Vaccines and vaccination 2008: the issues...the controversies (Proceedings)

Vaccination GUIDELINES for the cat were first published in 1998; canine GUIDELINES followed in 2003. By the end of 2006, both sets of GUIDELINES had been reviewed extensively, updated, and published. Today, the complete text of both the AAHA Canine Vaccine Guidelines (www.aahanet.org) and the AAFP Feline Vaccine Guidelines (www.catvets.com [NOTE: this is a new name for the AAFP website]) is available to the entire profession. Let there be no question...veterinarians continue to pay close attention to the numerous, sometimes controversial, presentations and publications that address how we should select and use vaccines in companion animal practice. Yet, whether or not you intend to implement any of the recommendations outlined, every clinician should at least read the GUIDELINES. These 2 publications serve as a critical resource for any veterinary practice engaged in administering vaccines to dogs and cats. The pace of change regarding vaccine technology along with new product introductions virtually mandates that veterinarians carefully assess the manner in which vaccines are selected and used.

Table 1: CORE Canine Vaccines and Recommendations for Administration

Today...there's simply no room for complacency with respect to developing a rational vaccination protocol. It's a fact...there are too many issues and too many new facts to ignore the changes impacting the selection and use of vaccine.

Table 2: NON-CORE Canine Vaccines and Recommendations for Administration

Perhaps the single most significant challenge regarding implementation of a vaccine protocol in practice today is the number of vaccines available today. At this writing, there are approximately 26 vaccine antigen types for the dog and 18 types for the cat...combined, there are over 150 proprietary (trade name) vaccines in the US! Just months after publication of the 2006 Feline Vaccination Guidelines, 2 new vaccines were licensed (VS Feline Calicivirus and Canine Malignant Melanoma-therapeutic vaccine); throughout 2008 it is reasonable to expect additional canine & feline vaccines will be licensed.

But...it's not just the number of new vaccines that impact vaccination protocols used in practice...it's the frequency of vaccination, it's the duration of immunity of the various vaccines we use, it's the dramatic change occurring in vaccine technology and development, it's vaccine safety, it includes medical, legal, and ethical responsibilities...and more.

TABLE 3: Miscellaneous Canine Vaccines not evaluated by the AAHA Canine Vaccine Task Force.

The objective of this presentation is not to attempt defining standards for vaccinating dogs and cats...nor is it to recommend a universal vaccination protocol. Instead, it's to facilitate the efforts of individual clinicians in implementing a rational vaccination program, consistent with current body of knowledge.

Table 4: CORE Feline Vaccines and Recommendations for Administration

Building the Protocol

The concept of CORE and NON-CORE vaccines is valid and has direct application in veterinary medicine today. Simply stated, this means separating the vaccines currently in your refrigerator into 2 separate groups: those that every dog and every cat will receive (CORE) and those that the attending clinician decides are necessary (or NOT necessary) based on health risk assessment of the individual patient (NON-CORE). While this may not sound especially important, there is value in assuring that every person in the hospital, technicians as well as veterinarians, is aware of the CORE vaccines and can consistently communicate the same vaccine message to clientele. The series of 4 tables that follow represent a list the CORE vaccines for the dog and cat and current recommendations for incorporating these vaccines into a rational vaccination protocol.

Table 5: NON-CORE Feline Vaccines and Recommendations for Administration

2008 Discussion Papers

A. Recommendations for Administration of Canine Vaccines-CORE & Non-CORE

B. Recommendations for Administration of Feline Vaccines-CORE & Non-CORE

C. UPDATE: Types of Vaccines Licensed for use in Dogs and Duration of Immunity

- Core Vaccines (Expanded List) and Duration of Immunity

- Non-core Vaccines

- Not Generally Recommended (Expanded List)

D. UPDATE: Types of Vaccines Licensed for use in Cats and Duration of Immunity

- Core Vaccines and Duration of Immunity

- Non-Core

- Not Generally Recommended

E. Antibody Titers vs. Annual Vaccination

F. Feline Vaccine-Associated Sarcoma: The Case against Adjuvant

G. The AAHA Canine Vaccine Guidelines: Triennial Vaccination vs. "3-Year" Vaccines

Leptospirosis Vaccination: The 2-Way or the 4-Way...or the NO WAY!

