Dissertations / Theses on the topic 'Communicable diseases in animals. Cattle'

Doctor of Philosophy
All surveillance systems are based on an effective general surveillance system because this is the system that detects emerging diseases and the re-introduction of disease to a previously disease free area. General surveillance requires comprehensive coverage of the population through an extensive network of relationships between animal producers and observers and surveillance system officers. This system is under increasing threat in Australia (and many other countries) due to the increased biomass, animal movements, rate of disease emergence, and the decline in resource allocation for surveillance activities. The Australian surveillance system is state-based and has a complex management structure that includes State and Commonwealth government representatives, industry stakeholders (such as producer bodies) and private organisations. A developing problem is the decline in the effectiveness of the general surveillance system in the extensive (remote) cattle producing regions of northern Australia. The complex organisational structure of surveillance in Australia contributes to this, and is complicated by the incomplete capture of data (as demonstrated by slow uptake of electronic individual animal identification systems), poorly developed and integrated national animal health information systems, and declining funding streams for field and laboratory personnel and infrastructure. Of major concern is the reduction in contact between animal observers and surveillance personnel arising from the decline in resource allocation for surveillance. Fewer veterinarians are working in remote areas, fewer producers use veterinarians, and, as a result, fewer sick animals are being investigated by the general surveillance system. A syndrome is a collection of signs that occur in a sick individual. Syndromic surveillance is an emerging approach to monitoring populations for change in disease levels and is based on statistical monitoring of the distribution of signs, syndromes and associations between health variables in a population. Often, diseases will have syndromes that are characteristic and the monitoring of these syndromes may provide for early detection of outbreaks. Because the process uses general signs, this method may support the existing (struggling) general surveillance system for the extensive cattle producing regions of northern Australia. Syndromic surveillance systems offer many potential advantages. First, the signs that are monitored can be general and include any health-related variable. This generality provides potential as a detector of emerging diseases. Second, many of the data types used occur early in a disease process and therefore efficient syndromic surveillance systems can detect disease events in a timely manner. There are many hurdles to the successful deployment of a syndromic surveillance system and most relate to data. An effective system will ideally obtain data from multiple sources, all data will conform to a standard (therefore each data source can be validly combined), data coverage will be extensive (across the population) and data capture will be in real time (allowing early detection). This picture is one of a functional electronic data world and unfortunately this is not the norm for either human or animal heath. Less than optimal data, lack of data standards, incomplete coverage of the population and delayed data transmission result in a loss of sensitivity, specificity and timeliness of detection. In human syndromic surveillance, most focus has been placed on earlier detection of mass bioterrorism events and this has concentrated research on the problems of electronic data. Given the current state of animal health data, the development of efficient detection algorithms represents the least of the hurdles. However, the world is moving towards increased automation and therefore the problems with current data can be expected to be resolved in the next decade. Despite the lack of large scale deployment of these systems, the question is becoming when, not whether these system will contribute. The observations of a stock worker are always the start of the surveillance pathway in animal health. Traditionally this required the worker to contact a veterinarian who would investigate unusual cases with the pathway ending in laboratory samples and specific diagnostic tests. The process is inefficient as only a fraction of cases observed by stock workers end in diagnostic samples. These observations themselves are most likely to be amenable to capture and monitoring using syndromic surveillance techniques. A pilot study of stock workers in the extensive cattle producing Lower Gulf region of Queensland demonstrated that experienced non-veterinary observers of cattle can describe the signs that they see in sick cattle in an effective manner. Lay observers do not posses a veterinary vocabulary, but the provision of a system to facilitate effective description of signs resulted in effective and standardised description of disease. However, most producers did not see personal benefit from providing this information and worried that they might be exposing themselves to regulatory impost if they described suspicious signs. Therefore the pilot study encouraged the development of a syndromic surveillance system that provides a vocabulary (a template) for lay observers to describe disease and a reason for them to contribute their data. The most important disease related drivers for producers relate to what impact the disease may have in their herd. For this reason, the Bovine Syndromic Surveillance System (BOSSS) was developed incorporating the Bayesian cattle disease diagnostic program BOVID. This allowed the observer to receive immediate information from interpretation of their observation providing a differential list of diseases, a list of questions that may help further differentiate cause, access to information and other expertise, and opportunity to benchmark disease performance. BOSSS was developed as a web-based reporting system and used a novel graphical user interface that interlinked with an interrogation module to enable lay observers to accurately and fully describe disease. BOSSS used a hierarchical reporting system that linked individual users with other users along natural reporting pathways and this encouraged the seamless and rapid transmission of information between users while respecting confidentiality. The system was made available for testing at the state level in early 2006, and recruitment of producers is proceeding. There is a dearth of performance data from operational syndromic surveillance systems. This is due, in part, to the short period that these systems have been operational and the lack of major human health outbreaks in areas with operational systems. The likely performance of a syndromic surveillance system is difficult to theorise. Outbreaks vary in size and distribution, and quality of outbreak data capture is not constant. The combined effect of a lack of track record and the many permutations of outbreak and data characteristics make computer simulation the most suitable method to evaluate likely performance. A stochastic simulation model of disease spread and disease reporting by lay observers throughout a grid of farms was modelled. The reporting characteristics of lay observers were extrapolated from the pilot study and theoretical disease was modelled (as a representation of newly emergent disease). All diseases were described by their baseline prevalence and by conditional sign probabilities (obtained from BOVID and from a survey of veterinarians in Queensland). The theoretical disease conditional sign probabilities were defined by the user. Their spread through the grid of farms followed Susceptible-Infected-Removed (SIR) principles (in herd) and by mass action between herds. Reporting of disease events and signs in events was modelled as a probabilistic event using sampling from distributions. A non-descript disease characterised by gastrointestinal signs and a visually spectacular disease characterised by neurological signs were modelled, each over three outbreak scenarios (least, moderately and most contagious). Reports were examined using two algorithms. These were the cumulative sum (CuSum) technique of adding excess of cases (above a maximum limit) for individual signs and the generic detector What’s Strange About Recent Events (WSARE) that identifies change to variable counts or variable combination counts between time periods. Both algorithms detected disease for all disease and outbreak characteristics combinations. WSARE was the most efficient algorithm, detecting disease on average earlier than CuSum. Both algorithms had high sensitivity and excellent specificity. The timeliness of detection was satisfactory for the insidious gastrointestinal disease (approximately 24 months after introduction), but not sufficient for the visually spectacular neurological disease (approximately 20 months) as the traditional surveillance system can be expected to detect visually spectacular diseases in reasonable time. Detection efficiency was not influenced greatly by the proportion of producers that report or by the proportion of cases or the number of signs per case that are reported. The modelling process demonstrated that a syndromic surveillance system in this remote region is likely to be a useful addition to the existing system. Improvements that are planned include development of a hand-held computer version and enhanced disease and syndrome mapping capability. The increased use of electronic recording systems, including livestock identification, will facilitate the deployment of BOSSS. Long term sustainability will require that producers receive sufficient reward from BOSSS to continue to provide reports over time. This question can only be answered by field deployment and this work is currently proceeding.

