PROTECT & PREVENT

A Quick Guide to Canine Leptospirosis

PREVENTION IS PROTECTION FOR YOUR PATIENTSLeptospirosis is a geographically widespread disease that affects many animal species – including humans. It is currently considered to be the most widespread zoonotic infection in the world.1 Prevention and protection are the first steps to containing it.

This Quick Guide will serve as an overview of leptospirosis andprovide quick resource information on:

• Clinical signs and diagnosis

• Transmission

• Risk factors

• Classification

• U.S. vaccination standards

1. Centers for Disease Control and Prevention. Leptospirosis - Healthcare Workers - Technical Information for Leptospirosis. https://www.cdc.gov/leptospirosis/health_care_workers/index.html. Accessed May 13, 2018.

Leptospires are spiral-shaped, long, thin bacteria that move bytwisting and flexing.

They thrive in warm, wet conditions and can survive for months in still or slow-moving water and damp soil. However, they must enter a host to multiply and cause disease.

In dogs, the early signs of leptospirosis can be vague and nonspecific, which makes recognition based on clinical signs difficult. As a result, it is likely that the disease is underdiagnosed. However, if not successfully treated at an early stage, the signs may progress into potentially fatal hepatic and/or renal failure.

The disease will typically occur in unvaccinated animals, but itcan also occur in vaccinated animals if the infecting serovar is not covered by the vaccine used.

Clinical signs of leptospirosis can include:• Fever, lethargy, anorexia, shivering, stiffness, or reluctance

to move

• Acute renal failure (polyuria, polydipsia, dehydration, vomiting, diarrhea, abdominal pain)

• Hepatic failure (icterus)

• Ocular signs (conjunctivitis, uveitis)

• Respiratory signs (Leptospiral Pulmonary Hemorrhagic Syndrome (LPHS), tachypnea, dyspnea)

• Bleeding disorders (hematuria, hematemesis, hematochezia, epistaxis, petechial hemorrhages)

• Vasculitis (peripheral oedema, pleural or peritoneal effusion)

SOME OF THESE CLINICAL SIGNS HAVE TRADITIONALLY BEEN ASSOCIATED WITH LEPTOSPIROSIS AND CAN BE FOUND IN ALL TEXTBOOKS. Some others, such as pulmonary hemorrhage, have only recently been recognized and are often missed as possible signs of leptospirosis. Clinical diagnosis can be complex and time consuming and, as a consequence, many cases will almost certainly go undiagnosed, making it likely that the true frequency of disease in the canine population is significantly underestimated.

CLINICAL DISEASE:BACTERIUM AND SIGNS

ISOLATION AND IDENTIFICATION OFTHE ORGANISMIsolation and/or identification of the organism – mainly from bloodor urine – is the gold standard for making a diagnosis, but culturing the organism is difficult and time consuming.

Polymerase chain reaction (PCR) is a useful alternative to isolation and culture. PCR assays for detection of leptospiral nucleic acid are increasingly offered by commercial diagnostic laboratories worldwide. Both conventional and real-time assays have been developed, and their use has been reported in the literature. Most PCR assays nowadays are simply designed to detect any pathogenic leptospiral strains, but they can’t currently identify serogroups or serovars.

SEROLOGYThe microscopic agglutination test (MAT) is most commonly usedand is considered to be the gold standard for serology. As such,it’s the current diagnostic test of choice for detecting antibodiesto canine leptospirosis. There are, however, a number of potentiallimitations, including:

• The MAT can only be performed by specialized labs.

• Test interpretation is somewhat subjective, and considerable variation can occur between labs.

• Agglutination antibodies can take time to appear, and dogs often test negative during the first week of illness.

FOR THIS REASON IT IS ALWAYS PREFERABLE TO HAVE SUITABLE PAIRED SAMPLES TESTED, WITH THE CONVALESCENT SAMPLE TAKEN IDEALLY 1-2 WEEKS LATER.

• Titers resulting from vaccination can be picked up and may cause confusion. In dogs, vaccine titers are usually lower than titers following infection. Taking paired samples will reduce this risk of confusion.

• A diagnosis on serogroup level is possible; classification at serovar level is not.

• False negatives are possible if not enough serovars are being used in the antigen panels. The MAT test is serogroup-specific and relies on sufficient representative serovars being used to cover all the serogroups required. If a dog is infected with a strain from an unusual serogroup not included in the MAT test panel then this may give a false negative.

• Cross-reactivity between serogroups can occur and this may result in an incorrect interpretation of which serogroup is responsible for the disease. This is a particular problem in the acute phase of the disease where paradoxical reactions can occur (where titers against noninfecting serogroups are higher than titers against the infecting serogroup).

DIAGNOSIS

Infected animals shed bacteria in their urine. Chronicallyinfected reservoir host species (such as rodents) or incidentalhosts (such as dogs) can shed leptospires for months – or evenyears – in the case of reservoir hosts.

Direct transmission occurs when an animal comes into contactwith infected urine; indirect transmission occurs through contact with contaminated water, soil, food, bedding, etc. Once shed, leptospires can survive in warm, wet conditions for monthsready to invade new hosts. And so the disease cycle continues.

Chronically infected reservoir host species (often wildlife such asrodents) maintain the disease in their environment. These reservoir hosts are often well adapted to the particular serovar they harbor and will not show clinical signs – but can shed leptospires for months, even years.

Incidental hosts, such as dogs, can suffer clinical disease afterinfection. They may shed leptospires for a shorter period, but arestill ready sources of infection.

TRANSMISSIONTO DOGS…

As leptospirosis is a serious zoonotic condition, it is a critical component of disease control to limit shedding from infected dogs.

