Leptospirosis- an Emerging Threat to Dogs

Leptospirosis is an important and relatively complex infectious disease.  It can affect almost all species of warm-blooded animals, including humans.  It has been recently recognized as a common problem in dogs.

There is a vaccine that can be given to prevent Leptospirosis in dogs.  Historically, vaccines were just given to large dogs with rural outdoor exposure.  This is no longer true.  Small dogs in urban and suburban environments are now recognized to be frequently infected.

Based on recent recommendations by the Academy of Veterinary Internal Medicine and the American Animal Hospital Association, we are now recommending that Leptospirosis vaccine be administered to all dogs starting at 12 weeks of age, because leptospirosis is contagious to humans, can be severe or fatal despite treatment, and exposure can occur regardless of breed, age, geography, or lifestyle.

Prevalence

Leptospirosis occurs on a worldwide basis, especially in regions with higher annual rainfall and warm climates like Florida.  Although the organism cannot reproduce outside of the host animal, it can survive for months in water or damp soil.  It is found in both urban and rural environments. It is more common where there is exposure to wildlife or rodents, and where there is standing water.

Outbreaks have been associated with dog day-care or kennel environments and dog parks.  Leptospirosis can develop in any age, breed or gender of dogs.  All dogs are now considered at risk for leptospirosis.

Causes/Transmission

The leptospire organism is a unique type of bacterium called a “spirochete.”  The name is derived from its slender, coiled (spiral) appearance under the microscope.

The organism is shed in the urine of the infected animal.  It enters the new host animal by penetrating mucous membranes after ingestion of contaminated water or soil.  It can also enter the body through abraded (open) skin.  Infrequent routes of transmission to new hosts include venereal contact, through bite wounds, and through the placenta.

Clinical Signs

Once the organism has infected the dog, it can replicate (reproduce) in many different tissues.  In dogs, the greatest numbers of organisms are usually found in the liver and kidneys.  The signs can be dependent upon which strain of the organism is involved.  For example, one particular strain of Leptospira impacts primarily on the liver, whereas another involves the kidneys.

Dogs who have a rapid onset of signs following infection (peracute infection) will have fever, depression, weakness, vomiting, and muscle pain.  The skin may have a jaundiced (yellow) tint and the mucous membranes (gums) will be pale.  The pulse and respiration rates may be increased and shock will develop.  If clotting problems occur because of damage to the lining of blood vessels, hemorrhage from the nose or bowel develops; obvious bruises will appear under the skin.  If the disease progresses to this point, death can rapidly follow from liver or kidney failure.

Dogs who do not develop more acute infections or survive such infections may go on to develop chronic liver or kidney problems.  In fact, the majority of dogs do not have the peracute infection described above, but are chronically infected.  In many dogs, the disease is subclinical, meaning that there are no apparent signs.

Prognosis

The prognosis is dependent upon several factors, including the strain of the organism, the dog’s vaccination status, damage done to individual organ systems, and the dog’s response to treatment.  In general, dogs that have a peracute infection are more likely to die than those more chronically infected.

Transmission to Humans

There is risk of the infected dog transmitting leptospiral organisms to humans.  The Centers for Disease Control receives reports of about 50-100 human infections per year.  As such, special precautions must be taken when handling these patients; in particular, contact with the dog’s urine must be avoided.  Even for dogs that appear recovered, the organism can be shed into the urine in large numbers for many months after treatment is completed.

Prevention

Vaccines should be administered annually to all dogs starting at 12 weeks of age, regardless of breed, because leptospirosis is contagious to humans, can be severe or fatal despite treatment, and exposure can occur regardless of age, geography, or lifestyle.  Initially, a two dose series is required, with doses 2-4 weeks apart.  After that an annual booster is given to maintain immunity.

Leptspirosis vaccine should be required for dogs by boarding or daycare facilities, because outbreaks have occurred in association with such facilities.

Vaccines are not perfect.  Commercially available vaccines protect dogs against some serovars (strains), but they do not provide immunity against other important serovars.  Leptospirosis vaccines can cause adverse reactions.  For dogs that have had a reaction to the leptospirosis vaccines, recommendations are made by the veterinarian on an individual basis.

Other methods of prevention include decreased access to potential sources of infection, such as marshy areas or standing water, and minimizing contact with wildlife and domestic animal hosts using fencing and rodent control.

If your dog has not been vaccinated against leptospirosis already, give us a call to schedule the vaccine.  Otherwise, we will review your dog’s vaccine history at the next preventive care exam.