Social animals, such as primates, incur many fitness-related costs as a direct result of living in groups of conspecifics. However, group-living also comes with benefits. Sociality is thought to have evolved in response to the need for individuals to negotiate their social environment in order to maximise the benefits and minimise the costs associated with group-living. Recently, researchers interested in animal sociality have turned to a set of sophisticated statistical tools, collectively termed 'social network analysis' in order to better understand the structure of animal social systems and the role of individuals within their social groups. Using a social network analytic approach, I explore the relationship between the ecological and social environments, and the implications of an uncertain social landscape for individual fitness and fitness-relevant processes in two species of Old-World monkeys: chacma baboons (Papio hamadryas ursinus) and vervet monkeys (Chlorocebus aethiops pygerythrus). My results suggest that individuals respond to fluctuating local conditions in diverse ways depending on behavioural context and their current reproductive state, and that the social environment experienced by an individual, and their active pattern of social engagement has important implications for infant survival. Finally, I investigate how network structure influences two fitness-relevant processes of flow in a population of vervet monkeys: information transfer and disease transmission. I conclude that the complex social life of animal groups emerges from many individuals trying to achieve the same fitness goals. Successful individuals exploit the complexity in their social environment and respond adaptively to an uncertain and inconstant set of local conditions by actively adopting social strategies that serve to enhance their fitness.

The most important tick-borne diseases (TBDs) occurring in Zambia that affect domestic animals, particularly cattle and small ruminants, are theileriosis (East Coast fever and Corridor disease), anaplasmosis (gall sickness), babesiosis (red water), and heartwater (cowdriosis). Of these, theileriosis is the most important, causing significantly more deaths than the other tick-borne diseases combined. Despite their importance, little is known about the occurrence and prevalence of haemoparasites in cattle in the communal areas of Zambia. Clinical signs and post mortem lesions are pathognomonic of mixed tick-borne infections especially babesiosis, anaplasmosis and East Coast fever (ECF). The main objective of this study was, therefore, to screen selected communal herds of cattle for tick-borne haemoparasites and identify the tick vectors associated with the high cattle mortalities due to suspected TBDs in the local breeds of cattle grazing along the banks of the Chambeshi River in Mungwi, Zambia. East Coast fever is endemic to the district of Mungwi, Northern Province, Zambia and vector control using acaricides has proved to be very costly for the small scale farmers. Also, Mungwi experiences increased cattle mortalities between December to March and May to July. All age groups of cattle are affected. A total of 299 cattle blood samples were collected from July to September 2010 from Kapamba (n=50), Chifulo (n=102), Chisanga (n=38), Kowa (n=95) and Mungwi central (n=14) in the Mungwi District, Northern Province, Zambia. Ticks were also collected from the sampled cattle from April to July 2011. DNA was extracted and the parasite hypervariable region of the small subunit rRNA gene was amplified and subjected to the reverse line blot (RLB) hybridization assay. The results of the RLB assay revealed the presence of tick-borne haemoparasites in 259 samples occurring either as single or mixed infections. The most prevalent species present were the benign Theileria mutans (54.5%) and T. velifera (51.5%). Anaplasma marginale (25.7%), Babesia bovis (7.7%) and B. bigemina (3.3%) were also detected in the samples. Nine percent of the samples tested negative for the presence of haemoparasites. In a number of samples (4%) the PCR products failed to hybridize with any species-specific probes but hybridized only with the genus-specific probes which could suggest the presence of a novel species or variant of a species. Of the four Theileria species known to occur in Zambia (T. parva, T. mutans, T. velifera and T. taurotragi), T. parva is the most economically important, causing Corridor disease in the Southern, Central, Lusaka and the Copper-belt provinces, while causing ECF in the Northern and Eastern provinces of Zambia. In our study, only one sample (from Kapamba) tested positive for the presence of T. parva. This was an unexpected finding; also because the tick vector, Rhipicephalus appendiculatus, was identified on animals from Kowa (14%), Chisanga (8.5%), Chifulo (6%) and Kapamba (1.4%). We can only speculate that the RLB hybridization assay may not have been able to detect the parasite in the animals sampled due to a too low parasitaemia. The samples should also be subjected to the T. parva specific real-time PCR assay to determine a more accurate T. parva prevalence in cattle in the Mungwi district, Northern Province. In Zambia, Babesia bovis and B. bigemina are recognized as being of economic importance in cattle. In our study, B. bovis was present in 7.7% of the sampled animals and B. bigemina in 3.3% of the animals. We detected B. bovis in all of the five sampled areas with the highest detection in Mungwi central (14.3%) and Kowa (10.5%). As expected, the tick vector Rhipicephalus (Boophilus) microplus was identified from animals from all of these areas. Babesia bigemina was only reported from Kowa (10.5%). The most abundant ticks identified from the sampled animals from Kowa were Rhipicephalus (Boophilus) decoloratus (36.3%) and Rhipicephalus (Boophilus) microplus (8.8%). These tick vectors have been implicated in the transmission of B. bigemina. Our findings are in concordance with results obtained by other authors who have speculated that an increase in the detection of B. bovis may indicate that B. bovis is becoming endemic in this part of the country. This could be due to uncontrolled movement of cattle that frequently occurs within Zambia. Heartwater (cowdriosis) is caused by Ehrlichia ruminantium, a rickettsial disease that affects domestic and wild ruminants. In Zambia, heartwater is mainly a disease of cattle, although outbreaks in sheep and goats have been reported and recorded. In our study, only one sample (from Kapamba) tested positive for the presence of E. ruminantium even though Amblyomma variegatum ticks were identified from 52.9% of the sampled animals from all study areas. The cattle sampled in our study are not regularly dipped and no game has been spotted in cattle grazing areas. It is possible that these cattle may have attained a state of endemic stability to heartwater. It is also possible that the RLB hybridization assay may not have been sensitive enough to detect E. ruminantium infections if the parasitaemia was very low. Samples should also be subjected to the E. ruminantium-specific pCS20 real-time PCR assay to determine more accurately the E. ruminantium prevalence in cattle in the Mungwi district, Northern Province. Anaplasma marginale (the causative agent of bovine anaplasmosis) has previously been shown to be present in all the provinces of Zambia and is the only Anaplasma species of importance to cattle in Zambia. In our study, 25.7% of the sampled cattle tested positive for A. marginale; it was detected in all areas except Chisanga. Amblyomma variegatum was identified from 52.9% of the sampled cattle, and Rhipicephalus (Boophilus) microplus from 12.1% of the cattle. Rhipicephalus (Boophilus) microplus has been incriminated as being a vector of A. marginale. Furthermore, three samples (from Kowa) tested positive for the presence of Anaplasma centrale. To our knowledge, no vaccination regime using A. centrale is being conducted in the Mungwi district of Zambia. The presence of A. centrale is, therefore, an interesting finding. The results of our study suggest that the cause of cattle mortalities in Mungwi during the winter outbreaks is mainly due to A. marginale, B. bovis and B. bigemina infections. This was confirmed by the results of the RLB hybridization assay, clinical manifestation of the disease in the affected cattle (own observation) and the tick species identified on the animals. It appears that in Mungwi, babesiosis due to B. bovis mostly infects cattle above one year of age. Calves appear to be less affected by B. bovis infection. There is need for further epidemiological surveys in Mungwi district, Northern Province, Zambia to get a better understanding of the epidemiology of these tick-borne haemoparasites affecting cattle. We conclude that integrated control policies should be developed to take account of multi-species pathogen communities that are commonly associated with clinical and sub-clinical TBD infections in Zambia.
Dissertation (MSc)--University of Pretoria, 2012.
Veterinary Tropical Diseases
unrestricted

