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

A study was conducted (November 2012) on the communal dipping system in Mnisi, Mpumalanga Province of South Africa to detect levels of blue tick resistance to commonly used acaricides. The larvae obtained from engorged females of the one host tick Rhipicephalus (B). microplus from twelve communal dipping areas were tested against various concentrations of amitraz, chlorfenvinphos and cypermethrin using the Shaw Larval Immersion Test method. Only R. (B). microplus ticks were identified from all sample areas, indicating a displacement of the indigenous R. (B). decoloratus tick in this area. Resistance testing using the Shaw Larval Immersion Test showed that no resistance to chlorfenvinphos was detected at any of the dip tanks, which was in keeping with the absence of known use of this product in the area. An important finding was the rapid development of resistance to the pyrethroids, which had only been in use for four months prior to conducting the study. Only one area (Hlalakane) yielded a R(B).spp population that was wholly susceptible to all three compounds. Resistance to amitraz was variable, with half (six out of 12) of the dip tanks comprising susceptible R(B).spp populations and two dip tanks with emerging resistance to amitraz. Possible risk factors which caused the resistance problems are discussed and acaricide management strategies recommended. / Dissertation (MSc)--University of Pretoria, 2015. / tm2016 / Veterinary Tropical Diseases / MSc

The Mnisi community is in the north-eastern corner of the Bushbuckridge Municipal Area, Mpumalanga Province, South Africa. This community is located at the livestock/wildlife interface sharing borders with several game reserves, and livestock are likely to be exposed to diseases with a wildlife reservoir, such as Corridor disease. Known tick vectors of important diseases such as Corridor disease, redwater, heartwater and anaplasmosis are present in the area. Although the farmers frequently dip their cattle in acaricide-filled dip tanks to control the tick burden, tick-borne diseases (TBDs) are still a major problem. This study was undertaken to determine if the symptoms of cattle in poor health in the Mnisi community could be attributed to TBDs. Corridor disease has previously been identified in cattle in the Mnisi community. Recent experimental studies have shown that T. parva DNA can be detected in infected cattle that survive the disease in the field. An additional aim of the study was therefore to identify T. parva carrier cattle in the area, and to search for evidence of selection of cattle-adapted T. parva parasites in carrier cattle. The study was conducted from July 2012 to June 2013. During the study period, samples from clinically sick cattle suspected of TBDs were collected to determine the cause of their symptoms. Blood smears from the clinically sick cattle were analysed using light microscopy while some cases were subjected to histopathology and T. parva-specific quantitative real-time polymerase chain reaction (qPCR). DNA extracted from blood samples and in some cases tissue samples collected from clinically sick cattle (n=137) was tested for the presence of haemoparasite DNA using the reverse line blot (RLB) hybridization assay. To identify T. parva carrier cattle, records from Hluvukani Animal Clinic and Bushbuckridge State Veterinary office were scrutinized to identify herds that may have been exposed to T. parva infection. Blood samples (n=670) were collected from herds that had recorded Corridor disease cases in the past three years, as well as herds that may have shared grazing with buffalo from the Kruger National Park and surrounding private game reserves. The indirect fluorescent antibody test (IFAT) was used to check for T. parva antibodies. Seropositive herds were revisited, as well as herds that had confirmed Corridor disease cases during the study period, and blood samples were collected (n=432). DNA extracted from these samples was screened for the presence of T. parva DNA using the T. parva-specific qPCR. In an attempt to find evidence of selection of cattle-adapted T. parva, the p67, p104 and PIM parasite genes were amplified from qPCR positive samples, and the amplicons were cloned and sequenced. Out of the 137 clinical disease cases examined from the study area, 24 cases of TBDs were diagnosed, of which 19 were Theileria related. The RLB hybridization assay confirmed the presence of tick-borne haemoparasites in the Mnisi community: 89 of the 137 clinical disease cases (65.0%) were found positive for one or more haemoparasite (Theileria, Babesia, Anaplasma and/or Ehrlichia species) while 48 (35.0%) were negative or below the detectable limit of the test. IFAT results indicated that there is a high seroprevalence of theileriosis (63.6%) in the Mnisi community area, but this may be due to cross reactions with other Theileria parasites known to be present (e.g. T. taurotragi). Fewer cattle (13.4%) were seropositive at the highest titre tested (160), and these are most likely to be associated with T. parva. In DNA extracted from blood samples from these seropositive herds, the T. parva-specific qPCR detected T. parva in eleven samples (2.6%). Eight of the eleven cattle were re-sampled six months later, but only one was still qPCR positive. All of the p104 and PIM sequences and two of the three p67 sequences were characteristic of buffalo-type T. parva alleles previously identified, implying that the T. parva infections in the cattle were transmitted directly from buffalo to cattle, and providing no evidence of selection of cattle-type alleles in the carrier animals. The study revealed that TBDs are a problem in the Mnisi community and surrounding area. Most important of the TBDs identified was Corridor disease, a notifiable disease in South Africa, which was the cause of most deaths among the cattle that were sampled. There was no evidence for the selection of cattle-derived T. parva alleles in any of the samples from T. parva carrier cattle, but a p67 sequence obtained from a clinical case was closely related to previously-identified alleles from cattle-derived isolates. Theileria parva DNA could only be detected in carrier cattle for a limited time post-exposure, suggesting that the infection will be cleared in infected animals before larvae or nymphs are available to pick up infections the following season. However, one bovine was still qPCR positive six months post-exposure, albeit with a very high Cp value (indicating a very low parasitaemia). The selection of T. parva parasites in cattle from the diverse T. parva population in African buffalo, therefore, remains a concern in the Mnisi community area, and at other livestock/wildlife interfaces in South Africa, but the risk is probably very low. / Dissertation (MSc)--University of Pretoria, 2015. / tm2016 / Veterinary Tropical Diseases / MSc

