Fed by unusually lush vegetation, rabbits have been breeding like rabbits around Colorado, increasing the risk for what normally is a relatively rare bacterial disease in the state. 

Fifteen people have contracted tularemia, or rabbit fever, so far this year - just five fewer than in record-setting 1983.

State and local health officials are urging doctors to keep the disease in mind in diagnosing patients, and warning homeowners to take precautions while mowing and gardening, especially where bunnies are prevalent.

Rabbit fever is found across the country, with an average of 135 cases typically reported each year, much of them in the south central United States.

While Colorado's share is relatively low, the disease - which also can be carried by rodents, birds, flies and ticks - poses a threat in a normally arid place where its symptoms of fever, chills, headaches and swollen glands could be mistaken for the flu.

The bacteria that causes tularemia usually is present among rabbits and other animals that carry it, but the additional vegetation has helped boost the animals' populations and left more bacteria in the environment for humans to pick up, state veterinarian Jennifer House said.

The greener conditions over the past two years also seem to be fueling two other diseases carried by rodents - hantavirus and plague.

So far this year, Colorado has had five cases of hantavirus, four of them fatal. It had six last year.

Colorado also has had one case of the plague - a relatively rare form which killed 16-year-old high school athlete Taylor Gaes. There were eight cases in the state last year. That's one more than normally is reported in the entire country in a given year.

Humans can become infected with tularemia through insect bites. They also can get it by touching an infected animal or inhaling the bacteria, which can remain alive in soil, including in animal droppings.

Health officials are warning people not to go barefoot or wear sandals and to wear bug spray or long sleeves and pants while working in their yards. They're asking people to not let their dogs chase rabbits or rodents or drink from puddles that could have tularemia bacteria.

Rabbit fever and the plague are both caused by bacteria and can be treated with antibiotics if discovered in time. However, hantavirus is caused by a virus, and there is no vaccine for it.

In Larimer County, health department spokeswoman Katie O'Donnell said officials see another cyclical reason for the increase in rabbit fever: a lack of rabbit predators due to recent outbreaks of mange and West Nile virus that have killed foxes, skunks and raptors.

The presence of rabbit fever was suspected in western Colorado's Mesa County for some time after reports of multiple rabbits found dead this spring. It wasn't confirmed until last week, when a rabbit found at Colorado National Monument tested positive.

The county's disease surveillance and response manager, Rene Landry, said she's also reminding people not to feed the plentiful rabbits.

"Even though they're cute, they carry a potentially serious disease," she said.