Ticks are obligate hematophagous arthropods at all developmental stages, primarily feeding on terrestrial vertebrates. They serve as vectors for numerous pathogens affecting both humans and animals. Accurate tick species identification currently requires an integrated approach combining morphological, molecular, and proteomic techniques. As part of a tick-borne disease surveillance program conducted in 2023 in the Kaffrine and Tambacounda regions of Senegal, ticks were collected from livestock in domestic environments to investigate the presence of Rickettsia spp. and other associated microorganisms. Specimens were identified using morphological keys, molecular markers, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), while pathogens were detected using quantitative PCR (qPCR) and sequencing. A total of 212 ticks were collected, representing three genera (Amblyomma, Hyalomma, and Rhipicephalus) and six species: Amblyomma variegatum (n = 60), Hyalomma rufipes (n = 52), Hyalomma truncatum (n = 22), Rhipicephalus evertsi evertsi (n = 59), Rhipicephalus linnaei (formerly Rh. sanguineus tropical lineage) (n = 9), and Rhipicephalus (Boophilus) decoloratus (n = 3). Among these, 36.8% (78/212) tested positive for at least one microorganism. Rickettsia spp. and Coxiella burnetii were each detected in 7.4% (16/212), while members of the Anaplasmataceae family were found in 5.2% (11/212). Specific identification confirmed the presence of Rickettsia africae, R. aeschlimannii, Anaplasma ovis, A. phagocytophilum, "Candidatus Ehrlichia rustica", "Candidatus Ehrlichia urmitei", Theileria ovis and T. mutans. These findings highlight the necessity of combining identification methods to enhance taxonomic precision, especially for closely related or morphologically ambiguous specimens. The presence of zoonotic pathogens reinforces the need for improved surveillance and awareness among health professionals.

Beyond the eschar: African tick-bite fever in a returning traveller - a diagnostic and public health consideration in Europe.

A scoping review on tick species and pathogens distributed in kenya and cross-border districts.

Tick-borne pathogens in Ghana: Emerging threat to animal and human health.

Zoonotic diseases account for over ∼60% of infectious diseases and present a significantly growing fatality threat in Africa. Live and wet markets (LWMs) in Africa function as key economic venues that support human livelihoods through social interaction and trade in food stuff, including meat and other animal-based products. These spaces concentrate and exaggerate human and animal contact, creating conditions conducive to zoonotic spill-over events. This narrative review, based on an opportunistic literature identification process, summarizes the diversity of ticks and tick-borne pathogens (TTBPs) associated with carcasses at African LWMs, as well as the awareness, perceptions, and control practices of stakeholders along the meat value chain. Findings show pervasive infestations by Amblyomma, Rhipicephalus, Hyalomma; limited reports of Haemaphysalis, Ixodes, and Demacentor species; along with the circulation of Rickettsia africae, Crimean-Congo hemorrhagic fever virus, Anaplasma spp., and Coxiella burnetii. Surveillance efforts remain geographically patchy, with strong bias towards East and West Africa. The knowledge of tick-borne zoonotic diseases is poor and shaped by sociodemographic factors, like education and occupational roles. Control measures, where practiced, are inconsistently applied and inadequate. Collectively, these findings flag African LWMs as understudied epidemiologically permeable hubs, with potential implications in the ecology of tick-borne zoonotic diseases.

