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    Comparative study of subclinical fascioliasis in sheep and goats : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Veterinary Science at Massey University
    (Massey University, 1991) Mengesha, Kinfe Melak
    The literature on the identification of Fasciola spp. and their intermediate hosts, the general life cycle of Fasciola and aspects of the epidemiology, clinical signs, diagnosis and treatment of infections is reviewed. Two experiments were carried out. The first involved 18 weeks observations on 5 adult male goats each infected with 150 metacercartae of F.hepatica and 5 uninfected controls. The second involved groups of 10 sheep and 10 goats each infected with 200 metacercariae with 5 uninfected controls of each species. In both experiments, faecal, haematological, biochemical and pathological examinations were conducted. The animals were also weighed regularly. In the first experiment, although only 15-35 flukes were established, measurable and, in many cases, statistically significant changes in a variety of parameters were observed. A depression in packed cell volumes relative to controls of approximately 20% occurred. Though haemoglobin, mean corpuscular volume and mean corpuscular haemoglobin concentration levels remained within the normal ranges, erythrocyte levels in the infected group were significantly lower than in the controls and there was a tendency for the anaemia to become macrocytic. This suggests that goats may be particularly susceptible to the effects of blood loss associated with Fasciola infections though further work is needed to confirm this. A marked peripheral eosinophilia and elevation in fibrinogen levels were observed in infected animals. Albumin levels decreased, globulin levels increased and the A/G ratio decreased significantly relative to the control group but all levels remained within the normal ranges. In infected animals, gamma glutamyl transferase (GGT) and glutamyl dehydrogenase (GD) levels rose to beyond the limits of the normal ranges although aspartate aminotransferase (AST) levels, which were also significantly elevated, did not. The results indicate that serum GD and GGT are particularly sensitive indicators of damage to the liver parenchyma and bile ducts caused by F.hepatica in goats and that GD is more sensitive than AST. Serum bile acids were estimated but no significant change was detected. The ratio between faecal egg counts and the numbers of adult flukes present at necropsy was consistently lower than described for sheep with a mean of approximately 13epg/fluke (range 9-23) at the final sampling and 18epg/fluke (range 11-29) in the previous week when the egg counts were highest. This is potentially of considerable diagnostic importance and needs further investigation. In the second experiment, the number of flukes established was extremely low in both species (mean 0.85% & 2.95% in the sheep and goats respectively) although more goats than sheep became infected. Pre-existing liver pathology in the sheep was a further complication. Consequently, little information of value was generated by the infection of goats and no data that could be used for comparative purposes were obtained from the sheep infection. However, combination of the data from the 13 infected goats from both experiments yielded some useful information in relation to serum enzyme levels. Correlations between the numbers of flukes recovered at necropsy and peak levels of serum enzymes and various haematological parameters in individual animals were examined though only those relating to enzyme levels were statistically significant. The correlation coefficients between peak enzyme levels and fluke numbers indicated that the relationship was strongest with GGT and weakest with AST. However, regression analysis showed that there was no predictive value in the relationship with any of the enzymes because of extremely wide confidence intervals for predicted fluke numbers.
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    The disposition of metronidazole in goats and its relevance to the treatment of anaerobic infections : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science at Massey University
    (Massey University, 1988) Dillon, Elizabeth Amanda
