Transmission Of Zoonotic Cutaneous Leishmaniasis Research Articles

Risk Assessment of the Role of the Ecotones in the Transmission of Zoonotic Cutaneous Leishmaniasis in Central Tunisia.

Zoonotic cutaneous leishmaniasis (ZCL), endemic in Central and Southern Tunisia, is caused by Leishmania major (Kinetoplastida: Trypanosomatidae), which is transmitted by the sand fly Phlebotomus papatasi. In Tunisia, the fat sand rat Psammomys obesus and the desert jird Meriones shawi are the principal reservoir hosts of L. major. The presence of the P. papatasi vector of the L. major etiologic agent of ZCL was assessed in the vicinity of villages in endemic areas of Central Tunisia. The study was performed from September through October 2019, a period corresponding to the main peak of activity of P. papatasi. Sand flies were collected from rodent burrows located at the ecotone level, which is the transition zone between the natural environment and human settlement. Sand flies were identified to species level and tested for the presence of L. major by PCR. Our entomological survey showed that P. papatasi is the most abundant sand fly species associated with rodent burrows, and this abundance is even higher in ecotones primarily occupied by P. obesus in comparison to ecotones occupied by M. shawi. Infections with Leishmania major were detected only in P. papatasi, with an overall minimum infection rate (MIR) of 2.64%. No significant difference was observed between the MIRs in ecotones of P. obesus and of M. shawi. Incidence of ZCL in the studied areas ranged from 200 to 700 cases per 100,000 inhabitants, with a mean incidence of 385.41 per 100,000. Higher ZCL incidence was identified in ecotones of M. shawi compared to ecotones of P. obesus. ZCL cases are positively correlated with the MIRs. Considering the short flight range of P. papatasi, increases in its densities associated with burrows of P. obesus or M. shawi at the ecotone level expand the overlap of infected vectors with communities and subsequently increase ZCL incidence. Therefore, control measures should target P. papatasi populations at the ecotones.

An agent-based model of a cutaneous leishmaniasis reservoir host, Meriones shawi

Meriones shawi (M.shawi) is the main reservoir host for zoonotic cutaneous leishmaniasis (ZCL) in Central Tunisia. The incorporation of environmental and climatic effects on the spread of ZCL in M. shawi remains difficult. This study presents an agent-based model (ABM) to overcome these difficulties and examine the impact of environment (i.e. vegetation cover) and climate (i.e. temperature) on M. shawi movement and prevalence. The model simulation considers two agent types: rodent agent and field unit agent. We tested the model according to two types of rodent movement: random and thoughtful. We integrated time dependent normalized difference vegetation index (NDVI) in order to test the land cover effects on rodent movement and ZCL transmission. The results confirmed that the spread of the disease depends on rodent movement. We observed that prevalence and distribution are the closest to field data when the vegetation cover is highest and that rodents go for thoughtful movement. In addition, we found that the nature of movement (random or thoughtful) and prevalence depends strongly on minimum food detection.

The Impact of Illegal Waste Sites on the Transmission of Zoonotic Cutaneous Leishmaniasis in Central Tunisia

Illegal waste disposal represents a risk health factor for vector-borne diseases by providing shelter for rodents and their ectoparasites. The presence of the Phlebotomus papatasi vector of Leishmania major, an etiologic agent of zoonotic cutaneous leishmaniasis (ZCL), was assessed at illegal waste sites located at the vicinity of villages in endemic areas of Central Tunisia. The study was performed over a two-year period over three nights from July to September 2017, and over three nights in September 2018. Household waste is deposited illegally forming dumpsites at the vicinity of each village and contains several rodent burrows of Psammomys obesus, the main reservoir host of L. major. Sandflies were collected from rodent burrows in the natural environment and in dumpsites using sticky traps and were identified at species level. Female sandflies were tested for the presence of L. major by PCR. Our entomological survey showed that Phlebotomus papatasi is the most abundant sandfly species associated with rodent burrows in these waste sites. The densities of P. papatasi in dumpsites are significantly higher compared to the natural environment. The minimum infection rate of P. papatasi with L. major in these illegal waste sites is not significantly different compared to the natural environment. Considering the short flight range of P. papatasi, increases in its densities, associated with burrows of P. obesus in illegal waste sites located at the edge of villages, expands the overlap of infected ZCL vectors with communities. Thus, illegal waste sites pose a high risk of spreading ZCL to neighboring home ranges. Waste management is an environmentally friendly method of controlling sandfly populations and should be included in an integrated management program for controlling ZCL in endemic countries.

