Majority of people living in South Africa rural settlements are in close proximity with tick-infested ruminants, hence they are at high risk of being infected with arthropod-borne zoonotic pathogens. Several cases of arthropod-borne diseases are commonly reported, especially in international travellers returning from South Africa, hence it is expedient to be aware of new vectors, host and pathogens [25,26].
Ticks collected in this study belonged to three genera; Rhipicephalus, Amblyomma, and Haemaphysalis were identified, with Rhipicephalus having the highest occurrence of 853 (71.1 %), followed by Amblyomma; 335 (27.9%), and Haemaphysalis; 12 (1%) (Fig 2). The three genera had previously been reported from South Africa [27,28,29], thus our result is a confirmation that these genera are the predominant tick species in the study areas.
Globally, various species of Amblyomma have been reported to be vectors of both animal and human rickettsial pathogens, which have resulted in increased risk of spotted fever group (SFG) rickettsiosis of late [30,31,32]. As a rare acute and multi-systemic febrile disease, spotted fever has been described to have mortality rate of over 50% in the absence of proper prophylaxis . A. hebraeum with a significant aggression for biting humans has been documented as a well-known vector of Rickettsia africae, a zoonotic tick-borne bacterial pathogen that is the etiologic agent of African tick-bite fever in sub-Sahara Africa with a morbidity rate of > 50% [34,35]. Thus, R. africae infection has been described, after malaria, to be liable for most febrile illnesses diagnosed in tourists returning from southern Africa [17,36].
The abundance of Rhipicephalus species in many West African countries has been described to have a magnitude higher than Amblyomma species (Biguezoton et al., 2016), which was formerly known as the main vector of heartwater Ehrlichia ruminantium in the region.
The most predominant tick species in this study was Amblyomma hebraeum and it had been formerly reported to be among the prevalent arthropod-vectors parasitizing different animals in South Africa, especially in the Eastern Cape , followed by Rhipicephalus species . The detection of R. africae genetic material in A. hebraeum and Riphicephalis species in this study is corroborated by the findings of , thus confirming the role of A. hebraeum and Riphicephalis spp. in the epidemiology of spotted fever group Rickettsia.
The findings from the study showed that the domesticated animals lived in close proximity with humans in the study area, apart from being released to graze freely in the vegetation, increase the possibility of zoonosis from infected ticks to humans. Equally, with the increase prevalence of immuno-compromised individual in this region, rickettsioses could probably act as an opportunist infections taking advantage of their medical condition and aggravate their delicate health conditions. South Africa has been considered as destination for many tourists of which many have been diagnosed of rickettsiosis upon returning to their countries; hence the incidence of rickettsioses among travellers from sub-Saharan Africa is approximately 21% .
Furthermore, about nine pathogenic Rickettsia species (R. africae, R. parkeri, R. mongolotimonae, R. conorii, R. honei, R. rickettsii, R. raoultii, R. australis, and R. rhipicephalis) belonging to the spotted fever group Rickettsiae were detected in different tick samples collected in this study. R. africae had been previously reported from ticks removed from different animals and humans in South Africa, thus its detection was expected [35,36,37], from its well-known vector; A. hebraeum. Subsequently, about 24 sequences, from the 74 obtained sequences for ompB gene of Rickettsia sp., showed between 98.9% - 99.3% homology with Rickettsia parkeri (KY124259, CP003341, AF123717, and KY1131111).
Rickettsia africae, a causative agent of African tick-bite fever (ATBF), belonging to Spotted Fever Group (SFG) Rickettsia, has been described as an emerging infectious pathogen in the African continent, affecting both humans and animals with devastating effects on livestock production and human health. Several seroepidemiological studies across the continent have described residence in livestock production areas as the major risk factor for seropositivity in rickettsiosis antigen [38,39]. The risk has been attributed to the abundance of Amblyomma sp. in most African countries , as species of Amblyomma have been implicated as vectors of R. africae infection, hence the increase in percentage of infected ticks could increase the probability of humans being bitten thereby leading to increase rate of human rickettsisosis.
ATBF has also been recovered from American travellers returning from Southern Africa , with a history of tick bite during their visit, as well as from positive human serum samples in western Africa . The detection of R. africae in the present study is supported by the findings of , who reported high detection rate of R. africae from species of Amblyomma ticks collected from domesticated animals. Likewise, , reported the detection of R. africae from A. variegatum in six Caribean Islands based on DNA sequences of ompA gene recovered from ticks.
In addition, the first detection of R. africae, the most widespread spotted fever agent in sub-Saharan Africa, has recently been described in Corsica, France , through PCR, from ticks that were manually removed from cattle , also reported the detection of R. africae from Amblyomma species in Algeria, using gltA and ompA gene amplification by PCR. In the same way,  equally reported a high incidence of R. africae from Amblyomma ticks, which has directly led to the human rickettsiosis among pregnant women, although in low incidence rate.
