Absence of Domestic Cat Hepadnavirus DNA in Clinical Samples from a Large Cat Population in the Porto Alegre Metropolitan Area, Southern Brazil

Resumo

Background: Infectious liver diseases are frequent in domestic cats. However, the etiological diagnosis remains challenging due to the nonspecific nature of clinical and laboratory findings. Domestic cat hepadnavirus (DCHV) (Orthohepadnavirus felisdomestici) is a circular DNA virus belonging to the genus Orthohepadnavirus within the family Hepadnaviridae, recently identified in domestic and wild felines. Similar to human hepatitis B virus (HBV), DCHV has been associated with chronic hepatitis and hepatocellular carcinoma in cats. The DCHV was firstly reported in Australia in 2018 and subsequently across multiple countries and continents countries, including Brazil. DCHV has been primarily detected in serum, whole blood, and liver tissue samples. However, viral DNA has also been identified in kidney, intestine, brain, heart, and lymph node tissues, suggesting the possibility of systemic. DCHV is currently classified in genotypes A and B, where genotype A is the most frequent reported worldwide, and genotype B was only reported in Japan and Brazil. The present study aimed to detect DCHV in serum and liver in a large domestic cat population from Porto Alegre and its metropolitan area, contributing to a better understanding of this virus molecular epidemiology.

Materials, Methods & Results: In total, 528 individual clinical samples were analyzed, obtained from domestic cats of different age groups and clinical histories. Of these, 451 were serum samples collected in veterinary diagnostic laboratories, and 77 were liver tissue samples from cats necropsied at the Department of Veterinary Pathology of the Federal University of Rio Grande do Sul (UFRGS). Detection of DCHV was performed using two different PCR assays, both aiming to amplify the polymerase (P) gene, including internal controls in all reactions. The second DCHV PCR was designed to amplify both genotypes A and B. None of the samples analyzed yielded a positive result for DCHV genome. This finding suggests the absence or a low frequency of DCHV in the domestic cat population from Porto Alegre metropolitan area, South Brazil.

Discussion: DCHV has been identified in cats from different regions worldwide, with prevalence varying among domestic cat populations. In the present study, a comprehensive investigation of DCHV occurrence was carried out in a large domestic cats sampling from Porto Alegre and its metropolitan area using two clinical specimens (serum and liver) as well as 2 different PCR assays.  DCHV DNA was not detected in any of the animals evaluated, suggesting the absence or low frequency of this virus in the here evaluated domestic cat population. These findings are consistent with previous studies reporting low DCHV detection rates in some geographic regions, including Brazil. In contrast, higher frequencies have been described in locations such as Hong Kong, Thailand, and Malaysia, indicating that regional, population-related, specific epidemiological factors may influence viral transmission dynamics. Expanded surveillance and further investigations are essential to determine whether the currently low detection frequency reflects truly limited viral circulation or arises from sampling and methodological constraints. Considering the hepatotropic potential of DCHV, the results of this study highlight the importance of continuous monitoring of this agent in feline populations. Expanded investigations across diverse epidemiological contexts will be essential to determine whether the absence of DCHV here observed reflects truly limited viral circulation or arises from methodological constraints.

Keywords: Orthohepadnavirus felisdomestici, Hepadnaviridae, molecular diagnosis, hepatotropic viruses, PCR.