Background: Re-vaccination against canine adenovirus (CAV) is performed in ≤3-year-intervals but its necessity is unknown. The study determined anti-CAV antibodies within 28 days of re-vaccination and factors associated with the absence of antibodies and vaccination response. Methods: Ninety-seven healthy adult dogs (last vaccination ≥12 months) were re-vaccinated with a modified live CAV-2 vaccine. Anti-CAV antibodies were measured before vaccination (day 0), and after re-vaccination (day 7, 28) by virus neutralization. A ≥4-fold titer increase was defined as vaccination response. Fisher’s exact test and multivariate regression analysis were performed to determine factors associated with the absence of antibodies and vaccination response. Results: Totally, 87% of dogs (90/97; 95% CI: 85.61–96.70) had anti-CAV antibodies (≥10) before re-vaccination. Vaccination response was observed in 6% of dogs (6/97; 95% CI: 2.60–13.11). Time since last vaccination (>3–5 years, OR = 9.375, p = 0.020; >5 years, OR = 25.000, p = 0.006) was associated with a lack of antibodies. Dogs from urban areas were more likely to respond to vaccination (p = 0.037). Conclusion: Many dogs had anti-CAV pre-vaccination antibodies, even those with an incomplete vaccination series. Most dogs did not respond to re-vaccination. Based on this study, dogs should be re-vaccinated every 3 years or antibodies should be determined.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This dissertation consists of an investigation on infectious canine hepatitis (IHC) and resulted in two scientific papers which are placed in the final part of this dissertation. The necropsy reports of 5,361 dogs necropsied over a 43-year period (1964-2006) were reviewed in search for cases of infectious canine hepatitis (ICH). Sixty two (1.2%) cases of the disease were found. Epidemiological, clinical and anatomopathogical data of these 62 cases are presented in the first paper. The second paper presents an immunoistochemistry (IHC) assay performed in the tissues of 27 dogs from the 62 cases surveyed in the first paper. Evaluated tissues by IHC included liver, kidney, spleen, lymph nodes, tonsils, lungs, small intestine, brain, and spinal cord. For each organ increasing degrees (from mild to marked) of intensity of immune staining were ascribed. The antigen of canine adenovirus type 1 was detected in most of evaluated organs, mainly in endothelial cells. / A presente dissertação consta de uma investigação sobre hepatite infecciosa canina e resultou na produção de dois trabalhos científicos que estão colocados ao final da dissertação. Os protocolos de necropsias realizadas em 5.361 cães durante um período de 43 anos (1964-2006) foram revisados em busca de casos de hepatite infecciosa canina (HIC) e sessenta e dois (1,2%) casos foram encontrados. Dados epidemiológicos, clínicos e anatomopatológicos desses 62 casos são apresentados e discutidos no primeiro trabalho. O segundo trabalho apresenta os resultados de um estudo imunoistoquímico (IHQ) realizado nos tecidos de 27 dos 62 cães pesquisados no primeiro trabalho. Os tecidos examinados incluíram fígado, rim, baço, linfonodos, tonsilas, pulmão, intestino delgado, encéfalo e medula óssea. Para cada órgão foram atribuídos graus crescentes (de leve a acentuada) de intensidade de imunomarcação. O antígeno de adenovírus canino tipo 1 foi marcado na maioria dos órgãos examinados, principalmente em células endoteliais.