Differential Diagnosis for Rectal Itching after Exposure to Unknown Worms from Puppy

Single Most Likely Diagnosis

• Enterobiasis (Pinworm Infection): This is the most common intestinal worm infection in the United States, often spread through fecal-oral contamination, which can easily occur when handling puppies that may have the infection. The primary symptom is intense anal itching, especially at night, which matches the patient's complaint.

Other Likely Diagnoses

• Hookworm Infection: Hookworms can be transmitted through contact with contaminated soil or feces from infected animals, including puppies. While less common than pinworms, hookworm infections can cause gastrointestinal symptoms, including itching around the anus.
• Roundworm (Toxocara) Infection: Roundworms are common in puppies and can be transmitted to humans through contact with contaminated feces. Infections can cause a range of symptoms, including gastrointestinal issues and, less commonly, anal itching.
• Tapeworm Infection: Though less likely, tapeworms can be transmitted from animals to humans, potentially causing anal itching among other symptoms, depending on the type of tapeworm.

Do Not Miss Diagnoses

• Echinococcosis (Hydatid Disease): While rare, this parasitic infection can be transmitted from animals to humans and can cause serious health issues, including cyst formation in various organs. Early diagnosis is crucial for effective treatment.
• Strongyloidiasis: This infection, caused by the Strongyloides stercoralis parasite, can lead to a condition known as hyperinfection syndrome in immunocompromised individuals, which can be life-threatening. It's essential to consider this diagnosis, especially in patients with weakened immune systems.

Rare Diagnoses

• Trichuriasis (Whipworm Infection): More commonly found in tropical regions, whipworm infections can cause gastrointestinal symptoms, including diarrhea and, occasionally, rectal itching. The risk is lower in regions with good sanitation.
• Anisakiasis: This is a rare infection caused by the Anisakis parasite, typically acquired through eating undercooked or raw fish. However, it's theoretically possible for the parasite to be transmitted through other means, making it a rare but potential cause of gastrointestinal symptoms, including rectal itching.