Leishmaniasis and the Sandfly

Sir,?Much evidence purporting to support the theory that sandflies transmit leishmaniasis has accumulated. This is not surprising for such evidence has been looked for too assiduously and Pasteur's dictum?? Be very careful when you are looking for a thing or you will be sure to find it'?has been frequently ignored in these investigations. Malone and Brooks (1944) gave reasons for believing that P. argentipes could not be vectors of kala-azar in nature. The attempted refutation of their arguments by Shortt (1946) was unconvincing, and Malone (1947) had little difficulty in disposing of Shortt's criticism and showed once again how weak the evidence in support of the sandfly theory is. Nevertheless, the spate of literature, which gushed forth for years in support of that theory, bids fair to drown all arguments to the contrary, no matter how sound those arguments may be. Maxwell-Lefroy (1909) noted that the life of an insect may be immensely prolonged by a diet which retards normal development. It is only with such insects that experimental transmission of kala-azar has been achieved. The diet of raisins, to which P. argentipes were subjected after the first blood meal, prevented development of the ovaries of the flies and is therefore admittedly an unnatural diet, yet, according to Shortt (1945), this diet appears to be essential to the success of such experimental transmission. A study of the literature concerning oriental sore shows that only under equally artificial conditions have Phlebot.omus been rendered capable of transmitting this disease. The literature abounds with claims that it is