Theileriosis is a lymphoproliferative tick-borne disease of cattle and other wild ruminants, caused by infection with a protozoan, Theileria parva. The disease is prevalent in cattle throughout Central, East and southern Africa, where it threatens 50% of the cattle population. There are various control and treatments methods used against theileriosis; however, they all have limitations. The available live immunisation method, the Muguga cocktail, does not confer protection against all field strains, particularly buffalo-derived T. parva. Attempts to develop a subunit vaccine have been promising but these have shown limited efficacy due to antigenic and genetic diversity of T. parva strains in the field. Thus, there is a need to search for additional vaccine candidates. A related study has identified potential vaccine candidates using a genome-wide in silico approach. Consequently, the aim of this study was to genotype one of the identified antigens. TP04_0028 was selected for genotyping among candidate genes with high expression levels in the schizont stage of both cattle- and buffalo-derived T. parva isolates. Specific primers were designed and optimised for PCR amplification and sequencing. The comprehensive analysis of sequences from 17 cattle- and 17 buffalo-derived T. parva, from East and southern Africa, showed conservation in 12 (60%) of the 20 TP04_0028 predicted epitopes, in both parasite types, irrespective of geographical origin. Eighteen of the 20 predicted epitopes are conserved amongst different BoLA alleles and an area of 7 overlapping epitopes could be the starting point for initial experimental evaluation of the immunogenic properties of TP04_0028. Once the immunogenicity of these epitopes have been tested and the extent to provide protection from cattle- and buffalo-derived infections have been verified, they may be considered for vaccine development. / Dissertation (MSc (Tropical Animal Health))--University of Pretoria, 2019. / Veterinary Tropical Diseases / MSc (Tropical Animal Health) / Unrestricted

Theileriosis is a lymphoproliferative tick-borne disease of cattle and other wild ruminants, caused by infection with a protozoan, Theileria parva. The disease is prevalent in cattle throughout Central, East and southern Africa, where it threatens 50% of the cattle population. There are various control and treatments methods used against theileriosis; however, they all have limitations. The available live immunisation method, the Muguga cocktail, does not confer protection against all field strains, particularly buffalo-derived T. parva. Attempts to develop a subunit vaccine have been promising but these have shown limited efficacy due to antigenic and genetic diversity of T. parva strains in the field. Thus, there is a need to search for additional vaccine candidates. A related study has identified potential vaccine candidates using a genome-wide in silico approach. Consequently, the aim of this study was to genotype one of the identified antigens. TP04_0028 was selected for genotyping among candidate genes with high expression levels in the schizont stage of both cattle- and buffalo-derived T. parva isolates. Specific primers were designed and optimised for PCR amplification and sequencing. The comprehensive analysis of sequences from 17 cattle- and 17 buffalo-derived T. parva, from East and southern Africa, showed conservation in 12 (60%) of the 20 TP04_0028 predicted epitopes, in both parasite types, irrespective of geographical origin. Eighteen of the 20 predicted epitopes are conserved amongst different BoLA alleles and an area of 7 overlapping epitopes could be the starting point for initial experimental evaluation of the immunogenic properties of TP04_0028. Once the immunogenicity of these epitopes have been tested and the extent to provide protection from cattle- and buffalo-derived infections have been verified, they may be considered for vaccine development. / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2019. / Veterinary Tropical Diseases / MSc (Veterinary Science) / Unrestricted

