Rabid Dog Identified in Chicago: What Veterinarians Need to Know
The Illinois Department of Public Health (IDPH) has confirmed a case of rabies in a dog in Chicago, marking the first rabid dog in Illinois since 1994 and the first in Cook County since before 1964. The case serves as a critical reminder that rabies, though rare in domestic animals, remains a real and evolving public health threat.
Case Summary
The dog, less than one year old, was adopted by a Chicago household from a local rescue. The animal originated from a litter of puppies transferred from a Florida rescue group in May 2025. Despite being vaccinated for rabies in June 2025, the dog tested positive for rabies via direct fluorescent antibody testing at the IDPH Chicago laboratory on December 19. A repeat test confirmed the result.
The dog exhibited behavioral abnormalities throughout its life, with worsening aggression, anxiety, growling, snapping, and increased barking noted on December 16. Rabies was not initially suspected due to vaccination status. The dog was euthanized on December 18 due to escalating behavioral concerns.
Importantly, the dog had bitten a person on December 11. In accordance with Illinois state law, the animal was either required to undergo a 10-day observation period or be tested for rabies. Postmortem testing revealed rabies infection.
Source of Infection Under Investigation
The source of rabies exposure remains unknown. Strain typing is underway to determine whether the virus is consistent with bat, fox, or raccoon variants. Currently, bats are the primary rabies reservoir in Illinois. The owners reported no known wildlife exposures, including bats, during the dog’s time in their home.
Given the dog’s vaccination timeline, IDPH notes it is possible the exposure occurred prior to rabies vaccination, highlighting the variability and length of rabies incubation periods.
Public Health Response
The Chicago Department of Public Health (CDPH) and IDPH are actively assessing all individuals who had contact with the dog to determine the need for rabies post-exposure prophylaxis (PEP).
Cook County Animal and Rabies Control (CCARC) is conducting follow-up with:
Owners of the dog’s littermates
Dogs potentially exposed to the rabid dog, including those at a dog daycare
Dogs that were current on rabies vaccination and had contact with the infected dog are being advised to:
Receive a rabies booster vaccination
Undergo 45 days of home quarantine with close monitoring for clinical signs
Clinical Considerations for Veterinarians
The incubation period for rabies in animals is typically 20–60 days, but cases can occur up to one year post-exposure. Clinical signs may include:
Aggression or behavioral changes
Restlessness or hypersensitivity
Excessive salivation
Lethargy or weakness
Vocalization changes or inability to raise the head
Hydrophobia
This case underscores that rabies should remain on the differential list, even in vaccinated animals presenting with unexplained behavioral changes.
A Reminder for Veterinary Teams
IDPH emphasizes the importance of:
Maintaining up-to-date rabies vaccination in pets
Pre-exposure rabies vaccination for veterinarians and staff, which provides protection against unrecognized exposures and reduces the number of vaccines required if PEP becomes necessary
While rare, this case demonstrates that rabies can still emerge in unexpected ways, including through rescue and transport pathways. Ongoing vigilance, strict bite protocols, and adherence to vaccination guidelines remain essential to protecting both animal and human health.
For additional details, IDPH recommends reviewing the document titled “Rabid Dog Identified Chicago Memo.”