Table 6: Miscellaneous Feline Vaccines not evaluated by the AAFP Feline Vaccine Advisory Panel

TO TITER...OR NOT TO TITER?

Antibody Titers vs. Annual Vaccination

Current vaccination guidelines for the dog (REF #1) and cat (REF #2) recommend triennial administration of core vaccines (see Table 1) rather than the conventional annual booster recommendation found on the package inserts of most products. Veterinarians seeking serologic evidence of sustained immunity to prior vaccination, along with client concerns over excessive vaccination practices, prompted an increase in requests from practices for antibody titers against selected canine and feline antigens. The widespread availability of "vaccine titers" has culminated in questions concerning indications for testing, interpretation of test results (POSITIVE vs. NEGATIVE), and the significance of using these tests as part of a patient's routine health care assessment. This issue of IMMUNOLOGY BULLETIN addresses these key points.

What is a titer?

A product of the B-lymphocyte, antibody (Ab) is an immunologically active glycoprotein that forms in blood, secretions, or on mucosa in response to an antigen (Ag), such a bacterium or virus. By definition, an antibody titer is a laboratory-generated value that represents the presence and concentration of antibody in blood (serum or plasma). Different classes of antibody, or immunoglobulin (Ig), having specialized functions, have been identified and named, e.g., IgA, IgG, or IgM. In veterinary medicine, antibody titers are typically reported for the IgG, and occasionally IgM, class of antibody. (REF #3)

In recent years, laboratories serving veterinary medicine have offered increasing numbers of serologic (antibody) assays. Diagnostic serology for fungal (e.g., crytptococcosis) and tick-borne disease (e.g., Rocky Mountain Spotted Fever and Ehrlichiosis) are among the most commonly requested tests. Antibody titers to commonly administered vaccines have become increasingly available, especially for canine distemper and canine and feline parvovirus. Rabies titers, although required by some countries prior to exporting dogs or cats from the United States, can only be performed by certified laboratories.

C. UPDATE: Types of Vaccines Licensed for use in Dogs and Duration of Immunity

As reported by a laboratory, an antibody titer is a titration of serum to determine the relative concentration of Ab in the sample. A series of dilutions are tested for activity. The highest dilution (1:256 is a higher dilution than 1:32) has the greatest activity (or concentration). Laboratories may report results as the reciprocal of the highest dilution (e.g, "256"). (REF #3) Reference range values are unique to each laboratory and to each test method used. It is impractical to compare titer results from different laboratories.

Laboratories reporting titers may also indicate that an Ab titer is "POSITIVE" or "NEGATIVE". It is important to understand that such terms only signify the presence (POSITIVE) or absence (NEGATIVE) of a significant concentration of Ab in the sample tested. It does not confirm the presence or absence of an infection...nor of immunity to infection.

D. UPDATE: Types of Vaccines Licensed for use in Cats and Duration of Immunity

What does a titer signify?

When submitting serum from an individual patient to assess serologic response to vaccination, the Ab titer reported only indicates prior exposure to a particular antigen. It does not distinguish between natural exposure, vaccination, or (in puppies/kittens) maternally derived Ab.

Furthermore, it must not be assumed that a vaccine titer reported as POSITIVE is confirmation that the patient is resistant to infection. There is considerable variation in the interpretation of a POSITIVE titer result. For example, leptospirosis Ab titers are used diagnostically to assess prior and current exposure, but a dog with POSITIVE titer typically does not derive protective immunity from Ab measured by this assay. Cats having a POSITIVE titer to feline herpesvirus-1 or calicivirus are likely to experience minimal clinical disease following exposure, but are not resistant to infection and subsequent viral shedding. (REF #4)

On the other hand, a POSITIVE Ab titer to canine distemper or parvovirus and feline parvovirus (panleukopenia) generally correlates with protection against challenge. (REF: #5 and 6). However, a POSITIVE Ab titer in an individual patient only reflects past immunity. The patient that is POSITIVE today may not be POSITIVE tomorrow.

