Leptospirosis, aka “Fall Fever”

Leptospirosis, aka “Fall Fever”

Rocky, a 1 year old Siberian Husky came in on a Monday morning in early September.  He had been sick since the previous Friday evening.  He presented with a fever, abdominal pain, lethargy, depression, vomiting, and he wouldn’t eat.  His lab work showed evidence of kidney disease, liver disease and thrombocytopenia (a low platelet count – platelets are responsible for helping blood to clot).

Rocky’s owners had adopted him about one month previously, and had been told he was “up to date” on his vaccinations.  Researching his medical records, we found that Rocky had been vaccinated for Distemper, Parvovirus and Rabies, but not for Leptospirosis.

Rocky was hospitalized and treated with aggressive IV fluid therapy, antibiotics and anti-emetics (drugs that help stop vomiting) with a presumptive diagnosis of Leptospirosis.  Throughout the day Buddy declined, to the point where he was severely depressed, and had stopped producing urine.  Rocky was transferred to a 24 hour emergency practice, where, despite continuing his aggressive treatment, he continued to do very poorly.  Because of his grave prognosis, Rocky’s owners elected to euthanize him early on Tuesday morning.

We had submitted blood and urine to the reference laboratory the day Rocky was hospitalized here.  We received the results 3 days later confirming the diagnosis; leptospires were detected in both Rocky’s blood and urine.

Dogs become infected by leptospires when abraded skin comes into contact with infected urine or with water contaminated with infected urine.  Wildlife including white-tailed deer, striped skunks, raccoons, opossums, red fox, gray fox, rats and mice carry and shed the disease, but do not get sick from it.  Cats also don’t get sick from leptospirosis, nor do they carry it.

In the metro-Detroit area rats are the main carriers of leptospirosis.  The organisms quickly 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 then kidney failure. Depending on the type of leptospire involved, other organ failure (especially liver) can be expected.  Younger animals tend to be more severely affected than older animals.  Most cases are diagnosed between July and December – hence the nickname ‘Fall Fever’ – and involve large breed dogs in rural or suburban environments. Recovered animals, those who have been treated with antibiotics and survived, can shed leptospires for months after recuperation.


Leptospira interrogans is shaped like a question mark and is a type of bacterium called a spirochete.

Leptospirosis is a zoonotic disease, meaning that people can also be infected by coming in contact with the organisms in an infected animal’s urine.  Fever, depression, loss of appetite, joint pain, nausea, excessive drinking, jaundice (yellow tinge to skin and mucus membranes), and excessive bleeding brought on by a low platelet count are the most common symptoms seen with leptospirosis in both humans and dogs.   The Centers for Disease Control and Prevention (CDC) monitor leptospirosis cases in people.  One third of the human cases come from contact with infected dogs, one-third from rats, and one third from other wildlife or domestic animals (cattle, sheep and goats).

Fortunately, Leptospira interrogans is sensitive to penicillin, which is given in the acute phase.   Penicillin is used to stop leptospire reproduction and limit bloodstream infection.  After 10 days of penicillin, tetracycline derivatives (such as doxycycline) are used to clear leptospires from the kidneys. Treatment with intravenous fluids is crucial to support blood flow through the damaged kidneys so that recovery is possible.

Use bleach to disinfect any areas at home that have been contaminated with urine, and always wear gloves when cleaning any urine.

Prevention of leptospirosis includes vaccination, control of rodents in the pet’s environment and removal of standing water.

Vaccination against leptospirosis is commonly included in the basic distemper shot (DHLPP – the “L” stands for leptospirosis).  The vaccine is given as a series of two vaccinations three weeks apart initially, then annually.  The leptospirosis vaccine may cause a vaccine reaction which can include hives, facial swelling, and rarely anaphylactic shock.  As technology has improved, however, vaccines made from leptospires grown in protein-free media have made a vaccination reaction far less likely.  Vaccination will reduce the severity of disease but will not prevent infected dogs from becoming carriers.