Looking out for leptospirosis
New tools to combat this ubiquitous disease
Leptospirosis is found worldwide in both wild and domestic animals, but in small-animal practice we are most concerned with this disease in our canine patients. The number of cases has been increasing worldwide; this may be caused by increased urbanization and contact with wildlife hosts, such as raccoons, skunks, opossums, and rodents. In addition we know that globally, leptospirosis is the most widespread zoonotic disease.1 As a result, small-animal practitioners around the world are becoming more vigilant about this infection.
A threat to all dogs, large and small
Small-animal practitioners have long considered leptospirosis to be a disease of large dogs—in particular, of the hunting breeds, which are most active swimming and running in wild outdoor settings. Because of the perception that these dogs are at increased risk of exposure, they are more commonly vaccinated against the disease.
Over the past 5–10 years, however, we have seen an increase in leptospirosis cases in small-breed dogs, often in urban settings. Historically, this subset of the canine population was less likely to be vaccinated, both because they are perceived to be at lower risk of exposure—after all, pugs and Pomeranians are not typically romping around woodland swamps—and because there is some evidence that small breeds may be more predisposed to reactions to this particular vaccine. But the infection is appearing more frequently in unvaccinated small dogs, and it is well known that urban rat populations can also be a common source of exposure for these breeds. Veterinarians should remember to consider leptospirosis in their smaller patients that present with symptoms that may suggest the infection.
Leptospirosis can show up anywhere
Veterinarians who practice in areas of the country that experience frequent outbreaks will often consider leptospirosis as a cause of illness in their sick patients. It is important to remember that while the prevalence of canine leptospirosis varies by region and season, it is seen most frequently after periods of high rainfall. And as we know, heavy rains can occur even in Arizona.
Reservoir hosts, such as raccoons, rodents, skunks, farm animals, and deer, may harbor persistent Leptospira spp. infections with little effect on their health. The shedding of these bacterial organisms into the environment through these hosts’ infected urine may occur for months or even years. After periods of heavy rainfall, particularly with flooding, the incidence of infections can increase dramatically as dogs are more exposed to the organisms in the wet environment.
Vague and common signs
The suggestion of a Leptospira spp. infection may be all that a given set of clinical signs has to offer. A particular challenge with diagnosing leptospirosis is that the signs are nonspecific and may resemble many other conditions. It is important to keep leptospirosis on your differential diagnosis list for dogs presenting with any of a wide range of problems, including fever, lethargy, anorexia, dehydration, vomiting, diarrhea, abdominal pain, muscle pain, and stiffness. Occasionally, uveitis, coagulopathies, and respiratory signs such as coughing and dyspnea may be evident. In many cases, the minimum database will reveal azotemia with inappropriately concentrated urine, indicating an acute renal injury, and may show increased liver enzymes, reflecting liver involvement. Altered white cell counts (increased or decreased) and reduced platelet counts are typical. Less commonly, however, dogs may appear outwardly healthy and the only abnormality noted is moderate to severe polyuria and polydipsia (PU/PD) and normal chemistry findings, with or without concurrent renal glucosuria. Leptospirosis is also suggested as a possible contributor to chronic liver and kidney disease in dogs.
New diagnostic options
Historically, the most common testing method for diagnosing leptospirosis has been with serology, using the microscopic agglutination test (MAT). Due to the complexity of performing this test, it can have an extended turnaround time and higher cost than other serologic tests. IDEXX is pleased to introduce a new enzyme-linked immunosorbent assay (ELISA) for Leptospira-specific antibodies. The trusted ELISA technology is available as a point-of-care SNAP test and as an IDEXX Reference Laboratories test. The SNAP Lepto Test and the Canine Leptospira spp. Antibody by ELISA both provide fast results at a lower cost to assist veterinarians in diagnosing this potentially life-threatening infection. When diagnosed early, the disease can be appropriately treated and the pet owners and staff better protected against a zoonotic infection.
In the acute stages of the infection, practitioners should also consider the Leptospira spp. RealPCR Test, which may detect the presence of antigens in the blood and/or urine. Often, the exact time of exposure is difficult to determine in dogs, and therefore for the most complete diagnostic workup, it is important to consider both serology and PCR testing when a patient presents with clinical signs consistent with leptospirosis.
Learn more about this dangerous disease and read our diagnostic update The In-House SNAP Lepto Test and the Leptospira ELISA at IDEXX Reference Laboratories. Help pet owners understand more about leptospirosis risk factors and how they can help protect their pets and themselves at pethealthnetwork.com.
Richard E. Goldstein, DVM, DACVIM, DECVIM-CA, Chief Medical Officer of the Animal Medical Center in New York City, talks about the SNAP Lepto Test.
Sarah Tasse, DVM
Dr. Tasse received her DVM from Colorado State University in 1997. After graduation she worked in a variety of small-animal private practices in both Colorado and New England. She joined IDEXX in August 2011 as a medical affairs marketing manager for Companion Animal Group, Rapid Assay.