Academic literature on the topic 'Fields of Research – 300000 Agricultural, Veterinary and Environmental Sciences – 300500 Veterinary Medicine'

This study investigated whether behavioural and cognitive dysfunction caused by mucopolysaccharidosis (MPS) IIIA can be detected early in affected dogs’ lives, and to describe the behaviours of these dogs. No other scientific papers have been published on this topic and the population of dogs examined in this study are the only MPS IIIA affected dog colony available worldwide for study. Three main tests were performed on the population of MPS IIIA affected dogs. Physical behavioural assessment tests were performed at six and eight weeks of age and from twenty weeks of age a cognitive function task was taught and then tested to measure the dogs’ performance. A previously validated questionnaire, the canine behavioural assessment and research questionnaire (C-BARQ), was completed at three, six and twelve months of age. The researchers in these studies were blinded to the MPS IIIA status of the dogs examined. The behaviours shown by the MPS IIIA puppies at six and eight weeks of age were not significantly different from the behaviours of the unaffected puppies. This finding supported the research of other MPS IIIA studies and suggests that clinical behavioural changes do not occur at such a young age. The behaviours shown by the MPS IIIA affected puppies appeared to be normal puppy behaviours similar to those described in previous research on puppies. The C-BARQ measured the behaviours shown by the MPS IIIA affected and unaffected dogs. Most of the MPS IIIA affected dogs’ behaviours were not significantly different from the unaffected dogs’ behaviours, but MPS IIIA affected dogs did retrieve significantly more than unaffected dogs at three months of age, and were less distractible at twelve months of age. It would be worth investigating these findings further to decide whether it suggests a subtle alteration in brain functioning. The cognitive function test showed a significant decrease in the success of the MPS IIIA affected dogs in the final maze test. This is the first study on dogs affected with MPS IIIA to find a decline in cognitive function before the occurrence of cerebellar clinical signs and this new knowledge may lead to future developments measuring therapy response and disease progression. The T-shaped maze testing may be valuable in future research on cognitive function in dogs with other diseases such as epilepsy. Thus this thesis provides valuable information on canine MPS IIIA and provides a foundation for future disease investigations.

Inherited rickets of Corriedale sheep is a newly discovered skeletal disease of sheep with simple autosomal recessive inheritance. The clinical signs resemble rickets in other species and include decreased growth rate, thoracic lordosis and angular limb deformities. Radiographic features include physeal thickening, blurred metaphyseal trabeculae and thickened porous cortices. Computed tomography scanning of long bones reveals increased bone mineral content and cortical area, but decreased bone mineral density. Gross lesions include segmental thickening of physes, growth arrest lines, collapse of subchondral bone of the humeral head, thickened cortices and enthesophytes around distal limb joints. Microscopically there is persistence of hypertrophic chondrocytes at sites of endochondral ossification, inappropriate and excessive osteoclastic resorption, microfractures and wide, unmineralised osteoid seams lining trabeculae and filling secondary osteons. Affected sheep are persistently hypophosphataemic and hypocalcaemic. Normal serum 25-hydroxyvitamin D3 concentration accompanied by a two-fold elevation in 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) suggested a defect in endorgan responsiveness to vitamin D as a likely mechanism, but this was not supported by in vitro studies using cultured skin fibroblasts. These studies revealed normal vitamin D receptor function and the presence of 24- hydroxylase mRNA in cells from affected sheep, even without induction by 1,25(OH)2D3. Inappropriate overexpression of 25-hydroxyvitamin D3-24- hydroxylase, the enzyme that breaks down active vitamin D, is therefore considered the probable cause of inherited rickets in Corriedale sheep. Such a mechanism has not previously been described as a cause of inherited rickets in humans or other animal species. Treatment of affected sheep with high oral doses of vitamin D3 weekly for 3 months showed a trend towards increased bone mineral density, thus supporting an intact vitamin D receptor. Preliminary studies on immune function revealed reduced numbers of CD4+ and CD8+ lymphocytes and reduced interferon-? production by lymphocytes stimulated with parasite antigen. This new form of inherited rickets may be widespread in

