The route of migration of Paragonimus siamensis Miyazaki & Wykoff, 1965 in the white rat.

After they were ingested, the metacercariae of Paragonimus siamensis excysted in the stomach, penetrated through the stomach wall and the first 3 centimetres of small intestinal wall into the abdominal cavity, then penetrated into abdominal muscle. The worms stayed in abdominal muscle for about one week, then appeared again in the abdominal cavity before entering the pleural cavity and lungs; they also appeared in thoracic muscle, diaphragm, liver, and muscle of foreleg. The worm's size increased steadily until worm reaches sexual maturity then body size increased slowly. Genital primordia could be recognized at one week, of the reproductive system vitellaria were the last to appear at week 5, and eggs were first seen in the 7-week-old worms.