Heartwater, caused by Ehrlichia ruminantium, causes significant economic losses to commercial small stock farmers, including commercial boer goat farmers in the Limpopo Province of South Africa. Heartwater is endemic in this region where Amblyomma hebraeum, the South African bont tick and the vector for this disease occurs. Due to their long mouthparts and specific attachment sites on goats, A. hebraeum is also associated with wounds, secondary abscess formation and lameness. Small stock farmers in the Limpopo Province employ various methods to control A. hebraeum and the negative effects associated with this tick, including heartwater. Two approaches where followed to focus on the control of A. hebraeum on the one hand and the detection and cryo-preservation of E. ruminantium from A. hebraeum on the other hand. The aim of this study was therefore twofold. By firstly determining the efficacy of a 1.0% fipronil pour-on solution against A. hebraeum by performing a therapeutic- and persistent efficacy trial and secondly to detect and cryo-preserve E. ruminantium from A. hebraeum ticks from a heartwater endemic region in the Limpopo province of South Africa. It was demonstrated that a 1.0% fipronil pour-on solution is 100% effective and has a persistent efficacy of seven days against A. hebraeum, but only if a targeted treatment approach is followed whereby the pour-on solution is applied to the predilection sites of A. hebraeum. A 1.0% fipronil pour-on solution can therefore be used by boer goat farmers to control A. hebraeum and the negative effects associated with this tick. In order to detect and cryo-preserve E. ruminantium from A. hebraeum ticks, ground-up-tick-supernatant samples were prepared in the laboratory from A. hebraeum ticks collected from goats and cattle at specified time intervals. To determine whether E. ruminantium was present in A. hebraeum ticks, DNA extraction, nested PCR of the pCS20 region of the E. ruminantium genome and demonstration of the amplified DNA by agarose gel electrophoresis was performed. The results demonstrated that E. ruminantium was indeed present in eight out of eight ground-up-tick-supernatant samples that were cryo-preserved. In future research, these samples may become very useful for isolating current strains of heartwater, which will ultimately lead to a better understanding of the disease and to facilitate the implementation of novel control methods. / Dissertation (MSc)--University of Pretoria, 2018. / Veterinary Tropical Diseases / MSc (Tropical Animal Health) / Unrestricted

Foot-and-Mouth Disease (FMD) is a disease of cloven-hoofed animals well-known not only for significant production losses but also restricted market access for livestock and livestock products from affected areas. It severely limits market opportunities for poor farmers and nations wishing to access more lucrative markets, both regionally and internationally. In the Northern Communal Area (NCA) of Namibia, FMD has not been detected in Kunene, Omusati, Oshana, Oshikoto and Ohangwena regions for the past 45 years or more, while outbreaks occurred in Eastern Kavango towards the end of 2008 as well as beginning of 2009 and there have been frequent outbreaks in the Zambezi region. Although, FMD has not been detected in five of the six regions of the Namibian NCA, no studies have been carried out to substantiate the FMD status in this highly potential livestock production area as required by the World Organisation for Animal Health (OIE). It is based on this fact that a study was carried out in the above mentioned regions to determine whether there is Foot-and-Mouth Disease Virus (FMDV) circulating in the cattle population of the NCA Namibia. A set of 4214 serum samples were taken from non-vaccinated animals against FMD in Area A, which included Kunene north, Omusati south, Oshikoto(NCA) and Oshana. Meanwhile, 5228 serum samples were taken from Area B, which consisted of Omusati north, Ohangwena and Kavango region where cattle had been vaccinated against FMD for the past 15 years or more. Samples were primarily screened for FMDV using the Ceditest® NSP ELISA and positive samples were subsequently tested with the Viral Neutralization Test (VNT). Herds containing animals that were positive on both tests were followed up and retested with the Ceditest® NSP ELISA and examined clinically for FMD signs. The initial results of the Ceditest® NSP ELISA in Area A and B revealed an apparent prevalence of 0.24% and 0.27% with corresponding 95% confidence intervals between 0.13, 0.44 and 0.16, 0.45 respectively. The follow up results found no clinical evidence of FMD and all subsequent Ceditest® NSP ELISA results were negative. The results indicate that the initial Ceditest® NSP ELISA positive cattle were false positive. Thus the overall outcome indicates that there is little chance of