Thesis (PhD)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Bovine tuberculosis (BTB), caused by bacteria of the Mycobacterium tuberculosis complex is reported to cause economic and public health negative impact in countries where it is prevalent. The control of the disease has been a difficult task worldwide. The main object of this thesis was to use molecular tools to generate useful information to contribute to the design of appropriate BTB control measures in Mozambique. To do so we considered a deep knowledge of the BTB history in Mozambique to be essential. The search was largely based on the reports produced annually by the Veterinary Services and other available information. We found reports of BTB in Mozambique as early as 1940. These cases were mainly identified as a result of post-mortem meat inspection. The higher numbers of cases reported were from 8 locations, namely Maputo, Magude, Vilanculos, Beira, Chimoio, Tete, Quelimane and Nampula, and served as a basis to decide the locations to perform prevalence and molecular epidemiologic studies. Prevalence studies were done in 10 districts selected based on the history of a high number of BTB case reports (intentionally biased towards locations presumably with higher prevalence), a high cattle density, but also to represent districts from the south, centre and north of Mozambique. A representative sample was defined, based on all livestock areas or villages in Massingir and Govuro Districts or by randomly selecting small-scale and commercial herds in 8 districts, specifically Manhiça, Chibuto, Buzi, Gondola, Mutarara, Mogovolas, Angoche and Mecanhelas. Results were obtained from 6983 cattle tested using tuberculin testing. Apparent prevalence varied from 0.98% in Massingir to 39.6% in the Govuro, with prevalence as high as 71.4% in some livestock areas/herds. The analysis of risk factors showed no noteworthy difference with respect to the sex of the animal. Younger age had significantly lower odds of infection compared to the older age class. There was a tendency of cattle from small-scale herds to have lower prevalence when compared to the commercial herds. From the prevalence studies, 187 tissue and 41 milk samples from BTB reactors were collected. Additionally 220 tissue samples were obtained from the Central Veterinary Laboratory routine diagnostic work. Samples were subject to bacteriological culture and a collection of 170 M. bovis isolates were obtained. Eight additional isolates were supplied from another study. All isolates were subjected to molecular typing using spoligotyping, and a sub-sample using MIRU-VNTR and regions of difference (RD) analysis. Fifteen different spoligotype patterns were identified of which 8 were not previously registered in the Mbovis.org database. The pattern SB0961 accounted for 61% of the isolates and was found in all areas of the country investigated. We hypothesize that this was one of the first clones to be introduced in Mozambique. Twenty-nine isolates had the pattern SB0140, which is specific for the European 1 (Eu1) clonal complex. Eleven isolates with this spoligotype were subjected to RD analysis, and all isolates had the Eu1 specific deletion. These were all isolated from cattle from the south of Mozambique and the majority from commercial farms that imported cattle, mainly from South Africa, where the Eu1 clonal complex is common. There were no isolates of the African 1 (Af1) or African 2 (Af2) clonal complexes that are frequent in Central-West Africa and East Africa, respectively. The clones identified from different farms and districts, strongly suggest routes of transmission and/or common source of infection. In conclusion, our results show a potential increase in the prevalence of BTB in Mozambique even taking into consideration i) that the selection of locations in our study was biased towards locations with a history of higher BTB prevalence and ii) the use of a more sensitive technique i.e. the testing in the middle neck region as opposed to the testing in the caudal fold as used in previous studies. Even if no cattle to human transmission was found in studies done in Mozambique so far, the evidence of M. bovis shedding through milk and the lack of correct practices to prevent animal to human transmission (consumption of raw milk), strongly suggests that there is zoonotic risk; a subject that needs to be investigated. The results presented in this work also strengthen the need to reinforce the current regulations that require a negative BTB test result before cattle importation. The same should be enforced for the internal movements, as the frequency of shared genotypes (Spoligotype and MIRU) from cattle originating from different parts of the country strongly suggest intra-contry transmission of BTB.
AFRIKAANSE OPSOMMING: Beestering (BTB), wat veroorsaak word deur bakterieë van die Mycobacterium tuberculosis kompleks, het ‘n negatiewe impak op die ekonomiese en publike gesondheid in lande waar dit voorkom. Die beheer van die siekte is ‘n moeilike taak wêreldwyd. Die hoofdoel van hierdie tesis was om molekulêre toetse te gebruik om nuttige inligting te genereer wat sal bydra tot die ontwikkeling van toepaslike BTB beheermaatrëels in Mosambiek. Om dit te kon doen, was dit noodsaaklik om ‘n indiepte kennies te hê van BTB geskiedenis in Mosambiek. Die soektog was gebaseer op jaarlikse verslae van Veearts Dienste en ander beskikbare inligting. Ons het verslae gevind van BTB in Mosambiek so vroeg as 1940. Hierdie gevalle is hoofsaaklik geïdentifiseer as gevolg van roetine na-doodse inspeksie van vleis. Hoër getalle van sulke gevalle is geïdentifiseer in 8 distrikte, naamlik Maputo, Magude, Vilanculos, Beira, Chimoio, Tete, Quelimane en Nampula; en het gedien as ‘n basis vir die seleksie van studieareas vir die voorkoms studies. Voorkoms studies is uitgevoer in 10 distrikte gekies op grond van die geskiedenis van 'n hoër aantal BTB gevalle in hierdie areas (doelbewus bevooroordeeld teenoor plekke vermoedelik met 'n hoër voorkoms), asook‘n hoë digtheid beeste, maar ook om distrikte in die suide, middel en noorde van Mosambiek te verteenwoordig. ‘n Verteenwoordigende steekproef is geïdentifiseer gebaseer op al die vee-gebiede of dorpe in Massingir and Govuro distrikte óf deur kleinskaalse en kommersiële kuddes lukraak te kies in 8 distrikte, spesifiek Manhica, Chibuto, Busi, Gondola, Mutarara, Mogovolas, Angoche en Mecanhelas. Resultate is verkry deur 6983 beeste te toets met behulp van die tuberkulien vel toets. Skynbare voorkoms het gewissel van 0,98 % in Massingir tot 39,6 % in Govuro, met voorkoms so hoog as 71,4 % in sommige vee gebiede/ kuddes. Die ontleding van risiko faktore het geen noemenswaardige verskil met betrekking tot die geslag van die dier gewys nie. Jonger ouderdom diere het ‘n aansienlike laer kans van infeksie gehad in vergelyking met die ouer ouderdom klas. Daar was 'n neiging van beeste van kleinskaalse kuddes om ‘n laer voorkoms te hê in vergelyking met die kommersiële kuddes. Van die voorkoms studies, is 187 weefsel- en 41 melkmonsters van BTB reaktors ingesamel. ‘n Addisionele 220 weefselmonsters is verkry vanaf die Sentrale Veterinêre Laboratorium se roetine diagnostiese werk. Monsters was onderhewig aan bakteriologiese kweking en 'n versameling van 170 M. bovis isolate is verkry. Agt bykomende isolate is voorsien deur 'n ander studie. Alle isolate was onderhewig aan molekulêre-tipering met behulp van spoligotipering en ‘n subgroep met behulp van MIRU-VNTR en analise van genomies diverse areas. Vyftien verskillende spoligotipering patrone is geïdentifiseer, waarvan 8 nie voorheen in die Mbovis.org databasis geregistreer is nie. Die SB0961 patroon is geïdentifiseer vir 61% van die isolate en gevind in alle dele van die land wat ondersoek was. Ons hipotese is dat hierdie een van die eerste klone was wat voorgestel is in Mosambiek. Nege en twintig isolate het die SB0140 patroon gehad wat spesifiek is aan die Europese 1 (EU1) klonale kompleks. Elf isolate met hierdie spoligotipering patroon is verder geanaliseer om genomies diverse areas te identifiseer, waarvan almal die Eu1 spesifieke delesie getoon het. Hierdie isolate is almal geïsoleer uit beeste van die suide van Mosambiek, asook beeste gevind op kommersiele plase wat hoofsaaklik vanuit Suid Afrika invoer- waar die EU1 klonale kompleks algemeen is. Daar is geen isolate van die Afrikaans 1 (AF1) of Afrikaans 2 (AF2) klonale komplekse nie, dikwels gevind in onderskeidelik Sentraal-Wes-Afrika en Oos- Afrika. Isolate wat in verskillende plase en distrikte geïdentifiser is dui roetes van transmissie en/ of a gemeenskaplike bron van infeksie aan. Ten slotte, ons resultate dui op 'n moontlike toename in die voorkoms van BTB in Mosambiek, selfs met inagneming dat i) die keuse van areas in ons studie is bevooroordeeld teenoor areas met 'n geskiedenis van hoër BTB voorkoms en ii) die gebruik van 'n meer sensitiewe tegniek d.w.s. toetsing in die middel nekgebied i.p.v. toetsing in die stert vou soos gebruik in vorige studies. Selfs al is geen bees-na-mens-oordrag gevind nie, is die bewys van M. bovis oordrag deur melk en die gebrek aan korrekte prosedures om dier-na-mens-oordrag te voorkom (verbruik van nie-gepasturiseerde melk), ‘n sterk bewys van die soönotiese risiko; ‘n onderwerp wat ondersoek moet word. Die resultate van hierdie ondersoek beklemtoon die behoefte om die huidige regulasies wat ‘n negatiewe BTB toetsuitslag vereis voor beeste ingevoer word, te versterk. Dieselfde maatreëls moet ingestel word vir interne beweging van beeste, omdat die frekwensie van gedeelde genotipes (Spoligotipering en MIRU) tussen beeste met oorsprong uit verskillende dele van die land aandui dat interne oordrag van BTB plaasvind.