TABLE 7: Core Vaccine Recommendations for the Dog and Cat

Interpretation of a NEGATIVE titer is somewhat more complex. Antibody is subject to catabolism over time. The absence of a measurable Ab titer does not necessarily correlate with susceptibility. Immunologic "memory", in the form of B-lymphocytes and plasma cells can be called on for a rapid immunologic 'boost' in the event of subsequent exposure. (REF #5) This is particularly true for canine distemper and canine/feline parvovirus.

Indications for Testing

Routine testing of dogs and cats for Ab titers to core vaccines is not generally recommended. While a POSITIVE titer likely correlates with protective immunity (canine distemper and canine/feline parvovirus), a NEGATIVE titer, a rare finding in previously vaccinated animals, does not necessarily define susceptibility.

Indications for testing are generally limited to the assessment of individual puppies and kittens for evidence of a response to the initial series of core vaccines. Serum can be submitted as early as 2 weeks following the last of vaccines in the series. Testing of puppies and kittens is reasonably limited to high risk groups (group housing environments, use of dog 'day-care' facilities, and frequenting dog parks). Today, there is no known breed-predisposed susceptibility to infection (e.g., Rottweillers and parvovirus) that justifies routine Ab testing. (REF #1)

Antibody testing, in lieu of vaccination, is also indicated in patients with a prior history of having experienced a known or suspected adverse vaccine reaction. Likewise, patients having recovered from an immune-mediated disorder, e.g., immune-mediated hemolytic anemia or thrombocytopenia, are reasonably subjected to antibody titers rather than booster vaccination. In the unlikely event a patient has a negative Ab titer, the decision to vaccinate or not is left to the discretion of the individual clinician. Rabies vaccination may not be an option in those States that do not recognize rabies vaccination waiver authority to veterinarians.

Vaccines are specifically indicated for administration to "healthy" animals. Patients suffering from chronic systemic illness (e.g., neoplasia) may not benefit from vaccination. Antibody testing may provide assurance that, despite the chronic illness, the patient is protected from exposure.

Conclusion

Routine use of serologic testing to assess immunity in the individual dog or cat carries significant limitations. Variation of test results reported by individual laboratories, the lack of uniform laboratory standards for performing titers, and the inability of these tests to reliably distinguish protected from susceptible patients requires the clinician to have a clear understanding of the meaning of test results.

References

Paul MA, Carmichael LE, Childers H, et al. 2006 AAHA Canine Vaccine Guidelines (revised February 2007). Full text and references are available at: www.aahanet.org

Richards JR, Elston TH, Ford RB, et al. The 2006 American Association of Feline Practitioners Feline Vaccine Advisory Panel Report. JAVMA, 229:1405-1441, 2006. Full text and references are available at: www.aafponline.org

Tizard IR. Veterinary Immunology: An Introduction. (7th Edition). Saunders-Elsevier, Philadelphia. 2004.

Lappin MR, Andrews J, Simpson D, and Jensen WA. Use of serologic tests to predict resistance to feline herpesvirus-1, feline calicivirus, and feline parvovirus infection in cats. JAVMA. 220:38-42, 2002.

Greene CE and Schultz RD. Immunoprophylaxis. In, Greene CE, ed. Infectious Diseases of the Dog and Cat, 3rd ed. 2006, Saunders-Elsevier, St. Louis, pp. 1069-1119.

Scott FW and Geissinger CM. Long-term immunity in cats vaccinated with an inactivated trivalent vaccine. AJVR. 60:652-658, 1999.

