SENTINELS OF THE CITY
Learn about our study species -- and how they interact
Our mammalian species of interest are coyotes and raccoons, but we also want to know about the organisms hidden within these animals -- their parasites. Keep reading to learn more about just how connected mammals and their parasites are.
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Hidden links
Did you know you can tell what an animal has been eating by examining its parasites? Urban carnivores tend to have variable diets, but they usually eat a lot of small mammals. Many of these small mammals, such as rodents and rabbits, are intermediate hosts to a variety of intestinal parasites for our carnivores. These parasites reproduce in the small intestine of the carnivores, their definitive hosts. The parasite eggs are then shed in the feces of the carnivores, and live in the environment until they are consumed by an intermediate host. Usually, these parasites are able to live within their hosts in relative harmony, but high parasite burden may have negative health effects, especially for individuals with weakened immune systems. Immunosuppression in our urban carnivores is often caused by sub-lethal doses of contaminants that disrupt hormonal function, such as heavy metals commonly found in urban soils and waterways, or rodenticides acquired from eating poisoned rodents.
But parasites are not all bad! They are important indicators of biodiversity, can help their hosts defend against other diseases, and can even absorb heavy metals before they are absorbed by their hosts. Maybe parasites are mitigating the effects of contaminant exposure in our urban carnivores. By investigating genetics, diet, heavy metal contamination, rodenticide exposure, and parasite load across socioeconomic gradients, we hope to be able to uncover apart these hidden connections and find out if carnivores can help us better understand human health risks. We don't know a lot about the intestinal parasites found within carnivores in our study areas, so this study also serves to record and understand local parasite communities and identify those which may have potential implications for people and domestic animals.
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Carnivores
Coyote (Canis latrans)
Coyotes are a highly successful species in the Anthropocene. Living in nearly every ecosystem type across North and Central America, coyotes have carved out a unique niche in urban areas. Found in every major metropolitan area in the United States, coyotes have become friend and foe to urban residents, depending on who you ask. But there's more to our toothy neighbors than meets the eye. Living with coyotes comes with many benefits: they help spread seeds and regulate pests like rodents. They are also close relatives of domestic dogs and share almost every single parasite with our canine friends, making them an important species to monitor for spread between domestic animals and wildlife.
River Otter (Lantra canadensis)
River otters are a highly versatile species. Unlike coyotes and raccoons, river otters spend time in aquatic environments, exposing them to terrestrial and aquatic pollutants. On the west coast, river otters forage both in fresh and salt water bodies. While this gives them access to a large diversity of foods, it also potentially exposes them them to more parasites.
Raccoon (Procyon lotor)
Raccoons are the ubiquitous urban carnivore across North America. Like coyotes and other urban-dwelling carnivores, raccoons often occur at higher densities in urban areas than in non-urban areas. Their mischievous ways often get them in trouble with human residents, but like coyotes they offer benefits such as seed dispersal and pest regulation. Unfortunately, raccoons are also hosts to parasites that have the ability to infect humans. Understanding prevalence of these parasites in our local raccoon populations can help us mitigate potential infections in vulnerable people, as well as understand what factors may lead to chronic infections.
Parasites
Taenia spp.
Taenia is a genus of parasitic tapeworms of mammals. We expect to find several species of Taenia, including Taenia pisiformis, in our coyote hosts. Rabbits are intermediate hosts for Taenia pisiformis, and when a coyote consumes a rabbit infected with its larvae, the worms are then able to grow to maturity and reproduce within the coyote's intestines. Each segment of the tapeworm, known as a proglottid, eventually produces eggs and detaches. The proglottid is then passed in the stool of the host. Since Seattle coyotes are eating a lot of eastern cottontail rabbits, there's a good chance we'll find this tapeworm in our salvaged coyotes. Even with high-intensity Taenia infections, canids rarely show external signs of infection. Some Taenia species are zoonotic, but the ones associated with coyotes and other canids are rarely contracted by people. Instead, those species of zoonotic concern are typically associated with pigs.
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Ancylostoma caninum and Uncinaria stenocephala
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A. caninum, also known as the southern hookworm, and U. stenocephala, also known as the northern hookworm, are in the family Ancylostomidae. Hookworms are nematodes, and female nematodes can shed thousands of eggs into the environment per day. Hookworms are special amongst our focus species in that they don't use an intermediate host -- the larvae live in the soil and can enter the host through the skin of the footpad, or are directly consumed during grooming or consumption of infected vegetation. They also tend to cause more serious symptoms in their carnivore hosts than the previously mentioned species, because they suck blood from the intestinal walls. Juveniles are especially vulnerable to hookworms, often suffering serious and even fatal anemia.
Echinococcus granulosus
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Echinococcus granulosus, also known as the hydatid tapeworm, also uses intermediate hosts to make its way into a carnivorous definitive host, and is found worldwide. This species is the smallest of the intestinal worms we are interested in, and requires a special sieving method to collect from the intestinal tract. E. granulosus uses ungulates as intermediate hosts, so we expect to find E. granulosus in our coyotes where deer and other ungulates are common. Infectious larvae live in the livers of the intermediate host until they are eaten by the definitive host, where they mature in the intestine. We are also monitoring for presence of Echinococcus multilocularis, a closely related species native to Europe and Asia that has recently been found in neighboring states and provinces and presents serious zoonotic concern.
Baylisascaris procyonis
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The raccoon roundworm is a nematode parasite of raccoons that uses small mammals and sometimes birds as intermediate host. A mature female B. procyonis living in a raccoon intestine can shed over 150,000 eggs in a single day, and eggs can last in the environment for a long time. Since raccoons use latrines, where many individuals all collectively defecate in one location, these latrines can have millions of raccoon roundworm eggs. B. procyonis eggs can only be killed with fire or boiling water, and while only rarely contracted by humans, can cause fatal illness in children.