<B>Question:</B> "My veterinarian asked me if I wanted my dog vaccinated for Leptospirosis. What the heck is this? How am I supposed to know if my dog needs this vaccine?"

<B>Answer:</B> Oh, good question! When I got out of veterinary school (EGAD-20 years ago), we vaccinated for Leptospirosis all the time. It was part of a dog's yearly Distemper/Parvovirus combination shot.

But, as time passed, two things happened: we began to recognize that certain breeds of dogs tended to have reactions to the Leptospirosis component of the vaccination and the strains of Leptospirosis that were affecting dogs weren't the strains that were in the vaccination! So, basically, dogs were reacting to the shot, it wasn't protecting for the strains of Leptospirosis that were infecting dogs on the east coast and Leptospirosis was exceedingly rare anyway. So, many veterinarians, like me, dropped the Leptospirsis from our vaccination protocols.

But, guess what? Leptospirosis is back. I became aware of its recurrance in our area shortly after Hurricane Katrina, when lots of wild animals and feral dogs ended up in our state after being rescued from the waterlogged states along the Gulf coast. But the good news is that at about the same time, a new vaccine became available that protected for four strains of Leptospirosis, including those that were infecting the animals in our area.

Leptospirosis, often shortened to Lepto, is a zoonotic disease--a disease that can be passed between animals and people. It is spread by a spiral-shaped bacteria in the urine of infected rodents, wildlife, and pets. Since Lepto can be passed on to humans, we really don't want it in our pet populations. But, here's the beef: there are more than 200 different strains of Lepto and certain strains appear to prefer certain hosts, like dogs, pigs, raccoons or even rats. With 200 different strains out there, it is difficult for a vaccine maker to keep up with the particular strains that are causing an outbreak at any one time.

The Leptospira organisms enter the body through mucous membranes (like gums or eyes) or through abrasions on the skin. People and animals can become infected from direct exposure to infected urine, but also through contaminated environments such as water or damp soil. People and pets are usually exposed to Lepto while camping or participating in outdoor recreational activities. Drinking or swimming in water that is infected with Lepto is the most common exposure, but wet soil can be contaminated as well and we certainly have a lot of that in the lowcountry!

The signs of Leptospirosis can mimic many other diseases and illnesses. The first signs in dogs are often depression, loss of appetite, vomiting, weakness, and generalized pain. Affected dogs may also drink water and urinate excessively and have swollen, red, and painful eyes. If caught early, treatment is usually effective and the survival rate is good. However, time is of the essence. A mere three or four day delay can lead to irreversible kidney failure.

The newer vaccination may be safer than the older/combination vaccinations. A study reviewing vaccine reactions in more than one million dogs vaccinated found that reactions occur about 13 times for every 10,000 vaccines given. So I feel a lot more comfortable about vaccinating dogs who spend time in wet environments.

If the vaccine appears to be safe and the disease deadly, shouldn't all dog owners vaccinate their pets?

Unfortunately, that question is difficult to fully answer. Because there are so many Leptospirosis strains, no one vaccine will cover every possible exposure a pet might have. The current vaccination only has four strains in it, but it does have some cross-over effects, meaning it may protect for other strains too. So, it may be pretty good at protecting your pet from getting sick, but it certainly isn't perfect.

Protecting your pet from Leptospirosis is a complex situation. Use your veterinarian to help assess your pet's risk factors as well as the benefits and hazards of vaccination. If you can, take steps to minimize your pet's exposure to this disease by removing animal pests such as rodents and draining areas of standing water.

But, if you have a hunting dog, he or she is going to be exposed to water that may have been infected by wild animals. Those dogs certainly need to be vaccinated.

(Dr. Katherine A. Saenger, DVM, owns Bees Ferry Veterinary Hospital and Boarding Kennel (www.beesferry.com) and is a former board member of the Charleston Animal Society (formerly John Ancrum SPCA.) If you have questions about pet behavior or health, or suggestions for column topics, e-mail her at vetsaenger@bellsouth.net, and watch the column in coming weeks for her responses.)