Ovariohysterectomy and castration are common surgical procedures in small animal practice that can result in clinically significant postoperative pain. One way of controlling postoperative pain is administration of a single analgesic or a combination of different classes of analgesics prior to the onset of noxious stimuli. A constraint to the perioperative use of traditional opioids and non-steroidal anti-inflammatory drugs (NSAIDs) is their undesirable side effects. In this series of experiments, the preventive (pre-emptive) analgesic efficacy of two popular human analgesics, tramadol (an ?atypical? opioid) and parecoxib (a NSAID with selective COX-2 inhibition) was evaluated in dogs. Initially, the efficacy and renal safety of parecoxib, tramadol and a combination of parecoxib, tramadol and pindolol (a -adrenoceptor blocker and 5-HT1A/1B antagonist) were screened in anaesthetised healthy dogs. These analgesics increased the dogs? nociceptive threshold to mechanical stimuli, without causing significant alterations in the dogs? glomerular filtration rate (GFR) estimated by plasma iohexol clearance. Subsequently, the efficacy of tramadol was compared with morphine, in dogs undergoing ovariohysterectomy or castration. The Glasgow composite measure pain scale-short form score (CMPS-SF) and changes in intraoperative electroencephalogram (EEG) responses were used to assess the efficacy of analgesics. Of the three treatment groups (preoperative morphine, 0.5 mg kg-1; preoperative tramadol, 3 mg kg-1; a ?combination? of preoperative low-dose morphine, 0.1 mg kg-1, and postoperative tramadol 3 mg kg-1), dogs given the ?combination? had significantly lower pain scores after ovariohysterectomy. In castrated dogs, preoperative tramadol (3 mg kg-1) and morphine (0.5 mg kg-1) were tested and no significant difference in the CMPS-SF score were observed between them. Changes in EEG variables were not specific between the treatment groups in ovariohysterectomised dogs. Finally, the efficacy of test drugs was evaluated against acute noxious electrical stimulation in anaesthetised dogs, using EEG. Median frequency of the EEG, a reliable indicator of nociception, increased significantly in tramadol and parecoxib groups, compared to morphine, after electrical stimulation. These studies demonstrated that tramadol and parecoxib can produce analgesia in dogs with insignificant side effects. The efficacy of tramadol appears to vary with the type of noxious stimulus. A complete prevention of noxious input by administration of analgesics pre- and post-operatively could have important clinical applications.

Yellow-eyed penguins have suffered major population declines and periodic mass mortality without an established cause. On Stewart Island a high incidence of regional chick mortality was associated with infection by a novel Leucocytozoon sp. The prevalence, structure and molecular characteristics of this leucocytozoon sp. were examined in the 2006-07 breeding season. In 2006-07, 100% of chicks (n=32) on the Anglem coast of Stewart Island died prior to fledging. Neonates showed poor growth and died acutely at approximately 10 days old. Clinical signs in older chicks up to 108 days included anaemia, loss of body condition, subcutaneous ecchymotic haemorrhages and sudden death. Infected adults on Stewart Island showed no clinical signs and were in good body condition, suggesting adequate food availability and a potential reservoir source of ongoing infections. A polymerase chain reaction (PCR) survey of blood samples from the South Island, Stewart and Codfish Island found Leucocytozoon infection exclusively on Stewart Island. The prevalence of Leucocytozoon infection in yellow-eyed penguin populations from each island ranged from 0-2.8% (South Island), to 0-21.25% (Codfish Island) and 51.6-97.9% (Stewart Island). The high prevalence on Stewart Island represented the infection of 100% of chicks and 83% of adult yellow-eyed penguins when tested by PCR. Sequencing of Leucocytozoon sp. DNA found similarities between infections in yellow-eyed penguin adults and chicks, but differences to Leucocytozoon sp. DNA obtained from Fiordland crested penguins. These findings support the suggestion of cross infection between adults and chicks, and indicate that endemic infection in yellow-eyed penguins is unrelated to that in Fiordland crested penguins. Examination by histology and electron microscopy showed tissue megaloschizonts and circulating round gametocytes. Megaloschizonts up to 440µm diameter showed an affinity for hepatic and splenic tissue and were observed releasing occasional intact cytomeres. Round gametocytes were observed within leucocytes in visceral sections, but not peripheral blood smears. The morphology of Leucocytozoon sp. in yellow-eyed penguins showed similarities to the pathogenic species L. simondi and L. sakharoffi but not L. tawaki. A successful treatment protocol for leucocytozoonosis has not been established, although treatment in a Fiordland crested penguin was able to suppress parasitaemia. The role of Leucocytozoon in yellow-eyed penguins as a cause of morbidity and mortality remains unclear. Further investigation into direct pathogenicity, and the interaction of concurrent disease and environmental influences is required. The findings of this thesis provide potential management recommendations and highlight areas requiring further investigation.