FMD virus circulation in the NCA Namibia. The survey also highlighted the need for taking into account sociological and cultural practices when designing a survey of communal cattle in order to get a representative sample of the cattle population. The study also recommended that Directorates of Veterinary Services (DVS) Namibia should maintain and continuously review FMD surveillance activities in the NCA, especially along the Angola – Namibia border and continuously harmonise these activities with Angolan counterparts. A more comprehensive study should be carried out to address the insufficient knowledge on sociological factors, which may influence sampling strategies in communal farming areas. / Dissertation (MSc)--University of Pretoria, 2015. / tm2015 / ab2016 / Production Animal Studies / MSc / Unrestricted

Protein is a fundamental part of nutrition in all animals but ruminants have the ability to metabolise and utilise non-protein nitrogen for this use. This allows for an economical alternative source of protein that does not compete with human resources. Previous evidence suggests that feeding high levels of protein to support increased demands for growth and production may have a negative impact on reproduction, since protein is rapidly converted to ammonia and further metabolised to urea which are both toxic to the reproductive system. Investigations within the South African climate indicated that the Nguni cow maintained higher blood urea nitrogen (BUN) levels during periods of drought than other cattle breeds. The Nguni breed is well adapted to extreme situations but as its popularity grows and the breed is promoted for emerging farmers it becomes essential to know if it possesses adaptations which could predispose it to reproductive failure if supplemented in the same manner as other commercial breeds. In this prospective experimental study, 22 multiparous cows of two breeds, the Hereford and the Nguni, were block randomised into a cross over design whereby all animals were fed a total mixed ration (TMR). The test group was provided with an increasing rumen degradable protein content in the form of feed grade urea. The control group was maintained on a urea free TMR. In the test group, the urea inclusion rate was increased weekly by 50 g to allow for rumen microflora adaptation and prevent acute urea toxicity. They reached a maximum inclusion rate of 200 g urea per cow per day. All animals had serum collected and oocytes aspirated by transvaginal ultrasound guided oocyte pick up (OPU) were counted and graded twice weekly. Following this, all usable oocytes were pooled per breed and treatment, and were subject to in vitro maturation, fertilisation and culture in order to assess the effect of elevated protein on oocyte competence and viability. Oocyte quality was defined as the number of oocytes with cumulus cells (Grade 1 3 oocytes) harvested per OPU, and oocyte viability was defined as the number of oocytes that cleaved by day 2 or that reached at least the morula stage by day 7 in the in vitro embryo system. Multivariable analyses were performed on BUN, antral follicle count (AFC) and number of grade 1 3 oocytes harvested per OPU session, and on the oocyte viability outcomes in the vitro embryo system. Nguni cows receiving 150 g dietary urea per day had lower mean BUN levels than Herefords (17.5 and 19.3 mg/dL respectively, P = 0.02). However dietary urea inclusion level, serum albumin level and sampling day were the only independent predictors of serum BUN. Nguni cows had lower mean antral follicle count (AFC) and number of oocytes harvested than Herefords (9.1 and 3.1, and 11.7 and 4.3 respectively, P < 0.01). The vet performing the aspiration, within day sampling order and BUN level >20 mg/dL were independently associated with the number of grade 1-3 oocytes after adjusting for AFC and the random effect of the individual animal. Increasing weighted mean serum albumin and decreasing weighted mean beta-hydroxybutyric acid (BHBA) were independently associated with the number of oocytes that cleaved (day 2) or that reached the morula stage (day 7) (P = 0.01 and P = 0.08 respectively). It was concluded that increasing dietary urea, low BCS and increasing serum albumin, but not breed, were associated with increasing BUN levels in cows. It was further concluded that BUN >20 mg/dL adversely affected the occurrence of cumulus cells around oocytes and that serum albumin and BHBA were, but neither dietary urea level nor breed was independently associated with viability of bovine oocytes in this study. Although the data were inconclusive about breed differences in protein metabolism, this study suggests that serum albumin has the potential to be used as predictor of the interaction between protein and energy metabolism and its effect on oocyte development. / Dissertation (MMedVet)--University of Pretoria, 2015. / tm2016 / Production Animal Studies / MMedVet