Climate change and potential distribution of zoonotic cutaneous leishmaniasis in Central Iran: Horizon 2030 and 2050

Objective: To investigate and predict the effects of climate change on the potential distribution of the main vector and reservoir hosts of the disease in Yazd province in the future. Methods: Distribution data for vector and reservoir hosts of zoonotic cutaneous leishmaniasis in Yazd province were obtained from earlier studies conducted in the area. MaxEnt ecological niche modeling was used to predict environmental suitability. BCC-CSM1-1(m) model and two climate change scenarios, RCP 4.5 and RCP 8.5 were used for horizons 2030 and 2050 climate projections. Future projections were based on data of a regional climate change model. Results: With both scenarios in 2030 and 2050, the results of jackknife test indicated that the mean temperature of wettest quarter and temperature annual range had the greatest effect on the model for the vector and the reservoir hosts, respectively. Conclusions: The climate conditions are the major determinants of zoonotic cutaneous leishmaniasis incidence rate in Yazd Province. These climate conditions provide favorable habitats for ease transmission of zoonotic cutaneous leishmaniasis in this endemic area. Habitats suitability for the vector and reservoir will be expanding in the coming years compared with the current conditions, such that, in horizon 2030 & 2050, the probability of the presence of the vector and reservoir within 38 580 and 37 949 km2, respectively, from Yazd province is above 60%. Moreover, an increase is predicted in the presence of the vector in the western parts and the reservoir in the northern and central parts of the province in the future. Understanding the role of environmental and bioclimatic factors in zoonotic cutaneous leishmaniasis occurrence can provide a guide for policy-makers in the creation and implementation of more effective policies for prevention and control.

Modeling zoonotic cutaneous leishmaniasis incidence in central Tunisia from 2009-2015: Forecasting models using climate variables as predictors.

Transmission of zoonotic cutaneous leishmaniasis (ZCL) depends on the presence, density and distribution of Leishmania major rodent reservoir and the development of these rodents is known to have a significant dependence on environmental and climate factors. ZCL in Tunisia is one of the most common forms of leishmaniasis. The aim of this paper was to build a regression model of ZCL cases to identify the relationship between ZCL occurrence and possible risk factors, and to develop a predicting model for ZCL's control and prevention purposes. Monthly reported ZCL cases, environmental and bioclimatic data were collected over 6 years (2009–2015). Three rural areas in the governorate of Sidi Bouzid were selected as the study area. Cross-correlation analysis was used to identify the relevant lagged effects of possible risk factors, associated with ZCL cases. Non-parametric modeling techniques known as generalized additive model (GAM) and generalized additive mixed models (GAMM) were applied in this work. These techniques have the ability to approximate the relationship between the predictors (inputs) and the response variable (output), and express the relationship mathematically. The goodness-of-fit of the constructed model was determined by Generalized cross-validation (GCV) score and residual test. There were a total of 1019 notified ZCL cases from July 2009 to June 2015. The results showed seasonal distribution of reported ZCL cases from August to January. The model highlighted that rodent density, average temperature, cumulative rainfall and average relative humidity, with different time lags, all play role in sustaining and increasing the ZCL incidence. The GAMM model could be applied to predict the occurrence of ZCL in central Tunisia and could help for the establishment of an early warning system to control and prevent ZCL in central Tunisia.

Coarse-resolution Ecology of Etiological Agent, Vector, and Reservoirs of Zoonotic Cutaneous Leishmaniasis in Libya

Cutaneous leishmaniasis ranks among the tropical diseases least known and most neglected in Libya. World Health Organization reports recognized associations of Phlebotomus papatasi, Psammomys obesus, and Meriones spp., with transmission of zoonotic cutaneous leishmaniasis (ZCL; caused by Leishmania major) across Libya. Here, we map risk of ZCL infection based on occurrence records of L. major, P. papatasi, and four potential animal reservoirs (Meriones libycus, Meriones shawi, Psammomys obesus, and Gerbillus gerbillus). Ecological niche models identified limited risk areas for ZCL across the northern coast of the country; most species associated with ZCL transmission were confined to this same region, but some had ranges extending to central Libya. All ENM predictions were significant based on partial ROC tests. As a further evaluation of L. major ENM predictions, we compared predictions with 98 additional independent records provided by the Libyan National Centre for Disease Control (NCDC); all of these records fell inside the belt predicted as suitable for ZCL. We tested ecological niche similarity among vector, parasite, and reservoir species and could not reject any null hypotheses of niche similarity. Finally, we tested among possible combinations of vector and reservoir that could predict all recent human ZCL cases reported by NCDC; only three combinations could anticipate the distribution of human cases across the country.

