Cattle ticks and tick-borne infections (TBIs) undermine cattle health and productivity in the whole of sub-Saharan Africa (SSA) including Nigeria. In this West African country, two thirds of the cattle population are reared in the central-northern regions, kept under the traditional pastoral husbandry of Fulani herders. Under the Fulanis’ management, cattle are grazed extensively, being exposed to infestation by several tick genera (i.e. Amblyomma, Hyalomma, and Rhipicephalus spp., sub-genus Boophilus spp. included), vectors of the causative agents of the most important bovine TBIs in West Africa: anaplasmosis, babesiosis and ehrlichiosis (cowdriosis). Nevertheless, the Fulani pastoralists do not usually employ chemicals to control ticks in their cattle, merely relying on traditional methods (i.e. manual removal of the most conspicuous specimens). This approach, however, does not prevent cattle from being re-infested, leaving the animals challenged by a broad variety of other tick species, most of which are vectors of economically relevant TBIs. Knowledge of tick and TBIs occurrence is an essential pre-requisite to assist field diagnosis and devising effective control strategies for a given area. Existing information on tick infestation of cattle in Nigeria is rather out-dated, mostly derived from studies carried out in the south of the country. Similarly, all studies published to date on cattle TBIs in the country do not include any molecular analysis, being based instead on cytological and/or serological diagnostics. Therefore, the aim of the present thesis was to assess the presence of cattle ticks and TBIs occurring in an area of Central Nigeria (i.e. Plateau State). This is a densely populated area with traditionally managed cattle, where no acarides have historically been employed on livestock. The work undertaken herein firstly reviews the information available to date on ticks and TBIs known to be endemic in Nigerian cattle, identifying gaps present in the existing knowledge, leading to the rationale of this study. An initial survey was conducted documenting the tick species infesting cattle in Central Nigeria, in order to assess the infestation rate of surveyed animals at the time of the year when the tick load on the host is known to be most abundant (i.e. the wet season). The survey provided novel information on tick populations in cattle in Nigeria disclosing the presence of a broad variety of species, most of which are vectors of hazardous TBIs. In order to conduct a molecular diagnosis of the TBIs within the study area, a novel methodology was developed (i.e. reverse line blotting, RLB). The application of this approach was based on a thorough review of its application to the diagnosis of TBIs worldwide as well as in SSA. The optimisation of the RLB at the University of Edinburgh to enable the detection of a broad-spectrum of TBIs in Nigeria, caused by an array of five genera of microorganisms (i.e. Ehrlichia and Anaplasma, Theileria and Babesia, Rickettsia spp.) is presented. The assessment of the analytical sensitivity of this technique for the detection of Anaplasma marginale, a highly endemic tick-borne pathogen in SSA, demonstrated a detection threshold of ≥ 7 infected cells (keeping the limit of a natural infection). The occurrence of TBIs in cattle in the study area was assessed during a large-scale epidemiological survey through the application of the validated RLB. This study disclosed the occurrence of a high prevalence of several bovine TBIs in Central Nigeria, some of which are of great veterinary and zoonotic concern. The RLB enabled the detection of carrier status as well as of numerous multiple infections (69.5%, 95% CI: 65.5–73.6%). Based on the findings presented, endemic stability for highly prevalent haemoparasites (i.e. Theileria mutans, Theileria velifera, Theileria taurotragi, Anaplasma marginale, Ehrlichia species Omatjenne) is postulated, whereas a more instable epidemiological scenario is hypothesized for other microorganisms (i.e. Anaplasma centrale and Babesia bovis), which might be connected with outbreaks of clinically apparent disease, sporadically seen in the study area. The effect of a monthly tsetse-borne trypanosomiasis-focused control programme (based on the application 0.005% deltamethrin spray formulation, applied only to the lower quarters of cattle) on the kinetics of bovine TBIs was assessed at the village level. Longitudinal monitoring of control and treated cattle was conducted over the period of eleven months. Results generated provide input to the improvement of future control strategies to be rolled out across SSA, aiming to achieve an integrated control of both trypanosomiasis and TBIs. The present thesis contributes to a better understanding of the epidemiology of bovine TBIs in Nigeria as well as in the rest of West Africa, using a highly sensitive tool of wide applicability. These findings will be shared with the local pastoralist communities to further promote effective yet sustainable, vector control, in tune with the traditional long-established practices.

The spotted fever rickettsia, Rickettsia helvetica, is an endemic tick-borne bacteria in Sweden. It causes infections in humans, manifested as aneruptive fever, headache, arthralgia and myalgia, and sometimes an inoculation eschar or a rash. There have also been two known cases of human infections with R. felis in Sweden. The present thesis starts by investigating dispersal of ticks and Rickettsia spp. by migrating birds flying from Africa to Europe. Almost 15,000 birds were searched and 734 ticks collected, mainly of the species Hyalomma marginatum complex. Almost half (48%) of the ticks were infected with Rickettsia spp., 96% of which was R. aeschlimannii, the remaining R. africae and undefined species. The next study focused on questing ticks over a large area in Sweden and determining the prevalence of Rickettsia spp., Anaplasma spp. and Coxiella burnetii. Rickettsia spp. was found in 9.5-9.6% of the ticks and A. phagocytophilum in 0.7%; no C. burnetii was found. The last three papers in the thesis focused on the clinical presentation of rickettsiosis, the symptoms associated with the infection in general and particularly in patients with neurological complications. A tick-exposed population in Sweden was investigated to gain a better understanding of symptoms due to rickettsioses, also in relation to co-infections with other tick-borne bacteria. Based on symptoms, it was not possible to distinguish what pathogen caused the infections. Most patients had erythema migrans, some had serological reactions to Rickettsia spp., Borrelia spp. or co-infections by Rickettsia spp., Borrelia spp. and/or Anaplasma spp. In the fourth and fifth papers, we found associations between antibodies against Rickettsia spp. and sudden deafness (in 10-24% of patients) and facial nerve paralysis (in 8.3-25% of patients). In three patients R. felis was detected in the cerebrospinal fluids.    Briefly, the thesis helps to clarify our knowledge about tick dispersal, shows a narrower prevalence estimate of Rickettsia spp. in Swedish ticks, and illuminates symptoms of rickettsioses and co-infections with other tick-borne infections. It also shows that presence of erythema migrans may be explained by more than Lyme disease and indicates a possible association between rickettsiosis and sudden deafness and facial nerve paralysis.