Molecular detection of zoonotic tick-borne pathogens in livestock in different provinces of South Africa
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Date
2012-12
Authors
Mtshali, Khethiwe
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State (Qwaqwa Campus)
Abstract
Ticks and tick-borne diseases are a burden in the livestock industry, decreasing productivity and compromising food security, leading to high socioeconomic impacts on agro-exporting nations. Apart from being agricultural pests they can transmit pathogens of zoonotic significance. The aim of the study was to therefore detect and determine with PCR the prevalence of tick-borne zoonotic pathogens i.e. Coxiella burnetii, Ehrlichia spp., Rickettsia spp., Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato from ticks collected from livestock. The sampling areas included both commercial and communal farms as well as domestic animals from KwaZulu-Natal, Free State, Eastern Cape, North West and Mpumalanga Provinces. As a result a total of 1947 tick samples were collected which were then identified and further processed for PCR amplification. Tick species collected included Rhipicephalus spp. (n = 570), R. sanguineus (n = 275), R. evertsi evertsi (n = 650), R. decoloratus (n = 228), R. appendiculatus (n = 10), Amblyomma hebraeum (n = 171), Hyalomma marginatum rufipes (n = 4), and Haemaphysalis elliptica (n = 38). The overall prevalence of infection with B. burgdorferi and A. phagocytophilum was 8±1.4% and 9±1.2% respectively, this was an unexpected finding since only one positive PCR confirmation of A. phagocytophilum has been reported in the country, since then no other studies have been successful in detecting this pathogen. There have been anecdotal cases of B. burgdorferi but the pathogen has, to the best my knowledge, not been detected and characterized by molecular methods. Both pathogens have not been isolated from ticks in South Africa previously. The tick vectors for these pathogens are not known to occur in the country, however this study managed to isolate A. phagocytophilum from R. sanguineus, R. appendiculatus, R. evertsi evertsi and H. elliptica and isolated B. burgdorferi from Rhipicephalus spp., R. evertsi evertsi, R. decoloratus and A. hebraeum which may act as main vectors and reservoir for livestock infections. I am however uncertain about their transmissibility neither to human hosts nor of their vectorial capacity, nevertheless tick species of Amblyomma readily bite humans and may be able to transmit both pathogens and could therefore pose a serious threat to the public. C. burnetii incidence was 16±1.6% amongst the ticks, this was also a first detection from ticks in the country but the findings seem to be consistent with previous serological studies, also all the tick species in the collection were found harboring the pathogen. The prevalence of E. ruminantium, E. canis and Ehrlichia/Anaplasma was determined to be 29±2.2%, 20±3.6% and 18±3.8% respectively. No significant Ehrlichia/Anaplasma species were characterized except for A. phagocytophilum as reported above. Rickettsia species that were isolated and characterized in the current study were R. africae and R. conorii as expected and the prevalence was 26±1.7%. All in all the target pathogens were successfully isolated, characterized and validated through sequencing reactions, however there still remains a task of determining the vectorial capacity of the ticks and evaluation of factors that could lead to their transmission to the public. In conclusion, these pathogens should be considered as part of routine screening in patients presenting with fevers of unknown origin especially amongst tourists where pathogens like Rickettsia seem to have become problematic in South Africa.
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Keywords
Thesis (M.Sc. (Zoology and Entomology))-- University of the Free State (Qwaqwa Campus), 2012, Ticks as carriers of disease, Tick-borne diseases, Tick-borne diseases in animals, Polymerase chain reaction