The South African poultry industry has been beset by sporadic H6N2 avian influenza infection (sub-lineage I and II) in chickens since the early 2000s, with economic losses resulting from reduced egg production and co-infection with other pathogens. An egg-based inactivated H6N2 vaccine (AVIVAC® AI; Deltamune (Pty) Ltd.) based on a 2002 sub-lineage I isolate is available, although substantial antigenic drift has occurred in H6N2 viruses since its implementation. Globally, seasonal and pandemic plant-produced hemagglutinin (HA)- based influenza virus-like particle (VLP) vaccines are in advanced clinical trials with proven efficacy, speed of production, cost-effectiveness, scalability and safety, although not yet established for poultry. In this study, H6 avian influenza VLPs (sub-lineage I and II, respectively) were transiently produced in Nicotiana benthamiana and tested for protective efficacy in the target host. A production platform has been established for H6 VLPs in N. benthamiana by optimising protein expression and purification to maximize yield and by assessing the feasibility of large-scale production and downstream processing in a preliminary study. Subsequently, the respective plant-produced H6 VLPs were formulated into vaccines and their capacity to reduce viral replication and shedding upon challenge with a 2016 H6N2 field isolate were established in specific-pathogen-free (SPF) chickens, in comparison to the commercial H6N2 vaccine. The plant-produced sub-lineage I VLP vaccine (768 HA units/dose) was highly immunogenic (mean hemagglutination inhibition (HI) titer 10.7 log2), reduced the oropharyngeal and cloacal viral shedding by more than 100- and 6-fold, respectively, and shortened the duration of oropharyngeal shedding by at least a week in comparison to the non-vaccinated control. Due to initial low yield of sub-lineage II VLPs, the maximum antigenic mass vaccine dose (48 HA units/dose)) resulted in substantially lower HA-specific antibody titers (mean HI titer > 4 log2), but still reduced viral shedding from the oropharynx by more than 5-fold in comparison to the non-vaccinated control. In contrast, the commercial vaccine not only failed to effectively reduce shedding in comparison to the non-vaccinated control, but exacerbated oropharyngeal shedding until day 21 after viral challenge, illustrating the antigenic dissimilarity between the commercial vaccine and a recent field virus. Plant-produced VLP vaccines, which facilitates differentiation between infected and vaccination animals (DIVA), presents a new generation of poultry vaccines that is highly efficacious and cost-effective with the major advantage of producing a tailored antigenically-matched vaccine candidate within a short space of time and holds enormous potential for the poultry industry. / Thesis (PhD)--University of Pretoria, 2020. / Production Animal Studies / PhD / Unrestricted

Animal diseases have always been one of the main constraints on animal production, especially in Africa where there are a variety of tropical and subtropical diseases. Knowledge of these diseases and the development of approaches to combat them is highly relevant to the socio-economic development of Africa and its fight against poverty. Serological tests were performed to determine seroprevalence and important risk factors for occurrence of respiratory pathogens in cattle on 423 biobanked sera collected from cattle at 11 dip tanks in the Mnisi communal farming area which is on the edge of the Kruger National Park. These pathogens are known to cause significant production losses in livestock by predisposing animals to secondary infections including pneumonia. A pentavalent, indirect ELISA test was performed to estimate seroprevalence of bovine herpesvirus-1, bovine respiratory syncytial virus, bovine viral diarrhea virus, parainfluenza virus-3 and bovine adenovirus-3 infections in cattle at the wildlife-livestock interface in the Mnisi communal farming area. Previous exposure to the five pathogens was determined. Additionally, the data was analyzed using the statistical software R to determine important risk factors that predicted exposure to the pathogens in cattle, namely population factors (distance from interface and month of collection) and individual characteristics (age, sex, body condition and breed). Age and body condition of the animals were found to have an effect on seropositivity while breed, sex, spatial distribution of the animals and month of sample collection did not have an effect. Recommendations to reduce pathogen exposure and improve production are made to the livestock owners in the Mnisi community. / Dissertation (MSc)--University of Pretoria, 2016. / Veterinary Tropical Diseases / MSc / Unrestricted

