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Rabies and canine distemper are fatal diseases of mammals and of concern in the Serengeti, Tanzania both for public health and wildlife conservation. This study investigates the epidemiology of these diseases through cross-sectional and longitudinal studies of two domestic dog populations bordering the Serengeti National Park. Chapter 2 demonstrates differences in demographic and behavioural characteristics between the two populations, leading to predictions of distinct patterns of rabies and canine distemper infection, and the requirement for different strategies of disease control. Chapter 3 compares the use of three rabies serological tests for seroepidemiological studies of domestic dogs. Non-specificity precluded use of the indirect ELISA, but a liquid-phase blocking ELISA (BE) and neutralization test (RFFIT) demonstrated rabies seropositivity among unvaccinated Serengeti dogs. The poor agreement between BE and RFFIT in unvaccinated dogs led to an investigation of specificity, which indicated that the BE was the more specific assay. In Chapter 4, incidence data and virus typing suggested that dogs, not wildlife, are the reservoir of rabies in the Serengeti. Case surveillance data indicated that rabies persists in higher- density dog populations, but occurs only sporadically in lower-density dog and wild carnivore populations. Rabies seropositivity occurred in dogs remaining healthy, demonstrating the existence of atypical infections. Mathematical models showed that rabies persistence in Serengeti dogs was more likely if seropositives were infectious carriers, rather than slow-incubators or immune animals. In Chapter 5, analysis of case-morbidity, mortality and age-seroprevalence data indicated that canine distemper was stably endemic in higher-density dog populations, but sporadically epidemic in lower-density dog populations. In conclusion, higher-density dog populations to the west of the Serengeti National Park are the most likely reservoir of both rabies and canine distemper in the Serengeti and disease control strategies should therefore focus on controlling infection in these populations.

New and emerging diseases in human and animal populations appear to be predominately associated with generalist pathogens that are able to infect multiple hosts. Carnivores are susceptible to a wide range of these pathogens and can act as effective samplers of their vertebrate prey, which are important reservoirs of many emerging diseases. This thesis evaluates the utility of carnivores as sentinels for pathogens present in their prey by exploration of four selected pathogen-prey-sentinel combinations in three rural study sites of varying habitat in northern England and Scotland over a twenty-two month period (2007-2009). Selected pathogens were Coxiella burnetii, Leptospira spp., Encephalitozoon cuniculi, and rabbit haemorrhagic disease virus (RHDV), selected prey species were wild rodents and rabbits, and selected carnivores were foxes, domestic cats and corvids. Seroprevalence to C.burnetii, Leptospira spp and E.cuniculi was assessed using adapted or novel test methodologies to enable their use for multiple mammalian species, however these were not applicable to corvids. RHDV seroprevalence was not assessed due to low acquisition of rabbit samples. Overall, seroprevalence to all three pathogens was significantly higher in predators than prey, at 24.2% and 12.4 % for C.burnetii, 22.73% and 1.95% for Leptospira spp and 39.06% and 5.31% for E.cuniculi in predator and prey species respectively. A similar pattern was found in all study areas and was consistent irrespective of individual prey or predator species, although serological evidence of exposure to E.cuniculi was not detected in domestic cats in any area. A semi-quantitative assessment of the time and financial costs of the study approach and application to hypothetical examples indicates that sampling carnivores is a much more costeffective approach to pathogen detection than sampling prey. The results indicate that carnivores can act as useful sentinels for broad-scale detection of pathogen presence and relative levels of prevalence in prey and predator populations. Careful selection of predator species and methods of sample acquisition are necessary to maximise their utility, and issues associated with diagnostic test performance and validation must also be acknowledged. Suggestions are made as to how this principle might be applied to future surveillance programmes. In addition, the study is the first report on the seroprevalence of C.burnetii, Leptospira spp and E.cuniculi in multiple wildlife species (field voles, bank voles, wood mice, foxes), the first detection of antibodies to C. burnetii in wildlife and cats, the first detection of antibodies to L mini, L hardjo prajitno and L hardjo bovis in wild rodents, and to L mini in cats, and the first detection of antibodies to E.cuniculi in wild rodents and foxes in the UK.

