by Denise A. Mankin, DVM

A recent rash of Parvo cases in Southern California has prompted a hard look at our patterns of vaccinating. Viruses continually build up tolerances to vaccines and what you faithfully used in the past may be less effective today. There has been alot of controversy over the need for vaccinations themselves or the "schedule" that has been recommended by both the maufactureres and veterinarians. The latest look at the vaccination program has given way to a new protocal of still vaccinating puppies, then giving a booster a year later and then to either do "titers" on each of the diseases, which is not financially practical at this time as each one costs about $40, or to just vaccinate every 3 years...not yearly as recommended previously...and take note of the word "recommended" as it was never a "law" like the rabies vaccine is.

All of us are familiar with parvovirus and its significance as an infectious disease in our canine companions. Many of us have heard the stories of puppies, sometimes whole litters, becoming infected and the subsequent struggle to survive.

To the frustrations of dog owners, breeders and veterinarians, the commercial vaccines have failed to immunize pupies at an early age primarily due to an inability of the vaccines to override the immunity puppies received from their dams...called "maternally derived antibodies."

As veterinarians, we have made recommendations of continuing vaccination schedules to 20 or 24 weeks of age in the hope of vaccinating when the maternal antibodies are low enough to allow the vaccine to do its work. During these weeks of repeated vaccinations, the immunity received from the dam is waning and cannot protect the puppies, leaving a "window" of opportunity for the virus. This window usually starts around 7 to 10 weeks of age.

Last year, a new vaccine ws introduced by Intervet. In multiple studies, Intervet's Progard vaccine has been shown to effectively override maternally derived antibodies and prevent the "window" from occuring. One such study conducted at the University of Wisconsin- Madison by Dr. R.D. Schultz, et al, compared six vaccines and their ability to provide protective immunity in puppies with similar levels of maternal antibodies. The puppies in the study were divided into six groups and each group was vaccinated with a different manufacturer's vaccine at six to seven weeks of age and at nine to ten weeks of age.

The puppies were then challenged with parvovirus five weeks after the second dose of vaccine was given. The results of the study show that three of the vaccines FAILED to protect the puppies from infection, clinical disease and death. These vaccines are BIO COR's Adernomune- 7L, Fhone Meieux's RM Conine 6 (DA2P-PL) and SOLVAY"S GALAXY 6MHP-L.

A fourth vaccine, SmithKline Beecham's Vangaurd 5/L provided significant protection against death, with one of the eight vaccinated puppies dying, but did not prevent infection and clinical disease in the remaining puppies.

Two of the six vaccines did provide protection from death and disease: Ft. DODGE's Duramune and INTERVET's PROGARD. Of these, Intervet's vaccine was shown to provide vaccine induced immunity in more of the puppies at an earlier age.

A comparison of SmithKline Beecham's Vanguard 5/L and Ft. Dodge's Duramunie and their ability to prduce protective immunity with Intervet's Progard was demonstrated in antoher study showing the ages at which the vaccines protected the puppies. For this study, three groups of puppies were vaccinated at 6, 9 and 12 weeks of age, each group receiving a different vaccine. The levels of antibodies were checked prior to vaccination and each week up to 15 weeks of age.

The study showed the response rate to the 6 week vaccination to be 54% of those puppies given the Intervet vaccine and 0% with the Ft. Dodge and SmithKline groups. After the 9 week vaccination, 100% of the Intervet group responded adequately while only 18% of the Ft. Dodge group did and 0% of the SmithKline group. After the 12 week vaccination, 82% of the Ft. Dodge group and 50% of the SmithKline group had responded with protective immunity.

Another concern of the veterinary community is the lack of immune response seen in certain dogs to repeated vaccinations long after the Interference from the maternally derived antibodies has waned. This has been reported primarily in large breeds of dogs with Dobermans
and Rottweilers being the most notorious for this problem. European studies have shown the Intervet vaccine's ability to provide protection even to these "chronic non-responders."

The recommended schedule for the Intervet vaccine is 6, 9 and 12 weeks of age with either the 5-way (without leptospirosis) or the 7- way (with lepto) with boosters being given annually. This vaccine schedule and the protection it provides can allow for earlier socialization of litters and
individuals with the concern of parvovirus infection.