Anaplasmosis, babesiosis, and heartwater are the three most important tick-borne diseases of cattle in South Africa and result in a large number of mortalities. Endemic stability contributes to disease control, but little is known about the conditions required for maintenance of endemic stability. Through the on-going Health and Demographic Surveillance System in Livestock in the study area of the Mnisi One Health Platform, Mpumalanga, a great deal of information is being collected about cattle in the area, with the eventual aim of developing mathematical models to describe and predict infections. More than 15000 cattle have been identified for tick burden assessment, serological analyses and parasite identification. However, little is known about the time-course of infection of cattle with various tick-borne haemoparasites. Therefore, this study aimed to investigate the time-course of infection in new-born calves (n=10) and the presence of haemoparasites in adult ticks over a one year period using reverse line blot (RLB) hybridization and quantitative polymerase chain reaction assays. Blood samples and adult ticks were collected monthly from new-born calves in two areas of the Mnisi communal area: five located in a peri-urban area and five at the wildlife/livestock interface. A total of 119 blood samples and 805 adult ticks were collected. The RLB results confirm the exposure of most new-born calves in the Mnisi communal area to non-pathogenic and pathogenic tick-borne haemoparasites in the genera Anaplasma, Babesia, Ehrlichia and Theileria in their first year of life. A total of 805 adult ticks were identified to species level using identification keys and molecular methods. Only two tick species, Amblyomma hebraeum and Rhipicephalus microplus, were found on the calves during the year. Non-pathogenic and pathogenic haemoparasites in the genera Anaplasma, Babesia, Ehrlichia and Theileria were detected in pooled DNA extracted from ticks that had digested their blood meal. Pathogen-specific qPCR results indicated that some of the pathogens could not be detected in the calves until six to seven months of age and A. marginale was not detected at all in three calves at the wildlife/livestock interface. These calves were either infected at levels below the detection limit of our assays, or they were not infected at all. If the latter, it is possible that exposure to related non-pathogenic haemoparasites might help to establish and maintain endemic stability. Factors such as cattle density and dipping methods within different areas in the Mnisi communal area may play a role in the number of infected tick vectors in an area, and thus in the time-course of infection in new-born calves. It is clear that detailed information for cattle in different localities in the Mnisi communal area will be required in order to build accurate mathematical models to describe and predict infections. / Dissertation (MSc)--University of Pretoria, 2019. / Veterinary Tropical Diseases / MSc / Unrestricted

Animal diseases impact on livestock production and threaten food security through loss of animal protein. Additionally, disease impacts may cause major production losses by adding to the cost of livestock production through the necessity to apply costly disease control measures. Taken together, farm animal diseases have been shown to increase poverty levels particularly in poor communities in Africa that have a high dependence on livestock farming for sustenance (Perry et al., 2009). Research to learn more about animal diseases is necessary for the development of appropriate policies and strategies to prevent, control and possibly eradicate costly animal diseases in order to increase socio-economic development and improve livelihood, especially in Africa (Perry et al., 2009). The purpose of this study was to investigate five viruses that cause upper respiratory tract infections in cattle: bovine alphaherpesvirus-1 (BoHV-1), bovine viral diarrhoea virus (BVDV), bovine respiratory syncytial virus (BRSV), bovine parainfluenza-3 virus (PI-3) and bovine mastadenovirus-3 (BAV-3), in the rural Mnisi farming community in the Mpumalanga Province, South Africa which is located adjacent to the Kruger National Park (KNP) and private game reserves (Figure 1). The Mnisi Community Project (MCP) is a University of Pretoria initiative that is based on an One Health approach at the human/livestock/wildlife/ecosystem interface. Within the Mnisi community there are a number of dip tanks to which cattle are obligated to attend weekly for FMD inspection. In return, cattle are plunge-dipped free of charge in acaricides, as an aid to control tick-borne diseases such a theileriosis, anaplasmosis, heartwater and redwater. These viruses are known to cause pathology of the respiratory tract and lead to morbidity and even mortality in some cases. In addition, two of the viruses studied here, BoHV-1 and BVDV, can suppress the immune system of the host and also increase the risk of secondary bacterial infections (Valarcher & Hägglund, 2006). This study used a cross sectional design to determine the spatially explicit herd-level antibody seroprevalence of five respiratory tract viruses. A total of 423 sera stored in the Hans Hoheisen Wildlife Centre biobank were collected at 11 dip tanks in the Mnisi communal farming area. A commercially available pentavalent, indirect enzyme linked immunosorbent assay (ELISA) was performed to estimate the seroprevalence of each. The overall proportion of sera that contained antibodies against each pathogen were as follows: 43.3% for BoHV-1; 30.5% for BVDV; 82.5% for BRSV; 44.4% for PI-3 and 83.2% for BAV-3. The prevalence of antibodies against the five respiratory viruses did not appear to be influenced by location, distance from the adjacent wildlife conservation area, time of the year, or sex. However, age was a risk factor as antibodies appeared less frequently in animals less than 12 months of age compared to animals between 12 and 24 months, or older than 24 months. Findings from this study should provide information for the cattle farmers and animal health sector that provide animal health and extension services about the risk of bovine respiratory disease in the Mnisi communal farming area. Appropriate measures to minimize exposure to viral respiratory tract infections are discussed. / Dissertation (MSc)--University of Pretoria, 2018. / Veterinary Tropical Diseases / MSc / 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