Chicago is the City of Broad Shoulders, the City by the Lake, the Windy City. It also continues to be the rattiest city, for the sixth straight year. According to Orkin Pet Control list of the rattiest cities in America, Chicago finishes at the top. And that makes it a hot spot for leptospirosis.
And it’s not just Chicago. No matter the location–urban, suburban, or rural–this is an issue for veterinarians to discuss with clients, as rats are a primary vector of leptospirosis. In fact, according to the Centers for Disease Control, risk of exposure to leptospirosis is an occupational hazard for veterinarians or people who care for animals.
Rounding out the top-10 ratty cities:
- #2 Los Angeles
- #3 New York
- #4 Washington DC
- #5 San Francisco
- #6 Detroit
- #7 Philadelphia
- #8 Baltimore
- #9 Denver
- #10 Minneapolis
Other cities are seeing a rise in rat numbers, too. According to Orkin, cities with the greatest increase in rat numbers (compared to last year) are Albuquerque, New Mexico; Green Bay, Wisconsin, and Albany, New York.
Although many animals can transmit leptospirosis, from farm animals to raccoons to mice, rats are the primary source of this water-loving bacterial infection transmitted by the urine of an infected animal.
Here’s the scenario: An animal urinates in any water, from a river to a condominium retention pond. A dog not vaccinated against leptospirosis takes a drink, even from an urban puddle where a rat may have urinated, and infection can occur when he later licks a paw. Contaminated community water bowls, such as those placed outdoors by shop owners, can also be a source of transmission.
Leptospirosis can also be dangerous to humans. In third-world countries leptospirosis is a reportable disease, as people share space in rivers with a wide variety of wildlife and farm animals that spread leptospirosis. People may even bathe in these infected waters. According to the Centers for Disease Control and Prevention, although incidence in the United States is relatively low, leptospirosis is considered to be the most widespread zoonotic disease (which means people get this disease from animals) in the world. It’s estimated that more than one million human cases occur worldwide each year, including about 59,000 deaths.
We can mitigate the risk of leptospirosis in dogs by vaccination. This lowers our own risk as well.
Vaccination is also important because with the pandemic leading to limited restaurant hours or to restaurant closures, rats have lost out on what is their most common food source in many parts of the country. As dumpster diving diminishes, “bold rats” are searching elsewhere for food during the day, resulting in more humans potentially being exposed.
The takeaway for clients: Sometimes dogs infected with lepto are obviously sick, but they don’t always show signs. Now imagine that infected dog having an accident indoors, and the person who cleans it up doesn’t wash hands thoroughly. Or a toddler crawls through the area and then puts hands to mouth. As a result, a person may become sick with leptospirosis, sometimes very sick. Vaccination for lepto not only protects dogs against the disease (although it is not 100 percent effective), it is arguably as important that they cannot transmit the illness to other dogs or people.
For those really into rats, Orkin provides this great rat fact sheet.
This article was reviewed/edited by board-certified veterinary behaviorist Dr. Kenneth Martin and/or veterinary technician specialist in behavior Debbie Martin, LVT.