Although it is a disease traditionally associated with an outdoor, rural environment, dogs can be at risk of leptospirosis almost everywhere. Broad risk factors for Leptospira exposure put virtually all dogs at risk. People living closer to wildlife in the suburbs – and urban rodent population – make both suburban and urban dogs at risk. However, the highest risk activities include:

• Exposure to habitats with known reservoir species (eg, wild rodents)

• Hunting or herding dogs

• Exploring the outdoors

• Access to still or slow-moving water sources

• Exposure to livestock

…AND HUMANS

RECOGNIZE THE RISKS

There are many pathogenic strains of leptospires that aretraditionally classified into specific serovars. This classification isbased on surface antigens. Currently, more than 250 pathogenicserovars are recognized. Antigenically related serovars aregrouped into serogroups.

When referring to a specific leptospira isolate, it is typical torefer to its serovar and serogroup classification. The followingtable shows the species and serogroup classification of someimportant serovars.

CLASSIFICATION OFLEPTOSPIRES

Serogroup Serovar

Canicola Canicola

IcterohemorrhagiaeIcterohemorrhagiae Copenhageni

AustralisBratislavaAustralis

GrippotyphosaGrippotyphosaDadas

Pomona Pomona

Next to the traditional classification into serogroups and serovars,which is based on antigenic relatedness, there is a differentsystem that classifies leptospires based on their genetic (DNA) relatedness. This method classifies leptospires into 19 differentgenomic species, of which 6 are pathogenic. This method ofclassification is based on genetic sequencing. Unfortunately, there isn’t a simple method of cross-correlation between the two classification systems. Consequently, new leptospira isolates are currently being characterized by both molecular and serological approaches. The traditional method of classification into serogroups and serovars is used in the field and is the most relevant method of classification for vaccination purposes.

DOUBLE THE SEROGROUPS – TWICE AS SERIOUSHistorically, canine leptospirosis has been associated with serovarsfrom serogroups Canicola and Icterohemorrhagiae. However, inrecent years a change has occurred in the epidemiology of canineleptospirosis, and nowadays cases of disease caused by serovarsfrom serogroups Pomona and Grippotyphosa are seen at leastas frequently. A number of recent independent surveys andpublications illustrate the current situation very clearly.

In 2017, leptospirosis cases spiked across the U.S. in all geographic locations and climates, such as cities, humid areas, and after flooding. In New Jersey, 5 dogs were infected and 3 of them died.3 Even dogs in arid climates, such as Arizona, where outbreaks have been reported in recent years, are at risk.4

The Centers for Disease Control (CDC) suggests dogs get vaccinated against

leptospirosis.1,2

Probability2

Low Medium High

1. Centers for Disease Control; Leptospirosis in Pets; https://www.cdc.gov/leptospirosis/pets/prevention/index.html; Accessed June 19, 2017. 2. “American Hotspots of canine leptospirosis in the United States of America.” The Veterinary Journal. 2017;222: 29-30. 3. Rare Infection Spread By Rat Urine Leaves At Least 3 Dogs Dead In New Jersey; http://newyork.cbslocal.com/2017/03/24/; Accessed June 16, 2017.

LEPTOSPIROSIS VACCINATION PROTOCOL IN THE U.S.

*2017 AAHA Canine Vaccination Guidelines

2017 AAHA Canine Vaccination Guidelines*

NONCOREVaccinations

Leptospira (killed) 4-serovarserovar canicola; serovar icterohaemorrhagiae; serovar grippotyphosa; serovar pomona.Administer by the SQ route.

Initial Vaccination(Dogs <16 Weeks

of Age)

Two initial doses, 2 to 4 weeks apart, are required: the initial dose may be administered as early as 8 to 9 weeks of age.

Initial Vaccination(Dogs >16 Weeks of

Age)

Two initial doses, 2 to 4 weeks apart, are required regardless of the dog’s age.

Revaccination(Booster)

Where risk of exposure is sustained, administer a single dose 1 year followingcompletion of the initial 2-dose series, thenannually thereafter.

REMARKS

Because there is limited cross-protection among serovars in the vaccine, administration of a 4-serovar leptospirosis vaccine is recommended over a 2-serovar vaccine.

4-serovar leptospirosis vaccines are available in combination with CORE vaccines and as a 4-serovar (only) product that is not combined with other vaccines.

For recommendations on managingdogs who are overdue for this vaccine,visit aaha.org/CanineVaccinesOverdue

Successful treatment of leptospirosis involves both supportivecare in managing the renal, hepatic, or other organ systemmanifestations of the disease and the use of antimicrobials toeliminate the infection. Antimicrobial therapy should be startedas soon as the disease is suspected and any diagnostic sampleshave been taken. Bearing in mind the potential seriousness of thedisease and the zoonotic risk, antimicrobial therapy should beinitiated before confirmation of the diagnosis.

Oral doxycycline is usually recommended as the drug of choicefor eliminating infection from various tissues and controlling urineexcretion (advised doses are 5 mg/kg, every 12 hours for at least14 days). In any animals too sick to tolerate oral therapy withdoxycycline, intravenous penicillins (eg, ampicillin at 20 mg/kg intravenously every 6 hours) should be given until any gastrointestinal signs have abated and the doxycycline therapy can start.1

TREATMENT OFTHE DISEASE

1. Sykes JE, Hartmann K, Lunn KF, et al., 2010 ACVIM Small Animal Consensus Statement on Leptospirosis: Diagnosis, Epidemiology, Treatment, and Prevention. J Vet Intern Med 2011;25:1–13.

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Further references: usa.nobivac.com and cdc.gov/leptospirosis