Role of domestic dogs in diseases of significance to humans and wildlife health in central Chile

Abstract

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.