Rabbit cardiomyopathy associated with a virus antigenically related to human coronavirus strain 229E

No prior work had resolved the etiology of a sudden, fatal cardiac condition observed in rabbit populations. This uncertainty drove researchers to investigate potential infectious agents linked to the observed myocardial damage. It was already known that various pathogens can induce inflammatory responses within cardiac tissues. However, the specific viral triggers for this particular rabbit pathology remained unidentified. Prior research has shown that coronaviruses frequently cause respiratory or enteric issues in diverse animal species. That gap motivated a detailed examination of the viral particles present in affected rabbit serum. Scientists aimed to determine if these particles shared structural or antigenic properties with known human viruses. This study provides the first characterization of the agent responsible for this acute, lethal rabbit disease.

The aim of this study is to characterize a newly identified, fatal disease affecting rabbit populations. Researchers sought to determine the etiology of the observed acute febrile illness and cardiac damage. They investigated whether a viral agent was responsible for the multifocal myocardial degeneration noted in necropsies. The team explored the relationship between this rabbit pathogen and known human coronavirus strains. They examined the transmissibility of the agent through various experimental routes. The study also assessed the susceptibility of other common laboratory animals to the virus. Furthermore, the researchers evaluated the ability of the virus to propagate in standard tissue culture systems. This work was motivated by the need to classify the agent and understand its potential for cross-species transmission.

The investigators performed a series of transmission experiments using tissue filtrates and infectious sera. They applied 0.1 micron filters to isolate the viral particles from host samples. Researchers assessed the morphology of these particles using standard microscopic techniques. The team employed immunofluorescent staining on frozen heart tissue sections to visualize viral antigens. They evaluated the host range by attempting to infect mice, hamsters, and guinea pigs. The study attempted to adapt the virus for growth within various tissue culture environments. Scientists monitored the clinical progression of the disease following inoculation until the 11th day. Finally, they analyzed convalescent sera from surviving animals to detect specific antibody responses against known viral strains.

The strongest finding is the identification of a virus with coronavirus-like morphology in the serum of infected rabbits. This agent causes multifocal myocardial degeneration and necrosis in affected animals. The virus cross-reacts antigenically with human coronavirus strains 229E and OC43. Immunofluorescent staining detects antigens in the heart tissue of sick rabbits but not in healthy ones. Surviving animals demonstrate seroconversion, producing antibodies that react with the 229E virus. The pathogen is transmissible through tissue filtrates and infectious sera diluted to 10(-6). No susceptibility to this agent was observed in mice, hamsters, or guinea pigs. Attempts to adapt the virus for growth in tissue culture were unsuccessful.

The authors propose the name rabbit infectious cardiomyopathy for this newly identified, fatal condition. This disease manifests through an acute febrile phase followed by significant heart muscle necrosis. The researchers confirm that a virus with coronavirus-like morphology is the causative agent. Evidence suggests this pathogen shares antigenic properties with human coronavirus strains 229E and OC43. Survivors of the infection develop specific antibodies that react with the 229E strain. The study highlights that this virus does not infect mice, hamsters, or guinea pigs. The origin of this agent remains unclear, leaving open the possibility of a cross-species transmission event. These findings establish a baseline for future investigations into the pathogenesis of this specific viral heart disease.