Application of predictive degree day model for field development of sandfly vectors of visceral leishmaniasis in northwest of Iran

Background & objectives: Temperature plays a significant role in insect’s development where arise in temperature, accelerates the insect’s metabolic rates, increases egg production and makesblood feeding more frequent. It also shortens the time period required for the development ofpathogens within insects. Visceral leishmaniasis (VL) is one of the most important vector-bornediseases transmitted by different sandfly species. In this study, a phenological model was used toestimate the number of generations, peak activity and temporal variability of sandflies in the mainVL foci in northwest Iran.Methods: Development requirements of different life stages of a Phlebotomus papatasi laboratorycolony were measured and were subjected to the formula for calculation of accumulated degree day(ADD) for field sandflies using the online soft (UC IPM), using horizontal cut-off method andsingle triangle model. Sandflies population dynamics was monitored in the field during the seasonalactivity in the region and its association with the ADD was tested using SAS software.Results: Populations of sandflies accommodated well with the amount of accumulated degree days(ADD) in the region. During the seasonal activity, a total of 639 ADD were produced which wasenough to support one complete life cycle and growth of the next generation up to late larvalinstar. Larvae of the second generation hibernate through winter and the first adult populationappears in the mid to late June of the next year when they receive at least 182 ADD from thebeginning of the spring. The highest population density of sandflies was observed in early August,followed by a rapid decrease in early September, with the adult population disappearing completelyin late September. This is the first degree day model related to sandflies in the most important VLfoci of Iran.Interpretation & conclusion: Further studies in various regions with variable climate arerecommended in order to better estimate and understand the development time, population dynamicsand activities of the vectors which in turn could be used in proper implementation of effectivevector control programmes

Comparison of Nomadic and non-Nomadic Lifestyles in Transmission of Visceral Leishaniasis

Background and Objective: Epidemiology of Visceral Leishmaniasis is affected by combination quality and interaction of Parasite-Vector-Host and environmental conditions. So, disease cycle related and eco-social factors and environmental risk factors co-analyzing, help to understanding these interactions, prognosis and orientation in disease control and treatment. This study was done to determine the role of nomadic and non-nomadic lifestyle in transmission of Kala-Azar in the Northwest of Iran. Materials and Methods: In this case-control study, firstly the prevalence of Kala-Azar among people living in selected villages were determined by both serological test (Direct Agglutination Test: DAT) and immunological test (Montenegro Skin Test: MST) in the Northwest of Iran, on the way of Shahsavan tribe travelling in summer/winter quarters villages. Then DAT was conducted on the dogs presenting in those villages during 2006. One year later Seroconversion rate was calculated through collection of the individual’s negative sera and re-analyzing them via DAT. Finally, occurrence of Visceral Leishmaniasis in relation with various involving factors like dog density/abundance and nomadic and non-nomadic lifestyle using Chi-Square test were determined. Results: Both MST and DAT were significantly higher in the nomadic lifestyle than in the non-nomadic lifestyle (P<0.05). Three values of prevalence (5.5%), seropositivity (2.7%) and seroconversion (2.5%) were higher in nomads than non-nomads. The GIS studies and electronically prepared maps showed that the endemicity and the infection rate are higher in nomads than non-nomads. There were a negative correlation between general distribution of Visceral Leishmaniasis in relation with environmental conditions altitude, mean temperature and rainfall. Conclusion: This study indicated that Nomadic lifestyle can play as a risk factor in transmission of Visceral Leishmaniasis due to nomads/dog contacting, their entering in the wild cycle of disease and travelling

Blood Meal Identification in Field-Captured Sand flies: Comparison of PCR-RFLP and ELISA Assays

 Background: We aimed to develop a PCR-RFLP assay based on available sequences of putative vertebrate hosts to iden­tify blood meals ingested by field female sand fly in the northwest of Iran. In addition, the utility of PCR-RFLP was compared with ELISA as a standard method. Methods: This experimental study was performed in the Insect Molecular Biology Laboratory of School of Public Health, Tehran University of Medical Sciences, Iran in 2006-2007. For PCR-RFLP a set of conserved vertebrate prim­ers were used to amplify a part of the host mitochondrial cytochrome b (cyt b) gene followed by digestion of the PCR products by Hae III enzyme. Results: The PCR-RFLP and ELISA assays revealed that 34% and 27% of field-collected sand flies had fed on hu­mans, respectively. Additionally, PCR-RFLP assays could reveal specific host DNA as well as the components of mixed blood meals. Results of PCR-RFLP assay showed that the sand flies had fed on cow (54%), human (10%), dog (4%), human and cow (21%), dog and cow (14%), and human and dog (3%). Conclusion: The results can provide a novel method for rapid diagnosis of blood meal taken by sandflies. The advan­tages and limitations of PCR and ELISA assays are discussed

