Les leishmanioses: un modèle d'étude des interactions hôte-parasite; implications pour la maladie humaine

Mediterranean visceral leishmaniasis : update on biological diagnosis

Visceral leishmaniasis (VL) is a severe life threatening parasitosis requiring early management of cases. It is an emerging disease in the Mediterranean region with a spread of endemic areas and an increase in case incidence. The patient profile has also evolved with more affected adults, presenting generally non-specific symptoms. Hence the interest of a systematic biological confirmation. The microscopic detection of Leishmania amastigotes in bone marrow aspirates (BMA) smears is the gold standard diagnostic technique. However, it requires invasive sampling. Serological tests searching for specific antibodies remain highly contributory, but their interpretation must always take into account the epidemiological context and the patient's clinical and biological features. Currently, the Western-Blot represents the most specific serological technique for diagnostic confirmation. VL diagnosis has greatly improved by the introduction of both rapid diagnostic tests (RDTs) and molecular biological techniques. RDTs using recombinant rk39 antigen are easy to perform and deliver results in less than 30 minutes. Real-time PCR (Polymerase Chain Reaction) is currently retained as the best technique for VL diagnosis. It is efficient on simple blood samples, allowing to avoid invasive BMA needed for microscopy. In addition, real time PCR estimates parasite load which is helpful for the post-treatment follow-up. In any case, the choice of techniques to be used should be strategic and adapted to the local epidemiology as well as to the means available.

[Epidemiological and clinical features of cutaneous leishmaniasis in Kairouan-Tunisia and characteristics in children]

Cutaneous leishmaniasis (CL) remains highly endemic in Tunisia. The governorate of Kairouan (Center) is one of the most affected particularly by zoonotic form due to Leishmania major. The purpose of this study was to describe the epidemiological, clinical and therapeutic features of the disease in this governorate and to identify any particularities in children. Three hundred and ninety cases were registered over 2 years (2012 and 2013). The average age was 29 years one month [± 22.7] (34.6% of patients were under 15 years). The cumulative incidence of CL was equal to 34.4 per 100,000 per year. It was higher in children (39.6 per 100,000 versus 29, p=0.004). Cases were diagnosed especially in autumn and winter (88.3% of cases between October and January, p<0.001). The average delay of consultation was one month and 22 days [± 2.5] after onset of lesions. The average number of lesions per patient was 2.7 [± 2.3] with a mean diameter equal to 2.2 cm. In addition to a higher incidence of the disease, two other features were found in "Children" group which are the presence of similar cases in the neighborhood (27.7% versus 13.4%, p=0.002) and preferential localization in the face (36.4% versus 11%) while the members were more affected in adults (63.5% versus 46.4%) (p<0.001). Meglumine antimoniate was prescribed for most of our patients (93.1%). The intramuscular route was used more than local one, probably because of high proportions of multiple lesions and facial localization.

[Leishmania epidemiology, diagnosis, chemotherapy and vaccination approaches in the international network of Pasteur Institutes]

Protozoan parasites of the genus Leishmania generate severe human diseases termed leishmaniases. Due to their frequency and the severity of certain clinical forms, these diseases represent a major public health problem and limit the economic growth in various developing countries. The presence of Pasteur Institutes in countries with endemic leishmaniasis has provided important incentives to develop a strong public health agenda in the Pasteur scientific community with respect to this important disease. A concerted effort is now coordinated through the recently created LeishRIIP platform (www.leishriip.org), which aims to identify synergies and complementary expertise between the eleven members of the international network of Pasteur Institutes working on various aspects of the disease including epidemiology, diagnosis, chemotherapy and vaccination.

[Comparative characterization of skin lesions observed in the three endemic varieties of cutaneous leishmaniasis in Tunisia]

BACKGROUND

The recent spread in the geographical distribution of the three forms of cutaneous leishmaniasis (CL) endemic in Tunisia has resulted in the coexistence of more than one species of Leishmania (L.) in some foci, rendering characterization on the basis of geographical criteria alone more difficult. The aim of the study was to establish clinical criteria associated with these noso-geographic forms, namely sporadic CL (SCL) due to L. infantum, zoonotic CL (ZCL) due to L. major and chronic CL (CCL) due to L. tropica.

PATIENTS AND METHODS

One hundred and twelve patients with biologically confirmed CL were involved in the study. Leishmania species was systematically identified by iso-enzyme analysis and/or PCR-RFLP. Details of the number, the location, the morphological aspect and the month of outbreak of the lesions were noted for each patient.

RESULTS

SCL lesions appeared later than ZCL lesions (53.8% of cases appeared from December onwards vs. 23.6%, P<0.001). ZCL lesions were often multiple (75%) and situated on the limbs (84.7%, P<0.001), whereas SCL lesions were single (92.3%, P<0.001) and located on the face (84.6%, P<0.001). CCL lesions were also single (78.6%) and located on the face (71.4%). The classical ulcerous presentation with scabs was mainly observed in ZCL patients (69.4%) and the erythematous presentation was described more frequently in SCL patients (75%; P<0.001).

CONCLUSION

The number, site, morphological aspect and month of outbreak of lesions could be considered as useful criteria that help differentiate between the three noso-geographical forms of CL prevailing in Tunisia. Such characterization is useful for the individual management of patients and for optimizing the combat against the disease.

[Visceral leishmaniasis in immunocompetent adults. About six cases]

OBJECTIVE

Studying the epidemiological variations of visceral leishmaniasis in Tunisia and proving the importance of parasitological investigations to raise the diagnosis.

PATIENTS AND METHODS

Six patients hospitalised during the period between January 1998 and January 2009 at Fattouma Bourguiba Teaching Hospital in Monastir, five men and an only one woman, aged from 26 to 70 years old, originating from the central and eastern regions of the country. Epidemiological, clinical, biological and therapeutic data were obtained from the patient's medical files.

RESULTS

The major clinical symptoms were fever, weakness and spleen enlargement. Biological data revealed the presence of anaemia in every case and leucopoenia associated or not associated with thrombopenia in four cases. The diagnosis of visceral leishmaniasis was confirmed by the identification of the parasite in the blood or in the bone marrow. All patients were treated with two courses of antimoniate of meglumine separated by a 6-week interval. The outcome was positive and the patients were cured.

CONCLUSION

Visceral leishmaniasis is increasing among adults in Tunisia. Moreover, it is spreading outside its epidemiological area in the north to reach the central and southern regions. It should be raised when fever and spleen enlargement occur. Biological data are hardly specific. Diagnosis is based on finding the parasite in human fluids, mainly by molecular techniques. The rapid establishment of a specific treatment is vital.

Pathocenosis: a holistic approach to disease ecology

The history of medicine describes the emergence and recognition of infectious diseases, and human attempts to stem them. It also throws light on the role of changing environmental conditions on disease emergence/re-emergence, establishment and, sometimes, disappearance. However, the dynamics of infectious diseases is also influenced by the relationships between the community of interacting infectious agents present at a given time in a given territory, a concept that Mirko Grmek, an historian of medicine, conceptualized with the word "pathocenosis". The spatial and temporal evolution of diseases, when observed at the appropriate scales, illustrates how a change in the pathocenosis, whether of "natural" or anthropic origin, can lead to the emergence and spread of diseases.