Which organism is incorrectly matched with its infection acquisition method?

The correct answer identifies the mismatch in the method of infection acquisition. Trypanosoma brucei rhodesiense is known to cause African sleeping sickness and is primarily transmitted through the bite of the tsetse fly, not sand fleas. The tsetse fly acts as a vector, and its bite introduces the parasite into the bloodstream of the host.

The other organisms listed have their infection acquisition methods accurately described. Giardia lamblia is correctly associated with ingestion of contaminated water where cysts are present, leading to gastrointestinal distress. Hookworm infections arise from skin penetration of larvae found in contaminated soil, a method acknowledged in studies of soil-transmitted helminth infections. Lastly, Toxoplasma gondii is accurately linked to ingestion of undercooked or raw meats containing the parasite or its cysts.

This understanding highlights the importance of identifying specific vectors or methods of transmission in parasitology to differentiate between various pathogens and their associated diseases.