A seroepidemiological study was undertaken in a pedigree dairy herd that had a history of abortions due to neosporosis. The infection in this closed herd was thought to have arisen from a point-source infection, after which sporadic abortions have occurred. All cattle were bled twice, once in the winter and again the following summer and antibodies to N. caninum measured using an ELISA. The overall seroprevalence of Neospora was found to be 18 %. Three data sets; age-prevalence data, dam-daughter pair analysis and family tree data showed vertical transmission to be an important route of transmission of neosporosis in this herd. Analysis of anti- Neospora antibody titres with respect to the stage in the breeding cycle of cows appeared to show no association on a herd level. Data was collected on the number of Artificial Insemination (AI) services per successful pregnancy which showed a significantly greater number of Al services in Neospora-seropositive cattle compared with Neospora-seronegative cattle. This is the first study to assess the effect of neosporosis on cattle fertility in a quantitative manner and suggests that a wider study is justified. N. caninum shares many similarities with T gondii and has widely been assumed also to have a world-wide distribution. Two regions of Africa, Ghana in West Africa and Tanzania in East Africa, were studied in a cross-sectional survey of neosporosis in cattle indigenous to these areas. A prevalence of 8.1 % and 2% was found in two different areas in cattle native to Tanzania. Despite sampling a significant number of cattle in all three ecological zones of Ghana and of several different breeds, no Neospora-seropositive cattle were found. Possible reasons for the apparent absence of N. caninum in West Africa are discussed. To determine the overall genetic diversity in laboratory isolates of N. caninum, RAPD and AFLP methods were used. Genetic diversity was found to be low amongst Neospora laboratory isolates, relative to T. gondii, but demonstrated that genetic heterogeneity does exist within the species. Both RAPD and AFLP data were subjected to pair-wise similarity and cluster analysis and showed that there was no clustering with respect to host or geographical origin. The genetic similarity between cattle and dog isolates suggests that these hosts are epidemiologically related. In order to exploit the genetic heterogeneity in N. caninum to analyse a wider range of clinical field samples, several methods were attempted to devise PCR-based sequence-specific typing approaches that could be used on infected bovine tissue. Microsatellite markers were identified in N. caninum DNA sequences, however none of the microsatellite regions gave rise to detectable size differences, although they remain to be tested on a wider range of field samples. Laboratory isolates of N. caninum were also analysed for polymorphisms with two conserved minisatellite probes, 33.6 and 33.15, but although hybridisation occurred to digested parasite DNA, identical fingerprints were obtained for each isolate. In a final attempt to identify sequence-specific polymorphic markers, intron regions from two genes, actin and tubulin, were amplified and sequenced in both laboratory and field isolates. This approach revealed a number of single nucleotide polymorphisms (SNPs) that were able to differentiate between some isolates of N. caninum and might serve as useful molecular markers. SNPs were found more frequently in the clinical field samples, suggesting that the diversity of N. caninum is greater than that represented by current laboratory isolates. Further genotyping of field samples will enable the genetic population structure of N. caninum to be determined to facilitate molecular epidemiological studies.