Feline Vaccine-Associated Sarcoma

The Case against Adjuvant

In 1999, the American Association of Feline Practitioners (AAFP) sponsored an Advisory Group of veterinarians to review available literature on feline vaccines and develop a set of Guidelines to facilitate efforts by veterinarians to implement rational vaccination protocols. In January 2000, that Advisory Group published the 2nd iteration of the AAFP Feline Vaccination Guidelines. In 2003, the American Animal Hospital Association (AAHA) sponsored the Canine Vaccine Task Force that developed vaccination Guidelines for the dog. Both groups have recently reconvened and will publish updates early in 2006. All of this activity has had significant impact in clinical practice as veterinarians are being challenged to provide comprehensive 'wellness programs' yet deal with significantly unfamiliar vaccination guidelines, particularly those recommending a 3-year booster interval for adult dogs and cats vs. customary annual booster vaccination.

Still today, the feline and canine vaccination Guidelines are not without controversy. In fact, one of the fundamental controversies behind the decision to develop Feline Vaccination Guidelines was the fact that, by 1999, it had become well established that routine administration of vaccine to cats, particularly FeLV and Rabies vaccines, resulted in the development of an aggressive, malignant sarcoma in some cats. In 1993, the prevalence of tumor formation was estimated to be 1 to 2 cats affected for every 10,000 vaccinated. Today, 15 years later, that estimate of prevalence remains virtually unchanged. Recent estimates are that between 1 in 10,000 and 1 in 3,000 cats will develop a tumor directly related to vaccine administration.

Despite the efforts of several research groups to identify the underlying cause of what is now called "Vaccine-Associated Sarcoma" (VAS), most of the literature on affected cats continues to deal with treatment, rather than prevention. Ironically, in 2001, the AVMA's Vaccine-Associated Feline Sarcoma Task Force published recommendations to administer FeLV vaccine in the LEFT rear leg, as distally as possible while recommending that rabies vaccine be administered in the RIGHT rear leg as distally as possible. The reason...if/when a tumor develops, the leg can be amputated!

This is hardly an acceptable solution to what is now recognized as the most significant adverse event associated with feline vaccination...and the ultimate question regarding VAS remains...

What can be done to mitigate the risk of VAS in cats?

Today, available research provides no definitive answer to this question. However...there exists a body of literature that implicates a link between the administration of adjuvanted vaccine...chronic inflammation induced by vaccine adjuvant...and tumor formation. That evidence is summarized below:

First...it's a cat thing! VAS has been reported in humans and in dogs...but documented cases are exceptionally rare compared to the VAS prevalence recognized in cats. Yet...it's not just vaccine. There are published reports documenting fibrosarcoma formation in cats that were caused by ocular trauma, repository drug administration, and nylon suture left in skin for an extended time. Interestingly, in July 2004, investigators at the University of Minnesota reported having identified an allele in cats that were predisposed to develop VAS (a commercial test is pending).

Second...it was 1985! A well documented story...in 1985, the first, and very popular, feline leukemia vaccine (aluminum adjuvanted) was licensed in the US. Being the first FeLV vaccine to reach the market, widespread use followed. Also in 1985, sale of modified-live rabies vaccine in the US was withdrawn and replaced with killed, adjuvanted rabies vaccine. Then, in 1987, the State of Pennsylvania issued legislation that required, for the first time, all cats receive a rabies vaccine. It was in 1991 that the Pathology Laboratory at the University of Pennsylvania, School of Veterinary Medicine reported a dramatic increase in the number of fibrosarcomas in cats. They went on to note that these tumors were particularly aggressive, were occurring in younger, versus older, cats, and that the tumors occurred in a location where veterinarians commonly administer vaccine. In 1991, the issue was raised that vaccines might, in fact, be the cause of fibrosarcoma formation in some cats.

Third...it was 1993! A study published in 1993 provided epidemiologic evidence to show causation between the administration of either FeLV and/or rabies vaccination and tumorigenesis in cats.

Fourth...studies in the UK! A 5-year study conducted in England in the mid-1990's, funded by the government, evaluated adverse vaccine reactions in dogs and cats. Reported results were quite striking in that the study showed cats receiving an adjuvanted FeLV vaccine (England is rabies-free, therefore rabies vaccine is rarely administered) had a 5 times greater occurrence of VAS than cats receiving only non-adjuvanted, modified live virus (MLV) vaccines.

