Non-core vaccines: FIP, canine corona, Lyme disease, and Bordetella (Proceedings)

Non-core vaccines are those which we as a profession have determined are not recommended for all dogs or cats. Vaccination, in general, has the benefit of potentially lessening the prevalence or severity of disease, ensuring that patients are examined on a regular basis, increasing practice revenue, and potentially saving clients money in the long-run. However vaccination has also been associated with acute severe, life-threatening illness (anaphylaxis, respiratory distress), subacute illnesses (IMHA), and potentially fatal long-term effects (vaccine-associated sarcomas). Short- and long-term efficacy of the non-core vaccines are also commonly called into question. There is no question that many of the non-core vaccines are controversial; this presentation will review the pros and cons for some of these vaccines based on the peer reviewed literature and the general impression of specialists, and conclude with the speaker's personal views on each product.

Feline Infectious Peritonitis

The prevalence of feline enteric coronavirus varies from 15% in single-cat households to 80% of breeding cats. Cats in multicat households, purebred cats, outdoor cats, and cats from shelters or humane societies have a higher rate of infection. The majority of cats develop no overt clinical signs, although mild transient diarrhea may occur. The virus replicates within the gastrointestinal tract epithelial cells and draining lymph nodes, and transient viremia may occur. Feline infectious peritonitis develops following mutation in the viral genome; alteration of the 3C or 7B protein (at one of several possible locations) allows the virus to lose its epitheliotropism, infect macrophages and monocytes, and disseminate throughout the host. The host invariably succumbs to vasculitis or intraparenchymal granulomas. It appears that once the mutated virus becomes systemically distributed it is no longer shed in the feces the way that non-mutated enteric coronavirus is; therefore FIP is not considered a contagious disease.

      Pros for vaccination:

           1. FIP is invariably fatal—any chance at preventing development of disease is worthwhile.

           2. FIP is most devastating in areas of high cat density; therefore vaccination will hopefully confer some herd immunity to these populations.

      Cons against vaccination:

           1. Once cats are infected with coronavirus (usually at a very young age) the FIP vaccine will not prevent mutations or dissemination of pathogenic FIP virus.

           2. The FIP vaccine does not reliably cause a decrease in the incidence of FIP.

           3. Preventative strategies in herd health situations are much more efficacious than the vaccine.

           4. The vaccine induces antibodies that are indistinguishable from anti-enteric coronavirus antibodies; therefore screening and removal of infected individuals is impossible after vaccination.

           5. Some studies have shown that vaccines could be associated with antibody-dependent enhancement of disease (although this is uncertain, as it was shown in experimental animals with viral strains of increased virulence).

      Bottom line—Two populations should be considered for this vaccine. Single cat/low-number multicat households (i.e. <5 cats) are at inherently lower risk for FIP outbreaks. Most of these cats are already infected with feline enteric coronavirus, so vaccination is of questionable benefit. In cattery and shelter situations good husbandry practices and/or screening and elimination of coronavirus carriers is known to be far more effective in preventing disease than the FIP vaccine. The American Association of Feline Practitioners does not recommend use of this vaccine, as it has not been shown to produce clinically relevant protection.

Canine Coronavirus

Canine coronavirus is an endemic cause of infectious enteritis in most dog populations. Surveys of various populations have revealed that up to two-thirds of dogs with diarrhea are shedding coronavirus. However studies looking at the prevalence of coronavirus shedding in feces of normal dogs are lacking, so it is unclear if shedding of virus implies that it is the cause of the clinical signs. Experimentally infected dogs develop moderately severe diarrhea and are transiently anorectic with occasional vomiting—feces are very malodorous, may be orange-tinged, and rarely melena or hematochezia are noted. Adult dogs generally recover without any intervention. Dehydration rarely occurs in more severe cases, but intravenous fluid therapy for 24-48 hours is typically sufficient to support these dogs until the disease completes its course. The only population which appears to truly have the potential for life-threatening disease is neonates/pediatric patients. Puppies are less tolerant of dehydration than older animals, and anorexia leads to hypoglycemia and organ failure. Although immunosuppressed patients are theoretically vulnerable as well, adult dogs have usually already developed resistance, and morbidity has not been recognized. The only method available for definitive diagnosis is electron microscopy of feces or gastrointestinal tissues; typically a presumptive diagnosis is made without further testing, and patients recover with minimal supportive care. Coronavirus is not zoonotic.

      Pros for vaccination:

           1. Diarrhea, even when transient, is a common owner complaint. Eliminating any potential cause is worthwhile.

           2. Herd immunity will hopefully decrease the likelihood that vulnerable animals will be infected.

      Cons against vaccination:

           1. Mild disease occurs in the vast majority of animals—the inherent risks of vaccination outweigh the potential benefit of eliminating the disease.

           2. Duration of immunity for this vaccine is unknown.

           3. By the time a full vaccine series can be administered to puppies they have usually aged past the typical vulnerable period.