    The recent commercial developments in goat farming in New Zealand, have led to an increase in the value of individual goats and to a growing interest in caprine diseases. The importance of anaerobic bacteria other than the Clostridia, as potential pathogens in humans and animals, has also only recently been recognised, even though anaerobic bacteria have been identified since 1861. Various members of this bacterial group are known to be involved in different conditions of goats, particularly in wound and foot infections. Metronidazole (Flagyl'Flagyl', May & Baker (NZ) Ltd.) is a bactericidal agent which has a specific action against anaerobic micro-organisms. This drug is already widely used in the treatment of selected diseases in dogs, cats and humans, but there was little information available on its use in goats. The study which forms the basis of this thesis, was to investigate the disposition of metronidazole in eight goats. Both IV and IM routes of administration were studied in the form of a cross-over experiment. Silicone tubing "cages" were implanted subcutaneously, so that the metronidazole concentration versus time profile could be determined, both in serum and in interstitial fluid. The analysis of serum and tissue cage fluid samples was undertaken using a high pressure liquid chromatography unit, which proved to be reliable over the range of concentrations tested. The system consisted of a Waters Model 6000 A solvent delivery system, a U6K injector, a Z-module radial compression separation system and a Waters programmable automator, Model 710. The mobile phase used was a 75:25 mixture of aqueous potassium hydrogen phosphate and methyl alcohol; this was adjusted to a running speed of 1.5 mls per min. A 450 variable wavelength detector was set at either 0.01 or 0.04 absorbance units, and a constant wavelength of 312 nm. Given these concentration profiles, a full pharmacokinetic analysis was carried out using standard statistical procedures. The following values were determined: maximum serum and tissue cage fluid concentrations (CmaxIV, CmaxIM, CmaxIVtc), time to maximum serum and tissue cage concentration (TmaxIV, cmaxIMtc TmaxIMtc), serum concentration (extrapolated) at zero time (B, B'), half-life (t1/2), elimination rate constant (B,B'), volume of distribution (Vd(area)), area under the concentration curve (AUC), total body clearance (ClB), absorption rate constant (kab), percentage penetration of metronidazole into tissue cage fluid, percentage of drug absorbed into the systemic circulation following IM administration (F), and the total amount of drug which was absorbed into the systemic circulation (in mg/kg). Following IV administration of a 0.5% w/v solution of metronidazole at a dose rate of 20 mg/kg BWgt, the t1/2 at 0.94±0.08 per hour (n=8) was rapid and consistent with a high figure for the elimination rate constant at 0.79 ± 0.09 per hour (n=8). The total body clearance, a more sensitive indicator of the biotransformation and excretion processes than t1/2, was also rapid (0.32 = 0.06 L/kg/hr) which is in keeping with the efficient drug metabolism of the goat. This may account for the low Vd(area) which was unexpected for a basic drug of this nature in the ruminant. Critical parameters for drug concentrations and durations of effect are summarized in Table I. Metronidazole was rapidly detected in both sera and interstitial fluid (within 0.25 hrs) following the intramuscular administration of a 40% suspension of metronidazole at a dose rate of 20 mg/kg BWgt. The uptake of metronidazole from the injection sites differed markedly between individual goats, resulting in a mean absorption percentage of 42.4%±8.8% (n±8), equivalent to 8.4 mg/kg BWgt. Maximum serum levels were achieved within approximately one hour of IM administration, but the peak was more than ten-fold lower than the corresponding concentration found in serum following IV administration. Peak tissue cage drug concentrations were not achieved until four hours after IM administration. The maximum drug concentration in tissue cage fluid was greater than the MIC upper threshold for a variety of anaerobic bacteria (12.5 mcg/ml), and this was maintained for 5.5 hrs. The lower limit of the MIC of 3.0 mcg/ml was exceeded for a correspondingly longer period. Further pharmacokinetic analysis of the experimental data made it possible to calculate specific medication schedules for the goat. These were established on the basis that serum metronidazole concentrations should be maintained at a level which was bactericidal for the majority of anaerobic bacteria, which included Bacteroides spp., Fusibacterium spp., and Clostridia spp. The recommendation given was that 0.5% w/v metronidazole solution should be administered at a dose rate of 20 mg/kg BWgt and repeated every 4-6 hrs. Using the 40% w/v metronidazole suspension, the dose rate should be 45 mg/kg BWgt and the medication should be repeated every 10-12 hrs. In each case the loading dose was only fractionally greater at 20.3 mg/kg BWgt and 48.5 mg/kg BWgt respectively. The drug concentration in interstitial fluid (tissue cage fluid), gave some indication of the antimicrobial activity in extravascular tissues, a feature which can not be extrapolated from a profile of serum concentrations.
