Changes of Sand Fly Populations and Leishmania infantum Infection Rates in an Irrigated Village Located in Arid Central Tunisia

Abstract

The current spread of zoonotic visceral leishmaniasis (ZVL) throughout arid areas of Central Tunisia is a major public health concern. The main objective of this study is to investigate whether the development of irrigation in arid bio-geographical areas in Central Tunisia have led to the establishment of a stable cycle involving sand flies of the subgenus Larroussius and Leishmania infantum, and subsequently to the emergence of ZVL. Sand flies were collected from the village of Saddaguia, a highly irrigated zone located within an arid bio-geographical area of Central Tunisia by using modified Centers for Diseases Control (CDC) light traps. Morphological keys were used to identify sand flies. Collected sand flies were pooled with up to 30 specimens per pool according to date and tested by nested Polymerase Chain Reaction (PCR) DNA sequencing from positive pools was used to identify Leishmania spp. A total of 4915 sand flies (2422 females and 2493 males) were collected from Saddaguia in September and in October 2014. Morphological identification confirmed sand flies of the subgenus Larroussius to be predominant. PCR analysis followed by DNA sequencing indicated that 15 pools were infected with L. infantum yielding an overall infection rate of 0.6%. The majority of the infected pools were of sand fly species belonging to subgenus Larroussius. Intense irrigation applied to the arid bio-geographical areas in Central Tunisia is at the origin of the development of an environment capable of sustaining important populations of sand flies of the subgenus Larroussius. This has led to the establishment of stable transmission cycles of L. infantum and subsequently to the emergence of ZVL.

Molecular detection and identification of Leishmania DNA and blood meal analysis in Phlebotomus (Larroussius) species

“…Recently, in a study conducted in the center of Tunisia, it was demonstrated that Ph. perniciosus was predominant in arid bioclimatic zones and irrigated areas [42,51].…”

“…Phlebotomus papatasi, the vector of L. major in Tunisia, is known to be abundant in arid and Saharan regions. Aridity seems to be a limiting factor for its distribution and it was described especially in non-irrigated areas [18,[42][43][44][45]. However, the high number of Ph.…”

“…papatasi, and Sergentomyia (Ser.) minuta infected with L. infantum DNA using conventional PCR [17][18][19]. At present, many studies have been performed for Leishmania detection and quantification by using real time PCR (qPCR) assay.…”

Leishmaniasis in Tunisia: History and New Insights into the Epidemiology of a Neglected Disease

“…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.…”

“…However, the vector hosts of the two other zymodemes MON-24 and MON-80 are still unknown (Figure 5). Recently, L. infantum DNA was detected in the sand flies mid gut of the Larroussius (P. langeroni, P. longicuspis, P. perfiliewi) and Phlebotomus (P. papatasi) subgenera as well as the Sergentomyia genus (S. minuta) [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 zymodemes.…”