For
example, the host species for the serovar “grippotyphosa” are
raccoons and skunks. When an animal belonging to the
host species is infected, the disease is usually mild and
may go unnoticed. The animal can live its lifetime
unaffected symptomatically by this bacterium, but at the
same time can be continuously shedding the organism. If
the same serovar, shed from the host animal, goes on to infect
an animal that is not a host species, such as a dog, the
severity of disease produced can range from undetectable
to severe. There are several serovars that are known
to cause disease in dogs, and these are most commonly found
in raccoons, skunks, voles, mice, cattle, and pigs.
Leptospirosis was an important disease affecting domestic
animals in the 1970’s. Thanks to an increased
awareness and a rigorous vaccination protocol, the incidence
of disease has decreased over the years. However,
dogs can become severely ill with the new serovars that have
recently emerged, prompting some concern in the veterinary
community.
The bacterium survives best in warm, moist weather, and
as a result, Leptospirosis is most commonly diagnosed in
the spring and autumn. The organism is shed in the
urine of infected animals and can survive in the environment,
under ideal conditions, for up to six weeks. Dogs may
become infected by contact with contaminated water bowls,
puddles and streams, wet grass, soil, or food. Infection
requires only ingestion of the bacterium or contact with
mucous membranes such as the gums or nose. It has been
reported that the incidence of infection is highest in large-breed dogs, such as Retrievers, Shepherds, mixed breeds,
and working dogs. This, however, is likely related
to the amount of time the dog spends outdoors, since larger
breeds tend to enjoy activities such as swimming a little
more than smaller breeds. Infection can occur in both
suburban and rural areas, with a higher incidence reported in
suburban locations.
The majority of Leptospirosis infections in dogs are subclinical,
meaning no obvious symptoms of illness are present. These
infections go unnoticed and the dog may exhibit no more than
some “flu” symptoms for one or two days. More
serious infections, however, are not uncommon and aggressive
treatment is necessary. Animals may not show
signs of disease for several weeks after infection with the
bacterium. The organism causes damage to the blood
vessels, especially in the kidney and liver. When
serious, kidney failure and severe liver disease can occur. The
dog may show non-specific signs of disease, such as vomiting,
dehydration, fever, loss of appetite, or sudden collapse. The
mucous membranes may develop a yellow tinge (indicating
liver disease) and the dog’s water intake may suddenly
increase (and subsequently urination). Permanent
organ failure and even death can result if the disease goes
untreated. In general, the earlier the disease is diagnosed
and treatment started, the better the prognosis for preserving
organ function.
Diagnosis of the infection is not always easy and can require
several consecutive blood tests for confirmation. Your
veterinarian will check for blood abnormalities and signs
of organ dysfunction, paying particular attention to the
liver and kidneys. A specific screen for antibodies
against the Leptospira serovars will also be done,
which appear in the blood seven to ten days after infection
and continue to rise for a little while afterwards. While
waiting for the test results, your veterinarian may begin
treatment after making a presumptive diagnosis based or your
dog’s history and symptoms.
As Leptospirosis can result in kidney failure and severe
liver disease, immediate and aggressive treatment with intravenous
fluids and a long course of antibiotics is required. A
lengthy stay in the hospital may be necessary until the dog
is stable enough to maintain adequate hydration on its own. The
antibiotics used are quite effective if a dog is treated
early on in the infection, with a good chance of recovery
if no organ damage has occurred.
Finally, it should be noted that Leptospirosis is zoonotic,
meaning that it can be transmitted to humans. This
can occur through contamination of the environment
or via an infected dog shedding the organism. It is
considered rare, however, for a human to acquire the disease
from an infected dog, and is usually related to occupational
hazard (such as veterinarians and wildlife rehabilitators). In
humans, most cases are mild and some may even go unnoticed. Rarely,
an infected person may experience severe disease with symptoms
such as sudden fever and chills, severe headache, vomiting,
muscle pains, and/or abdominal pain. If left untreated,
meningitis, kidney failure, and liver disease can develop,
much like in dogs. Sanitation is likely the most effective
way to prevent transmission from an infected dog to human,
with protective clothing, frequent hand washing, and disinfection
of possibly contaminated surfaces.
Since climate change results in warmer temperatures and
infection with Leptospira can be so devastating, vaccination
of dogs at risk is highly recommended. There is now a widely
used vaccine for the most important Leptospira serovars,
and its efficacy has been reported to be quite good. The
vaccine provides one year of protection, and dogs are boostered
annually along with their other vaccines. Rodent
and wildlife control in the area is also important to keep
the risk of infection low. It is difficult and
not practical to keep a dog from swimming, but it is recommended
that standing water be removed and that the dog’s water
and food bowl not be left outside. With all the
preventative measures in place, you can be sure that your
dog’s risk of infection will be low and that you are
doing the best you can to prevent Leptospirosis. |
