In vitro studies on the anti-tick properties of selected plant species against veterinary and economically important ticks in South Africa

The study examined the anti-tick properties of the extracts of Aloe ferox, Leonotis leonurus and Thymus vulgaris against Amblyomma hebraeum and Rhipicephalus appendiculatus. The extensive literature review as captured in chapters 2 to 4 of this study provides a critical outlook on the current understanding of the structural and behavioural features of ticks which enhance their parasitic way of life and their competence as vectors of various disease causing agents. In addition, the current tick control methods were explored with the specific intent to highlight their strengths and shortfalls. The literature review reveals that the current tick control methods are at the most partially effective since tick infestations on livestock and other animals continue to cause enormous economic losses particularly in developing countries. In this study, the acetone, ethanol and methanol extracts of A. ferox, L. leonurus and T. vulgaris were tested for anti-tick properties using modified versions of the in vitro petri dish and tick climbing bioassays to determine their repellency against adults of Am. hebraeum and Rh. appendiculatus ticks. In vitro models offer a viable alternative to the use of animal models. Results from the choice chamber bioassay used in this study show that the most repellent extracts against both tick species included 20% acetone extract of A. ferox (percentage repellency: 56.10%), 10% ethanol extract of L. leonurus (percentage repellency: 85.58%) and 10% acetone extract of T. vulgaris (percentage repellency: 99.59%). Results obtained using the tick climbing bioassay affirmed the observations from the choice chamber bioassay against Rh. appendiculatus. In particular data obtained from this study positions acetone extracts (EC50 = 2.49%), ethanol (EC50 = 21.47%) and methanol (EC50 = 0.89%) of T. vulgaris and ethanol extract (EC50 = 7.33%) and methanol extract (EC50 = 4.83%) of L. leonurus as potential repellent candidates against Am. hebraeum and Rh. appendiculatus ticks and should be further explored as repellents during in vivo studies. The GC-MS analysis conducted in this study revealed that A. ferox extracts had the lowest number of compounds (22) known to have anti-arthropod properties compared to extracts of L. leonurus (30) and T. vulgaris (39) suggesting that it is the number of these compounds in an extract that contributes towards the repellent strength compared to the amount of each individual compound.

Die studie het die teen-bosluis eienskappe van die ekstrakte van Aloe ferox, Leonotis leonurus en Thymus vulgaris teen Amblyomma hebraeum en Rhipicephalus appendiculatus ondersoek. Die omvattended literatuuroorsig, soos beskryf in hoofstukke 2 tot 4 van die studie, verskaf ‘n kritiese oorsig oor die huidige begrip van die strukturêle asook die gedrags kenmerke van bosluise wat hul parasitiese leefwyse en hul vermoë om as vektore van verskeie organismes verantwoordelik vir siektes op te tree moontlik maak. Daarbenewens is die huidige bosluis-beheer metodes ondersoek met die spesifieke voorneme om hul sterkpunte en tekortkominge te identfiseer. Die literatuuroorsig het getoon dat die huidige bosluis-beheer metodes slegs gedeeltelik effektief is aangesien bosluis infestasies van vee en ander diere steeds bydra tot enorme ekonomiese verliese veral in ontwikkelende lande. In die studie was die asetoon, etanol en metanol ekstrakte van A. ferox, L. leonurus en T. vulgaris getoets om hul teen-bosluis eienskappe te bepaal deur gebruik te maak van gewysigde weergawes van die in vitro petri bakkie en bosluis-uitklim essaiërings deur hul afwering van volwasse Am. hebraeum en Rh. appendiculatus bosluise te toets. In vitro modelle verskaf doeltreffende alternatiewe teenoor die gebruik van diere modelle. Resultate van die keuse-afdeling petri bakkie essaiëring gebruik tydens die studie het getoon dat die mees afwerende ekstrakte teen beide spesies die 20% asetoon ekstrak van A. ferox (persentasie afwering: 56.10%), 10% etanol ekstrak van L. leonurus (persentasie afwering: 85.58%) en 10% asetoon ekstrak van T. vulgaris (persentasie afwering: 99.59%) ingesluit het. Restulte verkry deur die bosluis-uitlim essaiëring het die waarnemings tydents die keuse-afdeling petri bakkie essaiëring teen Rh. appendiculatus bevestig. Die data verkry uit die studie dui op die asetoon ekstrakte (EC50 = 2.49%), etanol ekstrakte (EC50 = 21.47%) en metanol ekstrakte (EC50 = 0.89%) van T. vulgaris en etanol ektrakte (EC50 = 7.33%) en metanol ekstrakte (EC50 = 4.83%) van L. leonurus as moontlike afwerende kandidate teen Am. hebraeum en Rh. appendiculatus bosluise en moet verder ondersoek word as afweerders deur in vivo studies. Die GC-MS analise gedoen tydens die studie het getoon dat A. ferox ekstrakte die laagste aantal samestellings (22) geassosieër met teen-geleedpottige eienskappe het invergeleke met die ekstrakte van L. leonurus (30) en T. vulgaris (39) wat voorstel dat die aantal samestellings in ‘n ekstrak bydra tot die afweringsterkte invergelyking met die hoeveelheid van individuele samestellings.

