What is one common feature of anthelmintic agents?

Anthelmintic agents are primarily designed to target and disrupt the metabolism or function of parasitic worms (helminths) in order to eliminate them from the host. These agents interfere with essential biological processes in the parasites, such as energy production, nutrient uptake, or neuromuscular functions, leading to the immobilization or death of the worms. This mechanism is crucial for effectively treating infections caused by helminths, as it directly impacts the viability and reproduction of the parasites.

The other options do not correctly describe a common feature of anthelmintic agents. For instance, while some agents may impact various life stages of a parasite, not all specifically target the larval stages. Additionally, anthelmintics do not have any action against viral infections or function solely through modulation of the host’s immune system; their primary action is to directly interfere with the parasite's internal biological processes.