ABSTRACTBackgroundRickettsia spp. are obligate intracellular bacteria of the spotted fever group (SFG), typhus group (TG) and transitional group, with diverse vectors and significant zoonotic potential. While Rickettsia africae is well documented in South African ticks, the role of wildlife hosts in pathogen maintenance remains unclear.MethodsWe re‐screened 73 spleen samples opportunistically collected from 11 wild mammal species that previously tested negative for Rickettsia by reverse line blot hybridization (RLB). The samples were collected from Kruger National Park, Timbavati Private Nature Reserve, Mountain Zebra National Park and Lapalala Wilderness Reserve. In addition, liver, lymph node and blood samples from two impala were included to preliminarily assess multi‐organ dissemination. To increase detection sensitivity, we employed a nested PCR targeting the conserved gltA gene, in contrast to the 23S‐5S intergenic spacer (IGS) targeted by RLB.ResultsThe gltA region was successfully amplified by PCR from 32/73 animals (44%; confidence intervals [CI]: 32%–56%). Sequencing of 27 amplicons revealed SFG Rickettsia (n = 22), TG Rickettsia (n = 3) closely related to R. prowazekii and transitional group (n = 1) Rickettsia felis‐like sequences. One zebra (Equus quagga) sequence was phylogenetically unresolved, and one sample showed a mixed SFG–TG infection. Rickettsial DNA detections included new host records in giraffe (Giraffa camelopardalis), hippopotamus (Hippopotamus amphibius), impala (Aepyceros melampus), warthog (Phacocoerus africanus), white rhinoceros (Ceratotherium simum) and zebra. Detection across multiple tissues in impala supports systemic dissemination, consistent with experimental evidence of rickettsial persistence in vertebrate tissues.ConclusionsThese findings broaden the known host range and illustrate the complex dynamics of pathogen persistence, host diversity and co‐infection, although interpretation is constrained by the limited and uneven sample sizes, which preclude robust population‐level inference. Integrating high‐sensitivity molecular diagnostics with ecological and vector surveillance within a One Health framework will be critical to clarify wildlife reservoir status and mitigate zoonotic risk at the wildlife–livestock–human interface.

Amblyomma variegatum threatens the Caribbean cattle industry owing to its role as a vector for Ehrlichia ruminantium, the obligate intracellular bacterium that causes heartwater disease, an economically important and potentially fatal ruminant disease. Amblyomma variegatum is also a public health concern as a vector for Rickettsia africae, the causative agent of African tick-bite fever. Efforts to eradicate A. variegatum on Caribbean islands are ongoing to protect cattle from disease and prevent the spread of the vector and diseases to the American mainland. However, reinfestations often occur, possibly owing to the maintenance of ticks by non-cattle hosts that escape treatment. St. Croix in the US Virgin Islands has experienced such eradication challenges. To determine whether persistence of A. variegatum populations on non-cattle hosts contributes to cattle reinfestation on St. Croix, we analyzed 1 non-attached A. variegatum adult female collected from a human and 14 questing adult females collected via cloth dragging along vegetation transects in Lower Love, St. Croix, during 2023. We conducted host bloodmeal analysis by obtaining vertebrate cytochrome c oxidase subunit I (COI) sequences from A. variegatum DNA extracts using COI-targeted DNA capture and enrichment to identify the most recent host bloodmeal. We also screened tick DNA extracts for E. ruminantium and Rickettsia DNA using pCS20 Sol1 and PanR8 qPCR, respectively. Rickettsia species identification was determined using ompA polymerase chain reaction (PCR) and Sanger sequencing, followed by phylogenetic analysis. We identified vertebrate COI sequences for the genera Capra and Canis in two A. variegatum ticks. Although E. ruminantium was not detected, DNA from R. africae was present in all 15 ticks. These results suggest that goats, and possibly canines, may serve as alternative hosts for A. variegatum on St. Croix, US Virgin Islands, which complicates eradication efforts focused entirely on the treatment of cattle. Fortunately, E. ruminantium was not identified in any ticks. However, R. africae was ubiquitous, which may be of concern for public health.

