422 AKNTJAL REPORT SMITHSONIAN INSTITUTION, 195 5 



Nearly a century ago the relation between these bladder worms in 

 cattle and the adult tapeworm in the intestine of man was first deter- 

 mined by rigid experiments carried out in Germany. Before that 

 time bladder worms of all kinds were regarded as aberrant creatures 

 of unknown relationship and were given distinct names by zoologists. 

 The beef bladder worm was called Cysticercus bovis, a name that no 

 longer has any scientific validity but is still retained more or less in 

 the writings of parasitologists. 



Man acquires the beef tapeworm by eating raw or rare beef infected 

 with bladder worms. Wlien the cysticercus reaches the human in- 

 testine, the head of the future tapeworm, already fully formed, 

 becomes everted and attached to the intestine wall, but the bladder 

 is digested. The tapeworm grows by budding off segments in the 

 unsegmented region just below the head, known as the neck. The 

 newly formed segments, which are immature, mature gradually by de- 

 veloping in each a set of male and female reproductive organs. Fol- 

 lowing fertilization of the eggs by the sperm the internal organs in 

 each segment begin to disintegrate, the proglottid becoming filled with 

 the developed tapeworm eggs each of which harbors a microscopic 

 embryo. Meanwhile new segments are being budded off and this 

 pushes the others down, so that ultimately the egg-filled or gravid 

 segments come to be located in the lowest part of the strobila. It 

 takes about three months for the tapeworm in the human intestine to 

 reach the stage where it produces the gravid proglottids. These be- 

 come detached from the rest of the strobila and voided to the out- 

 side. This continues throughout the life of the tapeworm which may 

 extend for a year or longer. 



Considering the numerous eggs that a single tapeworm carrier may 

 expel to the outside with the gravid proglottids every day, we can 

 readily see that one such carrier, if he happens to live in a rural com- 

 munity where sanitary facilities are inadequate, can become a source 

 of infection for the cattle that happen to graze, or consume dry feed, 

 or drink water, in an area that has become contaminated with the 

 tapeworm eggs. That contamination of this sort actually occurs in 

 many places in the United States has been shown over and over again, 

 especially where the infected individual happened to be the caretaker 

 in a feed lot where cattle were being fattened. 



In Europe the incidence of infestation of cattle, especially calves, 

 with the beef tapeworm appears to be on the increase, according to 

 recent information. In the United States this parasite is not very 

 common in cattle but is present to a sufficient extent to cause more or 

 less serious economic losses to the meat industry. During the years 

 1948-53 approximately 16,500 to 27,000 beef carcasses slaughtered 

 annually under Federal inspection were found to be infected with 



