Which organism is an endoparasite seen in rodents?

• A. Aspiculuris tetraptera
• B. Giardia lamblia
• C. Dirofilaria immitis
• D. Taenia pisiformis

Answer: (A)

Endoparasites are organisms that live inside the body, often in the gastrointestinal tract. In rodents, a classic internal parasite is Aspiculuris tetraptera, a nematode (pinworm) that inhabits the lumen of the cecum and colon of mice and rats. Infection occurs when a rodent ingests infective eggs shed in feces; these eggs survive well in the environment and spread readily in colonies. Infections can be asymptomatic but may cause irritation, weight loss, and can confound experimental results, so they’re a common target for routine screening. Detection is typically by analyzing fecal samples for eggs or using a perianal swab.

Giardia lamblia is a protozoan that also lives in the GI tract, but it is not the rodent-specific endoparasite most classically described in standard rodent parasite lists. Dirofilaria immitis is a heartworm parasite of dogs and other carnivores with a life cycle not involving rodents as typical hosts. Taenia pisiformis is a tapeworm whose cycle centers on dogs as definitive hosts and rabbits as intermediate hosts; rodents are not the usual intermediate host for this species.