Dynamics of domestic cat hepatitis B virus infection in juvenile cats.

Domestic cat hepatitis B virus (DCHBV) is a homologue of human hepatitis B virus (HBV). This study investigated the dynamics of DCHBV infection in a cohort of 70 female cats, aged from 6 months to 10 years. The prevalence of DCHBV viremia was 7.1% (5/70), exclusively in juvenile cats, while antibodies for either the core or surface antigens, or both, were detected in 27.1% (19/70) cats. Most seropositive cats (16/19, 84.2%) had IgM for the core protein, a marker of early acute infection. A follow-up of four viremic cats over one year revealed persistent, high-titre viremia in serum (up to 1.39 ×1010 DNA copies/mL) and consistent viral shedding from mucosal surfaces, at the oral, nasal, ocular, rectal, and vaginal level. DCHBV DNA was detected in the ovarian tissue of one cat, but not in the amniotic fluid or the placenta. Most viremic animals (4/5) were initially seronegative, and seroconversion to the protective antigen, the surface protein, was delayed or absent during follow-up. Despite high viral loads, indicative of high virus replication rates in the liver, ALT, a marker of hepatocellular injury, remained within normal ranges. These findings suggest that juvenile, viremic cats can act as silent spreaders through horizontal and potentially sexual and vertical routes, underscoring the importance of screening juvenile animals to control DCHBV transmission.