infected dogs. Strange to say, although the dog has been found to be easily infected in the Mediterranean area, in India it seems to be partially immune and only contracts the disease after massive intraperitoneal injections of leishmania-infected organs.
The exact way in which the flea transmits the virus, if it be the transmitting agent, is not known whether the parasite undergoes important biological changes in the insect, or whether the latter functions merely in a passive or mechanical way.
Patton has put forward a claim for the bug as the transmitter of Indian kala-azar. It may be so, but conclusive proof has not been adduced. Should the conjecture be confirmed it would afford an explanation of the tendency of the disease to cling to particular localities and houses, and it would supply a valuable guide to prophylaxis.*[1]
Under natural conditions kala-azar, like other diseases caused by similar protozoal organisms, is probably transmitted by a living agent. There are certain facts, however, which tend to suggest that the carrier need not necessarily be a blood-sucking animal. In the first place, the parasite in man is not, as a rule, in great abundance in the peripheral circulation. Secondly, the parasite is often present in ulcerations of the skin and of the intestinal mucosa,suggesting elimination by these organs. Mackie found leishmania-like bodies in the mucus of dysenteric cases of kala-azar. Thirdly, we know that although some species of Herpetomonas are fostered by blood-sucking flies, such as Tabanus and Hœmatopota, others are found in non-biting forms, such as Musca, Sarcophaga, Pollenia, and Fucellia, which could become infected only by settling on ulcerations or on fæcal matter. It is conceivable that such insects might transmit the infection of kala- azar by depositing the parasites on wounds and abraded surfaces. It has been suggested that there
- ↑ * The discovery of a flagellated organism or of developing leishmania in the gut of an insect must not be regarded as adequate proof that the insect is the normal, or even a transmitter of the organism concerned.
