**5. Disease control**

*3.3.4. Transmission of CL*

84 The Epidemiology and Ecology of Leishmaniasis

in close proximity to active colonies of rodents [28].

located near *L. major* reservoir host biotopes [5].

people play also a role in attracting sandflies.

interact, persist and establish in new ecosystems.

south averages less than 200 mm [7].

ZCL is transmitted to humans by sandflies vectors when they are in close contact with infected reservoir hosts, as a result of activities including agricultural practices, housing and residence

Meriones species, even though a minor reservoir of Leishmania in Tunisia, is thought to contribute to the dispersal of Leishmania because of their large range compared to Psammomys which is more restricted. In addition, Meriones species of rodents tend to live in

Human activities that interfere with the ecologic niche of reservoirs such as deforestation and destruction of natural habitats can change the epidemiology of ZCL. Emergence of ZCL epidemics can take place when humans invade the territory of Psammomys [29] or the incidence can be reduced when burrows of rodents and chenopods are properly destroyed. Epidemics of CL in Tunisia may be associated with migration and the introduction of nonim‐ mune people into lands with existing transmission [30]. Prediction of such outbreaks depends on the availability of ecological information and one valuation of development areas before implementation of projects or population movements. Noticeable increase in the number of CL cases has been observed when susceptible population migrate to formerly unsettled areas

Poverty and CL transmission risk are tied closely together. Poor hygiene and inadequate sani‐ tation facilities (e.g., lack of wastewater treatment and disposal, open sewerage) may favor the proliferation of sandflies which increase human‐vector exposure. Crowding and proximity of

CL is a climate‐sensitive disease, occupying a characteristic "climate space" that is strongly affected by changes in rainfall, atmospheric temperature and humidity [31]. Climate conditions affect the leishmaniasis complex components (parasite‐reservoir‐vector) and their ability to

In Tunisia, there are two climate types. It is typically Mediterranean in the north where the terrain is mountainous, with hot, dry summers and mild winters, whereas the southern part close to the Sahara experiences a hot desert climate with high humidity. Annual average precipitation in the northern region reaches a high of 1500 mm, while rainfall in the extreme

A previous Tunisian study [31] indicated that the occurrence of significant environmental changes driven by agricultural development projects created suitable conditions that did not previously exist for the emergence of ZCL. Toumi and colleagues confirmed in their study [9] that the risk of disease in Sidi Bouzid is mainly influenced by the humidity related to the months of July to September during the same season and mean rainfall lagged by 12–14 months.

Another Tunisian study [7] showed that the most important climate risk factors explaining the variability of CL incidence over time are precipitation and temperature. The decadal increase in the number of ZCL occurrence in the region suggests that changes in climate increased minimum temperatures sufficiently and created conditions suitable for endemicity that did

close proximity to human settlements, and their main food source is gramineae.

Since the onset of ZCL epidemic in 1992 in the town of Sidi Bouzid, many control interven‐ tions were planned and evaluated by Pasteur Institute of Tunis with the cooperation of local health authorities. The control program was based essentially on manual pulling of chenopods around the town where *P. Obesus* was very dense, deep plowings of colonies of the rodent and their poisoning. These interventions led to a significant reduction in the incidence among humans with a prevention fraction of disease exceeding 90%.

Consequently, in 2000, the Tunisian National Control of Parasitic Diseases Program (PDP) introduced ecological surveillance of areas at risk for ZCL before the occurrence of the epi‐ demics based on the surveillance of the emergence of rodent colonies, such as *P. obesus.* Despite this significant effort, and the analysis of transmission dynamics of the disease in other regions, control strategies remain unsatisfactory, as indicated by the number of annual cases [5]. In fact, such actions are demanding and expensive, and consequently are often partially and intermittently performed. As such, it was therefore not possible to reduce the temporal and spatial spread of the disease [4].

Thereby, the national strategy for Leishmaniasis prevention and control has mainly focused on passive case detection and free diagnosis and treatment rather than on the reservoir and sandfly control.

Since ZCL is polymorph in terms of disease severity (number and size of lesions, duration for healing), we can hypothesize that some immune factors, depending on their intensity, will not protect against the development of the disease but rather against the severe forms. Their identification could help the development of a vaccine that protect against a severe disease, which could constitute an interesting option. The rationale for vaccine development is provided by the evidence that most individuals that had leishmaniasis or symptomless infection are resistant to subsequent clinical infections. The only proven CL vaccine (prac‐ ticed for centuries) is the deliberate inoculation of virulent Leishmania parasites, so‐called leishmanization [37].

In order to decrease the CL incidence in Tunisia during future years, some points are recom‐ mended and should be considered such as health education and awareness about disease, traffic control of immigrants and travelers to endemic regions, personal protection from sand‐ fly biting by curtains and bed nets, eliminating and destroying habitats of the reservoir rodent and spraying insecticides in habitats of sandflies [38]. Therefore, the high awareness among the community, health decision and policy makers were key elements for sustainability of surveillance and control measures in Tunisia. Constructing a risk map of geographical spread of ZCL across Tunisian regions is also important to guide such programs [39]. Indeed finding areas with high probability of presence for both vectors and reservoirs of ZCL will be benefi‐ cial to prevent human infection by planning relevant activities [28].
