In pasture-based systems, dogs that ingest uncooked prey animals may acquire which type of parasite?

In pasture-based systems, dogs that consume uncooked prey animals can acquire Sarcocystis spp. This parasite belongs to the group of protozoa that can be transmitted through intermediate hosts, such as herbivores. When dogs eat the muscle tissue of these infected prey animals, they can ingest the cysts, which can develop into adult parasites within the dog. Sarcocystis infections are associated with mild gastrointestinal symptoms but can lead to more severe complications in some cases.

In contrast, the other options do not typically relate to the ingestion of uncooked prey in the same manner. Aelurostrongylus abstrusus is a lungworm primarily associated with cats, and Toxocara canis is more commonly transmitted through ingestion of eggs from contaminated environments rather than directly from predation on prey. Giardia spp. is associated with contaminated water sources rather than primary transmission through prey animals. Thus, Sarcocystis spp. is the most relevant parasite in this context.