Tech Talks by Emily Harbury, LVT
I recently attended a veterinary conference in Spokane where one of the sessions was about the incidence of leptospirosis in Washington State. Here is some of what I learned, hoping to keep you current on leptospirosis prevention, recognition and treatment.
Leptospire bacteria are zoonotic, meaning they can be transmitted to other species including humans. Leptospirosis is a life threatening condition with worldwide significance. Any diagnosis is reportable to the CDC. Veterinary staff and owners who suspect, or have confirmation, of leptospire bacterial infections must use great caution to contain the bacteria. Diagnosis of Leptospirosis in dogs is rising in the U.S., but the virus has always been present and the rise in detection may be due to more accurate diagnosis. Of the 88 dogs tested thus far in Washington in 2016, 10 dogs were positive for leptospirosis. All of the infected dogs resided on the west side of the Cascade Mountains. Location of clinics with positive cases: 2 cases each on Bainbridge Island and in Seattle; 1 case each in Bellevue, Coupeville, Enumclaw, Nooksack, Poulsbo and Tacoma.
Dogs become infected by leptospires when abraded skin comes into contact with the bacteria. The bacteria are found in water or mud that has been contaminated by infected urine. Rodents are prime carriers of leptospires. If infected rodent urine contaminates soil, water or mud that comes into contact your dog’s abraded skin or mucus membranes, the organisms can get a foothold. Dogs can also be infected by bites or scratches from an infected animal.
The organisms spread through the bloodstream leading to fever, joint pain, and general malaise that can last up to a week. The organism settles in the kidneys and begins to reproduce, leading to further inflammation and kidney failure. Depending on the type of leptospire involved, other organ failure (liver) can be expected as well. Symptoms include fever, depression, loss of appetite, joint pain, nausea, excessive drinking, jaundice, and excess bleeding brought on by low platelet count. In most infected dogs the main symptom is excessive water consumption a week or two after an episode of unexplained fever.
Younger animals tend to be more severely affected than older animals. Leptospirosis tends to be most severe in unvaccinated dogs that are younger than 6 months old. Most cases are diagnosed in the fall in regions that tend to be wet. Hunting breeds may be most at risk as they are often in damp or swampy areas. In one study, acute kidney failure affected 90% of the dogs diagnosed with leptospirosis, 10-20% also suffered liver failure.
Blood testing to detect antibodies can be performed but 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 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. The PCR test, which detects even small amount of leptospire DNA, is an excellent test if vaccination has been recent, but PCR testing is not available in most 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. The problems with this test are that the urine sample must be fresh, most animal hospitals do not have the capability to do dark field microscopy, and Leptospires are only shed in urine intermittently.
Although positive diagnosis is difficult, treatment is fairly easy. Leptospires are sensitive to antibiotics. After the antibiotic has been used to stop leptospire reproduction and limit bloodstream infection, Doxycycline antibiotic is used to clear leptospires from the kidneys. IV 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 when cleaning any urine. Prognosis is guarded depending on the extent of organ damage. Recovered animals shed leptospires for months after recovery.
Vaccination against leptospirosis is available, however most vet clinics only carry a vaccine that covers two out of the four strains that affect dogs. It is difficult to assess whether it is important for you to immunize against leptospirosis; that is a decision for you and your veterinarian. Most recent outbreaks involve the serovars bacteria for which vaccination does not exist. Important aspects of prevention include controlling rodents or other carriers in the pet’s environment, and avoiding contact with contaminated water by your dog.