2.2. Detection of Specific Antibodies to Core Vaccines by VacciCheck and Expression of the Results

Each plasma/serum sample was tested with the in-clinic test Canine VacciCheck^® (produced by Biogal, Kibbutz Galed, Israel, and supplied in Italy by Agrolabo, Scarmagno, Italy) following the manufacturer’s instruction. VacciCheck^® is a rapid semiquantitative dot-ELISA-based kit able to determine specific antibody titers against CPV-2, CDV, and CAdV-1 in serum, plasma, or whole blood of dogs. This test has good specificity and sensitivity for each virus and can be very useful in daily veterinary practice to evaluate the real protection of dogs (and cats) against diseases preventable by core vaccines, as suggested by the international vaccination guidelines and by many other studies [1,33,45,46,47,48,49]. In this test, the antibody concentration is directly proportional to the color intensity of the related spots read by the CombScale and expressed as “S” units on a scale from 1 to 6. The S value of 0 (S0) is equivalent to an antibody titer <1:20 for CPV-2, <1:8 for CDV, and <1:4 for CAdV-1 and is considered negative, while the S value of 3 (S3) is equivalent of the threshold values of 1:80 for CPV-2, 1:32 for CDV, and 1:16 for CAdV-1. Antibody titers equal to or higher than S3 are considered indicative of a significant positive response, corresponding to a good protection against these three core diseases (Table S1). In this study, results were divided into four categories (unprotected, weak positive, medium positive, and high positive) based on the threshold values of each pathogen, and dogs with antibody titers equal to the different threshold values were considered medium positive. Medium to high positive results were expressed as Protective Antibody Titers (PATs) (Table S2), as already done in our recent previous study [50] following the suggestions of the literature [22,51,52,53,54,55,56,57,58].