Fig. 55.—Leishmania tropica. Smear from granulation tissue of Delhi boil or oriental sore. (MacNeal from Doflein after J. H. Wright.)
As the result of our knowledge that such lesions are caused by leishman bodies, Leishmania tropica, we have been forced to include among such sores clinical types entirely different from the classical oriental sore of Fayrer or Tilbury Fox. Even a keloid type of lesion described by the workers in the Sudan is known now to be caused by leishman bodies. In 1909 leishman bodies were demonstrated in ulcerative processes from Brazil and since that time we have divided cutaneous leishmaniasis into two groups, according to geographical distribution, that of the East, or oriental sore, and that of the West, or American leishmaniasis.
Oriental sore is found chiefly in North Africa, Asia Minor, Syria, Persia and India, and more recently cases have been reported from Italy and Greece and New Caledonia. American leishmaniasis is found chiefly in Central America, Brazil, Peru and the Guianas.
Epidemiology.—There is nothing definite known as to the epidemiology of cutaneous leishmaniasis. The fact that oriental sore almost always occurs on the uncovered parts of the body would suggest transmission by some insect as the house fly or mosquito rather than by the body louse, flea or bedbug, these latter showing no special preference for the uncovered skin.
There has been a great deal written about the origin of the disease in drinking water, various inorganic constituents having been incriminated as factors. In certain places, as Delhi, oriental sore has decreased among the British troops with the discontinuance of the use of water from certain city wells. We know that oriental sore is rather easily inoculable, it having been stated that certain people of Bagdad inoculated their children in order to insure against the possible appearance of the sore on the face with the resulting scar disfiguration. Wenyon found that the virus would not pass through the unabraded skin.
The disease is most prevalent about the end of summer and in the autumn. It is a disease of towns. Some have thought that it might be transmitted through the medium of the laundry. Not only can man be infected by inoculation but this is also possible with monkeys and dogs when a scarified area about nose or over eyebrows is inoculated with virus from a sore.
The lesions are similar to those in man but last a shorter time.
It has been suggested that the dog may be the reservoir of this virus as well as for that of infantile kala-azar. There is some experimental evidence to show that an animal which has recovered from a visceral leishmaniasis is immune to a cutaneous one.
There has been an idea that lizards or snakes might serve as the reservoir of virus for oriental sore and that species of Phlebotomus feeding on these reptiles might take in the flagellates and subsequently transmit them to man. Laveran, however, has been unable to infect lizards with L. tropica. Patton’s observations point to infection from the crushing of infected sandflies when biting the exposed surfaces of the skin.