Successful Transmission of Cutaneous Leishmaniasis by the Bites of Stomoxys calcitrans

Abstract

The experiments carried out by Sergent, Sergent, Parrot, et al., 1 Adler and Theodor, 2 , 3 , 4 incriminated the sandfly as the probable vector of cutaneous leishmaniasis. This hypothesis has been supported by the fact that it has been possible to infect sandflies under experimental conditions, and to produce the cutaneous lesions by the injection of crushed infected sandflies. Furthermore, the sandfly theory of transmission of cutaneous leishmaniasis has been attractive because of the readiness with which leishmanias exflagellate and multiply in the alimentary tract of these insects, and the epidemiological evidence apparent in the close correspondence of the distribution of certain species of sandflies with the distribution of cutaneous leishmaniasis. However, we have not been entirely satisfied with the sandfly theory of transmission because of the following facts:

1. Critical experiments designed to demonstrate the transmission by the bite of the sandfly have regularly failed. Although it is conceivable that infection may be accomplished by crushing an infected sandfly at the site of the bite, the likelihood of this occurring would appear to be rather remote to any person who has attempted to destroy a sandfly while in the act of biting.

2. There is no evidence that sandflies are attracted to lesions as preferential sites for feeding, and, as L. tropica is confined to the lesions, the probability of a sandfly acquiring the infection would be remote even though there was ample opportunity to feed on persons exhibiting suitable lesions.

3. Should a sandfly actually feed from the, oriental sore under natural conditions, it should be remembered that the parasites are limited to the endothlelial cells, and the likelihood of infected tissue cells being ingested with the blood must be rather small.