*2.1.2.3. Causative species*

The precise identification of the causative agent of SCL using the golden standard method has been started in the beginning of the 1990s of the last century. Thus, three zymodemes of the *L. infantum* taxon were identified as responsible of SCL. *L. infantum* MON-24 was the first identified dermotropic zymodeme [40]. Currently, it is the most isolated one from SCL lesion in Tunisia [24, 39, 41]. Its represents between 90.56 and 92.85% of all SCL cases in Tunisia [24, 41]. The second identified dermotropic zymodeme is MON-1. The first case of SCL caused by *L. infantum* MON-1 was reported by Aoun et al. in 2000 [38]. This dermoviscerotropic zymodeme is less frequent than *L. infantum* MON-24. Indeed, it represents between 7.14 and 8.5% of the SCL cases in Tunisia [24, 41]. The last one is the zymodeme MON-80. Only a single sporadic case of CL due to this zymodeme was reported in 2012 in Zaghouan, north Tunisia [24] (**Figure 3**).

#### *2.1.2.4. Transmission cycle*

The transmission cycle of *L. infantum* is not completely elucidated. While *L. infantum* MON-1 was isolated from the domestic dog *Canis familiaris* suggesting that this animal is the reservoir of this zymodeme, the reservoir hosts of the other zymodemes MON-24 and MON-80 are still unknown (**Figure 2**). In 2009, Benikhlef et al. [42] reported three cases of canine VL in Tunisia due to *L. infantum* MON-80; nevertheless, its role as reservoir for this zymodeme is still discussed. The zymodeme MON-24 was also isolated from dogs in Morocco and Algeria but never in Tunisia [43, 44].

*Phlebotomus perniciosus* was described as the vector of *L. infantum* MON-1. However, the vector species of MON-24 and MON-80 are still unidentified. In Tunisia, *P. perfiliewi* is abundant in *L. infantum* CL foci and was thereby suspected to be the vector of *L. infantum* [35]. Nevertheless, no *L. infantum* strain has been isolated from this phlebotomine sand fly species yet. Also, *L. infantum* DNA was detected from a *P. langeroni, P. longicuspis, P. perfiliewi, P. papatasi*, and *Sergentomyia minuta* using molecular tools [45, 46]. However, neither parasite isolation from these sand flies species nor *L. infantum* isoenzymatic identification were carried out in Tunisia yet to confirm their role as vector of *L. infantum* taxon.