Since 1982 farmers and veterinarians mainly from the North West province of South Africa noticed an increase in cattle with associated lameness and osteopathy of unknown aetiology. Affected cattle presented with varying degrees of lameness as well as peri-articular swelling especially of the stifle joint. Cattle of all ages, particularly those between the ages of 6 - 18 months developed lesions. Lesions were also noticed among different breeds, production stages and different farming enterprises (commercial and stud farming). The only common factor among the affected cattle was the environment in which they were farmed. Culling of affected animals, especially calves, reduced the number of replacement stock to a level where some farmers were not able to produce sufficient replacement stock, consequently suffering tremendous financial losses. Investigation into the aetiology of the new sporadic osteopathy was deemed necessary. Initially it was suspected that the condition was due to mineral deficiency, as affected cattle fed a supplement containing high levels of micro- and macro minerals responded positively within three weeks during a pre-trial. The study was conducted to determine the level of micro- and macro minerals required to be included in a supplement that would improve the clinical condition of cattle clinically affected by osteochondrosis. Results indicated no significant difference between supplemetary treatments. A comparison between the pre-trial and the current supplements indicated that the supplements in the present study had negative dietary cation anion difference (DCAD) values. Since negative DCAD compositions may result in mild metabolic acidosis, as supported by literature, and the acidic urine collected in a small sample of the test cattle, the hypothesis is advanced that it is unlikely that supplementation, regardless of its mineral concentration will improve the condition of the cattle if the DCAD value of the supplement is strongly negative. The hypothesis should be tested in forthcoming research and the following should be determined: (1) the specific effect a supplement with a negative DCAD value has when fed to cattle with clinical osteochondrosis, and (2) the optimal DCAD value of a supplement that would aid in limiting the severity of osteochondrosis in cattle. / Dissertation (MSc)--University of Pretoria, 2016. / Paraclinical Sciences / MSc / Unrestricted

Farmers in developing countries are faced with many diseases that limit the productivity of their animals, several of which are caused by tick infestations. To date, treatment of host animals with synthetic, chemical tick repellents and acaricides remains the method used to reduce the influence of the parasites on animal and human health. Awareness of the environmental health hazards posed by these acaricides, development of tick resistance leading to recurrent ectoparasitism, danger of misuse and presence of toxic residues in food, water and animal by-products has led to the search for safe and environmentally-friendly alternatives, one of which is the use of medicinal plants. Because there appears to be a need and to contribute to research in this field, extensive literature surveys of published scientific articles were conducted. The following aspects were addressed: the role of ticks in animal health, problems encountered in using synthetic, chemical acaricides, medicinal plants with in vitro acaricidal or tick repellent activities against immature and adult stages of ticks and bioassays employed. Veterinary databases (All Databases, CAB Abstracts and Global Health, Medline, Pubmed, Web of Science, BIOSIS Citation Index, Science Direct, Current Content Connect and Google Scholar) were searched. The search words included “acaricidal”, “tick repellent”, “medicinal plants”, “isolated compounds” and “antitick assays”. Meta-analysis was conducted using the Fixed-effect model in an Excel programme to compare the results. The tick climbing repellency and adult