PAI.WSITES AND I'AKASITIC DISEASES OE SWINE 
7 
Lift history. — Unlike most worm parasites, the eggs of this worm 
pass out with the urine. The eggs hatch on the ground and infective 
larvae develop in a few days. These larvae are swallowed with the 
food or they penetrate the skin. After several months of develop- 
ment in the liver the young worms migrate through this organ into 
the abdominal cavity. Some go astray and enter the lungs and other 
Ei«.ri;i: L'. — Worm parasites of Puerto Mean hogs: A., Kidney worms; H, lungworms ; C, 
pork measle worms: />. American swine hookworms; B. common hookworms; F, whip- 
worms: (1. strongyline stomach worms: //. red stomach worms: /. nodular worms; ./, 
thorn-headed worms ; A', ascarid. A to 1 approximately natural size, J and K slightly 
reduced. 
tissues. This parasite shows a remarkable adaptation or specializa- 
tion. Numbers of the young worms in the abdominal cavity appar- 
ently without following any natural body channel, get to the slender 
ureters by burrowing through the surrounding fat and puncturing 
these tubes, thus providing an artificial opening or avenue of elimina- 
tion for the ova. 
/ mportance. — The kidney worm is one of the most serious parasites 
of swine in Puerto Rico. Besides the unthriftiness and stunting of 
growth, there is considerable damage to carcasses from which wormy 