Brucellosis is a disease of socio-economic and zoonotic importance worldwide. In animals it is associated with the ingestion of feed that is contaminated with cyetic material from aborting herd-mates, while in humans it is associated with the consumption of unpasteurised milk and dairy products from infected animals. It may also be acquired from contact with infected material of animal origin by farmers, veterinarians, and abattoir and laboratory workers. Brucellosis was first reported in South Africa in the late nineteenth century. It is still present in the country today, with reported annual losses of at least R 300 million, and a national annual incidence of 5 000 cases in humans. The global incidence of human brucellosis is about half a million infections annually. As the incidence of human brucellosis is directly associated with prevalence in animals, control of animal brucellosis is emphasised. Veterinary control is compromised by the chronic nature and the variable incubation period of the disease, with an estimated up to 15% of cattle in infected herds aborting before sero-conversion. Latency, which involves about 5% of calves born from infected dams, is also problematic as these infected animals often test seronegative, only to seroconvert in the peri-parturient period, thus allowing opportunity for disease spread within and between herds before diagnosis is made. In addition, the currently used serological tests are at times unable to distinguish brucellosis from cross-reacting antibodies from other infections or brucellosis vaccines. x It was the objective of this study to investigate, under South African conditions, the value of the brucellin skin test (BST) in improving the sensitivity and specificity of the currently used serological tests. It has proved a valuable additional test in diagnosing early and latent infections as well as in differentiating brucellosis from cross-reacting organisms in unvaccinated cattle in Europe. The study also evaluated the benefit of replacing some of the currently used serological assays with the fluorescence polarisation assay (FPA). The FPA, a rapid and homogenous serological test with only a few operational steps, has been validated and is in current use in Canada. The study was carried out in Mpumalanga Province, on herds selected to reflect prevailing South African farming conditions. These herds were divided into certified Brucella abortus-negative herds (608 head) for the estimation of BST specificity, and confirmed B. abortus-infected herds (845 head) for the estimation of BST sensitivity. The results obtained indicated the BST had a specificity of 99.18%, and a relative sensitivity of 42.86%. However, 65.38% of BST-positive animals were negative on serology. When the high specificity is considered, together with the experiences of other researchers who found that the skin test became positive earlier than serological tests, these animals may be assumed infected. It is concluded that the BST is a valuable addition to the panel of diagnostic tests currently used to identify infected herds and individuals in South Africa. The FPA, with a relative sensitivity of 93.65% and a specificity of 98.85%, can potentially be of use as a screening test under South African conditions.
Dissertation (MSc)--University of Pretoria, 2012.
gm2014
Veterinary Tropical Diseases
unrestricted

Thesis (Ph. D.)--University of Missouri-Columbia, 2006.
"May 2006" The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Vita. Includes bibliographical references.

