Wildlife disease is of great importance to the health and safety of humans and domestic animals because 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. 


Through serological testing (using blood to identify disease), we look primarily for the presence of these diseases in the coyote population:  canine parvo, canine distemper, toxoplasmosis, and leptospirosis. Below is a look at some other diseases we monitor. 


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. 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. There is actually a limited number of days where the environment is suitable for the transmission to happen.

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 continuously. We tested blood samples from 85 radio-collared coyotes located across Cook County. Necropsies (postmortem examinations) of deceased coyotes showed a 41% infection rate heartworm, which was approximately 10 times greater than coyotes from rural areas in northern Illinois.


There are different types of mange with a range of severity among wildlife species. Scarcoptic mange is a debilitating disease associated with coyotes and their relatives, especially foxes. It is transmitted by a mite that infects an individual by burrowing into their skin. Extreme infection often follows:  the animals typically lose most of their hair, become susceptible to other infections, or often succumb to exposure. In urban areas, coyotes likely serve as the host for this pathogen, which can spread to pets and, rarely, people. Direct exposure to an infected animal is necessary which is why the risk is low. We have been monitoring mange in the Cook County coyote population since we began the coyote research in 2000. 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. Data has shown mange to be the most common disease-related mortality in this area.

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 may become more active during the day and often seek food or cover near houses, thereby increasing observations by the public. While animals with mange are difficult to look at given their poor state, animals can recover from the disease. It is best to leave the animals as they are; offering support by feeding infected individuals will only create more issues for those animals. Please see the story about coyote 571 to understand her bout with mange.


Coyote-strain rabies is restricted to southern Texas but coyotes are sometimes infected with rabies from other species. If a person is bitten by a coyote that is acting aggressive, he or she should be treated for rabies as a precaution. Anytime a person is bitten by a coyote (or any animal), animal care and human health professionals should be contacted.

a heartworm infected coyote heart
Prevalence of heartworm infection map
 frequency of mange-related mortalities in coyotes from Cook County, by year
coyote with mange
Coyote 115 at capture

We were not able to capture the first mate of Coyote 1 prior to his death (likely from a vehicle), but we captured her second mate, Coyote 115, on February 18, 2004, at the peak of the mating season. Coyote 115 was in excellent condition at 18 kg (40 lbs). He remained with Coyote 1 constantly until her death in 2010. Their relationship was interesting to observe, where at times they were inseparable, and other times they would take short breaks from each other. Still, they defended the same territory together continuously after 115’s collaring date.