Lepto is passed through contaminated urine. Animals that can be affected include raccoons, rats, mice, pigs, sheeps, goats and cattle. Once the wild animals urinate, it can enter into puddles, ponds or other water sources. Dogs can pick it up by swimming in contaminated water, walking through it, drinking it or eating grass that has been urnited on. However with all that said, lepto is a fairly rare diease. To say that your vet has seen it three times this year, is actually a pretty high number. I live in a very rural area and I have only seen one case this year.
If you plan to be outside, go camping, go swim at lakes, rivers or streams, go to dog parks or take Mav with you on trips to other areas I recommend the Lepto vaccine.....It is better to be safe then sorry and it is a disease that not only can pass to humans but it is very hard to treat in pets, if it can be treated at all without serious damage.....it is actually a bacterial infection that affects the kidneys.
Signs of lepto can range from slight to major signs: depression, weakness, abdominal pain, sudden unset of ulcers on the tongue or in the mouth, jaundice in the whites of the eyes, diarrhea often bloody and vomitting. Death can occur as soon as 5-10 days after signs are noticed. Recovery is very slow and there can be perm damage to the liver and kidneys.
In addition the Lyme was mentioned up there and it is spread and high in areas that have lots of ticks so if you are in one of those areas you may want to consider that one too....Here is a link to a page that shows a map of higher affected areas and explains it pretty well....
http://www.peteducation.com/article.cfm ... icleid=458