Table 1.

Examples and mechanisms illustrating effects of urbanization on the ecology of wildlife–parasite interactions

Host	Pathogena	Locality	Effects on host or parasite biology	Refs
Biodiversity loss and the dilution effect
White footed mouse Peromyscus leucopus	Borrelia burgdorferi (Lyme disease)	Northeast North America	Forest fragmentation, often near suburbs, linked with greater densities of infected ticks and white-footed mice; can result from loss of predators and less-competent hosts	18, 20
Passeriformes and other vertebrate hosts	WNV	North America	Seroprevalence in wild songbirds higher in areas densely populated by humans; non-passerine bird diversity associated with lower infection rates in mosquitoes and humans	21, 64
Resource provisioning and contact rates within urban-adapted species
Raccoon Procyon lotor	Baylisascaris procyonis (raccoon roundworm); other endoparasites	Northeast USA	Higher raccoon abundance and birth rates in urban–suburban areas; clumped resources increase within-species contact rates, leading to higher parasite richness and increased B. procyonis prevalence	9, 23
House finch Carpodacus mexicanus	Mycoplasma gallisepticum (mycoplasmal conjunctivitis)	East North America	Hosts more abundant in regions of high human population density; aggregation at bird feeding stations could increase contact rates and pathogen transmission	[65]
Red fox Vulpes vulpes	Echinococcus multilocularis (tapeworm)	European cities	Shifts in dietary behavior and lack of suitable intermediate hosts reduces prevalence in foxes inhabiting urban centers; risk to humans could increase owing to encounters with urban-dwelling foxes	24, 26
Mule deer Odocoileus hemionus	CWD	CO, USA	Disease more prevalent in highly developed and residential areas, possibly owing to host crowding and aggregated food resources	[66]
Interactions with reservoir hosts in or surrounding urbanized habitats
Gray fox Urocyon cinereoargenteus	CPV	San Francisco, CA, USA	Greater seroprevalence in wild canids captured in urban zone surrounding park; could be caused by direct or indirect contact with domesticated dogs	[28]
Allegheny woodrat Neotoma magister	B. procyonis	East North America	Declines in woodrat from fatal B. procyonis infections linked with exposure to raccoon feces; exposure could increase at the periphery of urban–suburban development	[46]
Red squirrel Sciurus vulgaris	Squirrel paramyxovirus	UK	Non-native gray squirrels introduced highly lethal virus; food provisioning in urban–suburban environments could increase squirrel contact rates and influence pathogen-mediated declines	54, 56
Environmental contaminants, host stress, and susceptibility to infection
Southern sea otter Enhydra lutris nereis	Toxoplasma gondii (meningoencephalitic disease)	West coast of USA	Infections higher in areas of maximum freshwater runoff associated with regions of high human density or activity; probably owing to exposure to cat feces via sewage contamination	[31]
Great tit Parus major	Stress biomarkers (no specific pathogen)	Southwest Sweden	Measure of oxidative stress affected by air pollution increased from rural–urban locations; greater stress and reduced plumage condition could be associated with susceptibility to disease	[67]
European blackbird Turdus merula	Acute stress response (no specific pathogen)	Munich, Germany	City-born hosts showed reduced acute stress response relative to forest-born conspecifics; indicates that species capable of evolutionary adaptation might thrive in urban environments and could be less affected by infectious diseases	[68]

^aAbbreviations: CPV, canine parvovirus; CWD, chronic wasting disease; WNV, West Nile virus