OTHER FLAGELLATES 



119 



studies both of its epidemiology and path- 

 ogenicity. However, Karapetyan (1960) 

 cultivated G. lamblia in chicken fibroblast 

 tissue cultures. 



GIARDIA LAMBLIA 

 STILES, 1915 



Synonyms : CercoiHOiias iiitestinalis, 

 Lamblia intestinalis, Giardia intestinalis , 

 Megasto))Hi entericiiiii , Giardia enterica. 

 European writers still call this species 

 Giardia intestinalis, but there was so 

 much confusion about the availability of 

 the specific names intestinalis and enter- 

 ica that Stiles (1915) established the pres- 

 ent name. 



Disease : Giardiosis. 



Hosts : Man, Old and New World 

 monkeys, pig. Hegner (1930) and Arma- 

 ghan (1937) infected laboratory rats and 

 Bonestell (1935) infected woodrats (Neo- 

 tonia fiiscipes) with G. huiiblia from man. 

 Haiba (1956) infected wild and laboratory 

 Rattus norvegicus , but failed to infect 

 wild R. rattus and laboratory mice with 

 G. lamblia from man. 



duodenalis type. The cysts are ovoid, 8 

 to 12j;i long and 7 to lO/i wide, and con- 

 tain 4 nuclei. 



Pathogenesis : There was considerable 

 controversy for many years whether Giardia 

 is pathogenic in man, but it is now gener- 

 ally agreed that it may be in some individ- 

 uals. Most infections are symptomless, 

 but in a fairly small number there is a 

 chronic diarrhea. The feces contain a 

 large amount of mucus and fat but no blood. 

 The diarrhea is accompanied by dull epi- 

 gastric pain and flatulence. Affected per- 

 sons have a poor appetite and lose weight. 

 In some cases the gall bladder may be in- 

 vaded and cholecystitis may be present, 

 but there is no proof that the protozoa 

 caused this condition. Pizzi (1957) reviewed 

 some of the literature on the pathogenicity 

 of G. lamblia and concluded that in heavy 

 infections it may also interfere with fat 

 absorption and produce a deficiency in fat- 

 soluble vitamins. It is more often patho- 

 genic in children than adults. 



The pathogenicity of G. 

 sv/ine is unknown. 



lamblia for 



Location : Duodenum, jejunum, upper 

 small intestine. 



Geographic Distribution : Worldwide. 



Prevalence : G. lamblia is common 

 in man. In 86 surveys of 134,966 people 

 thruout the world summarized by Belding 

 (1952), its prevalence ranged from 2.4 to 

 67. 5% with a mean of 10. 4%. It was found 

 in 7. 4% of 35, 299 persons in 24 surveys 

 in the United States, and in 6. 9% of 65, 295 

 persons in 20 surveys in the rest of the 

 world. It is about 3 times as common in 

 children as in adults. 



G. lamblia was reported from a pig 

 in Tennessee by Frye and Meleney (1932). 

 Its prevalence in swine is unknown. 



Morphology : The trophozoites are 9 

 to 21 ju long, 5 to 15 p. wide and 2 to 4/^ 

 thick; they are usually 12 to 15ju long. 

 The median bodies are curved bars of the 



Fig. 18. A. Giardia trophozoite. X 2800. 

 (After Filice, 1952). B. Giardia 

 bovis cyst. X 2900. (From 

 Becker and Frye, 1929) 