Thesis (MSc (Microbiology))--Stellenbosch University, 2008.
Mastitis is considered to be the most costly disease affecting the dairy industry. Management strategies involve the extensive use of antibiotics to treat and prevent this disease. Prophylactic dosages of antibiotics used in mastitis control programmes could select for strains with resistance to antibiotics. In addition, a strong drive towards reducing antibiotic residues in animal food products has lead to research in finding alternative antimicrobial agents. Streptococcus macedonicus ST91KM, isolated from bulgarian goat yoghurt, produces the bacteriocin macedocin ST91KM with a narrow spectrum of activity against Grampositive bacteria. These include mastitis pathogens Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, Staphylococcus aureus and Staphylococcus epidermidis as well as Lactobacillus sakei and Micrococcus varians. Macedocin ST91KM is, according to tricine-SDS PAGE, between 2.0 and 2.5 kDa in size. The activity of macedocin ST91KM remained unchanged after 2 h of incubation at pH 2.0 to 10.0 and 100 min at 100 °C. The peptide was inactivated after 20 min at 121 °C and when treated with pronase, pepsin and trypsin. Treatment with α-amylase had no effect on activity, suggesting that the mode of action does not depend on glycosylation. Precipitation with 60 % saturated ammonium sulphate, followed by Sep-Pak C18 separation recovered 43 % of macedocin ST91KM. Amplification of the genome of strain ST91KM with primers designed from the sequence of the macedocin prescursor gene (mcdA) produced two fragments (approximately 375 and 220 bp) instead of one fragment of 150 bp recorded for macedocin produced by S. macedonicus ACA-DC 198. Strain ACA-DC 198 was not available. However, the DNA fragment amplified from strain LMG 18488 (ACA-DC 206), genetically closely related to strain ACADC 198, revealed 99 % homology to the mcdA of S. macedonicus ACA-DC 198 (accession number DQ835394). Macedocin ST91KM may thus be a related bacteriocin described for S. macedonicus. The peptide adsorbed equally well (66 %) to L. sakei LMG13558 and insensitive cells, e.g. Enterococcus faecalis BFE 1071 and FAIR E92, and Streptococcus caprinus ATCC 700066. Optimal adsorption of macedocin ST91KM was recorded at 37 °C and 45 °C and at pH of 8 - 10. Addition of solvents decreased adsorption by 50%, suggesting that the receptors to which the bacteriocin binds have lipid moieties. The addition of MgCl2, KI and Na2CO3 completely prevented adsorption of macedocin ST91KM to the target cells, possibly due to competitive ion adsorption on the bacterial cell surface. The peptide has a bacteriocidal mode of action, resulting in lysis and the release of DNA and β-galactosidase. Atomic force microscopy of sensitive cells treated with macedocin ST91KM have shown deformation of the cell structure and developing of irregular surface areas. Antimicrobial susceptibility patterns were evaluated against eighteen mastitis pathogens. All isolates tested were resistant to methicillin and oxacillin, but had minimum inhibitory concentrations (MICs) falling in the intermediate and susceptible range against erythromycin. S. agalactiae and S. epidermidis had the highest sensitivity to macedocin ST91KM. A teat seal preparation containing macedocin ST91KM effectively released bacteriocin inhibiting the growth of the bacterial pathogen. Macedocin ST91KM could form the basis for an alternative dry cow therapy to prevent mastitis infections in dairy cows, as it is effective against pathogens that display resistance to conventional antibiotic therapy.

Mannheimia haemolytica is the principal bacterial agent associated with bovine respiratory disease (BRD). It has a significant economic impact on the beef feedlot industry. The current methods for BRD prevention and treatment have various problems and limitations, especially with reports of increased antimicrobial resistance in M. haemolytica. Bacteriophage therapy presents a novel method to mitigate M. haemolytica. This study aimed to isolate strictly lytic M. haemolytica-specific bacteriophages from bovine nasopharyngeal swabs and feedlot trough water. This was accompanied by an extensive characterization of temperate bacteriophages induced from representative strains of a M. haemolytica collection. Phage morphology, host specificity, genomic diversity, and comparative genomics were determined. Even though temperate bacteriophages are not ideal candidates for phage therapy, they can be engineered or modified to serve this function. Genome sequences of selected temperate bacteriophages also provide a foundation for future studies on the biology of these microorganisms.
viii, 107 leaves : ill. ; 29 cm

Aphanomyces invadans is the pathogen that causes epizootic ulcerative syndrome (EUS), an economically devastating fish disease in southern Asia. The present thesis considered possible improvements to current methods of monitoring EUS, and examined the mechanisms of the host immune response to A. invadans in order to establish whether they could be enhanced to reduce the impact of EUS on aquaculture. Monoclonal antibody (MAb) technology was considered as a possible improvement to the histopathological methods currently used in diagnosis of EUS. Five MAbs were raised to day-old A. invadans germlings. Four gave weak reactions to A. invadans and cross-reacted with other Aphanomyces spp, though they may be useful for future studies on A. invadans. The other, designated MAb 3gJC9, only cross-reacted with the crayfish plague pathogen, A. astaci, and was used for the development of an immunohistochemistry protocol that may be of use in diagnosis. Immunohistochemistry with MAb 3gJC9, which recognised an extracellular product (ECP) of A. invadans, was specific to A. invadans in fish tissue, although it also recognised A. astaci in plague-infected crayfish. It also recognised the mycelium in fish infected with ulcerative mycosis, indicating that ulcerative mycosis is synonymous with EUS. Preliminary observations indicated that both ECPs and what appeared to be a hitherto unreported early stage of the mycelium are important in the pathology of EUS. Studies in vitro on the macrophages of EUS-susceptible giant gourami Osphronemus gouramy and silver barb Barbodes gonionotus, and EUS-resistant Nile tilapia Oreochromis niloticus, found that their macrophages were able to inhibit the growth of A. invadans. The macrophages of striped snakehead Channa striata did not inhibit A. invadans, which may account for their high EUS-susceptibility, especially as A. invadans strongly inhibited the respiratory burst of snakehead macrophages. Studies on humoral immune responses revealed that complement inhibited A. invadans in the case of snakeheads, gourami and barbs but not tilapia or swamp eels Monopterus albus. The humoral responses of the latter were very different to the four other species, and not elucidated. Low levels of anti A. invadans antibodies were found in tilapia and gourami from an EUS-endemic region, and high levels in snakehead. Snakehead antibodies appeared to be able to inhibit A. invadans even when complement was removed, but lower levels were produced at the low temperatures typically associated with EUS. A range of potential immunostimulants were screened for the ability to enhance resistance to EUS. The two successful products were administered as feed supplements to snakeheads and barbs that were subsequently injected intramuscularly with A. invadans. One, the algal extract Ergosan, showed some beneficial effects on snakeheads although the challenge was inconclusive. The other, the vitamin supplement Salar-bec, accelerated the cellular immune response and reduced mortality in snakeheads and barbs, and enhanced antibody production in snakeheads. The antibody response of snakeheads was further studied by comparing the anti- A. invadans antibody level, inhibitory activity of sera in vitro and protective capacity of sera from EUS-naïve snakeheads to that of snakeheads recently exposed to EUS and those subject to long term EUS-exposure. Sera of populations recently exposed to EUS showed an increased level of antibodies, but little improvement in inhibitory or protective activity. Sera from snakeheads that had endured long term exposure showed a wide range of antibody levels, but marked increases in inhibitory and protective activity. Antibodies cross-reacted with non-pathogenic Aphanomyces spp. in all cases.

