Nomograph Analysis & Titer Testing Help Reduce Disease Susceptibility
Dog breeders who have experienced an outbreak of parvovirus or distemper in their kennel are not likely to take shortcuts to prevent it from happening again.
Despite efforts to adhere to best-practice measures, an immunology expert cautions that even a fully vaccinated dog may not be immune to these viruses that are part of the core vaccine regimen for puppies.
“Even when we do everything right, these viruses can still win if exposure happens at the wrong time,” explains Laurie J. Larson, DVM, director of the Companion Animal Vaccines and Immuno Diagnostics Service (CAVIDS)/Titer Testing Laboratory at the University of Wisconsin.
In puppies, there is a timing conundrum in which the natural immunity neonates receive from their mother via colostrum can have a null effect on puppy vaccines. The antibody-rich colostrum that puppies ingest during the first 12 hours of life can block for up to six months the modified-live vaccines intended to provide immunity from distemper, parvovirus and adenovirus.
Dr. Larson calls this gap in immunity coverage the “window of susceptibility.”
“As maternal antibody is declining, there is a period of time when puppies are no longer protected against disease-causing virus, but they are still blocked for vaccine protection,” she explains. “Puppies are at risk if they are exposed to a virus during the window of susceptibility.”
Because modified-live vaccines must infect to protect immunity, maternally derived antibody (MDA) interference is the main cause for vaccine failure in puppies less than 6 months old. Other causes include poor vaccine handling and storage, incorrect vaccine administration, passive transfer of immunity failure, and genetic issues in which some breeds and some individuals are more likely not to be protected.
Not surprisingly, the greatest risk of infection with the core vaccine viruses is during the first year of life. This accounts for why puppies under 1 year of age are the most frequent victims of the potentially fatal diseases, parvovirus and distemper.
Nomograph analysis of a female dog’s antibody titers within a year before whelping, ideally no later than two weeks before her due date or two weeks after whelping, improves immunization outcomes for her litter by providing a conservative estimate of the endpoint of the antibody block. A nomograph applies the known rate of degradation to quantitatively measured antibody titers to predict when passive immunity disintegrates and puppies are susceptible to viral infection.
“Nomograph testing helps us understand the best timing of vaccination to assure a litter will be effectively immunized,” Dr. Larson says. “Importantly, it allows for a tailored vaccination schedule to assure puppies are effectively immunized. It also allows us to measure puppy immunity at an earlier age post-vaccination than would otherwise be possible.”
A study done at the CAVIDS Laboratory that was published in Clinical Theriogenology in September 2020 compared the immunity protection of puppies under 1 year of age whose dams had nomographs to those whose dams did not have nomographs. The nomograph group of 506 puppies represented 49 breeds, and the group without nomographs comprised 235 puppies of 90 breeds including mixed breeds.
The nomograph group had a protection rate of 95.7 percent against distemper and 90.5 percent against parvovirus, with protection for both viruses established on average at 15.8 weeks of age. In contrast, the group without nomographs had a protection rate of 85.5 percent against distemper and 81.7 percent against parvovirus, and the average age of protection was 21.3 weeks and 22.5 weeks for distemper and parvovirus, respectively.
“This study confirms that nomograph analysis of maternal antibody titers against distemper and parvovirus gives veterinarians and breeders useful information to guide litter vaccination decisions and speed confirmation of immunity,” says Dr. Larson, the lead author. “Importantly, it shows that nomograph testing of breeding dams improves core immunization for puppies less than 1 year of age.”
Because veterinarians usually don’t have nomograph information for a litter indicating when maternal antibody dissipates, multiple doses of core vaccine are given following the standard vaccination schedule that starts at 6 to 8 weeks of age and ends at 16 weeks of age or older. The aim is to catch the right moment when the vaccine virus can infect the puppy and provide immunity.
“We suggest that breeders or owners do follow-up vaccinal titer testing of puppies at 18 weeks of age, or earlier or later as determined by nomograph, to confirm their immunity and protection against the core vaccine agents,” Dr. Larson says. “This allows us to ‘check our work’ to be sure vaccination provided immunity. This is important whether a nomograph was completed for the dam or not.”
The goal of vaccination with modified-live vaccines is to establish sterile immunity. “These vaccines are capable of inducing an antibody level that completely neutralizes these viruses so infection does not occur,” she says. “The virus is rendered ‘sterile’ by neutralizing antibody.”
Dog breeders who nomograph test their breeding females provide added value to puppy buyers, which ultimately enables their veterinarian to make better informed vaccination decisions. “For many owners, knowing for certain that their puppy has responded well to vaccination brings peace of mind,” Dr. Larson says. “Presuming that vaccination is equivalent to immunization may lead to unfortunate, but avoidable, viral infections.”
Best Practices Before Puppy Immunity Is Established
There will always be immunity risks when socializing and transporting puppies, says Dr. Laurie Larson, director of the CAVIDS Laboratory at the University of Wisconsin. She offers these tips to help keep puppies safe.
Assume puppies are susceptible to parvovirus, distemper and adenovirus until they have been proven immune through titer testing
Socialization is critical to development but should be done safely by avoiding unknown dogs and areas frequented by unknown dogs
Be sure other dogs near young puppies have been vaccinated
Vaccinate puppies before they are sold, even if nomograph analysis indicates there is a high likelihood of antibody blockage at that age