Ticks are blood-feeding arthropods that carry diverse pathogenic and nonpathogenic microorganisms, yet their dynamics within tick tissues remain poorly understood. We compared the microbial communities in the haemolymph, saliva, ovaries, midgut, and salivary glands of individual Amblyomma gemma and Hyalomma rufipes sampled from dromedary camel using V1-V2 16S rRNA gene metabarcoding. The haemolymph exhibited the highest bacterial diversity, followed by the saliva and ovaries, while the midgut and salivary glands had lower diversities. Keystone taxa exhibited varied connectivity across different tissues and played a crucial role in structuring microbial communities in both tick species. We exclusively detected Rickettsia africae in Am. gemma and Rickettsia aeschlimannii in Hy. rufipes. Both Rickettsia species showed negative correlations with dominant endosymbionts and environmental bacteria across multiple tissues. Coxiella endosymbionts were detected solely in Am. gemma and were most abundant in the salivary glands, while Francisella endosymbionts were dominant in Hy. rufipes’ salivary glands. Francisella endosymbionts were less abundant when R. aeschlimannii was high. In Am. gemma’s haemolymph and saliva, Wolbachia endosymbionts were prevalent, where they were inversely associated with R. africae at the individual tick level. In Hy. rufipes, Wolbachia endosymbionts were present in the ovaries, but not in the midgut. Candidatus Midichloria mitochondrii was found in all tissues of Hy. rufipes and predominantly in saliva, but was only detected in the ovaries, midgut, and salivary glands of Am. gemma. Positive interactions were found between Ca. Midichloria mitochondrii and R. aeschlimannii in Hy. rufipes’ saliva and ovaries, and Ca. Midichloria mitochondrii and Francisella endosymbionts in Am. gemma’s ovaries. Rickettsiella spp. were found in the saliva and haemolymph but not the midgut in both tick species. Environmental bacteria, such as Pseudomonas, Acinetobacter, Staphylococcus, and Corynebacterium, whilst abundant in the haemolymph and saliva were scarce in other tissues. Tick tissue significantly influences bacterial composition, with tissue-specific interactions between pathogens and endosymbionts suggesting bacterial functional specialization. The complex interactions observed between key endosymbionts and Rickettsia pathogens across tissues, including negative correlations with Coxiella, Francisella, and Wolbachia endosymbionts, and positive correlations between Ca. Midichloria mitochondrii and R. aeschlimannii, require further investigation. Identified keystone taxa may serve as targets for anti-microbiota vaccines.

BackgroundSand flies are small hematophagous insects known as leishmaniasis vectors. Similar to most arthropods, they harbor nonobligate endosymbionts that may influence host adaptation and pathogen transmission, but these symbiont communities remain poorly characterized in Leishmania-endemic African sand flies.MethodsWe screened 1700 wild-caught phlebotomine sand flies (1266 females, 434 males) from Kenya’s Baringo, Nakuru, and Kajiado counties, and 253 colony Phlebotomus duboscqi, for Rickettsia, Wolbachia, Spiroplasma, Cardinium, Arsenophonus, Microsporidia, and Leishmania by high-resolution melting analysis and sequencing of PCR products.ResultsIn wild sand flies (Phlebotomus and Sergentomyia spp.), Wolbachia spp. were most common (8.5%, 145/1700), with particularly high prevalences in Ph. mireillae (92.3%, 12/13), Ph. guggisbergi (73.2%, 82/112), and Ph. saevus (48.6%, 18/37), followed by Spiroplasma (1.4%, 23/1700), Rickettsia (0.7%, 12/1700), Cardinium (0.4%, 6/1700), Tubulinosema sp. (0.1%, 1/1700), and various gut bacteria (1.8%, 30/1700). In addition, we detected Rickettsia africae, a tick-borne pathogen causing African tick-bite fever (ATBF), in Ph. martini (4.7%, 5/106), Ph. guggisbergi (1.8%, 2/112), S. schwetzi (0.4%, 1/263), S. clydei (0.5%, 2/440), and Sergentomyia sp. (0.3%, 1/371). Notably, R. africae DNA was found in one male Ph. martini and Rickettsia sp. DNA in one male S. clydei and one male S. schwetzi, consistent with infection rather than blood-meal contamination. Furthermore, Rickettsia endosymbionts were positively associated with Leishmania DNA (OR = 20.31; 95% CI [4.93, 77.03]; P < 0.0001), including within Phlebotomus (OR = 13.54; 95% CI [2.33, 78.88]; P = 0.0017). Wolbachia also correlated with Leishmania overall (OR = 2.46; 95% CI [1.17, 4.79]; P = 0.011), though not within individual fly genera. Colony Ph. duboscqi harbored only Serratia and other gut bacteria.ConclusionsSand flies in Kenya harbored six endosymbionts, including the first detection of pathogenic R. africae in sand flies, and gut bacteria that may influence vector competence. The frequent co-occurrence of Rickettsia and Wolbachia endosymbionts with Leishmania indicates nonrandom associations between symbionts and parasite infection, without implying causality. These findings reveal previously undescribed sand-fly–microbe interactions, and highlight the need for experimental studies to test whether sand flies contribute to the ecology and potential transmission of ATBF.Graphical Supplementary InformationThe online version contains supplementary material available at 10.1186/s13071-026-07283-7.

