For a patient with foul-smelling diarrhea who recently returned from Borneo, what is the most likely causative organism?

The most likely causative organism for a patient presenting with foul-smelling diarrhea who has recently returned from Borneo is Giardia intestinalis. This protozoan parasite is often associated with travel to endemic regions, particularly those with poor sanitation or contaminated water supplies, which can be common in parts of Borneo. Giardia infection can lead to gastrointestinal symptoms, including diarrhea that is typically characterized by a greasy, foul odor due to malabsorption of fats and nutrients.

In travelers or individuals exposed to potentially contaminated water, Giardia is one of the most recognized infectious agents responsible for diarrheal illness. While other organisms can also cause diarrhea, the specific symptom of foul-smelling stools combined with the travel history strongly points to Giardia as the probable cause in this scenario.

Other organisms mentioned might cause diarrhea, but they typically present with different characteristics or are less likely given the specific context of recent travel to Borneo. Understanding the endemic diseases associated with specific regions is crucial for proper diagnosis and management of travel-related illnesses.