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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

Bovine respiratory disease complex (BRD) consists of a largely single clinical entity of bronchopneumonia that is usually associated with the assembly of large numbers of especially weaner cattle into a feedlot environment. It has a multifactorial aetiology and develops as a result of complex interactions between environmental factors, host or animal factors and pathogens. It is often difficult to determine the exact role played by the various pathogens involved in an individual outbreak of disease. None of the many organisms isolated will on their own, reliably reproduce the natural disease in experimental animals. Observations from research studies and clinical experience have indicated that the presence of mycoplasmas increases the severity of respiratory disease. However, the role of Mycoplasma spp. in BRD complex as a primary or secondary pathogen remains controversial. The various stresses associated with the feedlot causes a breakdown of the defense mechanisms that normally hold the nasal infections in check, resulting in a rapid proliferation of virulent Mannheimia haemolytica serotype A1 in particular and the spread to the lower respiratory tract. The various viruses and mycoplasmas have however been shown to have the same effect as stress on the Pasteurella populations of the nasal mucosa. More than 10 species of Mycoplasma have been isolated from the bovine respiratory tract, but not all are pathogenic. They are able to act as a stress-causing agent, leading to a decreased host defense mechanism by altering the immune responsiveness or by causing tissue damage and thereby allowing bacteria to invade and colonise the lung and so causing a severe pneumonia. M. bovis and M. dispar are the more important lung isolates, with M. bovis being the most invasive and destructive and has been shown to increase the severity of calf pneumonias. M. bovis has been isolated from bovine pneumonias, arthritis, mastitis, tendosynovitis, genitalia, keratoconjunctivitis and is considered to be the primary pathogen in endemic pneumonia in younger calves. According to the literature, mycoplasmas are isolated from 25% to 80% of pneumonic lungs in feedlot cattle and the aim of the study was to identify the isolation rates in South African feedlots over a period of 2000 to 2004. To achieve this, 446 transtracheal aspirates (TTA’s) were collected from more than 25 feedlots around South Africa, except for the western Cape. Collection criteria included: pulled for respiratory disease; febrile (≥40ºC); depressed; anorexia and/or lack of rumen fill; nasal discharge or failure to clean muzzle; cough; increased respiratory rate >40 and most importantly, no prior treatment. Samples were also collected from 31 ‘healthy’ animals as controls. Samples collected were used for Mycoplasma isolations, as well as the aerobic bacteria to establish an antibiogram profile of bacteria commonly isolated in cattle feedlots. Mycoplasma spp. were isolated from 52.8% of samples taken from sick animals, with 67 out of 201 isolates (33.3%) being identified as M. bovis. According to the literature, M. bovis, M. haemolytica or P. multocida are isolated from bronchial lavage fluids from healthy calves in only a few cases, with estimates being put at 5 – 10% levels for Mycoplasma. Isolation rates of Mycoplasma spp. from healthy animals in this study was 22.7%, which was considerably higher than anticipated and could possibly be due to problems with the definition of a healthy animal. Although the number of samples from healthy animals was relatively small in this study, it was possible to show that there was a statistically significant association between Mycoplasma isolation and respiratory disease, p = 0,001 and with an odds ratio (OR) of 3,75 in cattle from those feedlots included in the study and thereby proving the hypothesis put forward. / Dissertation (MMedVet (Bovine Medicine))--University of Pretoria, 2007. / Production Animal Studies / MMedVet / Unrestricted

