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ADULT WORM IN SWAIX lUTESTINE 

 CF BEAR, MAN, DOG 



MAN IS INFECTED BT EATING 

 MPROPERXT COOKED INFECTED FISH 



EGGS ARE PASSED IN FECES 

 AND REACH WATER 



NORTHERN PIKE, WALLEYE PIKE, PERCH, TROTTT 

 EATS INFECTED COPEPOD OR SMALL FISH 



.^ 



PLEROCERCOID LARVA 

 DEVELOPS IN MUSCLE 



OR VISCERA OF FISH 



:^\ <■ 



SMALL FISH EATS 

 IHFECTH) COPEPOD 



EGGS HATCH IN WATER AND 

 REIEASE CORACIDIDM 



CORACTrrtIM IS INGESTED BY 

 WATER FIEA (COPEPOD) 



PROCERCOID LARVA DEVELOPS 

 IN COPEPCJ) 



Figure ll.--Life cycle of the broad fish tapeworm, Diphyllobothrium latum. Outer circle (soLd line) includes the worm stages. Inner 



circle (broken line) includes the hosts. 



the larger fish. The damage done by the 

 larvae moving among the reproductive or- 

 gans may render the fish sterile. The life 

 cycle is completed when a larger bass eats 

 an infected smaller fish in which the larvae 

 have had time to become established in the 

 visceral cavity. The larva is then freed 

 in the intestine of the larger bass and 

 grows into the adult tapeworm. 



The large larva of another tapeworm, 

 Ligula intestinalis, is often seen in the body 

 cavity of minnows and suckers (fig. 14). 

 Sometimes it becomes so large in small 



fish that it causes the body wall to burst, 

 releasing the worm. This worm develops 

 into an adult in the intestine of fish-eating 

 birds. 



4. Roundworms (nematodes). The red worm, 

 Eustrongylides (fig. 12 and p. 7) may occur 

 among the viscera. Some smaller larval 

 nematodes may also be present. A very long, 

 thin nematode, Philonema, causes serious 

 damage to the reproductive organs of sal- 

 monid fish. Usually the adult nematodes in 

 the intestine are not noticed because of their 

 small size. None of these is harmful to 

 man. 