Thesis (PhD)-- Stellenbosch University, 2013.
ENGLISH ABSTRACT: The emergence and re-emergence of viral human pathogens from wildlife sources in the recent past has led to increased studies and surveillance of wildlife for potentially zoonotic agents in order to gain a better understanding of the pathogens, their sources as well as events that may lead to viral emergence. Of the >1407 known human pathogens, 13% are classified as emerging or re-emerging, and 58% as zoonotic; 37% of the (re-)emerging and 19% of the zoonotic pathogens are RNA viruses, accounting for the majority of recently emerged infectious diseases with a zoonotic origin, such as HIV, Ebola, Hendra, Nipah, Influenza and SARS. This study focusses on potentially zoonotic viruses hosted by rodents (Muridae family), shrews (order previously known as Insectivora/Soricomorpha, now reclassified as Eulipotyphla) and bats (order Chiroptera). Rodents and bats represent the largest (~40%) and second largest (~25%) mammalian orders and both occur on every continent except Antarctica. Together, the three mammalian orders investigated represent the most relevant potential sources of new zoonoses. In this study I investigated the occurrence of astroviruses, arenaviruses, coronaviruses and hantaviruses in South African small mammal species belonging to the orders mentioned above. These viruses have either been implicated in recent emerging zoonotic events or are considered to have the potential to cause cross-species transmissions resulting in a zoonotic event. In the first part of the study specimens collected from various bat, rodent and shrew species were screened for viral sequences by broadly reactive PCRs; positive samples were characterised by sequencing and sequence analysis. A separate part of the study focussed on hantavirus disease in humans: a seroprevalance survey was conducted to determine the presence of hantavirus antibodies in the local population. Additionally, acutely ill patients with potential hantavirus disease were tested in an attempt to identify possible acute infections and define clinical hantavirus disease in South Africa. Screening of rodent and shrew specimens resulted in the identification of eight novel arenavirus sequences. Seven of the sequences are related to Merino Walk virus, a recently identified South African arenavirus, and the eighth sequence represents a novel lineage of Old World arenaviruses. Screening of bat specimens resulted in the identification of highly diverse novel astrovirus and coronavirus sequences in various South African bat species, including the identification of a viral sequence closely related to the recently emerged Middle East Respiratory Syndrome coronavirus. While the study did not identify hantavirus infections in any of the acutely ill patients, it found seroprevalences similar to those observed in Europe and West Africa. The results obtained highlight the importance of small mammals in the emergence of potential zoonoses and further reinforce the importance of viral surveillance of relevant wildlife species. Further in-depth studies of naturally infected reservoir host populations are required in order to gain a better understanding of virus-host dynamics and the events that lead to virus emergence.
German Research Foundation (DFG) (project number: KR1293/9-1/13-1)
The Polio Research Foundation and the NHLS Research
Harry Crossley Foundation, the Polio Research Foundation and Stellenbosch University for granting scholarships and bursaries for PhD.

Bovine Tuberculosis is a chronic debilitating disease of cattle and other animals with a worldwide distribution and transmitted mainly through the inhalation of aerosols. The aim of this study was to determine the prevalence of BTB in the cattle population of selected dip tanks in Swaziland. Furthermore, the zoonotic risk to farmers whose cattle are infected with BTB was assessed by means of a questionnaire survey. Abattoir surveillance identified 16 dip tanks of study where at least 10 % of the cattle were tested for BTB using the comparative intra-dermal skin. In five of these dip tanks, the same cattle were tested for BTB using the IFN-γ Test. Eight BTB skin test positive animals were slaughtered and a detailed post mortem examination was conducted and samples collected for the isolation of M. bovis. Concurrent with BTB testing, a questionnaire survey was conducted to determine risk factors for humans. The prevalence of BTB was found to be 6.75 % in the study population and 20 % of BTB positive animals were diagnosed by both the CIST and IFN-γ, indicating a correlation for the test positive animals in the two tests. M. bovis was isolated from seven of the eight animals slaughtered. Farmers’ knowledge of BTB as a cattle disease and serious zoonosis is insufficient and inadequate while consumption practices of products of bovine origin exposes them to the risk of infection by M. bovis. There is a need to investigate the extent of M. bovis infections in the human population.
Dissertation (MSc)--University of Pretoria, 2013.
gm2014
Veterinary Tropical Diseases
unrestricted

Until recently, occurrence of milk fever (MF) has been attributed to prepartum calcium intake. However, researchers in Iowa have concluded that high prepartum dietary potassium (K) is the major cause of MF. Potassium concentrations have been increasing on manure fertilized soils over the last 20 years. Grasses grown on these fields mirror the increase in available soil K. When high K forages are fed to dry cows, it has been associated with increased MF in some, but not all cases. Our objective was to identify factors that differed between low and high occurrence of disorders when high K forages were fed. For 1 yr, monthly interviews were conducted on 10 dairies in Western Oregon. Close-up rations, dystocia rating, crowding, and cow comfort data were collected. Cows were diagnosed healthy or having one or more of the following metabolic diseases: MF, retained fetal membranes (RFM), and left displacement of the abomasum (LDA). Feedstuffs were collected each month and analyzed for dry matter, crude protein (CP), acid detergent fiber (ADF), and macrominerals. Of the multiparous cows (n=3,587) included, incidences of MF, RFM and LDA were 3.6, 11.3, and 1.5%, respectively. Increasing MF occurrence was associated with uncomfortable conditions, dystocia, increasing prepartum dietary Na and ADF, and increasing Ca to P ratios; there was also a dietary K by Mg concentration interaction. Increased dietary concentrations of Mg can prevent MF if dietary K is <2.6%. In addition, dietary conditions of K >2.6% and Mg >0.4% increase the occurrence of MF. Inversely, high concentrations of K can prevent MF in a Mg deficient diet. Dietary factors associated with an increase in the occurrence of RFM are increased dietary concentrations of Ca, S, CP, use of anionic salts, and the K forage source. Factors associated with an increase in hypocalcemia in the postpartum cow are crowding, uncomfortable housing, and a dietary K by Mg concentration interaction. In conclusion, improved cow comfort, and the addition of Mg to high K forage diets could decrease the risk of the cow exhibiting MF, RFM, and hypocalcemia.
Graduation date: 1999

The cattle tick, Rhipicephalus (Boophilus) microplus is a tick of veterinary and health importance globally, transmitting Babesia bovis and B. bigemina. Tick control is important and needed to prevent livestock diseases caused by tick-transmitted pathogens. Traditionally, tick control methods have resulted in development of acaricide-resistant ticks, environmental pollution and meat and milk contamination. Therefore, there is a need for alternative method and vaccines directed against tick feeding. The aim of this study was to identify proteins involved in tick feeding, tickhost-pathogen interactions and tick reproduction. Consequently, these will help in identification of antigens with the ultimate goal of developing anti-tick vaccines. R. (B.) microplus female ticks were collected at five different feeding stages. RNA was isolated from the salivary gland extracts (SGEs). The cDNA libraries were synthesized and sequenced with the Illumina MiSeq technology. Transcriptome data was analyzed with CLC Genomics Workbench, Trinity and Minia. The SGEs were also used to isolate the fractions: membrane, soluble and pellet protein for proteomic analysis. The proteomics data was analysed with Mascot, X!Tandem and Scaffold. Both the transcriptome and proteome analysis revealed the presence of major secretory protein families such as Kunitz, lipocalins, serpins, cement proteins and metalloproteases, while the majority of transcripts coded for housekeeping genes.
National Research Foundation (South Africa)
Life and Consumer Science
M. Sc. (Life Science)