Domesticated dogs used for hunting come into close contact with humans, domestic animals and wildlife, exposing them to ticks and tick-borne pathogens. It is crucial to include them in surveillance activities to monitor the spread of zoonotic pathogens and formulate effective preventive and control measures. This study sought to examine the diversity of tick species infesting hunting dogs and to detect the DNA of tick-borne pathogens they carry. Ticks were collected from 28 hunting dogs, morphologically identified using available taxonomic keys, and their identifications confirmed by molecular methods. Total nucleic acid was extracted from individual tick species and screened for pathogens using PCR and Sanger sequencing. A total of 142 ticks were identified, with Rhipicephalus sanguineus (85.94%) as the predominant species. This study reports the first molecular confirmation and report of Amblyomma sparsum, Haemaphysalis parva, Rhipicephalus leporis and Rhipicephalus linnaei in Ghana. Pathogen DNA was detected in 31 (21.83%) of the ticks, with the occurring pathogens as Hepatozoon canis (13.28%), Uncultured Anaplasma sp. (7.75%), Ehrlichia canis (7.04%), Rickettsia africae (1.41%) and Uncultured Rickettsia sp. (0.7%). The findings of this study indicate that hunting dogs can be useful sentinels in monitoring tick populations and the spillover of zoonotic tick-borne pathogens from wildlife to humans and domestic animals. This study highlights the need for education, surveillance, and tick control strategies in Ghanaian dog populations to reduce the threat of zoonotic disease establishment and transmission.

Tick‐borne pathogens, transmitted by ticks, infect humans and animals worldwide. The brown dog tick, Rhipicephalus sanguineus sensu lato, is a significant vector of a number of pathogens, including Ehrlichia canis, Rickettsia and Anaplasma species. In Ghana, there is limited information on the pathogens carried by Rh. sanguineus s.l. As such, Rh. sanguineus ticks taken from domestic dogs in Kumasi were screened for tick‐borne pathogens, including Coxiella burnetii, Rickettsia, Babesia, Theileria, Anaplasma, Ehrlichia and Hepatozoon species. A total of 204 ticks collected from 56 infested dogs were morphologically identified as Rh. sanguineus s.l. From the 88 pools screened, 36 (40.9%) were positive for pathogen DNA. The pathogens identified were Rickettsia africae (5 pools), Ehrlichia canis (10 pools) and uncultured Anaplasma sp. (21 pools) with maximum likelihood estimates as 2.48% (95% CI: 0.93, 5.38%), 5.22% (95% CI: 2.69, 9.15%) and 11.20% (95% CI: 7.32, 16.29%), respectively. There was no association between the detection of a pathogen and the tick sex or dog breed, age or sex. This study provides important baseline data on the circulation of tick‐borne pathogens in Rh. sanguineus s.l. ticks in Kumasi, with implications for both veterinary and human health. The presence of uncultured Anaplasma sp. suggests a wider diversity of tick‐borne bacteria with unknown pathogenicity. There is a need for integrated tick control, improved diagnosis and additional epidemiological studies to mitigate the impact of tick‐borne diseases in Ghana.

Ticks are blood-sucking arthropods which can vector various, pathogenic microorganisms between humans and domestic or wild animal hosts. In Cameroon, little is still known about the diversity of ticks and tick-borne pathogens found feeding on these various hosts. This study investigates the frequency of positive pools of Borrelia spp. and Rickettsia spp. in 415 DNA pools arising from 1148 collected ticks belonging to five genera and twenty-five tick species collected from both domestic and wild animals in Cameroon. Tick species were identified morphologically and confirmed molecularly when necessary. All tick pools were tested for Rickettsia spp. and Borrelia spp. using molecular methods of which 18.01 % and 10.38 % of tick pools tested positive for Rickettsia or Borrelia DNA, respectively. This is the first Borrelia spp. detection in ticks collected from wild animals in Cameroon. Three species of Rickettsia were found in ticks feeding on domestic animals, namely, Rickettsia africae, Rickettsia aeschlimannii, and Rickettsia massiliae. Borrelia spp. in Cameroon are closely related to Candidatus Borrelia javanensis from China, as well as Candidatus Borrelia africana and Candidatus Borrelia ivorensis from the Ivory Coast. Although the risk this Borrelia species could pose to humans or animals is currently not known, both Rickettsia species are known to cause human disease warranting continuous monitoring and future research to determine the overall public health risk these microorganisms could pose.

