Serum antibody titers to canine parvovirus type 2 (CPV-2), canine distemper virus (CDV), and canine adenovirus type 1 (CAV-1) were investigated in 1031 healthy adult domestic dogs (2 to 18 years of age). ) who were administered an annual exam. inoculation in the previous 11 to 13 months. The number of dogs that retained significant antibody titers against CPV-2, CDV, and CAV-1 was 888 (86%), 744 (72%), and 732 (71%), respectively. There were no differences between males and females in the antibody titers against the 3 viruses. Antibody titer to CPV-2 was significantly higher in young dogs than in older dogs, CDV antibody was significantly higher in older dogs than in younger dogs, and CAV titer was not associated with age.
Materials and methods
- Subject Dogs
A total of 1031 adult domestic dogs 2 to 18 years of age were examined. All dogs had received 2 or 3 vaccinations in their first year and received annual inoculations thereafter. Comparisons were made according to sex and age. The dogs were divided into 4 groups by sex (423 sexually intact males, 108 neutered males, 264 sexually intact females, and 236 neutered females) and into 16 age groups. The numbers of dogs in each of the ages from 2 to 18 years were 450, 120, 108, 76, 57, 48, 44, 46, 24, 18, 19, 8, 6, 3, 3, 0, 1, respectively. for each successive year.
- Serological tests
Serum samples were collected from dogs vaccinated in the previous 11 to 13 months and sent frozen to a commercial veterinary diagnostic laboratory (Marupi Lifetech, Osaka, Japan) for determination of serum antibody titers. Antibody titers for CPV-2 were obtained by a haemagglutination inhibition (HI) test, antibody titers against CDV by an immunoperoxidase (IP) test, and antibody titers against CAV-1 by a neutralization test. (NT).
- Antibody titer classification
Antibody titers were classified using commercial veterinary diagnostic laboratory (Marupi Lifetech) criteria, based on previous reports (14–20) indicating protective titer. The antibody titer that protects against disease as indicated by previous reports was designated as the cut-off titer. Titles below the limit are designated as low. Titers 4 times higher than the limit were designated high, based on the previous observation that titers decreased to 1/4 in 1 year.
Many initial reports showed 1:80 as a protective titer, but an older type of antigen may have been used. For the present test, 1:40 was designated cut-off because CPV-2b, a new antigen, was used and a level of 1:40 was shown to be protective in a challenge infection study (Rescamune P-ML technical information; Nippon Zennyaku Kougyou). “High” was ≥1:160 and “low” was ≤1:20.
Other reports have shown that the borderline protection titer against CDV was 1:32, as determined by an NT. However, in the present study, an IP test was used for titration, and 1:160 was found to be borderline based on regression analysis between the NT and IP tests. “High” was ≥ 1:640 and “low” was set at ≤ 1:80. As an antibody titer of 1:32 to 1:42 against CAV-1 was the most reliable previously reported value, the borderline protective titer was assigned to 1:40. “High” was ≥ 1:160 and “low” was set at ≤ 1:20.
- Statistical analysis
To determine whether there were gender differences in antibody titer, Mann-Whitney U tests were performed to compare the reciprocal of the dilution of antibody titers between groups. To investigate differences in antibody titers against CPV-2, CDV, and CAV-1 by age group, comparisons between the reciprocal of the dilution in each age group were performed using a logistic method in the JMP software system (JMP ® Statistical Discovery Software; Cary, North Carolina, USA). In all tests, P < 0.05 was considered to indicate a significant difference.
“High” status within the population Antibody retention status in 1031 dogs is shown in Table 1. “High” status against CPV-2 was observed in 888 dogs (86%), against CDV in 744 dogs (72%). %) and against CAV-1 in 732 dogs (71%).