Pathogen Transmission and the Risk of Spillover for Wild Carnivores in the Neotropics

Humans are rapidly transforming whole ecosystems by deforestation, habitat fragmentation, pollution, and climate change, among others. Increased human populations and the transformation of original habitats to productive lands have led to increased contact between humans, domestic animals, and wildlife. Although the maintenance and circulation of pathogens at the domestic and wild carnivore interface often involves bidirectional transmission, domestic carnivores have been identified as reservoirs for infectious agents that have produced numerous epidemics in different wild carnivore species worldwide. For instance, domestic dogs have been implicated in outbreaks of canine distemper and rabies in wild carnivores, while domestic cats have been shown to transmit feline leukemia and feline immunodeficiency to wild felids. Domestic dogs and cats are particularly abundant in urban areas of some developing countries where they can act as excellent reservoirs for pathogens, since they usually inhabit large populations, are not vaccinated, and are regularly allowed to roam freely, facilitating contact between infected and susceptible hosts. In contrast, in rural areas, where domestic dogs and cat densities and population sizes are often lower, theoretically highly virulent pathogens cannot be maintained, and infections fade out without external input of infectious animals from neighboring urban areas. On the other hand, wild carnivore populations are commonly found at low densities, many are solitary, and their numbers are often not sufficient to maintain infections for highly pathogenic generalist agents. In the neotropics, approximately 28% of wild felids and 30% of wild canids of the world are found; however, very few studies have assessed the transmission of pathogens at the wildlife-domestic interface in neotropical carnivores. This chapter aims to review the current knowledge on pathogen spillover from domestic dogs and cats to wild carnivores in human-dominated landscapes in the neotropics. We discuss evidence-based predictions on how relevant diseases can spread from domestic to wild carnivores, which in many cases are endemic or threatened.