Footrot (FR) is a highly infectious and debilitating disease of sheep, which has a significant economic impact on the sheep farming industry, in the UK and worldwide and causes significant suffering of sheep. Despite some recent advances, FR remains a scientifically challenging disease to understand. To help improve our understanding of disease pathogenesis, two culture-independent techniques were developed to examine the microbial succession events between the causative agent, Dichelobacter nodosus and an accessory agent, Fusobacterium necrophorum, the latter also postulated to be involved in disease initiation. The two populations were monitored in relation to disease initiation and progression during a longitudinal study and disease presentation in tissue biopsies (in situ). Finally, the distribution of these two species of bacteria in the environment was examined to highlight possible sources of infection. The work in this thesis has demonstrated that FR is a disease where expression is related to D. nodosus load present in the ovine interdigital space. D. nodosus (rpoD) load increased from that on a healthy foot to one presenting with interdigital dermatitis (ID) and feet with a higher D. nodosus (rpoD) load were more likely to go on to develop FR one week later. FISH analysis of the D. nodosus population present within the epidermis also revealed similar findings; D. nodosus cell counts increased during stages of ID, but the organism was less frequently detected in biopsies from feet with FR. Suggesting that ID might be the most infectious stage of the disease process. A fact that needs to be highlighted to farmers to encourage treatment at this stage of disease. In contrast, F. necrophorum (rpoB) load did not correlate with ID presentation or prior to the development of FR, but increased the week of FR onset. FISH analysis also revealed that F. necrophorum cell counts were higher in feet with FR than those with ID. It is possible therefore that F. necrophorum may thrive in the altered environment of a foot presenting with FR, possibly contributing to disease persistence and severity. Finally, both pathogens were detected in a range of environmental samples from a farm with endemic FR, highlighting possible sources of infection and material, which once contaminated with D. nodosus and F. necrophorum may contribute to the spread of FR. This study has provided an improved understanding of the microbial population dynamics involved in the development of ID and FR in sheep, which may have implications for control and treatment practices not only in the UK, but world-wide.

The European honeybee, Apis mellifera, is important economically not just for honey production but also as a pollinator. Bee pollinated plants contribute towards one third of the food eaten worldwide. However, honeybee numbers in some areas are declining. A range of interacting factors are thought to be involved, including pathogens and parasites, loss of forage, pesticide use, bad weather, and limited genetic variability. Pathogens are also known to cause changes in the behaviour of their hosts and these premortality and sublethal effects of disease may well play a role in colony declines and are the focus of this thesis. For individual bees the fungus Metarhizium anisopliae was used as a model pathogen and RT-Q-PCR was used to detect and quantify naturally occurring pathogens. In field colonies the level of infestation of the parasitic mite Varroa destructor was modified as a surrogate for disease load as the amounts of many viruses correlate with mite levels. Survival experiments showed that both disease load and forage availability had an effect on honeybee longevity and feeding the bees pollen increased their survival. Learning experiments showed that both the fungus and some of the bees’ naturally occurring pathogens caused changes in the learning ability of young adult and older forager bees. Young adult bees were better able to learn when infected with the fungus, possibly because it made them more responsive to the sucrose stimulus, whilst older forager bees where less able to learn when infected with the fungus. Harmonic radar was used to show that honeybee flight ability was affected by naturally occurring pathogens, especially deformed wing virus which caused bees to fly shorter distances and for shorter amounts of time than uninfected bees. Observation hives were used to study in-hive behaviour showing that bees with more pathogens were likely to start foraging earlier than healthier bees.

Circadian rhythms are biochemical, physiological, or behavioural over 24 hours. The avian circadian system is complex, involving numerous oscillators in the brain. I characterised two hypothalamic input mechanism (melatonin receptors and light) and one output mechanism (vasotocin) in the zebra finch. Melatonin receptors were cloned and expression levels investigated in the brain and in peripheral tissues. Receptors were found in all tissues, with some pronounced rhythmic mRNA expression. Tissue-specific differences in temporal distribution, peak expression and amplitude suggests melatonin have varied roles in different tissues and different receptors control/influence these roles. Effect of light in the hypothalamus was investigated by exposing light into the dark phase of an LD cycle and studying the difference in C-FOS expression. C-FOS was found in hypothalamic nuclei associated with photic transduction. C-FOS-IR cells were also found in the two known avian hypothalamic oscillators, the LHN and SCN. Arginine-Vasotocin is a neuropeptide involved in numerous bodily and nervous tissue functions, secreted within the hypothalamus and pituitary gland. Immunofluorescent experiments showed marked differences in expression, as different zeitgeber times and between species. This study has improved our understanding of avian circadian systems, providing new insights into the hypothalamic oscillator of a complex circadian organisation.