Corpus luteum (CL) dysfunction has been implicated among various factors predisposing early embryonic mortality in cattle. Two experiments were conducted to evaluate the efficacy of using human chorionic gonadotropin (hCG) given either at the time of breeding (day 0) , day 7 or 14 post breeding, in reducing that component of early embryonic mortality caused by CL dysfunction. The aims of experiment 1 were to investigate the effectiveness of using hCG, in inducing the development of accessory CL, their formation and growth, and the effect of such treatments on the function of both the induced and spontaneous CL. Thirty-four lactating Holstein cows were randomly assigned to one of four treatments. A single intramuscular injection of 1000 IU of hCG was given either at the time of breeding (day 0, n=8), day 7 (n=9) or 14 (n=9) post breeding or no hCG given (control, n=8). A real-time ultrasound machine was used to study follicular dynamics and CL growth. The CL and antral follicle diameter was determined using a built-in system of calibrated callipers. Ultrasound scanning was carried out on days 7, 9, 11, 14, 16, 18, 21, 28, 35 and 42 post breeding. Blood and milk samples, for progesterone (P₄) determination using radioimmunoassay, were collected on days coincident with ultrasonography. Diameter of the CL is presented as the sum of the diameter of all luteal tissue in each animal. Differences in CL diameter, milk and plasma P₄ were analyzed using the General Linear Models Procedures while pregnancy data were analyzed using Chi-Square analysis in Statistical Analysis Systems (SAS, version 6.3). Based on the day 7 ultrasound scanning, the incidence of twin ovulations was higher among cows treated on day 0 (3/8) compared to control cows (1/8) and day 7 (1/9). Accessory CL were detected in 7/9 of the day 7-treated cows compared to 4/9 among the day-14 treated cows. Least squares means (LSMeans) for CL diameter were significantly higher (P<0.001) among cows treated with hCG compared to control cows starting at day 7 continually until day 42. Plasma P₄ profiles were significantly higher (P<0.05), at days 18, 35 and 42, in cows treated on day 7 or 14 compared to control cows. The first detectable differences (P<0.05) between hCG treated and control cows, in milk P₄ occurred at day 21 and persisted until day 42. Pregnancy rates were highest among cows treated with hCG on day 7 where 6 of the 9 cows were diagnosed pregnant. Corresponding pregnancy rates for day 0, 14 or control cows, were 4/8, 5/9 and 3/8, respectively. In the second experiment, two trials were conducted at two different farms to investigate the efficacy of using hCG to increase milk P₄ and pregnancy rates. In trial one, 79 lactating Holstein cows were exposed to the treatment protocol described in experiment 1. In addition to the milk sample collection schedule given in experiment 1, a sample was collected on day 0. Milk samples were stored at 4°C and later transported to the UBC laboratories for P₄ analysis. LSMeans for milk P₄ concentrations were different only at days 16 and 18 post breeding. Pregnancy rates were improved (P<0.01) by hCG treatments. The respective pregnancy rates for cows receiving hCG on day 0 (n=20), 7 (n=20), 14 (n=20) or control (n=19) were 25, 35, 35 and 21 %. In the second trial, 121 lactating Holstein cows were randomly assigned to treatments as described earlier. Weekly milk samples were collected from each animal and assayed for P₄ as described above. LSMeans for milk P₄ were significantly different (P<0.05) among groups starting at day 14 until day 42 post breeding. hCG increased pregnancy rates over control cows. The pregnancy rates for cows treated on day 0, 7, 14 and control were 31, 50, 41 and 26 %, respectively. In conclusion, this study revealed that treatment with hCG induced accessory CL development, increased P₄ production and improved pregnancy rates. It is evident, too, that treatment with hCG on day 7 post breeding may have greater potential for improving pregnancy rates not only in dairy and beef cattle but equally beneficial to the embryo transfer programmes. Increased pregnancy rates confirm the hypothesis that CL dysfunction does cost the livestock industry appreciable losses in embryos. / Land and Food Systems, Faculty of / Graduate

The objective of this study was to evaluate the suspected endocrine disruptive effect of molasses included in cattle feed. During the mid 1990's a potentially serious, chronic syndrome was reported in well-managed beef and dairy herds from unrelated parts of South Africa. Farmers reported that it manifested as various combinations of seriously decreased production, increased reproductive disorders, apparent immune incompetence in previously immune competent animals, various mineral imbalances in non¬deficient areas and goitre, perceptible by enlarged thyroids. Farmers related this syndrome to certain batches of sugarcane molasses and molasses¬based products. Their opinion was based on observations that dramatic improvements in health and productivity often followed the withdrawal of the molasses component of the diet. The syndrome had all the characteristics of an "endocrine disruptive syndrome". Endocrine disrupting compounds (EDCs) are exogenous substances that have the potential to alter the functions of the