Which organism is incorrectly matched with its method of infection?

Trypanosoma brucei rhodesiense is indeed associated with the bite of the tsetse fly, not sand fleas. This organism is one of the causative agents of African sleeping sickness and is transmitted primarily through the bite of an infected tsetse fly, which is typically found in various regions of sub-Saharan Africa.

Understanding the correct transmission routes of various pathogens is crucial in microbiology, as it highlights the mechanisms through which different diseases spread. The other organisms listed have their transmission routes accurately matched with recognized methods of infection. For instance, Giardia lamblia is correctly associated with the ingestion of cyst-contaminated water, hookworms penetrate the skin in their larval stage from contaminated soil, and Toxoplasma gondii is correctly linked to the ingestion of undercooked or raw meats containing cysts. The mismatch in the first option underlines the importance of accurate knowledge regarding pathogen transmission to effectively control and prevent infections.