Similarly, the detection of R. africae by PCR on a skin biopsy of a returning 40-year-old Italian physician from Zimbabwe, who presented with fever and a neurological syndrome characterized by severe pain of the left leg was reported by . The global incidence rate of human rickettsisosis caused by R. africae has been reported to be above 5% among travellers who developed acute febrile infection after their returning from sub-Saharan Africa . The presence of R. africae from A. hebraeum and species of Haemaphysalis and Rhipicephalus has long been established in South Africa , hence South Africa has been described as an endemic region for ATBF.
Rickettsia parkeri, the causative agent of spotted fever rickettsiosis in human, was first discovered to parasitize A. maculatum ticks in the United State in 2004 , with infection in humans having similar clinical symptoms with R. rickettsii. Infection of humans living in the Gulf Coast (a tick endemic region) USA is very high as clinical specimen of twelve patients living in the endemic region that were submitted for laboratory evaluation confirmed six samples positive for R. parkeri, the etiologic agent of spotted fever rickettsiosis .
R. parkeri has also been described as a causative agent of human rickettsiosis in other countries like Argentina , and Brazil  with Amblyommatriste ticks haven been implicated as vectors for this infection . R. parkeri has equally been described as an emerging zoonotic pathogen in Mexico . Similarly,  reported a case of R. parkeri infection from a Spanish traveller returning from Uruguay, who was confirmed bitten previously by Amblyomma triste tick. Infection by this pathogen has also been reported in Canada, hence, it has been described to be the second most important cause of tick-borne rickettsiosis in the United States, Argentina and Brazil, after R. rickettsia [49,53].
Until now, R. parkeri has not been reported to infect humans in African continent; hence this is the first report of its existence in the continent, although from tick sample. However, with the zoonotic potential of R. parkeri which has been described from other continents, it is expedient that the public be aware of its existence and the appropriate authority to expedite action in preventing its outbreak.
Another spotted fever group pathogenic Rickettsia detected in this study was R. mongolotimonae which was first recovered from Hyalomma asiaticum tick from France in 1991  and in 1996, its pathogenicity in humans was first described in a female patient with an atypical tick-transmitted disease, followed by another human case from a 49-year old HIV patient in 1998 . A similar human case was described in Greece from another immune-compromised patient, who reported no contact with animal except working in the field where he was collecting olives. During his hospitalization, an engorged female Hyalomma anatolicum tick was recovered from his scrotum by the physician .
In addition, human cases of R. mongolotimonae have recently been reported in Sri Lanka from a 30-year-old female who returned from travelling to a jungle and was examined as an outpatient for fever  and also in Cameroon, from a 54-year-old woman who presented a clinical symptoms of fever, headache, chills, myalgia and arthralgia . Generally, R. mongolitimonae infection has been described to cause a mild, less fatal disease, nevertheless some complications have been reported, such as disseminated intravascular coagulation, shock, neurological disorders, atrial fibrillation, retinal vasculitis and acute renal failure .
The first human case of R. mongolotimonae, has been reported in South Africa, from a 34-year old patient who developed a severe headache and high fever, after he discovered a lesion on his right foot. This rickettsiosis was linked to a bite from H. truncatum with high endemicity in the region where the patient had been working and is known to parasitize humans . Other Rickettsia species associated with human diseases that have been described in South Africa include R. conorii and R. sibirica which are etiologic agents of African tick bite fever [61,62]. Despite the emergence and re-emergence of various species of Rickettsia with potential zoonosis, rickettsiosis is still considered as a neglected disease .
A study conducted in Kenya by , reported that a partial fragment of ompB gene was found to be the most identical to Rickettsia rhipicephalus with 99.0% homology as against a required homology of 99.2% to qualify it as R. rhipicephalus, thus suggesting the probability of R. rhipicephalus circulating in African continent. Rhipicephalus spp. has been described as the main arthropod vectors for this bacterium in different geographical regions, which could probably be distributed by migratory birds and wild animals. Similarly, human infections with R. conorii have been described in some European countries such as France, Spain, Portugal, and Greece [54,64].  also reported the detection of R. conorii from French athletes, who returned from South Africa and presented with headache, fever, regional lymphadenopathies, and multiple inoculation eschars.
The detection of R. conorii in different Rhipicephalus spp. in the study areas implies a wide range of its host and ecological variation which does have epidemiological consequences. Also, the populace living in proximity with domesticated animals, in the study area is at high risk of rickettsial infections, if bitten by infected ticks, as the presence of genetic materials of the organisms detected in this study indicates probable zoonotic potential, hence systematic study is further required to establish the detection of these pathogens from human samples.
Several studies on ticks have been previously conducted in South Africa, which have shown that varieties of SFG are in circulation in the country [28,66]. Similarly, a recent study conducted by , showed that different species of pathogenic Rickettsia are in circulation in the country.