Thuto e, e sekasikile boleng ba dithlotlhoa tsa kgopa (Aloe ferox), motekwane wa naga (Leonotis leonurus) le setlhatshana sa Thime (Thymus vulgaris) kgatlhanong le kgofa ya mohuta wa mebala (Amblyomma hebraeum) le kgofa e tshetlha ya tsebe (Rhipicephalus appendiculatus). Puiso e e tseneletseng ya dikwalo jaaka e supilwe mo kararolong ya bobedi go fitlha ya bone, e neela tshupo e e sekasikilweng mabapi le leago le mekgwa ya dikgofa e e tiisang mokgwa wa go ba setshedi se se tshelang ka tse dingwe (parasite) le bokgoni jwa sona go fitisa ditwatsi. Mo tlaleletsong, tsela tsa ga jaana tsa go laola dikgofa di sekasikilwe ka maikemisetso a go supa bokgoni le makowa a tsona. Tshekatseko ya dikwalo e supa go re tsela tsa ga jaana tsa go laola dikgofa ga di na bokgoni jo be feleletseng ke ka tsela eo dikgofa di tsweletseng go dira go re go nne le ditatlhegelo tsa ikonomi se golobogolo mafatsheng a a ntseng a gola. Mo thutong e, ditlhothloa tsa asetone, ethanole le methanole tsa kgopa (A. ferox), motekwana wa naga (L. leonurus) le setlhatsana sa Thime (T. vulgaris) di sekasekilwe go batlisisa fa di nale boleng kgatlhanong le dikgofa. Mo tshekatshekong e, go dirisitswe mananeo a a fetotsweng a a akaretsang tiriso ya sekotlojana le mokgwa wa go pagama go netefatsa ga ditlhotlhoa tse di na le boleng ba go koba dikgofa (A. hebraeum le R. appendiculatus). Mekgwa ya dipatlisiso e e sa diriseng diphologolo, ke tsela e e farologaneng ya go dira dipatlisiso. Dipoelo tsa tiriso ya mokgwa wa sekotlojana e e dirisitsweng mo thutong e, e supa go re dithlotlhoa tse di neng di le matla kgatlhanong le dikgofa di akaretsa tsa 20% asetone ya kgopa (A. ferox) (di thibela ka diperesente tse 56.10), 10% ethanole ya motekwane wa naga (L leonurus) (e thibela ka diperesente tse 85.58) le 10% acetone ya setlhatshana sa Thime (T. vulgaris) (e thibela ka diperesente di le 99.59). Dipoelo tse di fitlheletsweng fa go dirisiwa lenaneo la go pagama, di tiisa tse di bonweng ka mokgwa wa se kotlojana mabapi le Rh. appendiculatus. Ka go nepagala, dipoelo tse di fitlhetsweng, di supa ditlhotlhoa tsa asetone (EC50 = 2.49%), enthanole (EC50 = 21.47%) le methanole (EC50 =0.89%) tsa T. vulgaris le tsa ethanole (EC50 = 7.33%) le methanole (EC50 = 4.83%) tsa L. leonurus e le tse di na leng boleng ba go thibela dikgofa tsa Am hebraeum le Rh appendiculatus, ka jalo di ka sekasekiwa go diriswa mo diphologolong. Dipatlisiso ka GC-MS mo thuton e, di supa go re ditlhotlhoa tsa kgopa (A. ferox) di ne di na le palo e e ko tlase (22) go farologana le 30 ya motekwane wa naga (L. leonurus) le 39 ya setlhatshana sa Thime (T. vulguris). Se, se tshitshinya go re ke nomore ya dikompone e e natlafatsang ditlhothloa kgatlhanong le dikgofa go na le bontsi ba dikompone.

Ph. D. (Life Sciences)

Life and Consumer Sciences