           4. Anecdotally, practitioners who have begun administering this vaccine—and those who have stopped administering it—have not reliably reported a change in the frequency of dogs presenting with presumptive viral enteritis.

      Bottom line—Canine coronavirus is such a mild disease that the potential harm of vaccination outweighs the benefits. Minimizing the worries about overvaccination by giving the coronavirus vaccine at different visits than other vaccines increases the cost to the owner more than can be justified. The AAHA Canine Vaccination Task Force has officially recommended that this vaccine not be given, and internists in general agree with this.

Borrelia Burgdorferi (Lyme Disease)

Cases of Lyme disease in people in the United States are concentrated in the southeast and gulf coast, northeast, Great Lakes region, and Pacific states. This limited distribution is due to the available habitat of the Ixodes ticks which harbor and transmit Borrelia burgdorferi, the causal organism. In these regions large numbers of dogs are routinely exposed and are seropositive against B. burgdorferi. These antibodies are used as presumptive evidence of infection; infection is thought to be lifelong, as experimentally infected animals are not cleared completely even after prolonged courses of appropriate antibiotics. Antibody titers may remain increased for months to years. The vast majority of infected dogs are asymptomatic. However, clinical syndromes which have been epidemiologically associated with Lyme disease in dogs include intermittent and shifting polyarthritis, and glomerulonephritis which is typically rapidly progressive and associated with severe uremia and nephritic syndrome. Cases of neurologic or cardiac disease have also been reported, but it is even less clear if these are truly part of the Lyme disease complex.

      Pros for vaccination:

           1. Public awareness of Lyme disease is high—owners want to know that we are protecting their pets, even if they can't understand the complexities of the disease.

           2. Lyme-associated glomerulonephritis has a horrible prognosis. Any chance of stopping this disease is worthwhile.

           3. Dogs with Lyme disease-associated polyarthropathy may not respond consistently to therapy; prevention is worthwhile.

      Cons against vaccination:

           1. Bacterins are highly associated with vaccine side-effects, including fever, polyarthritis, and GI signs.

           2. It is possible that the vaccine is part of the pathogenesis of Lyme glomerulonephritis; this disease was not described until after vaccine use became widespread. First do no harm!

           3. Duration of immunity with bacterins is short; thus the immunity provided may not be worth the risks of vaccination.

      Bottom line—Even internists and pathologists can't agree at this point what syndromes are or are not definitely caused by B. burgdorferi...however the majority of us do think that Lyme disease is a true clinical entity in dogs. Although we do acknowledge that vaccination may be part of the problem, in the absence of evidence or a clearly increased prevalence of disease in those practices who vaccinate we are supportive of Lyme bacterins. However, because of the high incidence of side-effects and the possibility of causing disease vaccination should be limited to those animals that are at increased risk of exposure. These include large breed dogs, hunting/sporting dogs, and dogs with routine access to wooded/non-landscaped yards. Lyme vaccination should not be considered a substitute for good tick control. Beginning vaccination during the mid-winter is likely worth considering, as duration of immunity may be as short as 9-12 months; beginning the vaccine series at this time ensures that the time of lowest protection will fall during the time of year when fewest ticks are around. The most recent ACVIM Small Animal Consensus Statement on Lyme Disease in Dogs does not take a position on vaccination.

Bordetella Bronchiseptica

Bordetella bronchiseptica is the most common cause of infectious tracheobronchitis, or 'kennel cough.' It is highly transmissible and is one of the most common causes of infectious disease outbreaks in veterinary clinics, boarding kennels, and animal shelters. Dogs most commonly develop a loud honking cough, and may expectorate phlegm at the end of coughing fits; sneezing, rhinitis, and oculonasal discharge may occur. Spontaneous resolution occurs regardless of therapy in most cases. Rarely dogs may develop bronchopneumonia that requires hospitalization and more intensive support.

      Pros for vaccination:

           1. Vaccination may offer herd health by limiting outbreaks.

           2. Vaccination may protect those few dogs which later develop life-threatening pneumonia.

           3. Mucosal protection induced by the intranasal vaccine may result in fewer side-effects than other vaccines.

           4. Vaccination of dogs with established disease may reduce clinical signs (see #4 below)

      Cons against vaccination:

           1. Vaccinating animals immediately prior to boarding or exposure to other potentially infected dogs does not allow protection to develop rapidly enough to prevent disease.

           2. Disease is self-limiting, and protection may primarily be to assuage owner's annoyance at the cough.

           3. Vaccination itself causes mild clinical signs of disease.

           4. The argument that vaccination reduces clinical signs in dogs with established disease has not been systematically evaluated.

      Bottom line—The majority of dogs are not in high-risk environments where B. bronchiseptica vaccination would be deemed necessary. Exceptions are show dogs, where infectious tracheobronchitis would prevent them from competing in shows, long-term boarding situations at kennels, or dogs that have severe unrelated respiratory disease (where B. bronchiseptica infection would be debilitating) and who regularly come in contact with other dogs.