LEISHMANIA DONOVANI 413 



RELATION OF HUMAN TO CANINE KALA AZAR. — The important 

 question arises as to whether the naturally occurring disease of dogs is due 

 to Leishmania donovani or to some other species. The frequent associa- 

 tion of the disease in dogs with human cases in the Mediterranean area, 

 and the morphological identity of the parasites, are facts which make it 

 impossible to regard the organism from dogs as other than L. donovani. 

 Furthermore, the disease produced in dogs by inoculation with the parasite 

 from human sources is identical with the natural canine disease, while 

 the organism from the canine disease is inoculable to animals, with results 

 similar to those which result from inoculation of the human virus. 



The apparent absence of the canine disease in endemic areas in India 

 has been urged as evidence that the Indian disease is distinct from the 

 Mediterranean. The Indian disease is, however, inoculable to dogs, so 

 that the freedom of the Indian dog from infection probably depends on 

 some factor not at present understood. In the present state of know- 

 ledge, and lack of absolute proof of the method of transmission of the 

 disease, it is better to consider all the various systemic diseases in man 

 and dogs as due to one parasite, L. donovani. It is hardly necessary to 

 again remark that morphologically (in smears and cultures) the parasites 

 from the various sources are identical. 



Though it is admitted that the human and canine diseases are caused 

 by the same organism, this does not mean that the dog is to be regarded 

 as a reservoir of the virus. Some have maintained that in Italy the 

 disease necessarily passes from dog to man, but so many cases occur which 

 cannot be associated with any infected dog that it would appear that the 

 infection of the animal is as much an accident as the infection of the human 

 being. Areas occur in which, apparently, only dogs have the disease, 

 while in others only human cases are known. It is claimed, however, by 

 Basile (1916) that in Bordonaro in Sicily, where a high percentage of 

 naturally infected dogs occurred, the extermination of these has led to an 

 almost complete disappearance of the human disease. 



SUSCEPTIBILITY OF ANIMALS.— Nicolle (1908a, 1909o), and Nicolle, 

 Comte, and Manceaux (1908), were the first to show that L. donovani of 

 Mediterranean origin was inoculable to dogs and monkeys. The failure 

 to produce infection in animals by observers in India was advanced as 

 a proof of the existence of two species of leishmania in kala azar. It is 

 now known that the Indian virus, if injected in sufficiently large doses, 

 will give rise to infections as often as the Mediterranean virus. Infection is 

 produced most readily by intraperitoneal inoculation of large doses of the 

 material obtained by crushing an infected spleen, liver, or bone marrow 

 in normal saline solution. In larger animals, inoculation can be made 

 intrahepatically or intravenously. Subcutaneous inoculation does not 



