Leptospira
interrogans is shaped like a question mark and is a special
type of bacterium called a spirochete. When a Dog Becomes
Infected Dogs become infected by
leptospires when abraded skin comes into contact with the urine of
an infected host. The organisms quickly spread through the
bloodstream leading to fever, joint pain, and
general malaise which can last up to a week. The organism settles
in the kidneys and begins to reproduce, leading to
further inflammation
and then kidney failure. Depending on the type of leptospire
involved, other organ failure (especially liver) can be expected as
well. Make no mistake, leptospirosis is a life-threatening
disease. Typical symptoms: Fever, depression, loss of appetite, joint
pain, nausea, excessive drinking, jaundice, excess bleeding brought
on by low platelet count.. PEOPLE
CAN BECOME INFECTED, TOO! The
Infection in Humans
The Centers for Disease Control and Prevention monitor
leptospirosis cases in people, and it seems that one
third come from contact with infected dogs and one third come from
contact with rats. The same disease symptoms occur in humans as
would be seen in a canine infection.
Testing
Blood testing to detect antibodies against Leptospira
interrogans (microscopic agglutination testing) can be
performed. While a value of 1:800 or higher is supportive of a
positive diagnosis, confirmation is not made until a second
antibody level (called a titer) is run between 2 and 4 weeks
and shows a four-fold increase. Vaccination may
interfere with testing since obviously the entire point of
vaccination is to generate antibodies. If the dog has been
vaccinated in the last 3 months, testing will be difficult to
interpret; however, a single titer of 1:800 or higher against a
serovar for which there is no vaccine is considered a positive
result. The PCR test, which amplifies small
amounts of DNA, would be an excellent test if vaccination has been
recent but PCR testing is not available in most reference
laboratories. Urine may be submitted for
what is called Darkfield Microscopy. In this test, a dark
background may offset the paler leptospire organisms rendering them
visible. This sounds like a good way to make the diagnosis but the
problems are - the urine sample must be
fresh and most animal hospitals do not have the capability to do
dark field microscopy
- Leptospires are only shed
in urine intermittently.
The kidney may be biopsied
and special tissue stains may be used to detect leptospire
organisms. Obviously this is an invasive procedure. Treatment
Fortunately, Leptospira interrogans is sensitive to
penicillin, a readily available antibiotic. After penicillin has
been used to stop leptospire reproduction and limit bloodstream
infection, tetracycline derivatives are used to clear leptospires
from the kidneys. Since tetracyclines and penicillins are not a
good concurrent combination, often a combination of a penicilin
with a fluroquinolone type antibiotic (such as enrofloxacin)
is used to cover both phases of the infection. Intravenous fluids are
crucial to support blood flow through the damaged kidneys so that
recovery is possible. Any areas at home that have been contaminated
with urine should be disinfected with an iodine based product and
gloves should be worn in cleaning up any urine. Prognosis is
guarded depending on the extent of organ damage. Hemodialysis? In a recent study from the
University of California at Davis (JAVMA, Vol 216, No3, p271-5)
dogs judged as having mild to moderate increases in renal
parameters received traditional fluid therapy and 82% survived.
Dogs having moderate to severe elevations tended to receive
hemodialysis. Prognosis was worse for the severely affected that
did not receive hemodialysis, while 86% of those receiving
hemodialysis survived. In short, dogs with the most severe renal
toxin build up probably need referral to a critical care facility
that supports hemodialysis. VACCINATION
REACTIONS ARE COMMON! Vaccination
Options
Vaccination against Leptospira interrogans is only
available for the serovars called canicola, grippotyphosa, pomona
and icterohaemorragiae. As a result of long standing use of this
vaccine, it is hard to assess how important it is to vaccinate
against leptospirosis. (As you might imagine, most recent outbreaks
involve serovars for which vaccination does not
exist.) Vaccination against the
four serovars mentioned is commonly included in the basic distemper
shot (DHLPP - the L stands for leptospirosis). The vaccine can be
made up to omit the leptospirosis portion. Of all the sera in this
basic vaccine, it seems to be the leptospirosis portion that is
associated with hives, facial swelling, and even life-threatening
vaccination reactions much more than any of the other fractions. If
there is any question of an animal having a vaccine reaction,
leptospirosis vaccine is left out of the mix. Vaccination will
reduce the severity of disease but will not prevent infected dogs
from becoming carriers. | 
