The Most Widespread Animal-to-Human Disease in the World on the Rise

Veterinarians at the University of Florida’s Small Animal Hospital warned of a spike in cases of dogs with leptospirosis. The increase is concerning because leptospirosis is zoonotic, meaning it can be transmitted between animals and humans.

According to the Centers for Disease Control and Prevention (CDC), between 100 and 200 human cases of lepto are reported in the U.S. each year, with around half occurring in Hawaii. And while the incidence of lepto is relatively low in this country, it is thought to be the most widespread zoonotic disease in the world.

According to Dr. Carsten Bandt, chief of emergency and critical care service, in a typical year the hospital sees almost no cases of lepto, and over the last decade, there have been very few documented cases in pets in all of Florida.

However, between September 2013 and March 2014, the UF animal hospital saw 12 dogs with the infection.

For more information on how the disease affects humans, visit Centers for Disease Control and Prevention.

How Leptospirosis Is Transmitted to Dogs

The pathogen that causes the disease, Leptospira bacteria, is transmitted in the urine of infected animals. 

Rats are the most common carriers, but other animals that can carry and transmit the disease include raccoons, opossums, dogs, goats, sheep, pigs, cattle, and horses. The bacteria can be deposited in soil and water and survive for weeks or even months.

Several species (serovars) of Leptospira cause disease in dogs, and the prevalence of a particular serovar varies by region. There are over 20 different serovars in existence that could potentially infect dogs, and hundreds of non-pathogenic serovars.

Dogs pick up the bacteria through a cut or break in the skin when they come in contact with contaminated water or soil, or when they drink contaminated water. Most at risk for leptospirosis are pets that spend a lot of time in the water or in areas that get rain or snow runoff, as well as dogs that drink from puddles or ponds.

Symptoms of Infection

Many dogs with mild lepto infections never show any symptoms at all. Generally speaking, young dogs tend to get sicker than older dogs.

Clinical signs depend on the age and health of the dog, environmental factors affecting the bacteria, and the virulence of the particular species (serovar) of bacteria that is present.

When symptoms do occur they usually appear between 4 and 12 days after exposure to the bacteria, and can include fever, muscle pain, vomiting and diarrhea, loss of appetite, lethargy, depression, and blood in the urine. 

Since the infection primarily affects the kidneys and liver, in serious cases there can be jaundice, which is a yellowing of the skin and mucous membranes. 

In dogs, it is usually most obvious in the whites of the eyes. Jaundice indicates the presence of hepatitis (liver inflammation) as a result of the destruction of liver cells by the bacteria.

Blood clotting problems can also develop, which can result in blood in the stool and bleeding from the tissues of the mouth. In rare cases, leptospirosis can also cause respiratory distress and acute pulmonary (lung) hemorrhage.

Treating a Leptospirosis Infection

Some dogs exposed to leptospirosis recover without medical treatment because they never show overt symptoms. Unfortunately, an untreated dog who recovers from the infection can become a carrier and shed the bacteria in urine for up to a year.

Dogs that become seriously ill with leptospirosis must be hospitalized to receive antibiotics and appropriate supportive care to control vomiting and diarrhea, and to provide hydration and nutrition.

Dogs with milder infections can be managed at home as long as the owner takes appropriate hygiene precautions when cleaning up urine. If your dog has lepto and anyone in your family develops flu-like symptoms, it’s important that you inform your family physician that a leptospirosis infection is a possibility.

Preventing a Leptospirosis Infection in Your Own Pet

There is a vaccine for leptospirosis, but I don’t recommend it and I don’t give it to my patients. It’s a relatively weak bacterial vaccine that is short acting and can’t protect against all serovars of Leptospira.

This particular vaccine is a bacterin, which is made from killed bacteria. This type of vaccine by itself won’t prompt an immune response to make antibodies, so a powerful adjuvant is added that elicits a strong immune system response. 

Because of this, the vaccine also carries a significantly greater risk for adverse reactions. We also now suspect that the vaccine can actually trigger the disease in dogs, and it has also been linked to early kidney failure in older animals. 

For more information about why this vaccine is NOT recommended, download Dr. Patricia Jordan’s article.

Leptospira bacteria thrive in warm, humid climates and are often found in stagnant water. Dogs exposed to potentially contaminated water sources or wild animals are at much greater risk of developing an infection than city dogs.

Infection is most common in the summer months, the early fall, and during periods of flooding.

At home, you can reduce the risk of infection by safely controlling the rodent population in and around your home. If you live where infections are a problem, it’s important to keep your pet away from ponds, slow moving water, and standing or stagnant water.

If you have a healthy dog who suddenly has a fever, grows lethargic, perhaps is urinating excessively or is urinating bright fresh blood, you need to call your veterinarian immediately and get your pet in for a lepto test. 

Leptospirosis is a totally treatable bacterial infection -- it’s only when a diagnosis isn’t made early enough that dogs suffer unnecessarily.

Thanks to Dr. Karen Becker for sharing.

Human Concern

Leptospirosis infection can be life threatening to humans, leading to kidney failure, liver failure, and meningitis.

There was a recent case in central Indiana where a dog was presented to a veterinary clinic for diarrhea. Treatment and testing were initiated. During this time period, one of the animal caretakers started having fever, lethargy, and flu-like symptoms. 

When the dog came back positive for leptospirosis, the animal caretaker consulted her physician and was also diagnosed with Lepto. Both dog and animal caretaker made a full recovery because of the early diagnosis.

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