This systematic review analyzed tick and pathogen diversity across Africa,aiming to provide a continental overview of the distribution patterns and zoonotic potential oftick-borne pathogens (TBPs). Understanding these dynamics is essential for guiding surveillanceand control efforts across regions with diverse ecological and epidemiological contexts. The synthesis of findings was qualitative, as a formal meta-analysis and quantitativeassessment of study quality were not feasible due to the varied methodologies and outcomemeasures of the included studies. Data were systematically analyzed in R software, focusing ondescriptive statistics such as counts of tick species and the distribution of associated pathogens.To visualize these relationships, figures and graphs were generated using the ggplot2 package inR, and summary tables were created with gtsummary. Furthermore, Sankey diagrams weredeveloped via sankeymatic.com to effectively illustrate the flow and associations between tickspecies and the pathogens they harbor. West Africa exhibited the greatest number oftick species, followed by East and Central Africa. Five major tick genera were identified, withRhipicephalus being the most prevalent. A wide range of pathogens including rickettsial, viral,and protozoan agents were detected, 19 of which are known to infect humans. Crimean-Congohemorrhagic fever virus and Rickettsia africae were highlighted as particularly concerning dueto their wide distribution and zoonotic potential. Moreover, the presence of livestock pathogens such as Babesia bigemina and Ehrlichia ruminantium in both wild and domestic animals suggest a potential risk of spillover to humans. Despite ongoing efforts to combat tick-borne diseases (TBDs), significant gaps remain in understanding the interconnectedness of ticks, animal hosts, and human health across Africa. Strengthening diagnostic capacity, adopting a One Health approach, and enhancing cross-border collaboration particularly in areas with high livestock movement are urgently needed. These measures are vital for improving surveillance, preventing and controlling TBDs, and protecting both public health and economic stability across the continent.

Ticks are blood-feeding ectoparasites recognised for their ability to transmit several infectious pathogens to humans and animals. Tick-borne pathogen (TBP) surveillance generally relies on detecting pathogens in homogenates of entire ticks, including those acquired during blood feeding, which may not be transmitted by the tick. To better understand the pathogen transmission mechanism, it is essential to investigate the dissemination and concentration of TBPs in various tick tissues, which is important for elucidating transmission mechanisms in ticks and determining their vector competence. This, in turn, rests on procedures for isolating saliva, haemolymph, salivary glands, and the midgut of individual ticks in order to examine the location of TBPs within these tissues and fluids. In this study, we describe a protocol for tick tissue collection, including a novel procedure for the collection of haemolymph. The results confirm that Rickettsia africae occurs at higher levels in the haemolymph of Amblyomma gemma, affirming the likely role of this tick species as a competent vector for R. africae. In contrast, Hyalomma dromedarii exhibited high rates of R. africae in the midgut, but the bacterium was absent in the haemolymph. The presence of TBPs in the haemolymph is therefore a valuable indicator of vector competence, and rests on the availability of a method that ensures ease of collection.

BackgroundThe tropical bont tick Amblyomma variegatum, which is widespread in Africa and the Caribbean islands, is of both medical and veterinary importance as the principal vector of intracellular bacterial pathogens Ehrlichia ruminantium, causing heartwater in animals, and Rickettsia africae, causing African tick bite fever (ATBF) in humans. This tick species is highly invasive and has been reported to expand its geographical distribution as well as host range. Rickettsia africae is also recognized as a common endosymbiont in A. variegatum, but its transmission dynamics within this tick population remain poorly understood.MethodologyTo investigate the co-phylogenetic patterns between A. variegatum and R. africae, we sequenced the complete mitogenomes of A. variegatum and performed multi-locus sequence typing (MLST) of six housekeeping genes of R. africae. The resulting sequence data were used to examine the hypothesis that R. africae is predominantly transmitted vertically within A. variegatum populations, which would lead to congruent phylogenies between vector and pathogen.ResultsThere was geographical population sub-structuring in the mitogenomes of A. variegatum. The prevalence of R. africae in the examined ticks was 100%. The tanglegram showed non-strict co-cladogenesis between A. variegatum and R. africae. Furthermore, the Procrustes Application to Cophylogenetic (PACo) analysis and residuals of vector-pathogen associations showed no statistically significant association between A. variegatum and R. africae genotypes.ConclusionsThis study was the first to examine the spread of pathogenic/endosymbiotic bacterium R. africae in the A. variegatum populations using a mitogenomic approach. The results support both vertical and horizontal transmission of R. africae within A. variegatum. These findings also highlight the potential of R. africae to adapt to multiple animal species, which may complicate efforts to control it as a human pathogen.

