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 (usually through field work). The same disease symptoms occur in humans as would be seen in a canine infection. About the Organism The species Leptospira interrogans has been classified into subtypes called SEROVARS Over 200 serovars have been named. Testing Blood testing to detect antibodies against Leptospira interrogans (microscopic agglutination testing) can be performed. 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. 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.