First Detection of Leishmania major DNA in Sergentomyia (Spelaeomyia) darlingi from Cutaneous Leishmaniasis Foci in Mali

Background Leishmania major complex is the main causative agent of zoonotic cutaneous leishmaniasis (ZCL) in the Old World. Phlebotomus papatasi and Phlebotomus duboscqi are recognized vectors of L. major complex in Northern and Southern Sahara, respectively. In Mali, ZCL due to L. major is an emerging public health problem, with several cases reported from different parts of the country. The main objective of the present study was to identify the vectors of Leishmania major in the Bandiagara area, in Mali.Methodology/Principal FindingsAn entomological survey was carried out in the ZCL foci of Bandiagara area. Sandflies were collected using CDC miniature light traps and sticky papers. In the field, live female Phlebotomine sandflies were identified and examined for the presence of promastigotes. The remaining sandflies were identified morphologically and tested for Leishmania by PCR in the ITS2 gene. The source of blood meal of the engorged females was determined using the cyt-b sequence. Out of the 3,259 collected sandflies, 1,324 were identified morphologically, and consisted of 20 species, of which four belonged to the genus Phlebotomus and 16 to the genus Sergentomyia. Leishmania major DNA was detected by PCR in 7 of the 446 females (1.6%), specifically 2 out of 115 Phlebotomus duboscqi specimens, and 5 from 198 Sergentomyia darlingi specimens. Human DNA was detected in one blood-fed female S. darlingi positive for L. major DNA.ConclusionOur data suggest the possible involvement of P. duboscqi and potentially S. darlingi in the transmission of ZCL in Mali.

Dynamics of Leishmania infection rates in Rhombomys opimus (Rodentia: Gerbillinae) population of an endemic focus of zoonotic cutaneous leishmaniasis in Iran

Zoonotic cutaneous leishmaniasis (ZCL) due to Leishmania major is a great public health problem in the Old World. Leishmania major is widely distributed in populations of rodents in arid and savannah regions. In this study, seasonal variation of natural infection with Leishmania parasites in Rhombomys opimus (Rodentia: Gerbillinae) population of an endemic focus of ZCL in Iran was monitored. The study was conducted from October 2007 to October 2008 in the central part of the country. Nested polymerase chain reaction (PCR) assay was used for the detection and identification of Leishmania parasites, and the results were confirmed by PCR-restriction fragment length polymorphism (RFLP). The results showed that Leishmania infection rate was 55.8% (29 out of 52 gerbils) using nested PCR. The highest and lowest Leishmania infection rates were observed in fall and summer, respectively. Gerbils that were found to be infected only with L. major were 5.8%, and that with Leishmania turanica were 23.1%. A mixed natural infection was seen in the rodents with L. major and L. turanica (21.2%), with L. major and L. gerbilli (1.9%), and with all the three species (3.9%). Leishmania major infection alone was seen in fall and winter whereas mixed infection of L. major and L. turanica was observed in all seasons except in summer. Leishmania turanica infection was observed throughout the year. It is concluded that L. major, L. gerbilli, and L. turanica circulate in the population of R. opimus in central part of Iran. Leishmania major infection is usually accompanied by L. turanica in naturally infected gerbils with the highest rate in fall. It is recommended that the role of L. turanica in the epidemiology and transmission of ZCL should be reconsidered.

Short report: outbreak of cutaneous leishmaniasis in a nonimmune population of soldiers in Wadi Araba, Jordan.

An outbreak of zoonotic cutaneous leishmaniasis (ZCL) occurred in a battalion of 80 soldiers posted at Qurayqira camp in Wadi Araba in southern Jordan. The battalion spent an intermittent period of five and a half months in the area, during which 45.0% (36 of 80) of the soldiers showed clinical disease. Of the 44 clinically negative soldiers, 31 were tested with leishmanin and 11 (35.5%) were leishmanin positive. The number of lesions in infected soldiers ranged from one to 15 and were mostly on the face and extremities. This report shows the level of transmission of ZCL in Wadi Araba, which is presently undergoing economic expansion and development following the peace process of the Arab-Israeli conflict.