Rickettsial pathogens are among the emerging and re-emerging vector-borne zoonoses of public health importance. Reports indicate human exposure to Rickettsial pathogens in Namibia through serological surveys, but there is a lack of data on infection rates in tick vectors, hindering the assessment of the relative risk to humans. Our study sought to screen Ixodid ticks collected from livestock for the presence of Rickettsia species in order to determine infection rates in ticks and to determine the Rickettsia species circulating in the country. We collected and pooled Hyalomma and Rhipicephalus ticks from two adjacent regions of Namibia (Khomas and Otjozondjupa) and observed an overall minimum Rickettsia infection rate of 8.6% (26/304), with an estimated overall pooled prevalence of 9.94% (95% CI: 6.5-14.3). There were no statistically significant differences in the estimated pooled prevalence between the two regions or tick genera. Based on the nucleotide sequence similarity and phylogenetic analysis of the outer membrane protein A (n = 9) and citrate synthase (n = 12) genes, BLAST analysis revealed similarity between Rickettsia africae (n = 2) and Rickettsia aeschlimannii (n = 11), with sequence identities ranging from 98.46 to 100%. Our initial study in Namibia indicates that both zoonotic R. africae and R. aeschlimannii are in circulation in the country, with R. aeschlimannii being the predominant species.

Rickettsia africae causes zoonotic African tick bite fever, which is a disease of \"One Health\" importance. There have been reported cases of tourists from Europe and Asia who have been bitten by ticks whilst visiting South Africa\'s nature reserves, and on their return to their countries, the display African Tick Bite Fever sickness. Hence, the aim of this study was to determine the occurrence of Rickettsia africae in Amblyomma hebraeum ticks infesting livestock in the North West Province. A total of 358 A. hebraeum ticks were collected from 60 ruminants (cattle, sheep and goats) in Mafikeng City of North West Province, South Africa. Ticks were identified morphologically and further confirmed by sequencing of their ITS2 gene. DNA was extracted from 60 pools of ticks which consisted of 5-6 adult ticks that were from the same ruminant host. Infections with Rickettsia spp. were found in 48%, 40%, and 32% of cattle, sheep, and goats, respectively, in amplification by PCR using the ompA gene. The ompA gene sequences showed that the Rickettsia spp. were identified as R. africae. Although the animals from whom the ticks were collected did not exhibit any clinical symptoms, it is well recognised that R. africae is a disease with significant zoonotic potential. Thus, it is important to use the \"One Health\" approach to formulate prevention and control measures for this pathogen for animal and human health as well as the tourism sector due to the ecotourism importance of the resultant disease.

Ticks are arthropods of veterinary and medical importance which spread zoonotic pathogens that link animal and human health. In this study, ticks were collected from 448 livestock between February and December 2020 in the Kassena-Nankana Districts of Ghana and screened for the presence of zoonotic pathogens DNA using PCR and sequencing approaches. In total, 1550 ticks were collected and morphologically identified. Three tick genera were identified with Amblyomma variegatum (63%) as the predominant tick species collected. DNA was extracted from 491 tick pools and screened for the presence of DNA of Rickettsia spp. based on the 115 bp fragment of the 17 kDa surface protein and 639 bp of the Outer membrane protein A (ompA) gene and the 295 bp fragment of the transposase gene of Coxiella burnetii IS1111a element. From the 491 pools screened, the DNA of Rickettsia spp. and C. burnetii was detected in 56.8 and 3.7%, respectively. Coinfections were identified in 2.4% of the tick pools. Characterization of the Rickettsia spp. in this study based on the ompA gene showed that the DNA of Rickettsia africae and Rickettsia aeschlimannii accounted for 39.7 and 14.7%, respectively, and were 100% similar to sequences in GenBank. Most R. africae and C. burnetii infections occurred in ticks collected in the wet season, whereas R. aeschlimannii occurred mostly in the dry season. These pathogens are potential public health threats, thus there is a need to implement control measures to reduce the risk of infections in vulnerable populations.

