Ecology and molecular epidemiology of tick-borne infection in Kachia Grazing Reserve, Nigeria

Adam, BM

Abstract

Ticks and tick-borne infections (TBIs) are serious veterinary and medical concerns in much of sub-Saharan Africa (SSA). Despite their economic importance, information on the epidemiology of these infections in many SSA countries, including Nigeria, is lacking or inadequate, resulting in potentially inappropriate disease control strategies being implemented. Therefore, the aim of this thesis was to investigate the diversity and burden of ticks, and the epidemiology of several TBI-causing pathogens (Anaplasma spp., Ehrlichia spp., Babesia spp. Theileria spp., Rickettsia spp., and Bartonella spp.) in Nigerian livestock. Firstly, the thesis was undertaken by critically reviewing and updating the existent knowledge of the veterinary and medical importance of TBIs, with particular focus on those ticks and pathogens present in SSA. Secondly, two cross-sectional surveys of livestock (cattle, sheep and goats) inhabiting the Kachia Grazing Reserve (KGR) in North Western Nigeria were carried out in which animals were systematically surveyed for TBIs in ticks and blood samples. Thirdly, ticks were identified and TBIs in ticks and livestock blood were detected and identified using molecular methods. Finally, laboratory and field data were collated and analysed using statistical models to quantify the epidemiology of each TBI and clarify epidemiological determinants. A total of 478 domestic ruminants were randomly selected and surveyed for the presence of ticks. 172 ticks were collected and identified of which most of these ticks 137 (80 %) were identified as Ambloymma variegatum, 20 (8.7 %) were Rhipicephalus species and 15 (11.6%) Hyalomma species. The prevalence of tick infestation was significantly higher on goats than either sheep or cattle. Male animals were found to be statistically less infested by ticks than female (p<0.006). In addition, young animals less than (<24 months) were found to be significantly less parasitised than adults animals. Interestingly, ticks were significantly more frequently found on animals with a “good” body condition compared to animals with either a poor or medium body condition. No significant variation in tick infestation rates was observed between KGR blocks. The infection rate of ticks occurred in 20.3% of Theileria/Babesia species (T. ovis, T. velifera and B. caballi), 84% in Rickettsia species (R. africae and R. massilae) and 55.8% for Ehrlichia/Anaplasma species (E. canis, A. platys and Anapalsma spp.).
In cattle, a total of 225/268 (84.0 %) animals were found infected, with 201 (75.0 %) of them being infected by two or more microorganisms, with up to 92 possible combinations of pathogens detected. Theileria mutans and Theileria velifera was the most prevalent microorganism (69.4% and 69.4%) respectively, followed by (52.4 %), Theileria equi-like (56.0 %), Anaplasma marginale (54.9 %), Ehrlichia spp. (Omatjenne) (50.4 %), Theileria spp. MSD4 (36.2 %), Babesia bovis (22.8 %), Babesia bigemina (16.0 %), Anaplasma centrale (7.5 %), Bartonella species (3.4 %), Babesia caballi (3.0 %), Rickettsia species (2.6 %), Anaplasma phagocytophilum (1.9 %), and Ehrlichia ruminantium (1.1 %). The prevalence of infection was greater in older animals than younger animals, but this difference was not statistically significant (χ2 = 3.39, P = 0.065). In sheep, a total of 178/257 (69.3 %) animals were found infected, with 101 (38.2 %) of them being infected by two or more microorganisms, with up to 36 possible combinations of pathogens detected. Theileria equi-like was the most prevalent microorganism (42.4 %), followed by Rickettsia species (19.8 %), Anaplasma centrale (17.5 %), Theileria velifera (12.1 %), Ehrlichia spp. (Omatjenne) (10.1 %), Theileria mutans (8.9 %), Theileria spp. MSD4 (7.0 %), Babesia bovis (2.7 %), Bartonella species (0.8 %), Babesia caballi (0.4 %), Ehrlichia ruminantium (0.4 %) and Typhus group (0.4 %). The prevalence of infection was greater in older animals than younger animals, but this difference was not statistically significant (χ2 = 2.00, P = 0.156). In goats, a total of 50/196 (22.5 %) animals were found infected, with 28 (14.2 %) of them being infected by two or more microorganisms, with up to 14 possible combinations of pathogens detected. Theileria equi-like was the most prevalent microorganism (14.3 %), followed by Anaplasma centrale (13.3 %), Theileria mutans (13.3 %), Theileria velifera (13.3 %), Theileria spp. MSD4 (13.3 %), Anaplasma marginale (6.6 %), Babesia bovis (5.6 %), Rickettsia species (3.1 %), Babesia bigemina (2.0 %), Ehrlichia spp. Omatjenne (1.5 %), Bartonella species (1.0 %) and Babesia caballi (1.0 %). The prevalence of infection was greater in older animals than younger animals, a significant difference was observed (χ2 = 3.89, P = 0.048) In conclusion, the outcome of the present study has contributed to the knowledge on the epidemiology of tick-borne diseases in the country and the information will serve as a data baseline to policymakers in making an informed decision in tick control programmes and surveillance of diseases in the study area and the country at large.

Citation

Adam, B. Ecology and molecular epidemiology of tick-borne infection in Kachia Grazing Reserve, Nigeria. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Nov 12, 2019
• Publicly Available Date: Nov 12, 2019