A 5-month-old puppy vomits thick white nematodes with three lips at the anterior end. What parasite is identified?

The description of a 5-month-old puppy vomiting thick white nematodes with three lips at the anterior end is indicative of Toxocara canis. This parasite is a roundworm that commonly infects young dogs and is known for having a characteristic appearance, including a smooth, white body and three prominent lips at the front.

Toxocara canis eggs are typically ingested from the environment, which is why puppies and younger animals are more susceptible due to their exploratory behavior and undeveloped immune systems. This parasite can cause various health issues in puppies, including vomiting and malnutrition, because they compete for nutrients in the intestines.

The other options do not match this specific description: Ancylostoma caninum is a hookworm that has a different morphology and typically attached to the intestinal wall, causing anemia rather than vomiting visible worms. Dirofilaria immitis, known as the heartworm, does not present in the gastrointestinal tract and typically affects the heart and lungs, so it would not be observed in vomit. Ascaris suum is a roundworm primarily affecting pigs and would not be an option for a puppy parasite.

Thus, the identification of Toxocara canis aligns perfectly with the described