CHILOMASTIX MESNILI 



old; Miss Nutt records infections in children 3 weeks, 

 3 months, 9 months, 1 1 months and 12 months old. Dobell 

 suggests that the higher incidence among children may be 

 due to the greater ease of finding the organisms in their 

 stools. It seems more probable that some type of host 

 resistance develops with age. The cysts may be unable to 

 excyst or the escaping trophozoites may find the intes- 

 tinal contents of adults less favorable than those of chil- 

 dren for their growth and reproduction. 



5. OTHER INTESTINAL FLAGELLATES 

 (l). CHILOMASTIX MESNILI 



Not so much is known regarding the host-parasite 

 relations of Chilomastix mesnili, Embadomonas intes- 

 tinalis and Tricercomonas intestinalis as of the species 

 already described. Chilomastix mesnili (Fig. loa, lob) 

 is a common inhabitant of man and has been reported 

 from many parts of the world. The average incidence of 

 infection as indicated by the results of various surveys is 

 about 10 per cent. Transmission takes place no doubt 

 usually in the cyst stage and infections result from the 

 ingestion of contaminated food or drink. That flies may 

 play a role in transmission was shown by Root (1921) 

 who found that trophozoites might pass through the 

 digestive tract of Musca domestica within 7 minutes ap- 

 parently unharmed, and that cysts could live in the intes- 

 tine of this species for 80 hours. Washed cysts, according 

 to Boeck (1921b) may live for six months or more in 

 water at room temperature and can withstand tempera- 

 tures up to 72° C. 



169 



'-fa 



L 1 D R A R Y I 3; 