Arthropods, especially ixodid ticks, have been incriminated in the epidemiology of Spotted Fever Group rickettsioses globally leading to an increasing spectrum of emerging and re-emerging zoonoses with attendant consequences on trade and tourism. The objective of this study was to determine the role of ixodid ticks infesting small ruminants in Plateau State, Nigeria, in the epidemiology of Spotted Fever Group Rickettsiae (SFGR) in the study area. DNA from 130 out of 323 ixodid ticks collected from 179 goats and 121 sheep owned by agro-pastoralists in Plateau State were screened for the evidence of SFGR by molecular methods. Six tick species from four genera were identified: Amblyomma, Hyalomma, Rhipicephalus (Boophilus) and Rhipicephalus. Rhipicephalus sanguineus sensu lato (s.l.) was the predominant (54.5%) species among collected ticks. Tick infestation was significantly associated with the species of small ruminants, the sex of the animals and the sampling locations except for Jos South. Conventional PCR targeting the 381 bp of the citrate synthase (gltA) and 820 bp of the outer membrane protein B (ompB) genes detected DNA of SFGR in nine and eight samples, respectively. Sequence analysis revealed that five sequences obtained from Amblyomma variegatum were 99-100% identical to Rickettsia africae and three sequences from Rh. sanguineus (s.l.) were 100% identical to Rickettsia massiliae reported from Spain. To our knowledge, this is the first report of the detection of R. africae DNA in Am. variegatum collected from small ruminants in Plateau State. Ixodid ticks infesting small ruminants in Plateau state harbor DNA of SFGR with potential veterinary and public health implications.

Amblyomma hebraeum is the main vector of Rickettsia africae, the causative agent of African tick bite fever in southern Africa. Because pathogen dispersal is known to be influenced by tick adaptations to climate or host species, this study aimed to analyse the genetic diversity of A. hebraeum and R. africae infection of ticks collected from cattle in the Eastern Cape province of South Africa. DNA was extracted, amplified, and sequenced for the COI and ITS2 markers from A. hebraeum samples and the 17 kDa and ompA genes for rickettsial detection. Between six and ten haplotypes were identified from 40 COI and 31 ITS2 sequences; however, no population structuring was observed among sites (ΦST = 0.22, p < 0.05). All A. hebraeum isolates clustered with southern Africa GenBank isolates. Rickettsia africae was detected in 46.92% (95% CI = 41%-53%, n = 260) of ticks. All R. africae isolates clustered with strain PELE and Chucks, which were reported previously from South Africa. These results confirm that A. hebraeum populations are undergoing a recent population expansion driven by cattle movement, facilitating local and long dispersal events across the Eastern Cape province.

African tick bite fever, an acute febrile illness, is caused by the obligate intracellular bacterium Rickettsia africae. Immune responses to rickettsial infections have so far mainly been investigated in vitro with infected endothelial cells as the main target cells, and in mouse models. Patient studies are rare and little is known about the immunology of human infections. In this study, inflammatory mediators and T cell responses were examined in samples from 13 patients with polymerase chain reaction-confirmed R. africae infections at different time points of illness. The Th1-associated cytokines IFNγ and IL-12 were increased in the acute phase of illness, as were levels of the T cell chemoattractant cytokine CXCL-10. In addition, the anti-inflammatory cytokine IL-10 and also IL-22 were elevated. IL-22 but not IFNγ was increasingly produced by CD4+ and CD8+ T cells during illness. Besides IFNγ, IL-22 appears to play a protective role in rickettsial infections.

African tick bite fever (ATBF) is one of the most important rickettsial infections in international travellers to sub-Saharan Africa. The heterogeneity of Rickettsia africae infection rates among tick vector species has been studied. However, this information has not been systematised to allow for comparative estimates. Quantifying the trends and heterogeneity in R. africae infection rates among the different tick vector species is paramount in understanding the role in transmission to humans. A systematic search was conducted in PubMed, Web of Knowledge, Google Scholar, and SCOPUS from 2005 to 2020. The selection criteria included all studies in sub-Saharan Africa reporting R. africae infection rates in tick adults, nymphs, and larvae. A quality effects model was used in the meta-analysis due to the observed heterogeneity with an assessment of publication bias using funnel plots. The prevalence estimates were conducted by geographic region and tick genus from 32 studies reporting R. africae infection rates in ticks from sub-Saharan Africa. A total of 12,301 ticks comprising of adults (96.19%, n=11, 832), nymphs (3.6%, n=443) and larvae (0.2%, n=26) and 1214 pooled samples were evaluated for R. africae infection. The overall prevalence of R. africae was higher in Amblyomma spp. (48%, 95% CI: 26-70%) compared to Rhipicephalus spp. (1%, 95% CI: 0-5%), Hyalomma spp. (1%, 95% CI: 0-3%) and other tick genera (1%, 95% CI: 0-4%) throughout all regions. The highest prevalence in Amblyomma spp. was recorded in western Africa (53%, 95% CI: 14-90%) and in Rhipicephalus spp. in southern Africa (2%, 95% CI: 0-5%). Cattle were the most frequently sampled hosts across all tick vectors (62.98%, n=5492), followed by goats (19.07%, n= 1663) and sheep (9.1%, n= 793). To our knowledge, this is the first systematic and quantitative analysis of R. africae infection in tick vectors collected from mammalian hosts in sub-Saharan Africa. The results highlight a marked heterogeneity between species in different regions of sub-Saharan Africa and provide initial estimates of infection rates.

