New forms of old disease, leptospirosis, threaten dogs in U.S., Cornell veterinarians warn
By Roger Segelken
A potentially fatal bacterial disease that damages the liver and kidneys of dogs, humans and other animals – leptospirosis – is appearing in new forms in the United States. Citing an alarming increase in leptospirosis cases, bacteriologists in the Cornell University College of Veterinary Medicine's Diagnostic Laboratory are urging dog owners to watch for symptoms of the disease until improved vaccines are available.
"We're especially concerned about some of the new types of lepto, such as grippotyphosa, that we first documented in the New York City metropolitan area in dogs, but which probably is not confined there. We're finding grippotyphosa in the Northeast and in other areas of the country," said Patrick McDonough, a veterinary bacteriologist at the Cornell Diagnostic Laboratory. That laboratory is the official diagnostic center for animal disease control in New York state and each year conducts more than 700,000 diagnostic tests for animals of all species, including humans.
While currently available vaccines do protect against some serovars (serological varieties) of leptospirosis, newer serovars, such as grippotyphosa and pomona, are not included in that protection, McDonough noted, saying: "There is room for improvement in the vaccination protocols." Worldwide, there are more than 200 known serovars of leptospirosis infecting many kinds of mammals, including rodents and cattle.
Leptospirosis is spread by a spirochete (or spiral shaped) bacteria called leptospires in the urine of rodents and other infected animals, as well as in water, such as pond water. The leptospires enter the body through mucous membranes or through abraded skin.
For dog owners, the first signs of leptospirosis in a pet often are several days of anorexia, vomiting, lethargy, depression, muscle pain and sometimes diarrhea or bloody urine. Veterinarians examining dogs with leptospirosis find depression, fever, dehydration, jaundice and abdominal pain. The disease damages the animal's liver and kidneys, sometimes resulting in renal failure and death.
If the disease is caught in time, McDonough said, it can be successfully treated with penicillin and – when the kidneys have recovered – with a lengthy course of tetracycline drugs. During their recovery, dehydrated animals need intravenous fluids and "good, supportive nursing care," he added.
"Until vaccines are upgraded to include these new types of lepto, we're advising dog owners to watch for flulike illnesses in their pets," McDonough said. "If the dog has been exposed to the urine of another domestic animal or a wild animal, either directly or in ponds or run-off water that collect urine, and if you notice these flulike signs, the pet should be tested for lepto."
Noting that leptospirosis is a zoonotic disease that can pass from animals to humans, Cornell Diagnostic Laboratory Director Donald Lein said the infection can be an occupational hazard for people who work with animals. "This used to be called 'milkers' disease,' and there is real potential for its spread among dairy farm workers, as well as people handling other animals." He said that personnel in large dairy farms, where hundreds of cows are milked several times a day, must work in pits at eye-nose-and-mouth level to a continuous stream of cows – and to an aerosol form of their urine that could contain leptospires.
"Leptospirosis is a disease that's been around for a long time," McDonough said. "Now we're recognizing new types. Certainly in different areas of the country there are endemic types of lepto that aren't found in other areas, and each area might have its unique lepto problem."
from the Diagnostic Laboratory
College of Veterinary Medicine, Cornell University
What causes leptospirosis?
Leptospirosis is caused by spirochete (or spiral-shaped) bacteria called leptospires. The leptospires live in fluids from infected animals, including urine, saliva, blood and milk. The disease-causing organisms are transmitted by direct contact with the fluids or with an infected animal, as well as by indirect contact, including contamination on vegetation, food and water, soil and bedding materials. Disease transmission is increased in crowded conditions. The disease may be carried for years in animals that serve as host reservoirs without the animals showing clinical signs of the disease. The leptospires enter the body through mucous membranes or through breaks in the skin.
Where are leptospires found?
The leptospires cannot survive for long outside their ideal environment: water or other fluids, moderate temperatures around 25 degrees Celsius (77 degrees Fahrenheit) and neutral or slightly alkaline pH. Stagnant water or slowly flowing streams may carry the leptospires; worldwide, leptospirosis infection increases with flooded conditions. A 1996 outbreak of leptospirosis among white-water rafters was traced by the U.S. Centers for Disease Control and Prevention to contaminated river water in Costa Rica. Leptospires are known to survive in urine-soaked soil for six months. Summer and early fall are the most likely times for leptospirosis transmission to dogs. Milk from infected dairy cows may carry leptospires, although heat from the pasteurization process should kill the microorganisms.
What are the symptoms of leptospirosis?
In general, the disease resembles the flu with fever, headache, chills and myalgia (muscle pain). Dog owners may notice vomiting, lethargy, depression, muscle pain and sometimes diarrhea or bloody urine in the pets. The disease damages the liver and kidneys and, if untreated, may cause death.
How is leptospirosis treated?
Dogs are treated with a course of antibiotics and with intravenous fluid to overcome dehydration. Diagnosis is based on clinical signs and laboratory tests, including tests for the disease-causing organism, urinalysis and blood tests.
Can vaccination prevent leptospirosis in dogs?
Currently available vaccines for dogs cover only the icterohaemorrhagiae and canicola forms of leptospirosis but not certain emerging forms in dogs, such as grippotyphosa and pomona. Vaccine makers are now attempting to include protection for emerging forms of leptospirosis.
Do humans catch leptospirosis?
Leptospirosis is a so-called zoonotic disease that can be transmitted from animals to humans. People can catch the disease from water that is contaminated by infected wild or domestic animals, as well as from more direct contact with animals, such as rodents, raccoons, skunks and cattle. A well-known Hollywood actress is now recovering from leptospirosis. Public health authorities suggest keeping dogs away from children's play areas, including sandboxes and wading pools.
Why are cats not affected by leptospirosis?
Tests for antibodies show that some cats are exposed to the disease, but cats almost never show clinical signs of leptospirosis. Some experts believe that cats have developed a kind of immunity to leptospirosis from their longtime association with rodents.