In treating an unspecified trematode infection, which drug would most likely be effective?

Praziquantel is the drug of choice for treating infections caused by trematodes, also known as flukes. This class of parasites includes species responsible for diseases such as schistosomiasis and fascioliasis. Praziquantel works by causing severe contraction and paralysis of the parasite's muscles, which makes it easier for the host's immune system to clear the infection. It is effective against a variety of trematodes as well as cestodes (tapeworms).

In contrast, while niclosamide and thiabendazole can be used for certain parasitic infections, they are not primarily effective against trematodes. Niclosamide is mainly used for tapeworm infections, and thiabendazole is more effective against nematodes (roundworms). Tetracycline, an antibiotic, is typically used for bacterial infections and has no significant effect on helminths (worms), including trematodes.

Therefore, considering the specific target of the drug class and its efficacy, praziquantel is the most suitable choice for treating a trematode infection.