Leptospirosis is a disease that humans and canines can both acquire from several different sources.
Rodents are the main carriers of the disease and almost any contact with an infected animal can transfer it. This includes direct and indirect contact. For example, one of the most common ways the disease is transmitted from rodent to canine is through the consumption of infected water.
During warmer weather, the Leptospira can easily survive in stagnant or slow moving bodies of water. Freezing temperatures usually kill the bacteria. For this reason Lepto is most common during the summer months.
Symptoms of Leptospirosis range from fever to vomiting to hypothermia to kidney failure. This disease can quickly become fatal so watch for sign and see a vet if your dogs shows symptoms.
Treatments once acquired are simply antibiotics and fluids while trying to control vomiting.
Luckily there is a vaccine for the disease and care should be taken to make sure your dog is vaccinated against Lepto every year in the early spring.
Consult your Vet on the topic, especially if you and your dogs spend a lot of time outdoors.