BackgroundTicks pose a major threat to livestock and human health in sub-Saharan Africa, with climate change and pastoral movements fueling their spread. Few studies have integrated multiple sample types to characterize tick-borne pathogens (TBPs) in cattle in Kenya. This knowledge gap hinders the development of effective surveillance and control strategies, leaving vulnerable populations and their livestock susceptible to these persistent threats.MethodsWe screened 280 bovine blood samples, 589 tick pools, and 284 non-invasive skin swabs from cattle in northern (Marsabit) and southern (Kajiado) Kenya by high-resolution melting analysis and Sanger sequencing of PCR products.ResultsRhipicephalus spp. (47.1%), Hyalomma spp. (30.8%), and Amblyomma spp. (22.1%) were prevalent, with Rhipicephalus evertsi only found in Kajiado and Rhipicephalus camicasi in Marsabit. In blood, Anaplasma spp. (62.9%; A. marginale, A. platys, A. ovis) and Theileria spp. (34.6%; T. velifera, T. mutans) were dominant. Tick pools harbored Coxiella burnetii, Rickettsia africae, Rickettsia aeschlimannii, Anaplasma marginale, Theileria velifera, T. ovis, and Babesia occultans, and for the first time two co-circulating Ehrlichia ruminantium strains (Welgevonden and Kumm2). Notably, C. burnetii and T. ovis were detected only in Marsabit, and T. mutans only in Kajiado. Skin swabs from tick predilection sites (ears, anal region) yielded R. africae, R. aeschlimannii, and T. velifera at low positivity, while nose swabs were negative.ConclusionsDetection of zoonotic pathogens such as C. burnetii and R. africae underscores critical public health risks, and co-infections in cattle reinforce the need for robust, integrated surveillance. Although skin swabs demonstrated limited diagnostic yield, they remain a promising non-invasive sampling approach. These findings highlight the value of targeted acarological research and coordinated control programs under a One Health framework.

Rickettsia spp. are Gram-negative obligate intracellular bacteria, with Rickettsia africae being transmitted by Amblyomma ticks and posing a zoonotic risk. The status of diseases like rickettsiosis is largely unknown in Somalia. Our study investigates rickettsial exposure in livestock across two different regions in the country. A cross-sectional study collected 372 (190 goats, 133 cattle, 49 sheep) serum samples from the Benadir and Lower Shabelle regions of Somalia. Indirect immunofluorescence assays (IFA) were used to detect anti-R. africae and anti-Rickettsia rhipicephali antibodies, with sera diluted in two-fold increments starting at 1:64. Out of 372 samples, 188/372 (50.5 %) (endpoint titer: 64-2048) were seropositive for rickettsial antigens, with R. africae alone detected in 78/372 (21.0 %) and R. rhipicephali alone in 38/372 (10.2 %). Co-reactivity to both rickettsial antigens occurred in 72/372 (19.4 %) of samples. Cattle showed the highest seroreactivity at 90.2 %, mainly for R. africae, followed by sheep at 28.6 %, and goats at 28.4 %. Cattle and sheep were more likely to be seropositive than goats (OR: 24.5 and 1.1, respectively). This study provides the first serological evidence of Rickettsia spp. in ruminants from Somalia. Our findings suggest heightened susceptibility in cattle, posing health risks to humans, especially if cattle are considered sentinels for human exposure to R. africae.

Ticks spread pathogens that affect both human and animal health and often cause significant economic losses to the livestock industry. However, there is limited data on the distribution of ticks and tick-borne pathogens, particularly those affecting cattle in Cameroon. In this study, ticks were collected from cattle in Buea, the capital of the South West Region of Cameroon, to determine their diversity and identify tick-borne pathogens through PCR and sequencing. The tick samples were screened for pathogens using assays that target the rOmpA gene (ompA) of Rickettsia, the ssrRNA gene of Babesia and Theileria and the Ehrlichia genus 16SrRNA gene. A total of 458 ticks were collected with Rhipicephalus annulatus (65.6%) as the predominant species. From 68 tick pools screened, 26 (38.2%) were positive for pathogen/ symbiont DNA. The pathogen identified was Rickettsia africae (22.1%). This study reports the first molecular detection of the symbiont Candidatus Midichloria mitochondrii (22.1%) in the sampled tick species. It was observed that male ticks were significantly more likely to test positive for R. africae (OR = 208, 95% CI = 28.6 - 4553, p&lt;0.001). Animal handlers may face the risk of these zoonotic infections and as such, there is a need to employ protective measures to prevent or reduce pathogen spread.