Slaughter by ventral neck incision (VNI) is performed on some animals without prior stunning in New Zealand and other countries. A single incision with a razor sharp blade is made in the ventral aspect of the neck, sectioning both carotid arteries and jugular veins, though, not the vertebral arteries. There are a number of potential welfare concerns surrounding slaughter by VNI including pain due to the incision, which may lead to distress during the time before loss of consciousness. The aims of this thesis were to identify cortical responses indicative of noxious stimulation due to slaughter by VNI using analysis of the electroencephalogram (EEG) power spectrum and to investigate the effects of non-penetrative captive bolt (NPCB) stunning on these cortical responses. The studies utilised adaptations of a minimal anaesthesia model, which has been validated in a range of mammalian species. Surgical dehorning was used as a validation technique for this methodology in cattle and demonstrated a ‘typical’ EEG response to noxious stimulation. Cattle slaughtered by VNI without prior stunning produced specific responses in the EEG that strongly indicated responses to noxious stimulation. Causation was investigated in cattle where blood flow through the brain remained intact during neck tissue incision (NTI) or the major blood vessels of the neck were isolated and transected independently of other neck tissues (BVT). The response to neck incision in intact animals was principally due to the noxious sensory input due to incision of neck tissues and not mainly as a result of loss of blood flow through the brain. NPCB stunning produced states of cortical activity that were incompatible with the maintenance of sensibility and pain perception. Experimental examination of the time to onset of undoubted insensibility was attempted in cattle subsequent to a pilot study in sheep. The generation of somatosensory-evoked potentials was problematic in cattle. The conclusions of this thesis are that incision of neck tissues during slaughter without prior stunning constitutes a substantial noxious stimulus. Were an animal conscious, this stimulus would be perceived as painful until the onset of hypoxiainduced insensibility. This would represent a significant compromise to animal welfare.

