EXPERIMENTAL KALA-AZAR IN THE GREY MONKEY

“OF THE SUDAN (CERCOPITHECUS SABAUS).

By Lizutenant W. E. MARSHALL.

Royal Army Medical Corps.

(From the acai Laboratory of the Wellcome Tropical Research

Laboratories, Khartowm.)

SUCCESSFUL experimental inoculation of animals with kala-azar has become a well-recognized fact in the case of the parasite of infantile kala-azar (Leishmania infantum). Nicolle and his col- leagues, pioneers in this work, have frequently infected monkeys and dogs. So far they have only succeeded in infecting these animals by intraperitoneal inoculation, and subcutaneous injection has only given a local reaction without general infection. They also found that passage of the disease from monkey to monkey attenuated the virus, but the same phenomenon did not occur in dogs. They recognize differences in the infection in these two animals. In the monkey there is marked enlargement of the spleen, and the disease resembles the human type of the disease. In the dog the spleen is only slightly enlarged and the infection is insidious. One of the dogs inoculated with the disease, and which died seventeen months. after inoculation, showed no symptoms for fifteen months. They also found that in a series of dogs there was great variation in the susceptibility of the individual animal. With regard to immunity they have found that in an animal incompletely cured, or only just recently recovered, a second inocu- lation produces a severe and fatal result, whereas in an animal cured for some time immunity is conferred. Immunity is also ‘produced by the virus of Oriental sore. Excision of the spleen in the dog has produced no effect on the course of the disease.

Nicolle and his colleagues have also found that Leishmaniosis occurs as a natural infection in the dog, and this has recently been confirmed by Gabbi and Basile in Italy, Critien in Malta, Alvarez in Lisbon, and the Sergents in Algiers. Basile recognizes two different forms of natural infection in the dog, the acute and

chronic, and he thinks that the former, which affects principally young dogs and lasts from three to five months, plays a more important part in the spread of the disease. He was able to infect three young dogs by keeping them beside cases of infantile kala-azar, and he thinks the flea (Pulex serraticeps and perhaps