Rickettsia africae is a gram-negative bacterium, which causes African tick bite fever (ATBF) in humans. ATBF is a febrile disease mainly affecting travellers to southern Africa. This bacterium is known to be transmitted by Amblyomma hebraeum and Amblyomma variegatum ticks. In southern Africa, the principal vector is A. hebraeum. Febrile disease is a serious issue in the study area. There is a high prevalence of non-malaria illness caused by Rickettsia, so there is a need to have more knowledge on these species. Infection rates and transovarial transmission efficiency of R. africae in A. hebraeum ticks were investigated in a rural area of Mpumalanga province, South Africa. Adult and engorged A. hebraeum female ticks were collected from cattle. Larvae were collected by dragging a cloth at ground level using 100 steps, equivalent to an area of 100 m2. Tick identification was performed according to standard taxonomic keys using a microscope. Engorged ticks were incubated to oviposit and egg masses were collected. DNA was extracted from the ticks, larvae and egg masses, and screened for gltA and ompA genes, using quantitative real-time PCR and conventional PCR, respectively. Positive ompA amplicons were sequenced and phylogenetic analysis showed 99.8-100% identity with R. africae. Infection rates were 13.7 and 12.7% for adults and larvae, respectively. Transovarial transmission of R. africae in A. hebraeum from this study was 85.7%. The results provide a clear indication that people living in the study area and travellers that visit the area are at risk of contracting ATBF.

African tick-bite fever (ATBF), caused by Rickettsia africae, is the main tick-borne rickettsiosis and the second most frequent cause of fever after malaria in travelers returning from sub-Saharan Africa. General descriptions on ATBF were made in the first two decades after recognized as a new infectious entity, and since then, many authors have contributed to the knowledge of the disease by reporting clinical cases in scientific literature. We developed a systematic review that evaluated all available evidence in the literature regarding clinical, epidemiological, and laboratory features of confirmed R. africae rickettsiosis cases. We followed the recommendations made by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guide. A total of 48 scientific publications (108 confirmed cases) were analyzed in order to extract data for developing this review. Overall, our results show that R. africae rickettsiosis is more frequent in males in the age group of 18-64 years, more than 80% of the cases occurred in European travelers, South Africa was the country where most infections were acquired, and almost 40% of cases occurred in clusters. Clinically, more than 80% of the cases had fever and eschar (55% developed multiple eschars), rash was present in less than the half of cases, and lymphangitis was not a common sign (11%). Headache, myalgia and regional lymphadenopathy were predominant nonspecific clinical manifestation (mean of 60%, 49% and 51%, respectively). Our results show that at least 70% of R. africae cases had altered laboratory parameters, most often showing an increase in transaminases and C-reactive protein. Tetracycline-class antibiotics, as monotherapy, were used in most (>90%) of the patients. Overall, only 4% of cases had complications, 12% required hospitalization, and there was a 100% rate of clinical recovery.

A survey study was carried out to identify tick species parasitizing wild lagomorphs in Mediterranean ecosystems in southern Spain and to determine the occurrence of Rickettsia species present in these ticks in this region. A total of 1304 European wild rabbits (Oryctolagus cuniculus) and 58 Iberian hares (Lepus granatensis) were individually examined for the presence of ticks. Ticks were found in 42.9% and 50% of the wild rabbits and hares sampled, respectively. A total of 1122 ticks were collected and five species, including Rhipicephalus pusillus, Hyalomma lusitanicum, Haemaphysalis hispanica, Ixodes ventalloi and Rhipicephalus sanguineus sensu lato (s.l.), were microscopically and molecularly identified at the 16S rRNA gene. This is the first study on Ixodidae parasitizing Iberian hares. The presence of Rickettsia DNA was assessed in 254 tick pools (according to hunting states, lagomorph species, tick species and tick development stage) using PCR assays targeting the rOmpA, rOmpB and gltA. Twenty-seven pools (10.6%) were positive to Rickettsia DNA. Five zoonotic Rickettsia species were identified, being Rickettsia massiliae the most frequent (4.7%), followed by Rickettsia sibirica subsp. mongolitimonae (2.8%), Rickettsia slovaca (2.0%), Rickettsia aeschlimannii (0.8%) and Rickettsia africae (0.4%). The results suggest that wild rabbits and Iberian hares are parasitized by a wide range of tick species and that these lagomorphs may play an important role in the sylvatic cycle of some zoonotic Rickettsia species in Mediterranean ecosystems. Our data represent the first report of R. massiliae, R. aeschlimannii, R. slovaca and R africae in ticks collected in wild lagomorphs in Europe, and the first report of not imported R. africae in this continent. Since R. slovaca and R. africae DNA was detected in tick species different to their main vectors, further studies are warranted to unravel the role of wild lagomorphs in the epidemiology of these vector-borne pathogens.