endocrine system and consequently cause ill health. The EDCs comprise a diverse group of compounds that are widely used in detergents, in the paint and plastics industries and as wetting agents in agricultural remedies. Contamination of molasses with these compounds could occur as a result of uptake of chemicals by growing sugarcane or by the use of contaminated river water in the extraction of sugar from chopped sugarcane. It was essential to investigate the safety of molasses, currently available as stock feed in South Africa and the rest of the world, to allay any fears created by the farmers. Four batches of molasses previously collected from four different sugar mills located in different parts of the country were screened for potential endocrine disruptive activity, including oestrogen and thyroid activity and immune suppression. Two batches of molasses were selected to be used in a calf feeding trial. Thirty-two, 4 to 6 week-old Holstein bull calves of approximately the same weight, and supplied by the same rearing facility, were included in a single phase, three treatment, parallel design experiment. Calves from the three experimental groups were housed in the same facilities, under the same conditions and fed diets with similar composition. Two of the groups had molasses (Umzimkulu and Komatipoort) included in their rations and the control group was fed a ration where no molasses was added, but fermentable sugars and minerals were included. The weight gain of the calves was recorded over a six-month study period. Regular clinical examinations were conducted and clinical pathology parameters, immune responses and endocrine effects were evaluated. Even though endocrine disrupting effects were detected in in vitro screening tests, these could not be reproduced in calves under experimental conditions. The two batches of molasses utilized in the calf feeding trial did not induce major differences in any of the parameters measured, except a lower weight gain in the Umzimkulu molasses fed group which tended towards significance. It appears improbable that these two batches of molasses had any endocrine disruptive or immunosuppressive effects. Therefore, these two batches of molasses per se were not deleterious when fed to calves. / Dissertation (MSc (Veterinary Sciences))--University of Pretoria, 2006. / Paraclinical Sciences / unrestricted

The aim of this study was to determine the efficacy of vaccination in preventing LSDV excretion in semen and negative effects on semen quality. Lumpy skin disease (LSD) is caused by a virus in the genus Capripoxvirus of the family Poxviridae. The virus has been reported to be excreted in the semen of experimental infected nonvaccinated bulls. Nevertheless, vaccination has been the most widely used method to reduce and prevent the spread of the disease. This work was done to determine the efficacy of lumpy skin disease vaccination in preventing the excretion of lumpy skin disease virus (LSDV) in semen of experimentally infected vaccinated bulls. It also determined further the effect of vaccination and experimental infection on semen quality. Six serologically negative bulls 11-16 months of age were vaccinated with an attenuated Neethling strain of LSD vaccine, and a repeated dose of vaccine was given twenty one days later. These bulls were then experimentally infected by intravenous injection with a virulent field strain of LSDV (V248/93). Six unvaccinated bulls were similarly infected to act as controls. All animals were observed for clinical signs, blood and semen was collected and evaluated twice a week until day 40 post vaccination and every two days until day 28 post-infection when the trial was terminated. Serology was done using the serum neutralization test and viraemia was determined by virus isolation. Semen was examined by polymerase chain reaction (PCR) for the presence of virus. Semen evaluation was done visually and microscopically. Two of the unvaccinated controls developed severe LSD, two showed mild symptoms and two were asymptomatic. No clinical abnormalities were detected following vaccination, and clinical signs were limited to mild lymph node enlargement in four bulls following challenge of the vaccinated bulls. There was a significant difference (P<0.05) in semen quality after experimental infection of the unvaccinated bulls. In the vaccinated bulls, semen quality showed no significant difference (P>0.05) following vaccination and challenge. Three of the vaccinated bulls were serologically positive at the time of experimental infection and four at the end of the trial. Five unvaccinated bulls were found to be viraemic during the course of the trial. No vaccinated bulls were found to be viraemic at any stage. Four unvaccinated bulls excreted the virus in their semen during the course of the trial. Viral nucleic acid was not detected in any semen samples following vaccination or challenge in vaccinated bulls. This study provides evidence that vaccination against LSD prevented the excretion of viral particles in semen. It also illustrated that LSD vaccination prevented any effect on semen quality after experimental infection with virulent virus. / Dissertation (MSc (Production Animal Studies))--University of Pretoria, 2006. / Production Animal Studies / unrestricted