The first aim of this research was to determine the prevalence of IBV in broilers within the Canterbury province, New Zealand, in late winter and to search for associations with management or environmental factors. The second aim was to study how ambient stressors affect the immune system in birds, their adaptive capacity to respond, and the price that they have to pay in order to return to homeostasis. In a case control study, binary logistic regression analyses were used to seek associations between the presence of IBV in broilers and various risk factors that had been linked in other studies to the presence of different avian pathogens: ambient ammonia, oxygen, carbon dioxide, humidity and litter humidity. Pairs of sheds were selected from ten large broiler farms in Canterbury. One shed (case) from each pair contained poultry that had a production or health alteration that suggested the presence of IBV and the other was a control shed. Overall, IBV was detected by RT-PCR in 50% of the farms. In 2 of the 5 positive farms (but none of the control sheds) where IBV was detected there were accompanying clinical signs that suggested infectious bronchitis (IB). Ambient humidity was the only risk factor that showed an association (inverse) with the prevalence of IBV (p = 0.05; OR = 0.92). It was concluded within the constraints of the totally enclosed management systems described, that humidity had an influence on the presence of IBV, but temperature, ammonia, carbon dioxide, oxygen or litter humidity had no effect. In another study environmental temperatures were changed in order to affect the biological function and adaptive capacity of chickens following infection with IBV. The 'affective states' of the animal were assessed by measuring levels of corticosterone (CORT) in plasma and tonic immobility (TI). It was found that low (10 +/- 2°C) and high (30 +/- 2°C) temperatures exacerbated the respiratory signs and lesions in birds infected with IBV as compared to those housed at moderate (20 +/- 2°C) temperatures. The chickens housed at high temperatures showed significantly decreased growth, a higher proportion of hepatic lesions (principally haemorrhages) and a longer tonic immobility period, but there was no significant alteration in the plasma levels of CORT. The birds housed at low temperatures developed a higher proportion of heart lesions (hydropericardium, ventricular hypertrophy) and had significantly higher levels of plasma CORT than birds housed under moderate and/or high temperatures. The specific antibody response to IBV decreased in birds housed under high temperatures. Interestingly the birds housed at high temperatures developed significantly higher levels of haemagglutinin antibodies to sheep red blood cells (SRBC) than those birds housed under low or moderated temperatures. Cell mediated immunity was not significantly affected by heat or cold stress in the first 13 days of treatment but at 20 days the levels of interferon gamma in the birds subjected to low temperatures were lower than in the high temperature group. In other trials, the exogenous administration of low physiological doses of oral CORT (as compared to high pharmacological doses typically used in such experiments) to birds resulted in suppression or enhancement of the immune response depending on duration of treatment and/or dose and nature of the antigen. To our knowledge, this is the first study to show that exogenous CORT can produce an enhancement in the immune response in chickens. iv In conclusion, environmental stressors such as high or low temperatures do affect the physiology of the fast-growing broiler. The adjustments the birds have to make to maintain homeostasis impacts on the course of common infectious diseases, such as IB, that normally is mild in the New Zealand poultry industry. The administration of exogenous CORT showed that this hormone may be part of the physiological stress response and acts as a messenger to prepare the immune system for potential challenges (e.g., infection).

The lens of the eye is a vital tissue in the visual system, responsible for the collection and focusing of light on to the retina. Comprised of epithelial cells at differing stages of differentiation, the transparency of the lens is dependent on the highly ordered crystalline structure of lens proteins. The lens consists of several proteins including crystallins (α, β, γ) that make up 90% of the soluble protein, and the lens cytoskeletal proteins. Cytoskeletal proteins contribute only a fraction of the total lens protein, but are thought to play an important role in the establishment and maintenance of transparency. Calpain-induced degradation of these proteins may be involved in the development of cataracts. This has been an area of research at Lincoln University where a flock of sheep genetically predisposed to cataract maintained as a cataract development model. The aim of this research was to investigate the distribution of cytoskeletal proteins in the lens, and to examine the effects of calpain proteolysis on these proteins, with the goal of establishing the role of the lens cytoskeletal proteins in the ovine cataract model. A combination of techniques was used including immunohistochemistry, which required the development of a specific protocol for ovine lenses. Cytoskeletal proteins were identified using immunohistochemistry in lens tissue sections and exhibited characteristic distributions. Actin displayed preferential distribution in the short sides of the fibre cells in the cortex of the lens but was absent in the lens nucleus, while spectrin in the cortex and nucleus was associated with the fibre cell membrane. Filensin was observed in the outer cortex of lens sections associated with the fibre cell membrane and cytoplasm, although the pattern of localisation was indistinct due to the abundance of filensin breakdown products. Vimentin displayed membrane and cytoplasmic association in the outer cortex that diminished toward the lens nucleus, with membrane associated vimentin only persisting in the deeper regions of the cortex and nucleus. Additionally, the effect of novel calpain inhibitors (Cat0059 and Cat811) in preventing proteolysis of lens cytoskeletal protein was investigated and compared with calpain inhibitors developed elsewhere (SJA6017). The inhibitors were tested at between 10 and 0.1 μM (100 nM). All inhibitors were effective at 10 μM. SJA6017 provided significant protection to vimentin at 1 μM. Cat0059 was found to protect spectrin and filensin at 1 μM, but not vimentin, while inhibitor Cat811 was found to protect spectrin only. SJA6017 added to assays at 100 nM offered significant protection to spectrin, and Cat0059 was found to protect filensin and spectrin to a significant degree at 100 nM, indicating the novel inhibitors were comparable to those developed elsewhere in terms of their effectiveness. Taken together, the evidence presented in this thesis shows the cytoskeletal proteins as crucial elements in the lens. Their pervasive presence coupled with evidence that lens cytoskeletal proteins are sensitive to calpain-induced proteolysis that is inhibited with novel calpain inhibitors suggests that the lens cytoskeletal proteins may be useful targets in cataract prevention for future research.