immersion tests were the most commonly used assays to test for repellency and acaricidal activity respectively. Ethanol was the most commonly used extractant and Rhipicephalus (Boophilus) microplus was the most commonly studied tick across all the reviewed papers. More than 200 plant species from several countries globally have tick repellent or acaricidal properties discovered using in vitro assays. A large proportion of the published work was done in tropical countries such as Brazil, India and South Africa where ticks cause major problems. The median efficiency values for acaricidal, larvicidal, egg hatching inhibition, inhibition of oviposition, repellency, acaricidal effects of the Lamiaceae and Asteraceae family using a total of 1428, 1924, 574, 281 and 68 events were 80.12 (CI95%: 79.20 - 81.04), 86.05 (CI95%: 85.13 - 86.97), 83.39 (CI95%: 82.47 - 84.31), 53.01 (CI95%: 52.08 - 53.93), 92.00 (CI95%: 91.08 - 92.93), 80.79 (CI95%: 79.87 - 81.71) and 48.34% (CI95%: 47.42 - 49.26) respectively. Extracts of some species including Azadirachta indica, Gynandropsis gynandra, Lavandula angustifolia, Pelargonium roseum and Cymbopogon species have good acaricidal and larvicidal activities with 90-100% efficacy, comparable to those of currently used acaricides, although, usually at higher dosages. Compounds with acaricidal activity such as azadirachtin, carvacrol, linalool, geraniol and citronellal were listed. As a country, South Africa is rich in vascular plant flora, possessing over 10% of the world’s vascular floral species. Only a fraction of its plants have been rigorously studied and analyzed for their biological activity against ticks and seventeen plant species based on their ethnoveterinary use in tick control were selected for this study. The plants are Aloe rupestris Baker, Antizoma angustifolia (Burch.) Miers ex Harv., Calpurnia aurea subsp. aurea (Aiton) Benth., Cissus quadrangularis L., Clematis brachiata Thunb., Cleome gynandra L., Ficus sycomorus L., Gnidia deserticola Gilg., Hypoxis rigidula Baker var. rigidula, Maerua angolensis DC., Monsonia angustifolia E. Mey. ex A.Rich., Pelargonium luridum (Andrews) Sweet, Ptaeroxylon obliquum (Thunb.) Radlk, Schkuhria pinnata (Lam.) Kuntze ex Thell., Sclerocarya birrea (A.Rich.) Hochst., Senna italica subsp. arachoides (Burch.) Lock. and Tabernaemontana elegans Stapf. Crude extracts of the above mentioned plants were prepared using four different solvents (acetone, ethanol, ethanol/water and hot water). The extracts at a concentration of 200 mg/ml were screened for their acaricidal efficacy against adult Rhipicephalus turanicus ticks using the contact assay. The plant species with the highest acaricidal efficacies for their acetone and ethanol extracts were C. aurea, S. pinnata and S. italica with mortality of 97, 93, 90% and 93, 93, 87% respectively. The ethanol/water and hot water extracts of many of the plants had low acaricidal activities (<60%). An acaricidal dose-response bioassay of two-fold graded decreasing concentrations (100 to 3 mg/ml) of the acetone and ethanol extracts of S. pinnata, C. aurea and S. italica was determined using the adult immersion tests. The LC50 values for the acetone extracts were 35.75, 111.24 and 42.05 mg/ml respectively and for the ethanol extracts were 37.07, 98.69 and 37.50 mg/ml respectively compared with the positive control (cypermethrin) with LC50 of 2.41 mg/ml. In order to evaluate the potential safety of these plants, cytotoxicity against Vero and HepG2 cells was determined. Most of the plant extracts were non-cytotoxic to the two cell lines (LC50>100 μg/ml) and there was a statistically significant higher toxicity to HepG2 cells compared with Vero cells. The ethanol/water and hot water extracts of most of the plants were less toxic to the cells (LC50>1000 μg/ml) compared with their acetone and ethanol extracts. The selectivity indices of S. pinnata, C. aurea and S. italica were low. Particularly good acaricidal activities were displayed by C. aurea subsp. aurea extracted using four different solvents on R. turanicus ticks. The plant extract also had lower cytotoxicity against the cell lines tested and was selected as the most promising plant species, based on its efficacy and potential safety for further studies. / Thesis (PhD)--University of Pretoria, 2017. / Paraclinical Sciences / PhD / Unrestricted

