T30 THE AMOEBAE LIVING IN MAN 



of the gut. Later (Kartulis, 191 3) he states that he has observed two 

 dogs with amoebic dysentery, and that one of these also developed a 

 liver abscess. Darling (1915),* in Panama, studied a fatal case of 

 amoebic dysentery in "a large hound used for hunting deer." The 

 dog's colon was ulcerated, and many amoebae were present in the 

 ulcers and in the bloody mucous stools. They resembled "£. tetra- 

 geua" — to judge from his description, they were indistinguishable from 

 this species {E. histolytica). Darling considers the possibility of his 

 dog having acquired its infection from man, but sa3's (incorrectly) that 

 " dogs are not susceptible to infection by E. tetragena," and accordingly 

 proposes provisionally to name the Enlamoeha of the dog E. venaticinn.t 

 Ware (1916) has since described an outbreak of amoebic dysentery 

 among foxhounds in India. Altogether nine dogs were affected, of 

 which one died and eight were apparently cured by the hypodermic 

 administration of emetine. The amoebae were active organisms, some 

 of them containing ingested red blood corpuscles. " Mr. Shunker 

 pronounced them to be extremely like entamoeba histolytica " (sic). 

 They were therefore believed to belong to this species. 



Now it is known that dogs can be experimentally infected with 

 Entamoeba histolytica irom man. Losch (1875) injected 4 dogs "/)^r os 

 et anuin" with amoebae from his celebrated original case of dysentery. 

 One of them contracted amoebic dysentery, with typical ulceration of 

 the bowel. Hlava (1887) also is said to have obtained positive results 

 with 2 out of 17 dogs similarly treated, though Kartulis (1891) failed to 

 confirm these experiments. Kruse and Pasquale (1894) record that they 

 infected a dog with dysentery amoebae from man. Harris (1901) 

 succeeded in infecting 3 puppies — though 4 older dogs were negative — 

 by means of rectal injections of bloody mucous stools containing active 

 amoebae from a human case of amoebic dysentery. All the infected 

 animals had dysentery, with typical amoebic lesions of the bowel post 

 mortem, and two of them developed amoebic abscesses of the liver in 

 addition. Dale and I (1917) have also infected 2 puppies by rectal 

 injection of E. histolytica belonging to a strain propagated through a long 

 line of kittens. 



It is thus clear that the dog, like the cat, is susceptible to infection 

 with E. histolytica. In both animals infection results in acute dysentery, 

 and may be followed by liver abscess — as in man. The dog — again like 

 the cat — apparently does not become a carrier of the parasite : at all 

 events, nobody has yet discovered the cysts of E. histolytica in the stools 

 of infected animals, and Darling (1915) expressly notes their absence in 

 his case. The two infected puppies which I have seen both recovered 

 spontaneously, and neither subsequently passed cysts. They were 

 specially examined to determine this point. One of them was finally 

 sacrificed, and showed no signs of ulceration of its intestine. | It 

 seems to me doubtful whether emetine has any curative action on 

 amoebic dysentery in the dog — in spite of the findings of Ware (1916) : 

 for it is possible that his dogs might have recovered without treatment, 

 and it has been found (Dale and Dobell, 1917) that emetine will not cure 

 amoebic dysentery in the cat — which behaves in other ways similarly to 



* First recorded, but not fully described, in Darling (1912). 



t This is presumably a mistake — venatica (or possibly venaticoriim) being intended? 



t Vide Dale and Dobell (1917). 