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    An assessment of methods for the quantitation of lung lesions in sheep and goats : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy at Massey University
    (Massey University, 1991) Valero-Elizondo, German
    Although pneumonia is one of the most common diseases of ruminants worldwide, there is a wide variation in the way research workers have assessed the severity of pneumonic lesions. The problem is further complicated by the variable accuracy observers may have in judging the proportions of pneumonic areas in affected lungs. The work reported here was undertaken to evaluate the methods available for quantitation of pneumonia in livestock killed in slaughterhouses. Some of the methods were then used to investigate the prevalence and variety of pneumonic lesions in the lungs of 4284 goats killed in a North Island slaughterhouse during the winter months. A preliminary study of the postmortem change in lung volume demonstrated that the greatest decrease occurred from 3 to 24 hours postmortem, at which time there was an average loss of volume of 10%. A measurable decrease in lateral area occurred after 8 hours postmortem, and peaked at 96 hours with an average decrease of 8%. Image analysis was efficient in detecting changes in lung area, but the positioning of the lungs at the time of photography was a source of measurement error. In assessing pneumonic surface areas there was no advantage in photographing a mid-sagittal section of the lungs over a dorso-lateral view of the whole lungs, but lungs separated into left and right sides before photography gave less distortion than if left attached to the trachea. An image analysis technique proved to be more accurate than a paper silhouette technique for measuring lung areas. While measuring the densities of the lungs, it was found that the density of the non-pneumonic portions of lung varied markedly between animals. This variation should be taken into account by using a formula to calculate the proportion of pneumonic tissue within each lung. A formula was derived which can be applied in all species when an objective estimate of the amount of pneumonic tissue is necessary, or a volumetric rather than an area value is required; but the need to sample and measure a non-pneumonic portion makes this technique inappropriate for routine work. It was concluded that even though the percentage of lung volume impaired by pneumonia may be theoretically more important than the percentage of affected area, its measurement is too time consuming for routine use. Simple measurement of whole lung density is a poor indicator of the extent of pneumonia, while the measurement of pneumonic areas tended to overestimate the volume of pneumonic tissue. This is compounded by the irregular shape of the lungs and differences in spatial distribution of lesions. A survey of 4284 goat lungs revealed only ten cases of bronchopneumonia. Forty-one percent of the lungs had lesions compatible with Muellerius capillaris: 33% had lesions compatible with Dictyocaulus filaria, and 8% had both types simultaneously. The prevalence of parasitic lesions increased with age. There was a statistical correlation between the severity of dictyocaulus lesions, the presence of nodular muellerius lesions, and low carcass weight. The carcasses of goats with mild to severe Dictyocaulus filaria lesions were from 0.81 to 1.52 kg lighter than those of animals without these lesions. The carcasses of goats with more than 10 nodular (Muellerius capillaris) lesions were 0.75 kg lighter than those of animals without these lesions. Twelve sets of lungs had lesions of chronic bronchiectasis. Parasite larvae were seen in the bronchial lumina of three of them. The microscopic appearance varied from a moderate dilatation of occluded bronchi which retained an intact epithelium, to large foreign-body granulomas where the remaining bronchial outlines were barely discernible. Subpleural lymph nodes were a common finding in more than 4% of goat lungs. Their frequency varied between flocks from as little as 2% to as much as 27%. Their distribution, architecture, and differentiation from the pulmonary lymphoid nodules described in cattle with dictyocaulus reinfection syndrome are discussed. Multifocal fibrous pleural plaques were found in two cases of the over 4000 goat lungs sampled. They have not been described previously in the veterinary literature. Pleural adhesions were found in 350 cases (8.16%). The relatively higher frequency of pleurisy versus pneumonia suggests that pneumonia in goats in the North Island of New Zealand completely resolves in most cases and probably has a seasonal occurrence, with a much lower prevalence than chronic non-progressive pneumonia of sheep.
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    A study of Leptospira interrogans infection in deer and goats in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Microbiology at Massey University, Palmerston North, New Zealand
    (Massey University, 1988) Flint, Stephen Harry
    In order to determine the prevalence of leptospirosis in deer and goats both serological tests and the culturing of bacteria from urine samples were used. The serological tests enabled an assesment to be made as to the nature and extent of antibody levels. To ensure confidence in the serological results, it was necessary to validate the standard microscopic agglutionation test (MAT). Repeat tests demonstrated reproducible results that were within one two-fold serial dilution. Enzyme linked immunosorbent assays (ELISA) were investigated as alternatives for both the detection of antibodies and Leptospira antigens. These assays demonstrated greater sensitivity than the MAT for the detection of antibodies, but were less sensitive than standard methods for the detection of antigen. Using the MAT, antibodies to australis, ballum, bratislava, copenhageni, hardjo, pomona, and tarassovi were detected in serological surveys of deer and goats. In deer, the most frequently recorded antibody titres were to ballum, bratislava and copenhageni. As 87% of the antibody titres <80, there appears to be a low level of active infection. In some areas there was a high prevalence of antibody titres to hardjo. In goats, 70% were found to have antibody titres ≥10 to one or more serovars with antibodies to ballum and bratislava the most frequently recorded. As 90% of the antibody titres were <80, there appears to be a low level of active infection in goats. Antibodies to bratislava, a serovar that has not been isolated in New Zealand, were widespread in both deer and goats. The possibility that these resulted from mixed infections was considered but not resolved. Unsucessful attempts were made to purify mixed cultures using specific antisera. The possibility of serological cross reactions of antibodies to other serovars with bratislava was supported by the increased serological response of deer and goats to vaccination with hardjo and pomona antigens. Western blot studies identified several common antigens between bratislava and pomona. A study of a deer farm showed a high prevalence of antibody titres to hardjo corresponding to a similar prevalence of antibody titres to balcanica believed to be due to the antigenic similarity of these two serovars. Balcanica was isolated from urine samples from these deer and is believed to be the first isolation of this serovar from deer. Studies of six goat, farms showed low antibody levels and no Leptospira were isolated from urine samples.