The aim of this study was to investigate if a vaccine can be developed against epoxyscillirosidine, to prevent yellow tulp poisoning in livestock. Moraea pallida Bak. (yellow tulp) poisoning is the most important cardiac glycoside toxicosis in ruminants in South Africa. Cardiac glycoside poisonings collectively account for about 33 and 10% mortalities due to plants, in large and small ruminants, respectively. The toxic principle contained by yellow tulp 1α, 2α-epoxyscillirosidine, is a bufadienolide. Epoxyscillirosidine, proscillaridin and bufalin, were conjugated to [hen ovalbumin (OVA), bovine serum albumin (BSA) and keyhole limpet haemocyanin (KLH)]. Adult male New Zealand White rabbits were vaccinated in 3 trials. In trial 1 (T1) and 2 (T2), experimental (n=7) and control (n=5) animals were vaccinated with epoxyscillirosidine-OVA (0.4 mg/rabbit) and OVA (0.8 mg/rabbit), respectively. In T1 Freund’s (complete and incomplete) and in T2 Montanide was used as adjuvant, respectively. In Trial 3 (T3), five equal groups of 3 animals each, were vaccinated with proscillaridin-BSA (group 1), bufalin-BSA (group 2), epoxyscillirosidine-KLH (group 3), epoxyscillirosidine-BSA (group 4) and BSA (group 5), with Montanide as adjuvant, on days (D) 0, 21 and 42 (0.8 mg/rabbit, intradermally). Blood was collected before each vaccination and at 3 weeks after the last vaccination. Antibody response was determined using an indirect ELISA. There was a poor immune response associated with the dose and/or adjuvant in T1. However, after increasing the dose of the immunogen to 0.8 mg (per rabbit) and changing the adjuvant to Montanide, in T2 and T3, antibodies against the conjugates were successfully raised. In T3, epoxyscillirosidine-KLH (group 3) induced the highest immune response. Furthermore, proscillaridin and bufalin antibodies cross-reacted with epoxyscillirosidine and its OVA conjugate in the ELISAs. Preparatory to in vitro studies to assess the efficacy of the raised antibodies to neutralize epoxyscillirosidine, a rat embryonic cardiomyocyte (H9c2) cell line was established and the cytotoxic effect of epoxyscillirosidine was determined. Cells (10 000/well) exposed to epoxyscillirosidine (10–200 μM) for 24, 48 and 72 h were evaluated using 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and the lactate dehydrogenase (LDH) assays. Cells (100 000/well) exposed to epoxyscillirosidine (40–200 μM, for 24, 48 and 72 h), were processed and viewed with a transmission electron microscope (TEM). Cell viability indicated a hormetic dose/concentration response, characterized by higher viability (relative to control) at low doses (10–40, 10 and 10–20 μM for 24, 48 and 72 h, respectively) and decreased viability at higher doses. The cytotoxic effect and ultra-structural changes were dose and time dependent. Numerous cytoplasmic vacuoles, karyolysis and damage to the cell membrane, indicative of necrosis, were observed. The animal vaccination trial was scaled up, to generate more antibodies, for the in vitro neutralization studies. Six, adult Mutton Merino whethers were vaccinated with epoxyscillirosidine-KLH (2 mg subcutaneously), on D0, 21 and 42. Immune response was determined with an indirect ELISA. Antibodies were concentrated and purified using ammonium sulphate precipitation, before evaluation of in vitro neutralization efficacy. There was no significant (p > 0.05) difference in viability, between cells exposed to a pre-incubated solution of antibodies and epoxyscillirosidine and the epoxyscillirosidine exposed control cells. The antibodies failed to neutralize the toxic effect of epoxyscillirosidine. In conclusion, conjugated epoxyscillirosidine was an effective immunogen following conjugation to carrier proteins and antibodies were raised in vaccinated animals. Although antibodies against epoxyscillirosidine-KLH were raised in sheep, they failed to neutralize the toxin in the in vitro H9c2 cell model. This is possibly because higher ratios of antibodies to toxin are needed to effectively neutralize epoxyscillirosidine than those used in this study. Since antibodies failed to neutralize epoxyscillirosidine in the current study, further studies could optimize the vaccine to produce more specific antibodies with stronger affinity and avidity to be able to neutralize epoxyscillirosidine. Furthermore, the antibody purification method could be adjusted or changed for optimal results in the future. Antibodies against the related commercially available bufadienolides, namely proscillaridin and bufalin, cross-reacted with epoxyscillirosidine and could be investigated in future studies to prevent yellow tulp poisoning by vaccination. / Thesis (PhD)--University of Pretoria, 2018. / Paraclinical Sciences / PhD / Unrestricted