Ethiopia is home to a diverse group of ixodid ticks that are known to transmit disease to both animals and humans. Recent advances in metagenome sequencing show there is more microorganism diversity found in ticks than previously known. Compared to amplicon-based gene identification methods, agnostic metagenomic sequencing provides broader insights into the diversity of microorganisms in ticks, providing knowledge that will better enable public health measures in preventing the spread of zoonotic disease. In the present study, metagenomic sequencing was used to look at the microbial diversity of ticks collected from livestock in Ethiopia. This study identified six bacterial genera (Coxiella, Francisella, spotted-fever group (SFG) Rickettsia, Spiroplasma, Ehrlichia, and Borrelia), one genus of eukaryotic parasite (Babesia sp.), and one virus species (Parapoxvirus bovinestomatitis) from 154 tick pools representing 22 species of ticks among four genera (Amblyomma, Haemaphysalis, Hyalomma, and Rhipicephalus). We were able to differentiate between pathogenic and nonpathogenic microorganisms, highlighting concerns among traditional gene-targeted screening methods. Among all pooled samples, the predominant microorganisms included Coxiella-like endosymbionts (55.2%), SFG Rickettsia (38.3%), and nonpathogenic Francisella spp. (26.0%). Rickettsia africae was the predominant pathogenic agent detected, and phylogenetic analysis of two samples from A. gemma and A. variegatum confirmed the presence of R. africae. This study highlights the power of metagenomics applied to potential vectors of zoonotic disease, and it expands the knowledge on tick-pathogen associations in Ethiopia.

Abstract African tick bite fever (ATBF) is an emerging rickettsial disease of the spotted fever group increasingly seen in international travellers returning from sub-Saharan Africa. It is caused by Rickettsia africae, an intracellular Gram-negative bacillus, and transmitted by Amblyomma ticks, which feed on cattle and wild game. Risk factors for transmission include safari tourism, game hunting and travel to endemic areas in sub-Saharan Africa and the West Indies. The exact prevalence of seropositive individuals in endemic areas is unknown but may be as high as 80%. The estimated prevalence among travellers is 4.0–8.6%. ATBF is characterized by an acute, influenza-like illness with fever, headache and myalgia. The incubation period is 6–7 days. Typical cutaneous findings include solitary or multiple inoculation eschars with associated regional lymphadenopathy. A generalized vesicular or maculopapular rash can also be seen. It is typically a mild illness; however, rare complications include subacute neuropathy and myocarditis. ATBF is primarily a clinical diagnosis and empirical treatment should not be delayed. In cases of diagnostic uncertainty, detection of rickettsia from serology or tissue can be useful for confirmation. While eschar biopsies have traditionally been used, eschar swab and/or crust samples can also be used for the molecular detection of rickettsia. We present a case of rickettsiosis, likely caused by R. africae, in a man who presented with a 4-day history of fevers, headache and myalgia following recent travel to South Africa for safari. On examination he had a solitary inoculation eschar at his left upper thigh with associated tender left-inguinal lymphadenopathy. He was febrile but otherwise vitally stable. Investigations were notable for raised C-reactive protein and mild lymphopenia. He was commenced on empirical doxycycline and ciprofloxacin to cover for eschar-associated diseases, and a dermatology opinion was sought with a view to performing a diagnostic biopsy. As per specialist advice, eschar swab and crust samples were recommended instead with paired serology. Rickettsiae serology was negative; however, eschar polymerase chain reaction was positive for Rickettsia species. The cycle threshold value was too high for the exact species to be sequenced; however, given the travel history and clinical findings, a presumptive diagnosis of ATBF was made. The patient completed a 14-day course of doxycycline with resolution of symptoms. Our case highlights the value of using noninvasive eschar samples to support the diagnosis of ATBF. It is a simple, quick method that can be performed in a variety of clinical settings compared with traditional eschar biopsy.