hyalomma. The various proteins in saliva of Hyalomma secreted into the blood stream of host and the prolonged attachment are responsible for the successful engorgement of female ticks in spite of host immune defense system. The various immunological approaches that have been tried by researchers in order to cause tick rejection are also discussed. In addition, the novel biological control approaches involving the use of entomo-pathogenic nematodes and Bacillus thuringiensis (B. thuringiensis) serovar thuringiensis H14; an endotoxin, for their acaricidal effect on different species and life cycle stages of Hyalomma are also presented.