Other studies conducted in the US have demonstrated mutations in the tumor suppressor gene (tp53) in cats that developed fibrosarcoma following administration of adjuvanted vaccine.

While these studies don't prove a cause-and-effect relationship between the administration of adjuvanted vaccine and fibrosarcoma, the evidence is compelling!

In 2005, Merial introduced the first recombinant, FeLV vaccine...the only non-adjuvanted FeLV vaccine available in the US. It is my opinion that this is an important step forward in the effort to reduce the risk of VAS in cats. The reason today, veterinarians practicing in the US have more choices than ever before when it comes to selecting and administering feline vaccine. Of particular importance is the fact that, with the exception of FIV vaccine, for every adjuvanted feline vaccine on the market, there is a non-adjuvanted vaccine licensed for use in cats.

The reality is that we may never actually establish a definitive etiology behind VAS in cats...but, today, with the facts that do exist, there is good justification for avoiding the use of adjuvanted vaccine in cats as a means of mitigating the risk of VAS!

The AAHA Canine Vaccination Guidelines

Triennial Vaccination Recommendations vs. the "3-Year" Vaccines

In 2005, introduction of a so-called "3-Year" canine vaccine by various vaccine manufacturers quickly led to concerns by practicing veterinarians that any effort to comply with the AAHA Canine Vaccine Guidelines required selection and use of these products. This is clearly not the case.

It's important to note that the recommendations of the AAHA Canine Vaccine Task Force for triennial booster administration are based on data derived from vaccines that were on the market 5 years ago. Independent studies support the fact that extended durations of immunity (protection) against canine distemper, parvovirus, and adenovirus-2 are provided by all of the licensed (core) vaccines that were on the market between 2000 and 2003.

Any implication that a "3-year vaccine" must be used when adhering to current vaccination recommendations is wrong...and misrepresents the intent of the 2006 AAHA Canine Vaccine Guidelines.

There is no legal mandate, no 'standard of care' requirement, or ethical responsibility for veterinarians to only administer a 3-year vaccine in order to comply with the AAHA Canine Vaccine Guidelines.5

The following points should be considered if adopting all or part of the AAHA Canine Vaccine Guidelines:

1. Discretion in the selection and use of vaccines. Vaccination guidance set forth by the AVMA's Council on Biologic and Therapeutic Agents (COBTA) supports the fact that veterinarians are allowed discretion to exercise professional judgment in the selection and use of vaccines (also called 'biological products'). With the exception of rabies vaccination, there are no defined standards or statutes that dictate which vaccine a veterinarian must use under which circumstances. Likewise, any vaccine marketed as a so-called "3-year" vaccine is treated the same as any other core vaccine in the AAHA Canine Vaccine Guidelines.

2. "Off-Label" or NOT?. "Annual vaccination", as indicated on a vaccine label, is a recommendation, not a requirement. The term "Off-Label" or, more appropriately, "Extra Label" specifically refers to the use of an approved drug in a manner that is not in accordance with the approve label directions. "Extra Label" use of veterinary drugs is outlined by the FDA's Animal Medicinal Drug Use Clarification Act of 1994 (AMDUCA). AMDUCA does NOT apply to vaccines...only drugs. Veterinarians may opt for triennial administration using any of the core, modified-live or recombinant vaccines on the market today (whether or not it is designated as a "3-year" product).

That said...it is important to remember that veterinarians do have a responsibility to exercise "reasonable care" or "ordinary care" when selecting and administering vaccine. The potential for liability is not dependent on whether or not a veterinarian uses a biologic product in accordance with a manufacturer's recommendations; the potential for liability centers on the veterinarian-client-patient relationship...it is the veterinarian's duty to follow the "standard of care"...while the AAHA Canine Vaccine Guidelines represent a standard of care use by veterinarians practicing in the United States, the Guidelines do not represent the only standard of care.