Ticks and tick borne-diseases (TBD) are major challenges to cattle production among smallholder farmers in the semiarid areas of South Africa. Nguni cattle have been reported to be resistant to ticks and TBD, however, the mechanisms responsible for the trait are not fully understood. The broad objective of this study was to determine the mechanisms of resistance to ticks in Nguni cattle reared in the semiarid areas of South Africa. Tick infestation levels, body condition scores (BCS), packed cell volumes (PCV) and the molecular prevalence of A. marginale were determined in Nguni (n = 70) and local crossbred (n = 79) cattle reared in the semiarid areas of South Africa. Relationships among skin thickness, hair length, coat score and tick counts were assessed in seven to nine month old Nguni (n = 12) and Bonsmara (n = 12) heifers. As a follow up, cutaneous hypersensitivity responses to unfed larval extracts (ULE) of the ticks Rhipicephalus decoloratus and Rhipicephalus microplus were examined in heifers to determine host immunity to the ticks. Tick counts and inflammatory cell infiltrates in skin biopsies from feeding sites of adult R. microplus ticks in nine-month-old Nguni and Bonsmara heifers were also evaluated. The molecular prevalence of A. marginale was similar in the Nguni (47.7 %) and local crossbred (52.3 %) cattle. Nguni cattle suffered less severe losses from and were more vi resilient to A. marginale infection than local crossbreds. Nguni heifers had lower coat scores, hair length and tick counts than the Bonsmara heifers. The relationship between tick counts and coat score was positive and linear in the Nguni (y = 1.90x – 0.40) and quadratic in Bonsmara (y = -7.98x2 + 12.74x - 3.12) heifers. Bonsmara cattle showed a more intense immediate reaction and no delayed hypersensitivity reaction to ULE of Rhipicephalus ticks. Nguni heifers presented a less intense immediate reaction and a delayed hypersensitivity reaction at 72 h post inoculation with ULE of Rhipicephalus ticks. Reactions to R. decoloratus ULE produced a more intense skin response at all time intervals in both breeds than that of R. microplus. Parasitized sites in Nguni heifers had higher (P < 0.05) counts of basophils, mast and mononuclear cells than those in the Bonsmara heifers. Conversely, parasitized sites in Bonsmara heifers had higher (P < 0.05) neutrophil and eosinophil counts than those in the Nguni heifers. Tick count was negatively correlated (P < 0.05) with basophil and mast cell counts. There was a positive correlation between eosinophil counts and tick counts in both breeds, and between tick counts and mononuclear cell counts in the Bonsmara breed. It was concluded that smooth and short coats, delayed type hypersensitivity and cutaneous basophil and mast cell infiltrations are responsible for increased tick resistance in the indigenous Nguni cattle breed of South Africa.
Ph.D. University of KwaZulu-Natal, Pietermaritzburg 2013.

