Climate Change Influences on the Potential Distribution of the Sand Fly Phlebotomus sergenti, Vector of Leishmania tropica in Morocco

BACKGROUND

Leishmaniases are a vector-borne disease, re-emerging in several regions of the world posing a burden on public health. As other vector-borne diseases, climate change is a crucial factor affecting the evolution of leishmaniasis. In Morocco, anthroponotic cutaneous leishmaniasis (ACL) is widespread geographically as many foci across the country, mainly in central Morocco. The objective of this study is to evaluate the potential impacts of climate change on the distribution of ACL due to Leishmania tropica, and its corresponding vector Phlebotomus sergenti in Morocco.

METHODS

Using Ecological Niche Modeling (ENM) tool, the estimated geographical range shift of L. tropica and P. sergenti by 2050 was projected under two Representative's Concentration's Pathways (RCPs) to be 2.6 and RCP 8.5 respectively. P. sergenti records were obtained from field collections of the laboratory team and previously published entomological observations, while, epidemiological data for L. tropica were obtained from Moroccan Ministry of Health reports.

RESULTS

Our models under present-day conditions indicated a probable expansion for L. tropica as well as for its vector in Morocco, P. sergenti. It showed a concentrated distribution in the west-central and northern area of Morocco. Future predictions anticipate expansion into areas not identified as suitable for P. sergenti under present conditions, particularly in northern and southeastern areas of Morocco. L. tropica is also expected to have high expansion in southern areas for the next 30 years in Morocco.

CONCLUSION

This indicates that L. tropica and P. sergenti will continue to find suitable climate conditions in the future. A higher abundance of P. sergenti may indeed result in a higher transmission risk of ACL. This information is essential in developing a control plan for ACL in Morocco. However, future investigations on L. tropica reservoirs are needed to confirm our predictions.

Involvement of tryparedoxin peroxidase (TryP) and trypanothione reductase (TryR) in antimony unresponsive of Leishmania tropica clinical isolates of Iran

Clinical resistance to pentavalent antimonial compounds has long been recognized as a major problem in the treatment of human leishmaniasis. Trypanothione metabolism, the main form of thiol, has shown to play a central role in antimony resistance of laboratory-generated resistant Leishmania spp. and field-isolated resistant L. donovani; but the mechanism of antimony resistance in the clinical isolates of L. tropica causing anthroponotic cutaneous leishmaniasis (ACL) is less studied. Patients were selected among confirmed positive ACL cases who referred to Pasteur Institute of Iran, Tehran, from endemic regions of north-east and south of Iran. L. tropica clinical isolates were collected from patients who were either treatment-responsive (MAS=S1 to S5) or unresponsive (MAR=R1 to R4) to Glucantime® (meglumine antimoniate=MA). Isolates were tested for sensitivity to trivalent antimony (SbIII) in promastigotes and to pentavalent antimony (SbV) in intracellular amastigotes stages. Intracellular thiol levels were assayed and trypanothione-dependent components, including trypanothione reductase (TR) and tryparedoxin peroxidase I (TryP) were analysed at protein level and enzymatic activity in isolates. The MAR isolates had an approximate two fold increase in the levels of intracellular thiols (P< 0.05) accompanied by an average 5-10 fold increase in in vitro resistance to antimony. TryP was amplified at the protein level in all MAR strains as compared to the MAS strains (range: 2.8-5.6 fold). All MAR isolates metabolized H₂O₂ at higher rates than MAS isolates (8.55±0.75 nmol/min/mg vs. 3.14±0.36 nmol/min/mg) (P< 0.05). In addition, levels of TryR protein were also markedly elevated in 3 out of 4 MAR isolates (range: 2.2-4.1 fold). This was accompanied by overexpressed TryR activity (mean level of 46.83±2.43 for extracts of MAR vs. 20.98±3.02 for MAS strains) (P< 0.05). Elevated levels of TryP, active enzyme in peroxide detoxification, were observed in MAR parasites resulting in an increased metabolism of H₂O₂. TryR activity was overexpressed on average in extracts of MAR strains, but not in all isolates. Enhanced anti-oxidant defenses through thiol metabolism may play a significant role in clinical resistance of ACL patients to Glucantime.

Host's immune response in unresponsive and responsive patients with anthroponotic cutaneous leishmaniasis treated by meglumine antimoniate: A case-control study of Th1 and Th2 pathways