3. A so-called "3-year" vaccines is not specifically recognized in the AAHA Canine Vaccination Guidelines. The AAHA Canine Vaccination Guidelines have been revised and will be published in March 2006. In that document, the 3 year booster recommendation for CORE vaccines administered to adult dogs is clearly outlined. Regarding CORE vaccines, the only significant change from the 2003 document is new data supporting an extended (3 years or longer) duration of immunity derived from the recombinant canine distemper vaccine. It is important to understand that the triennial booster recommendations in the 2006 Canine Vaccine Guidelines have been made without regard for a specific vaccine manufacturer, a specific vaccine, or any product sold as a "3-year" vaccine.

4. "Annual Booster" recommendation is currently under review. Vaccine labels usually, but not always, recommend booster inoculations "annually". Such wording dates to the 1950's when the USDA originally required vaccine manufacturers to stipulate the frequency of vaccine administration. The "annual booster" recommendation was based on limited data available on the first attenuated canine distemper vaccines produced for use in clinical practice. This somewhat arbitrary annual booster recommendation has been unchallenged until recently. Today, wording to the effect that "annual booster vaccination is recommended" is currently under review by the USDA.

NOTE: examination of vaccine labels today (for several manufacturers) reveals recent changes wherein the USDA has allowed manufacturers to include "3-year duration of immunity" data on the label. Interestingly, the wording "annual booster recommended" remains. It is still the veterinarians discretion as to whether or not revaccination is recommended annually or triennially.

Leptospirosis Vaccination:2-Way...or...4-Way...or...NO Way?

Leptospirosis is a gram negative, worldwide zoonotic infection. All mammals are susceptible. Transmission rates are very high with only 10 organisms needed to cause infection and disease. Almost all species of mammal are susceptible – there are over 250 serovars. All pathogens belong to the genus Leptospira. There is tremendous geographic variation in prevalence of serovars: The United States has 6-7, Latin America has 15-20, while Scandinavia has a number of unique serovars not typically seen in the US. In order to persist, leptospires need a maintenance host, a role that humans do not serve. The maintenance host (typically wildlife) does not become clinically ill despite the fact that organisms are sustained in the kidneys and shed months to years or for the life of the animal. Natural hosts do not make significant antibody titers when infected. Immediately following infection, there is a significant rise in Antibody followed by a rapid decline. In addition, leptospires can be maintained in the liver of wildlife hosts. Different species show differences in pathogenesis (raccoon more susceptible than dogs).

On the other hand, incidental hosts, ie, humans, are epidemiologically irrelevant in outbreaks because they are usually short term hosts with acute severe disease; all ages are susceptible. The organism is cleared as the host recovers and urinary shedding is short term. Incidental hosts, following infection, produce high titers and are relatively easy to detect if illness ensues.

The route of infection of leptospirosis is either direct or indirect through contact with urine (especially through mucous membranes). The actual infectious dose is not known, although the organisms are highly infectious and can spread through tissues rapidly. They can cross the placenta and infect fetuses. Any damaged skin allows entry.

Pathogenesis: within 15-20 minutes after being deposited in the eye – organisms can be found in blood. A low-level bacteremia develops after which it spreads to liver, kidney, spleen, etc. The antibodies that do develop are effective at clearing the organism from the tissues. In the incidental hosts the antibodies are so effective they can completely clear the organisms making diagnostic confirmation problematic. In addition, Leptospires can be transmitted across the placenta. In maintenance hosts – the antibodies clear the organisms from spleen, etc. but leave organisms in select sites like the kidney, which leads to long-term shedding.

Clinical Infections in Dogs: First described in 1899, in dogs, the serovars L. icterohemorrhagiae and L. canicola represented the predominant infecting serovars. Such infections were common in the US throughout the 70's and 80's. However, most authors agree that the frequent use of vaccines against these common serovars has effectively reduced the disease prevalence. In the mid to late 1980s, leptospirosis in dogs reemerged with the principle serovars being reported as: L. grippotyphosa,L. pomona, and L. bratislava.