The lens of the eye needs to be transparent with a high refractive index to focus images on the retina. In cataracts the lens becomes opaque, eventually leading to blindness. There are many possible causes of cataract but a lot of evidence implicates oxidative damage as contributing to opacification. This includes epidemiological studies showing that diets rich in antioxidants lowered the prevalence of cataract. This research tested the hypothesis that if cataracts were at least partially caused by oxidative damage then their progression would be slowed by application of antioxidants. The antioxidants used were two plant compounds found in the diet, resveratrol and quercetin. The system used was sheep lenses cultured in Eagles Minimal Essential Medium (EMEM). Lenses remained transparent for up to 7 days in EMEM but became opaque within 24 h when exposed to 1 mM hydrogen peroxide (H2O2). The lens is exposed to H2O2 in vivo as it is found in the aqueous humor. Prior Lenses pre-treated with quercetin reduced but did not prevent opacification. Lens cell death, as determined by measurement of leakage of lactate dehydrogenase, was found to increase with H2O2 and the increase was prevented by pre-treatment with antioxidants. The role of the endogenous antioxidant glutathione was also investigated. It was found that H2O2 decreased the amount of reduced glutathione in the lens cortex and increased the levels of oxidised glutathione but only at levels of 2 mM and above. Thus the results of this research indicate that H2O2 at low concentration (1 mM) is able to damage lens cells and cause opacification without affecting the reduced glutathione levels and that the exogenous antioxidants have some ability to protect the lens.

The eco-epidemiology of bovine tuberculosis (Tb) in wild deer (mainly red deer Cervus elaphus) in New Zealand was investigated. Bovine Tb is caused by Mycobacterium bovis. Specific aims were to clarify the likely routes of infection in deer, and to determine the status of deer as hosts of Tb, the likely rates and routes of inter- and intra-species transmission between deer and other wildlife hosts, the role of deer in spreading Tb, and the likely utility of deer as sentinels of Tb presence in wildlife. As the possum (Trichosurus vulpecula) is the main wildlife host of Tb, the research also included some investigation of transmission routes in possums. Patterns of infection were measured in 994 deer killed between 1993 and 2003. Tb prevalence varied between areas (range 8–36%). Few deer had generalised infection, with 21–68% of infected deer having no visible lesions, depending on the area. The retropharyngeal lymph nodes and oropharyngeal tonsils were commonly infected. No dependent fawns less than 0.75 years old were infected, indicating intra-species transmission is rare in wild deer. Where possums were not controlled, the net (cumulative) force of infection in young (1–4 y) deer was 0.10–0.24 per year in males and 0.09–0.12 per year in females, but much lower in older deer (less than 0.05 per year). Possum control reduced the net force of infection quickly, and eventually to zero. However, Tb persisted in possum-controlled areas through immigration of infected deer and, for almost a decade, through the survival of resident deer infected before possum control. Tb was lost from infected deer at an exponential rate of 0.13 per year, mostly as a result of deer recovering from infection rather than dying from it. Wild deer do die of Tb, but there was no discernible effect on age structure. The occurrence of infection in deer was not linked to the local deer or possum density at their kill sites (i.e. in their home range), but the area-wide prevalence of Tb in deer was closely correlated with Tb levels in possums, which were in turn correlated with area-wide measures of possum density. For wild deer in New Zealand, Tb is a persistent but usually inconsequential disease of the lymphatic system. It is acquired mainly by young