A Nasty Canine Disease Re-emerges

Climate change, wild animals contributing to leptospirosis increase in dogs, says researcher

by Kate Roberts
(Guelph, March 17, 2005) A loving lick to the face from the family dog may be a welcome feeling, but it could carry a number of pathogens that are dangerous to humans. One of these pathogens is a re-emerging canine bacterium, says a University of Guelph researcher – and it could have dire health consequences for dogs and their owners.

The bacterium, Leptospira, can cause the infectious – and potentially deadly – disease leptospirosis. Leptospira lives in its host’s kidneys, and once infected, dogs show a variety of symptoms that can range from lethargy and depression to vomiting, kidney failure or even death.

The disease emerged widely in dogs across North America in the 1970s before being controlled by vaccination. But new cases of leptospirosis have been increasing in the past several years. University of Guelph Prof. John Prescott, Department of Pathobiology, has been working with colleagues Dr. Beverley McEwen in the Animal Health Laboratory and University of Guelph veterinary small animal clinicians, including Prof. Paul Woods, to follow the re-emergence of this disease. This resurgence isn’t quite the same as past outbreaks, says Prescott: this time, the infection is caused by different strains, and it’s being transported in new ways.

He believes climate change and the raccoon population are among the accomplices in spreading leptospirosis.

“In the 1970s, the type of leptospirosis seen was transmitted from dogs to other dogs, and so it was easily controlled with vaccinations,” says Prescott. “But these new strains are being passed from raccoons to dogs. Vaccinating the entire raccoon population is impossible.”

 Raccoons are natural carriers of Leptospira – the bacterium is well adapted to living in their kidneys – and dogs can be infected by exposure to raccoon urine. This, says Prescott, could explain why the disease is found mostly in urban areas, where there are high numbers of raccoons. An increase in infection in the urban wildlife carriers, such as raccoons and skunks, also appears to have happened in the past several years.

Climate may also have played a role in the sudden increase in leptospirosis cases. The Leptospira bacteria thrive in wet, warm conditions such as those seen in the fall, and the average temperatures for the fall seasons have increased since 1990.

 “For example, the year 2000 had the greatest resurgence of canine leptospirosis, and it was by far the warmest fall, and the third wettest, in the last decade in Ontario,” says Prescott. “That creates an environment that allows Leptospira to survive.”

Leptospirosis poses a threat to humans too: not only can it sometimes be transmitted from animals through their saliva, but the infection is sometimes hard to diagnose in dogs because they may only show a few, if any, disease symptoms. Humans could unwittingly put themselves at risk. Leptospirosis is known as an occupational disease, meaning that people who are commonly in contact with animals – such as veterinarians, trappers and farmers – are more likely to be infected.

However, because it is usually spread through urine – and raccoons often urinate in streams, creeks or rivers – people can be exposed to the bacteria through canoeing, swimming and fishing, says Prescott.

Humans afflicted with leptospirosis can suffer a variety of symptoms similar to those of the flu. As in dogs, severe cases can cause kidney failure and other serious illness in humans. Fortunately, the disease can be easily treated with antibiotics if caught early.

Because of the warming climate and the apparently increasing spread of infection in urban wildlife, Prescott and his team are speaking to veterinarians about vaccinating dogs against the new Leptospira strains with new vaccines designed to control the problem.

Please contact your vet for more information.

http://www.uoguelph.ca/research/news/articles/2005/March/leptospirosis.shtml