Clinical presentations of infected dogs typically, although not always, involves young, large breed dogs presented for acute onset lethargy and significant fever (103° to 104° F). Muscle pain, vomiting, and dehydration are common. Acute onset icterus in a young, outdoor dog always places leptospirosis at the top of the differential diagnosis list. Other signs include bleeding diathesis, tachypenia, cardiac arrhythmia, and shock (vascular collapse). A sub-acute form of clinical leptospirosis is reported in dogs presented for renal failure, with no known predisposing cause. Affected dogs will also have high fever, myalgia and even hyperesthesia.

Hematologic findings typically include leukocytosis and thrombocytopenia. Several significant biochemical abnormalities may be detected in the same patient: azotemia (or uremia), elevated ALT and alkaline phosphatase, hyperamylasemia (with concurrent increase in lipase), and hyperbilirubinemia. Abdominal ultrasound exam may be consistent with intussusception, acute renal failure (large kidneys), and pancreatitis.

1. Microagglutination Test (MAT) – the 'gold standard' test used in the US and throughout the world, Human and Veterinary. Specific, but difficult to standardize, insensitive for some serovars, and vaccinated animals cause False + results. Dogs with Lyme don't react to the test. Samples sent to 3 different labs will have 3 different titers. Maintenance hosts which are chronically shedding will be seronegative. Vaccination titers usually last only 60-120 days post vaccination and titers are less than 1;800. But, titers don't correspond to immunity. Diagnosis: In chronically vaccinated animals, MAT titers can reach 1:1600. Interpretation – the highest titer is assumed to be the infecting serovar. Titers can go up after successful treatment so getting additional samples may confuse the picture. Antibiotics will kill organisms stimulating an immune system leading to high convalescent titers. Don't re-test treated patients for at least 6 months following treatment.

2. Urine Dark Field – RARELY helpful...too many false + results ; not sensitive.

3. Histolopathology – insensitive diagnostic test because biopsies are seldom representative of infected tissue.

4. Culture is the only technique in which can identify the serovar, difficult, expensive, takes 10 to 16 weeks depending on the serovar and is very hard, considering that the shedding period is only about 3 weeks after acute infection. Have to have urine before the animal has been treated.

5. PCR – sensitive (can find less than 100 organisms) – But, is not serovar specific. They have not been used in enough samples or compared to gold standards. Because it works in human blood does not mean it will work in dog urine.

6. Acute & Convalescent Titers: baseline titer is repeated in 1-2 weeks. Single antibody titer is difficult to establish without knowledge of vaccination Hx and clinical signs. A 4-fold increase in serial titers is diagnostic.

Treatment – No "initial" treatment with amoxicillin...just use doxycycline @ 5 to 10 mg/kg, PO, bid, for 2 weeks. Management of underlying kidney and/or renal disease is a must. 10-30% die. Post recovery: L. canicola – dogs shed from months to years. L. icterohemorrhagiae – dogs shed several months, other serovars – dogs shed 3 weeks to a month.

Vaccination: Is there a significant increase in the occurrence of canine leptospirosis to justify routine administration of vaccine to all dogs presented to the practice?

The answer is "NO". Based on recommendations of the AAHA Vaccine Task Force, published in the 2006 Canine Vaccination Guidelines, leptospirosis is categorized as a NON-CORE (or "optional") vaccine. It is regarded by many as the most reactive vaccine used in dogs and, as such, should only be administered to dogs with a reasonable risk of exposure or dogs that reside in geographic locations where confirmed cases of leptospirosis have been recognized.

Immunity is serovar specific (there's NO cross protection); need at least 2 initial doses and boost once per year. Leptospirosis vaccines are the most reactive vaccines. There's a need for less reactive vaccines. Do we need to vaccinate? Yes...when and where the risk is established. Some have stipulated that there is a re-emergence of leptospirosis...still, cases are uncommon. There is no evidence that the 4-way vaccines are less reactive than the 2-way vaccines.

Does zoonotic potential of Leptospirosis justify vaccination? NO...not necessarily...vaccination protects the dog..vaccination does NOT consistently or reliably prevent infection or shedding!