How did a dog with Pearsonema plica get infected with this parasite?

The correct answer highlights the life cycle of Pearsonema plica, which is a type of nematode that primarily infects dogs. A dog becomes infected by ingesting earthworms that contain the third stage larvae of this parasite. The earthworm serves as an intermediate host, where the larvae develop into an infective stage before they are consumed by the dog.

Once ingested, the larvae can invade the dog's urinary bladder, leading to the various signs of infection. Understanding this transmission route underscores the importance of monitoring environments where dogs may consume earthworms, especially in areas where such parasites are prevalent.

The other methods presented do not accurately reflect the life cycle of Pearsonema plica. Direct contact with infected urine does not facilitate the transmission of this specific parasite. Similarly, while rodents can carry various parasites, they are not the host for Pearsonema plica. Exposure to contaminated soil does not directly relate to this parasite's life cycle since infection relies explicitly on the ingestion of infected intermediate hosts like earthworms.