Dear Dog and Cat Loving Friends,
On April 12, 2024, the New York City Department of Health issued a Health Advisory about the ongoing rise in the number of Leptospirosis cases in humans. This announcement should concern all New York City dog families because Leptospirosis is a serious bacterial infection and a direct health threat to dogs.
The City does not track dog infections, but in 2023, twenty-four people were diagnosed with Leptospirosis, which exceeded the number of Lepto cases reported in any year prior. And in 2024, in the first 3 ½ months of the year, six human cases have already been reported, which rate, while when annualized is roughly the same as 2023, should actually be lower because the Winter cold should have killed the fragile bacteria and so lowered the reported number over that early period. This high number of human Lepto cases reported in the Winter months, then, is both surprising and concerning. (I do note that 2024’s excessive rain and unseasonably warm temperatures may have supported the growth of the bacteria in NYC during typically colder months).
While the specific number of dog Lepto infections is not known, it is thought to be increasing as well. In my three decades of NYC veterinary practice, I have seen only three cases of Leptospirosis in dogs, and they have all been in the last four years.
Leptospirosis is a zoonotic disease that is present worldwide. It is caused by a spirochete bacterium from the genus Leptospira. This bacterium is spread into the environment by the urine of infected rats, and with appropriate conditions, Leptospira bacteria can persist in the environment for weeks.
Lepto transmission occurs when dogs have direct contact with urine from infected rats or rat-urine contaminated water, soil, food, garbage or other materials. Dogs are specifically at risk as they sniff and lick garbage and garbage bags, which New Yorkers know are favorite areas for rats to gather. The bacteria can enter a dog’s blood stream through open wounds or mucous membranes like those in the dog’s nose and mouth.
Although both dogs and humans get this disease, it is unlikely to be transmitted between dogs and people, and it is rare for the disease to pass from person to person, and from dog to dog.
However, when a case of leptospirosis is confirmed in a dog, the patient is in fact considered infectious and handling of all of their body fluids in hospital is done while wearing proper PPE until appropriate antibiotic treatment is given.
Leptospirosis makes dogs very sick. Affected dogs lose their appetites, vomit and drink excessive amounts of water as the bacteria damage the dog’s liver and kidneys. The disease is treatable with antibiotics, however prompt diagnosis and treatment are necessary.
More importantly, the disease is preventable. In addition to ensuring dogs avoid areas where rats may be, there is an effective vaccination against this disease that should be given to every dog that goes outside, even if a dog walks only on the “fancy streets” they are still at risk of Lepto infection due to the ubiquity of rats in most cities.
The leptospirosis vaccine is given as two initial doses, separated by two to four weeks, followed by an annual booster. It can be given to puppies as young as 16 weeks of age which is the earliest dogs should go outside in the City. This vaccine occasionally makes the recipient feel under the weather for the remainder of the day but does not have serious reported side effects.
In 2022, the American Animal Hospital Association recommended that the Leptospirosis vaccine should be considered a core (essential) vaccine based on the steep increase in this disease’s prevalence.
Given the recent Health Department recent Advisory, I urge everyone to make certain that their dogs are properly immunized against Leptospirosis.
Chow, Chow, Chow for now,
Dr. Amy