The higher proximity among humans, domestic animals and wildlife favours disease spill-over both from wildlife to domestic animals and vice versa, which is a potential risk for the extinction of wildlife populations and could be influencing the emergence and/or re-emergence of zoonotic diseases. The domestic dog (Canis familiaris) is the most abundant and widely distributed carnivore worldwide and is known to be carrying many infectious diseases. Among these diseases, domestic dogs are known to be source of canine distemper virus (CDV), canine parvovirus (CPV) and Echinococcus granulosus to wild carnivores and human being. Populations of domestic dogs inhabiting urban areas can be the source of infection of directly transmitted pathogens, since in these areas a high density of domestic dogs can facilitate the maintenance of these infections to both domestic and wild carnivore populations. In addition, the knowledge of the diseases present in the domestic dog populations in close proximity to wildlife is essential for conservation planning and for control of both zoonotic diseases and diseases of conservation concern. This thesis explores the effect of urbanization on the epidemiology of CDV, CPV, and E granulosus in domestic dogs and wild carnivores of the Coquimbo region of Chile as for example, chilla (L. griseus) and culpeo (L. culpaeus) foxes and assess the risk factors that could be facilitate disease transmission between canid inhabiting urban and rural areas. The first of the chapters containing original data, Chapter 3, describe the demography of dogs in the study area, indicating that urban sites have a greater population and a higher density of domestic dogs, a high growth rate and therefore a high turnover of susceptible than rural areas, which can be of relevance for the differences in diseases transmission patterns between these sites. Chapter 4 describe the degree of interaction between wild and domestic carnivores and its effect on interespecific disease transmission; indicating that in the study area there are many opportunities for domestic/wild carnivores interactions, as for example livestock predation by carnivores, by approaching to peridomestic environments, facilitating in this scenario the transmission of CDV, CPV and also E. granulosus by predating on livestock contaminated with cyst echinococcosis. Chapter 5 indicate that urban areas hold domestic dog populations with higher CDV seroprevalence than rural sites and probably these areas are the source of infection to rural sites. In contrast, a more stable CPV seroprevalence was found between urban and rural areas, indicating that possibly this pathogen follow an endemic state across the study area. Chapter 6 describe the factors for E. granulosus prevalence in domestic dogs, livestock and human being, suggesting that more cases of E. granulosus in livestock and in humans are found in provinces of the Coquimbo region with higher percentage of rural population; however, and unexpectedly, more cases of E. granulosus in domestic dogs were found in urban areas, although analysis of risk factors indicated that those domestic dogs inhabiting in the borders of urban areas, were at greater risk of being infected with E. granulosus than those in the centre of these areas. The results of this study exemplify how three pathogens are found in urban areas which can be source of infection to domestic and wild carnivores in the study area.

The capacity of zoonotic pathogens to infect multiple hosts creates surveillance challenges but also provides opportunities to gather data from animal species that can be used to understand risks to human health. This thesis presents a conceptual and practical assessment of the utility of domestic dog serosurveillance for the detection and surveillance of two pathogens, influenza A and Leptospira spp. The first chapter gives a theoretical framework that can be used to explore the attributes of animal sentinels and assess their utility in different contexts. In subsequent chapters, this framework is applied in a practical assessment of the utility of a domestic dog serosurveillance approach for the detection and surveillance influenza A and Leptospira spp. at two sites in Africa. Two cross-sectional surveys of the avian and mammal populations at a site in Northern Cameroon were conducted in early 2006 to determine if H5N1 influenza A viruses had circulated in this area and in which species that presence could be detected. Serological and molecular evidence of extensive H5 virus circulation in the domestic duck population was identified. 47% of domestic ducks at the Maga site were cELISA positive for anti-influenza A antibodies and 20% were HI test positive against an H5N1 antigen. There was also evidence of exposure to H5 subtype viruses in the local dog and pig populations. At the Kibera site in Nairobi, a cohort study was established to carry out surveillance of influenza A and Leptospira spp. in the domestic dog population and cross-sectional surveys of the domestic poultry and rodent populations were completed. There was no indication of influenza A circulation in any of the animal species surveyed, indicating low risk of zoonotic influenza A infection in the human population of Kibera. In contrast, there was extensive molecular and serological evidence of the presence of Leptospira spp. in both the rodent and dog populations. 18% of 236 trapped rodents were PCR positive for kidney carriage of pathogenic leptospires and the estimated seroprevalence of anti- Leptospira antibodies in the dog population ranged from 5-36% during the course of the study, indicating high potential risk of leptospirosis infection in the human population. The results indicate that dog serosurveillance can be used as useful tool for the determination of broad-scale patterns of pathogen presence and relative levels of population exposure. However, there are limitations of the data that can be gathered from animal sentinels and the complexities introduced particularly by incomplete understanding of diagnostic test performance must be recognized. Animal sentinel surveillance may be of most use for addressing fundamental questions of what pathogens are present where. In the developing world particularly where disease burden data are still lacking, dog sentinel serosurveillance can provide essential baseline data that can be used to target future research and resource allocation.

