The encroachment of housing developments on wildlife habitat has changed the rules of the vaccine game.
Separate studies conducted by the Florida and Colorado veterinary medical associations revealed that more than 60 percent of dogs diagnosed with leptospirosis lived in urban or suburban environments. Previous findings showed dogs living in rural areas to be most susceptible.
“Leptospirosis has changed its face over the last few years,” says Kari Swan, DVM, who works in professional services at Fort Dodge Animal Health of Overland Park, Kan. showed dogs living in rural areas to be most susceptible.
“Leptospirosis has changed its face over the last few years,” says Kari Swan, DVM, of Fort Dodge Animal Health in Overland Park, Kan.
“Wildlife doesn’t always relocate when people move in,” Dr. Swan says. “This means pets are susceptible to multiple transmittable diseases because the carriers are in their back yards. This is why veterinarians need to be vigilant and systematic about assessing all canine and feline patients’ risk for exposure to diseases that may be prevented with a vaccine deemed non-core.”
All Dogs at Risk for Lepto
The Florida and Colorado studies surveyed veterinarians in the states’ fastest-growing counties. Veterinarians’ responses in the November 2008 surveys showed that small dogs, weighing less than 25 pounds, comprised 40 percent of the leptospirosis-positive dogs.
“In the past, large-breed hunting dogs were diagnosed most frequently,” Swan says. “Those were the dogs most commonly exposed to the bacteria, but now that the bacterium has come to us, any suburban or urban dog, regardless of size, can have equal exposure.”
Educating clients about diseases not routinely vaccinated against remains very important, considering the death rate from Leptospirosis cases in Colorado was almost 40 percent. In all states, emerging serovars such as L. Pomona and L. grippotyphosa are less likely to promote clinically recognizable hepatopathy such as icterus or jaundice, further hampering client awareness and veterinary diagnosis of infection.
“Veterinarians need to think about making vaccines such as leptospirosis and Lyme disease core in their practice, if necessary,” Swan says. “These diseases can masquerade as another medical issue, and cats mask signs of illness, extending the time the problem goes untreated.”
Veterinarians need to use risk-assessment tools, follow individual protocols and not act in generalities, Swan says. Pet side screening tests such as Idexx’s 3Dx snap test can help determine the prevalence of Lyme disease. Since leptospirosis is zoonotic, screening dogs that show clinical signs consistent with the disease not only helps to determine prevalence but can protect owners from exposure and illness.
“Veterinarians need to balance the information they have about their region and the individual pet’s exposure risk,” Swan says.
“Veterinarians are still the clients’ key source of information, so you can’t expect clients to ask about these things or offer up the information needed to determine risk.”
Our mobile society has increased pets’ exposure as well. A pet may live primarily indoors, but clients may not realize that exposure to disease can occur just as easily during travel.
The Non-Core Question
When should non-core vaccines be given?
“Assessments are supposed to determine if the risk of exposure is greater than the possibility of a negative vaccine reaction,” says Roberta K. Lillich, DVM, president of the American Assn. of Feline Practitioners. “Tens of thousands of unvaccinated cats die from FIV and FeLV, yet vets hesitate to vaccinate due to sarcoma risk. This is an unwarranted fear on the feline side of medicine.
“Some vets choose not to vaccinate because they feel giving the vaccine that results in a sarcoma would be their fault, and if a low-risk unvaccinated cat contracts a disease it’s not.”
Assessments should include testing the animal for potential diseases instead of only treating them for clinical signs and looking for improvement. Not testing means that subclinical cases, which could have benefited most from a vaccine, continue to go untreated.
Perhaps the biggest hurdle with non-core vaccinations is the lack of knowledge about the occurrence of the disease in the region. The lack of a national monitoring system is part of the problem.
“There needs to be a way to educate vets on geographic necessity for non-core vaccines,” says Dr. Lillich, who practices at Abilene Animal Hospital in Abilene, Kan. “Reporting would have to be mandatory for accuracy.”
Many veterinarians follow American Animal Hospital Assn. guidelines for core and non-core vaccines. While AAHA and AAFP guidelines are updated about every two years, the groups do not make specific state recommendations.
“I follow AAHA guidelines,” says Patricia Forsythe, VMD, of All Paws Animal Clinic in Royal Palm Beach, Fla. “I don’t want to overvaccinate patients, but I don’t routinely take titers, either. You can send blood to any of the three companies that measure titers and you may get three different results. I determine need for non-core vaccines based on the client and patent’s lifestyle, but having knowledge of other local cases would help make that determination.”
According to the American Veterinary Medical Assn.’s Council on Biologics and Therapeutic Agents (COBTA), the immune status of an animal relative to all the infectious diseases of concern cannot be determined without conducting challenge testing.
“COBTA says serologic results do not appear to be a sensitive indicator of immune response for some diseases or vaccines in cats and dogs,” Dr. Forsythe says. “Studies concluded that there are variations within and among laboratories, as well as lack of validated sensitivity, specificity and confidence intervals, leading to the conclusion that serologic testing is generally unreliable. COBTA noted that the U.S. Department of Agriculture licensing of serologic tests does not require validation of this type.”
Red Rock Biologics of Woodland, Calif., manufacturers a vaccine, Crotalus atrox Taxoid, intended to protect dogs against Western Diamondback rattlesnake venom. The company claims some cross-protection with Eastern Diamondback rattlers but none against the venom of the Mojave rattlesnake.
“Because of the lack of experience and paucity of field validation of efficacy, the AAHA Task Force doesn’t have a position on the use of this vaccine,” says Shana Hestand, DVM, a veterinary adviser with the American Animal Hospital Assn.
“The canine vaccine task force has discussed getting together to review core vaccines and look at new vaccine research, but a date hasn’t been set. So far there isn’t a vaccine veterinarians are clamoring to add to the core list.”
“There’s no ‘one size fits all’ when it comes to vaccines,” says Alice M. Wolf, DVM, Dipl. ACVIM, Dipl. ABVP, a professor emeritus at Texas A&M University’s College of Veterinary Medicine.
“Recommendations and risk assessment for each individual patient is needed, as all the guidelines suggest.”