This study was conducted to confirm the presence of bovine tuberculosis (BTB) and determine its prevalence, based on skin test reactivity, in cattle reared under extensive farming conditions in the Govuro district, Inhambane province, Mozambique. The study was comprised of a primary screening test using the single intradermal test (SIT) in randomly selected animals from Colonato and Sede dip tanks in Govuro. Positive reactors to the SIT were tested again with bovine and avian tuberculin using the single intradermal comparative test (SICTT) 7 weeks after the SIT. The sample size was calculated using Win Episcope 2.0 based on 95% confidence to detect a 2% expected prevalence using the SIT, with a 1% accepted error and accounting for a total population size of 7208. The calculated sample size was 682 animals. To compensate for the probability of 20% default in reading, the sample size was increased to 853. During the testing process (SIT), it was evident from the first 3 reading days that the apparent prevalence (61, 94%) was higher than expected (2%), hence we decided to stop when the total number of cattle was 530. During the testing process (SIT), it was evident from the first 3 reading days that the apparent prevalence (61.94%) was far higher than expected (2%), hence we decided to stop when the total number of cattle was 530. This was due to the fact that, at such a high prevalence, it would not be necessary to achieve as high a precision as 1% accepted error. A sample size of 530 would be sufficient to achieve a precision of 4% accepted error, which was regarded as more than adequate. The 530 cattle, 3 or more years of age, were selected using systematic random sampling from the two dip tanks (Colonato 371 and Sede 159 animals). All animals were identified by numbers painted, dorsally on the sacral region. Out of 530 tested cattle by SIT, 268 were read, and 166/268 (61.94% with 95% confidence interval [CI]: 55.8 – 67.8%) were found positive, with visible swallow at the injection site. Apparent prevalence (AP) was found to be 61.94% while the true prevalence (TP) was 75.92%. The predictive value of a positive result (PV+) was found to be 87.9%. No significant difference in apparent prevalence between the two areas was detected by Fisher’s exact test (P = 0.11). By SICTT, out of 28 animals positive reactors to SIT, 21 were possible to read, and 13/21 (61.9%; 95% CI: 55.1 – 89.3%) were found positive. A three year old bull, positive reactor to the SIT, was slaughtered, and a detailed post mortem was carried out and organs with visible lesions were collected for further laboratory testing (histopathology, culture and isolation of M. Bovis and PCR). Later on, 30 more positive reactors to the SIT test were slaughtered: 25/30 (83.3%) showed visible lesions compatible with BTB, and total condemnation of carcass was made in 3/25 (12%) due to generalized lesions. The high prevalence rate of skin test positive animals as well as gross lesions and histopathology were confirmed to be BTB by the isolation and identification of M. Bovis by culture and PCR. Our results suggest that bovine tuberculosis is highly prevalent in Govuro district and may thus represent a potential health problem of zoonotic tuberculosis in humans. Our results suggest that BTB has reached the plateau phase of endemicity in cattle in Govuro district. In this context, the positive predictive value of the SIT is very high and thus the use of the SICTT as a confirmatory test has a limited value and should not be advocated. Our results further indicate that no other prevalence study of BTB should be conducted in the next few years in Govuro district, unless comprehensive control measures are implemented. The focus of further studies should be on the isolation and the molecular characterization of M. Bovis from cattle and humans in order to assess transmission routes and the role played by BTB in human TB cases in Govuro district. Copyright / Dissertation (MSc (Veterinary Tropical Diseases))--University of Pretoria, 2009. / Veterinary Tropical Diseases / unrestricted

No description available.