Ticks and tick borne diseases remain a huge threat to livestock productivity the world over. While several efforts have been made to control ticks, current control measures are still not adequate. Conventionally, tick control programmes are heavily reliant on the use of synthetic chemical acaricides while the impact of other less frequently used control methods has not been fully established. Unfortunately, heavy chemical use has led to a number challenges that include: unsustainable high costs of acaricides, development of tick resistance, environmental pollution, contamination of animal products with chemical residues and many other topical issues. Ethnoveterinary plants are however an alternative but possibly effective, environmentally benign and safe option that can complement and in some cases substitute synthetic chemical acaricides. In this study, plant species identified in Zimbabwe and found elsewhere in southern Africa were characterised for anti-tick properties with the aim of developing an ethnobotanical product for use. The initial step involved the identification of plants through an ethnobotanical survey carried out in 4 arid and semi-arid districts of Zimbabwe, namely Muzarabani, Chiredzi, Matobo and Kadoma. These areas were purposively selected on the basis of high cattle production and high likelihood of use of traditional practices in primary animal health care. More than 51 plant species were recorded and a ranking according to frequency of mention showed that Cissus quadrangularis, Aloe sp., Lippia javanica and Psydrax livida were the most popular plants mentioned by farmers. The most common method for preparation was crushing and soaking in water before spraying the animals. Despite the farmers acknowledging that they had access challenges to the normal government-provided dipping services and having knowledge on traditional practices of tick control, the actual use of these practices was low. It was concluded that farmers and other knowledgeable people do have plants they know that have anti-tick properties, thus providing a good basis for the development of ethno-based tick control products. In order to confirm farmer claims of efficacy of the plant extracts and to find ways of increasing that efficacy, three in vitro screening experiments were done using the modified Shaw Larval Immersion Test on Rhipicephalus (Boophilus) decoloratus tick larvae. Different extraction methods were used in the screening: crude water extracts, acetone extracts and solvent – solvent fractions of acetone extracts of Maerua edulis. Results showed that contrary to the high activity reported by farmers in the surveys, water extracts were not toxic to the tick larvae. Perhaps the high activity reported by farmers, if confirmed may be associated with the repellence of volatile emissions from the plants. The addition of a liquid soap as a surfactant however increased the efficacy of the M. edulis tuber aqueous extract to activity levels comparable with those of an amitraz-based commercial acaricide, which was the positive control. The use of the organic solvent acetone as an extractant markedly increased the efficacy of 13 of the plant species under study, particularly M. edulis, Monadenium lugardae and Kleinia species. The chloroform and hexane fractions from M. edulis exhibited very high activity, possibly indicating that less-polar compounds are responsible for the observed activity. Thus, the use of water as a sole extractant is limited in terms of extracting compounds active against ticks, but organic solvents and acetone in particular increase the efficacy of the extracts. In the case of M. edulis less polar extracts and fractions were most active against the ticks. Because Maerua edulis consistently showed good activity in all prior testing, it was further tested using low-cost optimisation strategies like the use of hot water, a surfactant and a different organic solvent (methanol). Hot water extraction and use of a surfactant increased efficacy of the crude extracts of the M. edulis leaves against ticks to satisfactory levels compared to cold water extracts. There was no significant difference between the positive control and methanol-extracted M. edulis. It is, however, the use of ordinary soap