The objective of the present study was to compare the host's immune responses between unresponsive and responsive patients with anthroponotic cutaneous leishmaniasis (ACL) treated by meglumine antimoniate. A case-control study was carried out in an endemic focus in Iran. Blood samples were taken from patients and peripheral blood mononuclear cells (PBMCs) were isolated. Two wells were considered for each isolate of unresponsive and responsive patients; one was exposed to L. tropica (Lt-stimulated cells) and the other remained non-exposed (non-stimulated cells). After 24 h of incubation, whole RNA was extracted from each sample. Real-time quantitative PCR was carried out to confirm the differences in expression levels of IL-12 P40, IFN-γ, IL-1β, IL-4 and IL-10 among isolates. Data were analyzed and P < 0.05 was considered to be statistically significant. In our study, Lt-stimulated cells and non-stimulated cells in unresponsive groups demonstrated significantly lower expression levels of IL-1β, IL-12 P40 and IFN-γ genes and higher expression levels of IL-4 and IL-10 genes, compared to Lt-stimulated cells and non-stimulated cells in responsive groups. There was a negative correlation between IL-12 P40 with IL-10 and IL-1β with IL-10 in ACL Lt-stimulated cells in unresponsive group, while a positive correlation between IL-12 P40 with IL-1β and IL-12 P40 with IFN-γ in ACL Lt-stimulated cells in responsive group. Probably, different immune responses caused by various factors play a major role in the pathogenesis and development of unresponsiveness in ACL patients. The profile and timing of cytokine production correlated well with the treatment outcome of Leishmania infection.

Epidemiology and Control of Leishmaniasis in the Former USSR: A Review Article

BACKGROUND

All types of the Old World's leishmaniasis were endemic on the territory of the South regions of ex-USSR. Epidemiological situation was well under control during the USSR era, due to implementation of complex anti-leismaniasis measures. These interventions were dramatically stopped as a result of the collapse of the USSR.

METHODS

Most relevant publications on epidemiology and control of leishmaniases in the Republics of Central Asia and Transcaucasia of the ex-USSR were screened.

RESULTS

Within the endemic area, the foci of different kinds of leishmaniasis are often overlapped thus calling for deployment of integrated measures. The anthroponotic cutaneous leishmaniasis (ACL) was reported in settlements and towns of Central Asia and Transcaucasia of the ex-USSR. The natural foci of cutaneous leishmaniasis were widespread in the desert of Turkmenistan, Uzbekistan, Kazakhstan and Tajikistan. The northern boundary of the zoonotic cutaneous leishmaniasis (ZCL) area coincided with the northern boundary of the distribution of great gerbils - the main reservoir of this infection in the ex-USSR. Visceral leishmaniasis (VL) occurred in the Central Asian Republics and in the republics of the Transcaucasia. Holistic approach was adopted by the programs targeting the source of infection, vector(s) and man.

CONCLUSION

The presence rise in the number of cases of different types of leishmaniasis in the ex-USSR strongly necessitates that health authorities should consider these diseases as an important public health problem. The immediate task would be rebuilding a comprehensive surveillance system consisting of active and passive case detection mechanism along with immediate treatment of the patients.

Rearing and Biology of Phlebotomus sergenti, the Main Vector of Anthroponotic Cutaneous Leishmaniasis in Iran

BACKGROUND

Establishment of sand flies laboratory colonies is essential to understand various biological aspects of Phlebotominae sand flies. The aims of the current study were to establish the colony of Phlebotomus sergenti Parrot (1917), the main vector of anthroponotic cutaneous leishmaniasis in old world, and to study biological parameters of this species.

METHODS

The sand flies were reared at 26-28 °C temperature, 14:10 (light: dark) photoperiod and 70-80% relative humidity. Larval diet was a composted mixture of rabbit faces and rabbit pellets which is prepared through a special process. First to fifth generations of P. sergenti were used to define biological parameters.

RESULTS

Results showed that, P. sergenti blood feeding percentage were 42% on chicken, 21% on BALB/c and 37% on golden hamster. Average time of blood digestion, egg incubation, 1^st instar larva, pupa and adult emerging was recorded at 3.4, 8.7, 15, 33.3 and 41.2 days after blood feeding, respectively. Mean number of laid eggs was 55.1 and retained eggs were 35 per a female. Fecundity and production rate were 61.6%, and 42.2% respectively. Average longevity recorded at 15.2 days for females and 14.8 days for males.

CONCLUSION

Colony of P. sergenti has been established for the first time in Iran. Average interval time from egg to adult of this species was 32.5 days. Chicken and golden hamster were recommended as a blood source for colony initiation and routine blood feeding, respectively.

The emergence of anthroponotic cutaneous leishmaniasis following the earthquake in southern villages of bam district, southeastern iran, 2010

BACKGROUND

The objective of this study was to assess the epidemiological characteristics of a new emerging focus of cutaneous leishmaniasis (CL) in southern villages of Bam District, southeastern Iran, 2010.

METHODS

A house-to- house census survey of 5544 individuals were interviewed and physically examined for the presence of active lesions or scars. Diagnosis was confirmed by direct smears, cultures and identification by PCR. The data were entered into a computer and SPSS ver. 15.

RESULTS

Overall, 1.2% of the inhabitants were infected, 0.5% active and 0.7% scars and females were more significantly infected (1.7%) than males (0.8%), (P= 0.003). All age groups were equally affected. Most of the lesions were on the face and majority had single lesion. Most of the cases appeared from 2006 to 2008 during the CL epidemic in the city of Bam. PCR indicated L. tropica as the causative agent.

CONCLUSION

The presence of non-immune individuals along with suitable ecological conditions could induce a new emerging focus of ACL in villages.