Unravelling the complexities of a disease with multiple wildlife host and multiple tsetse vector species is no easy task. After over a century of field observations, experimental studies, anecdotal evidence and conjecture, the role of wildlife in the transmission of trypanosomes is still unclear. Recently, however, frameworks used in the studies of other vector-borne diseases with wildlife reservoirs showed that not only is it possible to understand transmission, but that spatio-temporal predictions of human disease risk and targeted control are realistic aims, even in such complex systems. This thesis explores the epidemiology of human African trypanosomiasis (HAT) in the Serengeti-Mara ecosystem in Northern Tanzania, where recent cases in tourists have highlighted the disease as a public health and economic concern. Assessment of the prevalence of trypanosome infections in different wildlife species is the first step in investigating the relative importance of different species in disease transmission. Identification of trypanosomes relies on sensitive and specific diagnostic tests. Polymerase chain reaction (PCR) protocols based on interspecies differences in the length of the ribosomal internal transcribed spacer (ITS) regions have been widely used in livestock to identify multiple trypanosome species in one PCR reaction. This study represents the first assessment of these protocols on blood samples collected from wildlife. Clonal sequence analysis of PCR products revealed a large range of trypanosomes circulating in wildlife, including Trypanosoma congolense, Trypanosoma brucei, Trypanosoma simiae Tsavo, Trypanosoma godfreyi and Trypanosoma vivax. In addition sequences similar to known sequences, termed Trypanosoma simiae-like and T. vivax-like trypanosomes, may reflect further diversity. However, further characterisation is needed before ITS protocols can be used widely for epidemiological studies in wildlife. The prevalence of T. brucei s.l. and T. congolense varied widely between species. This variation was predominantly explained by taxonomic classification, suggesting intrinsic differences in response to trypanosomes. Trypanosoma brucei rhodesiense, the subspecies responsible for HAT, was identified in lion, hyaena and reedbuck. Age significantly affected the prevalence of T. congolense in lion and hyaena, with the highest prevalence in subadults. The lack of statistically significant differences in prevalence between animals sampled live or after death confirmed that post-mortem sampling provides a method for increasing sample sizes in wildlife studies. The complex relationship between tsetse density and prevalence of trypanosome infections illustrated the difficulties of assessing data from diverse ecosystems with many potential confounding factors. A cross-sectional study of Glossina swynnertoni and Glossina pallidipes, the main tsetse species in Serengeti, highlighted the difficulties of integrating the results of microscopy and PCR to generate meaningful measures of the prevalence of transmissible T. brucei infections for epidemiological studies. However, PCR results suggested that G. pallidipes may be more important as a vector of T. brucei s.l. than has been previously recognised. Spatial variation in both tsetse density and the prevalence of trypanosome infections suggests human disease risk is heterogeneous. The results of this study, along with relevant literature, are considered within the context of frameworks used for other vector-borne diseases and the implications for disease management discussed.