ASCP Parasitology Practice Exam 2025 - Free Parasitology Practice Questions and Study Guide

Clonorchis sinensis is classified as a liver fluke, specifically a type of parasitic flatworm known as a trematode. This organism primarily affects the liver and bile ducts of its hosts, particularly humans, and is transmitted through the consumption of undercooked freshwater fish that contain the larval stage of the fluke.

Liver flukes are characterized by their flat, leaf-like shape and their life cycle involves several stages, including passes through snail hosts. Clonorchis sinensis can cause clonorchiasis, a condition associated with various gastrointestinal symptoms and potentially serious complications such as cholangitis or cholangiocarcinoma due to long-term infection.

In contrast, the other choices pertain to different groups of parasitic organisms. Ascaris lumbricoides is a roundworm that causes ascariasis; Trichuris trichiura, also a roundworm, is responsible for whipworm infections; and Enterobius vermicularis is the pinworm that primarily infects the human intestinal tract. Each of these species has different anatomical characteristics, life cycles, and transmission routes, distinguishing them from liver flukes like Clonorchis sinensis.