Protozoa associated with megaesophagus
Megaesophagus and megacolon occur as complications of chronic Chagas disease.
T. cruzi causes Chagas' disease 
Chaga's disease

1.  Acute form

Occurs in infants and children.
Presents with fever, unilateral face swelling, lymphadenopathy, splenomegaly and chagoma (Localized swelling of the skin).

2.  Chronic form

Occurs in adolescent and adults
Presents with cardiac arrhythmias and neurological manifestations.
Complications → megacolon, megaesophagus, cardiomyopathy.

Romana's sign
When entry of the parasite is through the conjunctiva, an edematous swelling of eyelids of one eye develops.
Trypanosome
Amoeba
Giardia
Gnathostoma