independent deer, usually orally via the tonsils, and probably as a result of licking infected possums. Many species fed on deer carrion, including possums. Most possums encountering carrion did not feed on it, but a few fed for long periods. Other scavengers such ferrets (Mustela furo), hawks (Circus approximans), and weka (a hen-sized flightless native bird; Gallirallus australis) fed in a way that probably increased the infectivity of carrion to possums. Commercial deer hunting may have facilitated the historical establishment of Tb in possums. Scavenging (including cannibalism) and interactions with dead and dying possums are identified for the first time as potentially important routes for transmission of Tb to possums, and I develop new hypotheses involving peri- and post-mortem transmission in possums that explain many of the epidemiological patterns that are characteristic of the disease in possum. In continuous native forest, deer home range size averaged 250 hectares for six young females, and over twice that for two males. Over 90% of infected deer are likely to die within 2 km (females) or 6 km (males) of where they acquired Tb, but deer could occasionally carry Tb up to 30 km. Deer will be useful as sentinels, but only where other sentinels are rare, because the force of infection for a deer with a single infected possum in its home range is only 0.004 per year, compared to greater than 0.2 per year for deliberately released pigs. Deer are occasionally capable of initiating new cycles of infection in wildlife, but deer control is not essential to eradicate Tb from wildlife.

Mucins play important roles in host-pathogen interactions, influencing host resistance, establishment of infection, as pathogen recognition sites and a source of nutrients. They are highly glycosylated molecules and changes in monosaccharide composition during parasitism have been reported. Effects of parasites on monosaccharide component of fundic and duodenal mucins of sheep were investigated in 3 age ranges (i) 4-4.5, (ii) 6 and (iii) 8-9 months old: (1) noninfected; (2) infected with 10,000 Haemonchus contortus and euthanased 21 days post infection (p.i.); (3) infected with 50,000 Teladorsagia circumcincta and euthanased 28 days p.i. Three days-old lambs and 9 weeks-old lambs: (a) milk-fed, (b) solid-fed and (c) solid-fed, infected with T. circumcincta were also included. The effects of H. contortus and T. circumcincta infection in mucin changes were significantly different in the fundus, however, both of them shared some similarities. Infected sheep showed lower proportion of fucose and sialic acids in fundic and duodenal mucins compared with non-infected animals, the level of sulphation varied depending on the age of infected sheep: decrease in young sheep but increase in older animals. H. contortus infection also caused increased proportions of GlcNAc and Gal in fundic mucins and duodenal mucins respectively at all ages, however, in T. circumcincta infection, it was shown that the alterations of mucins were age-dependent. T. circumcincta infected sheep showed the significant changes at young ages (4-6 months-old) while 8-9 months-old animals showed less change in fundic mucins compared with non-infected animals. Effects of H. contortus and T. circumcincta infection differed in the fundic mucins but were similar in the duodenum. The study showed that parasitism caused the modifications of monosaccharide composition in gastrointestinal mucins of sheep. These alterations may result from parasite species differences, causing different effects from the host’s immune response. The changes in mucin profiles observed in the duodenum of sheep infected with abomasal nematodes suggested that the host may respond to parasitism. This would facilitate the use of mucins from accessible sources, without euthanasing the animals, to investigate the changes in mucin compositions which can be used to diagnose the susceptibility or resistance of sheep to parasites