A scoring method to standardize lesion monitoring following intra-dermal infection of Leishmania parasites in the murine ear

For several decades the murine experimental model of Leishmania infection has been invaluable in deciphering events occurring during the innate immune response and those involved in the differentiation of CD4+ T helper cells. Initially, most studies inoculated mice subcutaneously into the hind footpad with a high dose of stationary phase parasites (1 to 3 × 106). In recent years, new protocols have been adopted to better mimic the natural transmission of the parasite caused by the bite of infected sand flies. To this end, low numbers of parasites (10–1000 metacyclic promastigotes) are injected intradermally in the ear. However, given the different anatomy of the ear compared to the footpad, monitoring lesion development in the ear is technically more difficult and until now there has been no consensus on how to monitor lesion progression in this anatomic region. The various methods, which are currently used, are listed below: