Which of the following diseases is commonly known to affect rabbit health?

Rabbit hemorrhagic disease (RHD) is a highly contagious viral infection that is particularly lethal to rabbits. This disease is caused by the Rabbit Hemorrhagic Disease Virus (RHDV) which primarily affects domestic and wild rabbits. The symptoms of the disease can include sudden death, difficulty breathing, and severe bleeding, although infected rabbits may sometimes show no clinical signs at all before succumbing to the illness.

Understanding RHD is crucial for rabbit owners and caretakers as it emphasizes the importance of vaccination, biosecurity measures, and quick veterinary care if any symptoms are observed. The other diseases listed, while they may affect various animals, are not as specifically associated with rabbits or are less prevalent within rabbit populations compared to RHD. For example, gastric torsion, though serious, is more commonly associated with other species, pneumonia can be caused by various pathogens and is not specific to rabbits, and heartworm is primarily a concern for dogs and cats. This makes rabbit hemorrhagic disease the most relevant and critical concern for rabbit health among the options provided.