Bacteriophage therapy has been exploited for the control of bacterial diseases in fauna, flora and humans. However, the advent of antibiotic therapy lead to a cessation of most phage research. Recently, the problem of antibiotic resistance has rendered many commonly used antibiotics ineffective, thereby renewing interest in phage therapy as an alternative source of control. This is particularly relevant in the case of bovine mastitis, an inflammatory disease of bovine mammary glands, caused by strains such as Staphylococcus aureus subsp. aureus Rosenbach 1884. Antibiotic resistance (primarily towards penicillin and methicillin) by staphylococcal strains causing mastitis is regularly reported. Phage therapy can provide a stable, effective and affordable system of mastitis control with little to no deleterious effect on the surrounding environment or the affected animal itself. Several studies have delved into the field of biocontrol of bovine mastitis using phages. Results are variable. While some phage-based products have been commercialized for the treatment of S. aureus-associated infections in humans, no products have yet been formulated specifically for the strains responsible for bovine mastitis. If the reliability of phage therapy can be resolved, then phages may become a primary form of control for bovine mastitis and other bacterial diseases. This study investigated the presence of S. aureus and its phages in a dairy environment, as well as the lytic ability of phage isolates against antibiotic-resistant strains of mastitic S. aureus. The primary goals of the thesis were to review the available literature on bovine mastitis and its associated control, and then to link this information to the use of phages as potential control agents for the disease, to conduct in vitro bioassays on the selected phages, to conduct phage sensitivity assays to assess phage activity against different chemical and environmental stresses, to morphologically classify the selected phages using transmission electron microscopy, to characterize the phage proteins using one-dimensional electrophoresis, and lastly, to characterize phage genomes, using both electrophoresis as well as full genome sequencing. Twenty-eight phages were isolated and screened against four strains of S. aureus. Only six phages showed potential for further testing, based on their wide host range, high titres and common growth requirements. Optimal growth conditions for the host S. aureus strain was 37°C for 12hr. This allowed for optimal phage replication. At an optimal titre of between 6.2x10⁷ to 2.9x10⁸ pfu.mlˉ¹(at 10ˉ⁵ dilution of phage stock), these phages were able to reduce live bacterial cell counts by 64-95%. In addition, all six phages showed pathogenicity towards another 18 S. aureus strains that were isolated from different milk-producing regions during a farm survey. These six phages were named Sabp-P1, Sabp-P2, Sabp-P3, Sabp-P4, Sabp-P5 and Sabp-P6. Sensitivity bioassays, towards simulated environmental and formulation stresses were conducted on six identified phages. Phages Sabp-P1, Sabp-P2 and Sabp-P3 showed the most stable replication rates at increasing temperatures (45-70°C), in comparison to phages Sabp-P4, Sabp-P5 and Sabp-P6. The effect of temperature on storage of phages showed that 4ºC was the minimum temperature at which phages could be stored without a significant reduction in their lytic and replication abilities. Furthermore, all phages showed varying levels of sensitivity to chloroform exposure, with Sabp-P5 exhibiting the highest level of reduction in activity (74.23%) in comparison to the other phages. All six phages showed optimal lytic ability at pH 6.0-7.0 and reduced activity at any pH above or below pH 6.0-7.0. Exposure of phages to varying glycerol concentrations (5-100%) produced variable results. All six phages were most stable at a glycerol concentration of 10-15%. Three of the six isolated phages, Sabp-P1, Sabp-P2 and Sabp-P3, performed optimally during the in vitro assays and were used for the remainder of the study. Morphological classification of phages Sabp-P1, Sabp-P2 and Sabp-P3 was carried out using transmission electron microscopy. All three phages appeared structurally similar. Each possessed an icosahedral head separated from a striated, contractile tail region by a constricted neck region. The head capsules ranged in diameter between 90-110nm with the tail length ranging from 150-200nm in the non-contractile state and 100-130nm in the contractile state. Rigid tail fibres were also visible below the striated tail. The major steps in the virus replicative cycle were also documented as electron micrographs. Ultra-thin sections through phage plaques were prepared through a modification of traditional methods to speed up the process, with no negative effects on sample integrity. The major steps that were captured in the phage replicative cycle were (1) attachment to host cells, (2) replication within host cells, and, (3) release from cells. Overall results suggested that all three phages are strains from the order Caudovirales and are part of the Myoviridae family. A wealth of information can be derived about an organism based on analysis of its proteomic data. In the current study, one-dimensional electrophoretic methods, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and ultra-thin layer isoelectric focusing (UTLIEF), were used to analyse the proteins of three phages, Sabp-P1, Sabp-P2 and Sabp-P3, in order to determine whether these strains differed from each other. SDS-PAGE analysis produced unique protein profiles for each phage, with band fragments ranging in size from 8.86-171.66kDa. Combined similarity matrices showed an 84.62% similarity between Sabp-P1 and Sabp-P2 and a 73.33% similarity between Sabp-P1 and Sabp-P3. Sabp-P2 showed a 69.23% similarity to Sabp-P3. UTLIEF analysis showed protein isoelectric charges in the range of pI 4.21-8.13, for all three phages. The isoelectric profiles for each phage were distinct from each other. A combined similarity matrix of both SDS-PAGE and UTLIEF data showed an 80.00% similarity between phages Sabp-P1 and Sabp-P2, and a 68.29% similarity between Sabp-P1 and Sabp-P3. Sabp-P2 showed a 70.59% similarity to Sabp-P3. Although the current results are based on putative protein fragments analysis, it can be confirmed that phages Sabp-P1, Sabp-P2 and Sabp-P3 are three distinct phages. This was further confirmed through genomic characterization of the three staphylococcal phages, Sabp-P1, Sabp-P2 and Sabp-P3, using restriction fragment length analysis and whole genome sequencing. Results showed that the genomes of phages Sabp-P1, Sabp-P2 and Sabp-P3 were all different from each other. Phages Sabp-P1 and Sabp-P3 showed sequence homology to a particular form of Pseudomonas phages, called "giant" phages. Phage Sabp-P3 showed sequence homology to a Clostridium perfringens phage. Major phage functional proteins (the tail tape measure protein, virion structural proteins, head morphogenesis proteins, and capsid proteins) were identified in all three phages. However, although the level of sequence similarity between the screened phages and those already found on the databases, enabled preliminary classification of the phages into the order Caudovirales, family Myoviridae, the level of homology was not sufficient enough to assign each phage to a particular type species. These results suggest that phage Sabp-P1 might be a new species of phage within the Myoviridae family. One longer-term objective of the study is to carry out complete assembly and annotation of all the contigs for each phage. This will provide definitive conclusions in terms of phage relatedness and classification.
Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Brucellosis is one of the neglected diseases in Nigeria. In Lagos, the commercial capital of Nigeria with about twenty one million people, a descriptive cross-sectional study was carried out in order to determine the sero-prevalence of brucellosis among people at risk in some selected abattoirs and secondary health care facilities (hospitals) in the state. Mixed sampling method was employed at the abattoir while convenient sampling method was used in sampling the respondents at the hospitals. Sera samples from three hundred and one (n=301) abattoir-based workers and traders; and one hundred and twenty one (n=121) hospital-based individuals which include people with febrile illnesses and blood donors were tested for brucellosis using Rose Bengal Plate test (RBPT), with indirect ELISA being used as a confirmatory test. Of the 301 abattoir-based workers and traders, 27 (8.97%) were sero-positive to the infection when Rose Bengal Plate test antigen was used. The twenty seven individuals consists of fifteen (15) butchers; four (4) veterinarians; two (2) meat transporters and bone/cow horn dealers each as well as one each of blood meal producer, abattoir engineer, water seller and meat supplier. When blood samples from the sero-positive individuals were subjected to ELISA, 3 (11.1%) were sero-positive to the brucellosis, while one is equivocal. These results confirm that agglutination observed on RBPT might be related to unknown cross-reactions and confirmation with a different test was necessary. None of the hospital-based respondents is sero-positive to the infection. The clinical signs significant for the infection in this study were fever, joint pain, lower backache, regular headache and miscarriage. Brucellosis awareness level among the respondents was very low. Data was analysed using (SPSS) version 20.0 at α0.05 significant level. The significant risk factors for human brucellosis according to this research are consumption of fura (unpasteurized milk) and wara (fresh cheese). The study revealed that brucellosis is not only an occupational disease but can also affect people who trade or live in proximity with infected animals.
Agriculture, Animal Health and Human Ecology
M. Sc. (Agriculture)

Text in English
Corridor disease is an economically important tick-borne disease of cattle in southern Africa. The disease is caused by Theileria parva and transmitted by the vectors, Rhipicephalus appendiculatus and R. zambeziensis. There is currently no vaccine to protect cattle against T. parva that is permitted in South Africa. To develop recombinant anti-tick vaccines against Corridor disease, comprehensive databases of genes expressed in the tick’s salivary glands are required. Therefore, in Chapters 2 and 3, mRNA from the salivary glands of R. appendiculatus and R. zambeziensis was sequenced and assembled using next generation sequencing technologies. Respectively, 12 761 and 13 584 non-redundant protein sequences were predicted from the sialotranscriptomes of R. appendiculatus and R. zambeziensis and uploaded to public sequence domains. This greatly expanded the number of sequences available for the two vectors, which will be invaluable resources for the selection of vaccine candidates in future. Further, in Chapter 3, differential gene expression analysis in R. zambeziensis revealed dynamic expression of secretory protein transcripts during feeding, suggestive of stringent transcriptional regulation of these proteins. Knowledge of these intricate expression profiles will further assist vaccine development in future. In Chapter 4, comparative sialotranscriptomic analyses were performed between R. appendiculatus and R. zambeziensis. The ticks have previously shown varying vector competence for T. parva and this chapter presents the search for correlates of this variance. Phylogenetic analyses were performed using these and other publically available tick transcriptomes, which indicated that R. appendiculatus and R. zambeziensis are closely related but distinct species. However, significant expression differences were observed between the two ticks, specifically of genes involved in tick immunity or pathogen transmission, signifying potential bioinformatic signatures of vector competence. Furthermore, nearly four thousand putative long non-coding RNAs (lncRNAs) were predicted in each of the two ticks. A large number of these showed differential expression and suggested a potential transcriptional regulatory function of lncRNA in tick blood feeding. LncRNAs are completely unexplored in ticks. Finally, in Chapter 5, concluding remarks are given on the potential impact the R. appendiculatus and R. zambeziensis sialotranscriptomes may have on future vaccine developments and some future research endeavours are discussed.
Life and Consumer Sciences
Ph. D. (Life Sciences)