The Cook County, Illinois, Coyote Project






Wildlife disease is of great importance to the health and safety of humans and domestic animals with 73% of emerging and reemerging pathogens are known to be zoonotic (transmitted from animals to people).   There is increasing evidence suggesting that urbanization and resultant land-use changes contribute to the emergence of wildlife diseases through multiple mechanisms, with consequences for human and pet health.

In light of the increasingly close association between wildlife and humans in Cook County, surveillance and proactive research is needed to guide and interlink human health and wildlife management programs with the goal of limiting the risk of human exposure to zoonotic diseases.



  •  Heartworm

  •  Mange

In rural areas, coyotes serve as a host for canine heartworm, an important parasite for domestic and wild canids (dogs and their relatives), and to a lesser extent other domestic animals and even humans.

Canine heartworm is a filarial nematode with a 6-month life cycle that requires both mosquitoes and canid hosts.  The adult worm is large and resides in the cardiopulmonary vasculature of its canine host.  The severity of the infection depends on the number of worms and the length of infection. 


Heart infected with heartworm

The parasite is transmitted from an infected canine to an uninfected canine via a mosquito vector.  Once infected, the ambient temperature of the mosquito dictates the development of the microfilaria to the infective L3 larval stage.  Thus microfilarial development only occurs above a threshold temperature, which becomes the heartworm transmission season.

Whereas a number of studies have described the coyote-heartworm relationship for rural populations, little information is available for metropolitan areas and sample sizes were limited. As the number of coyotes in the urban areas continue to increase, it is possible that prevalence of the heartworm may also change.  Therefore, we have tested for heartworm in coyotes within Cook County with serology (the study of blood) and necropsy (postmortem examination).

We tested blood samples from 85 radio- collared coyotes located across Cook County.  When we compared our infection rates to similar data for rural coyotes across the state, we found that the rate of infection among coyotes in Cook County was approximately 10 times greater than coyotes from rural areas in northern Illinois.



 Prevalence of heartworm infection in rural coyotes across southern, central, and northern Illinois (from Nelson et al. 2003) and in urban coyotes in Cook County.


Mange is a debilitating disease associated with coyotes and their relatives, especially foxes.  It is transmitted by a mite that infects an individual and burrows into their skin.  Extreme infection often follows, to the detriment of the animal, and the animal typically loses most of their hair and becomes susceptible to other infections or often succumbs to exposure.

In urban areas, coyotes likely serve as the host for this pathogen, which can also spread to pets and, rarely, people.  We have been monitoring mange in the Cook County coyote population since we began the coyote research in 2000. 


 A radio-collared, mange-infected coyote walking across a driveway in the middle of the day. This animal died a few days later as a result of the infection

 Initially we did not observe mange in Cook County, but that changed in 2002, and mange has been maintained at low levels in most years.

However, in areas where the disease is common, it has contributed to human-coyote conflicts.  Our results have revealed that coyotes with extensive mange infections are not aggressive (we have yet to record a pet attack by a mange-infected coyote), but they become more active during the day and often seek food or cover near houses, thereby increasing observations by the public.

 Frequency of mange-related mortalities in coyotes from Cook County, by year.




The Cook County, Illinois, Coyote Project

The Ohio State University