that may bring relief to rural farmers who are generally unable to have access to organic solvents. From the observation that the hexane and chloroform extracts of the M. edulis leaf and roots were very active against the ticks, cytotoxicity of the extracts on African Green monkey kidney (Vero) cells and bovine dermal cells was determined to shed some preliminary insights on safety aspects of the plant. Neither extract had high toxicity against these cell lines. The LC50 was greater than 20 _g/ml which is considered as a maximum threshold for indicating toxicity of plant extracts. After confirmation that non-polar fractions of M. edulis were active against ticks and that cytotoxicity results showed that the extracts are relatively non-toxic to animal cell lines, attempts to isolate and identify the active compounds in the chloroform fractions of M. edulis were made without much success. Using column chromatography, an impure compound was isolated in the chloroform fraction but the amount was too low for characterisation by NMR. When the compound was analysed using Gas Chromatography-Mass Spectrometry, a number of chemicals in the isolate were avident but which did not have the pre requisite high similarities with the compound library to be considered. Because of the low quantities no further work was done to further purify and test the compounds against the ticks. For purposes of confirming laboratory activity under field conditions, M. edulis, C. quadrangularis and Aloe vera crude water extracts combined with a surfactant (liquid soap), were tested on Mashona cattle at Henderson Research Station (Zimbabwe) over 7 weeks during the period of peak tick infestation. Only M. edulis tuber extracts with a surfactant were as effective as the amitraz-based positive control. There was no significant difference in activity between the other plant extracts and the negative control. It can be concluded that there is scope to use M. edulis tubers extracted with locally available surfactant as a tick control product. This whole study therefore shows that ticks can be controlled using locally available plant materials provided they are prepared and applied properly. While the overall aim of the study of producing a working plant based tick control product was not met, there is sufficient data from the study to justify developing crude formulations from M. edulis that can be used to control ticks. / Thesis (PhD)--University of Pretoria, 2019. / Paraclinical Sciences / PhD / Unrestricted

Mastitis is one of the most economically important diseases in dairy cattle worldwide. Not only does it have a negative effect on milk production, it also is one of the main reasons for culling dairy cattle. Pathogens causing mastitis in dairy cattle can be grouped into either contagious (or host adapted) or environmental pathogens. In different parts of the world it was shown that the prevalence of these differently grouped pathogens is dependent on various risk factors. Furthermore, it was shown that control measures implemented against contagious intramammary infections caused a relative shift over time towards a higher prevalence of environmental intramammary infections. In this study udder health data from the Onderstepoort Milk Laboratory (OML) was compared over two different years, 2008 and 2013, with regards to the prevalence of specified mastitogenic pathogens in total mixed ration (TMR) dairies and pasture-based dairies. Furthermore, the within-herd prevalence of Streptococcus uberis (Str. uberis) in Str. uberis positive herds was compared between the two years and the two management systems. Statistically significant differences were found in the prevalence of most of the major contagious and environmental mastitogenic pathogens between 2008 and 2013 and between the TMR and pasture-based dairies. Coagulase-negative staphylococci (CNS) has the highest prevalence in both TMR and pasture-based for both 2008 and 2013. Streptococcus uberis overall showed an increase in prevalence from 2008 to 2013, with the highest prevalence in pasture-based dairies in 2013. Staphylococcus aureus (S. aureus) showed a statistically significant decrease in TMR and pasture-based dairies from 2008 to 2013. The within-herd prevalence of Str. uberis increased from 2008 to 2013 with the highest within-herd prevalence in pasture-based dairies in 2013. / Dissertation (MMedVet)--University of Pretoria, 2015. / tm2016 / Production Animal Studies / MMedVet