The Fleas (Siphonaptera) in Iran: Diversity, Host Range, and Medical Importance

BACKGROUND:Flea-borne diseases have a wide distribution in the world. Studies on the identity, abundance, distribution and seasonality of the potential vectors of pathogenic agents (e.g. Yersinia pestis, Francisella tularensis, and Rickettsia felis) are necessary tools for controlling and preventing such diseases outbreaks. The improvements of diagnostic tools are partly responsible for an easier detection of otherwise unnoticed agents in the ectoparasitic fauna and as such a good taxonomical knowledge of the potential vectors is crucial. The aims of this study were to make an exhaustive inventory of the literature on the fleas (Siphonaptera) and range of associated hosts in Iran, present their known distribution, and discuss their medical importance. METHODOLOGY/PRINCIPAL FINDINGS:The data were obtained by an extensive literature review related to medically significant fleas in Iran published before 31st August 2016. The flea-host specificity was then determined using a family and subfamily-oriented criteria to further realize and quantify the shared and exclusive vertebrate hosts of fleas among Iran fleas. The locations sampled and reported in the literature were primarily from human habitation, livestock farms, poultry, and rodents' burrows of the 31 provinces of the country. The flea fauna were dominated by seven families, namely the Ceratophyllidae, Leptopsyllidae, Pulicidae, Ctenophthalmidae, Coptopsyllidae, Ischnopsyllidae and Vermipsyllidae. The hosts associated with Iran fleas ranged from the small and large mammals to the birds. Pulicidae were associated with 73% (56/77) of identified host species. Flea-host association analysis indicates that rodents are the common hosts of 5 flea families but some sampling bias results in the reduced number of bird host sampled. Analyses of flea-host relationships at the subfamily level showed that most vertebrates hosted fleas belgonging to 3 subfamilies namely Xenopsyllinae (n = 43), Ctenophthalminae (n = 20) and Amphipsyllinae (n = 17). Meriones persicus was infested by 11 flea subfamilies in the arid, rocky, mountainous regions and Xenopsyllinae were hosted by at least 43 mammal species. These findings place the Persian jird (M. persicus) and the Xenopsyllinae as the major vertebrate and vector hosts of flea-borne diseases in Iran including Yersinia pestis, the etiological agent of plague. We found records of at least seven vector-borne pathogenic agents that can potentially be transmitted by the 117 flea species (or subspecies) of Iran. CONCLUSIONS/SIGNIFICANCE:Herein, we performed a thorough inventary of the flea species and their associated hosts, their medical importance and geographic distribution throughout Iran. This exercise allowed assessing the diversity of flea species with the potential flea-borne agents transmission risk in the country by arranging published data on flea-host associations. This information is a first step for issuing public health policies and rodent-flea control campaigns in Iran as well as those interested in the ecology/epidemiology of flea-borne disease

First report on the shortest CPB peptide chain in the Leishmania donovani complex and bioinformatical interpretations in relation with this mutation

Background and Objective: Visceral Leishmaniasis or Kala-azar is an important infectious disease in northwestern Iran. Members of the Leishmania donovani complex, L. donovani and L.infantum, are the two main parasites causing the disease in the world. In this study immunophenotype characters such as N-glycosylation, and T-cell and B-Cell epitopes of CPB gene was evaluated in the Leishmania parasites isolated from sandflies of the region. Materials and Methods: Partial of the CPB (702-741 bp) of Leishmania parasites was amplified and sequenced and used for bioinformatics analysis such as test three dimensional (3D) protein structure, N-glycosylation, and T-cell and B-Cell epitopes. Results: In 7 out of 3477 sand flies there was a positive PCR test for systeine protease B, gene. Also according to findings of this study, both agents of kala-azar L. donovani and L. infantum were bing transfered by sand flies of Phlbtomus perfiliewi transcaucasicus in North West Iran. DNA analysis of the CPB gene showed a cytosine insertion at 5’ end of the proofreading frame of the gene resulted in a stop codon (TGA) seven AA further down and hence translation is halted. This caused a short amino acid chain with only 76 AA much shorter than normal CPB peptide with 234-247 AA. This mutation has not been found in the L.infantum strain resulted in a normal CPB peptide. AA analysis showed no N-glycosylation site, T-cell and B-Cell epitopes on the short peptide of the L. donovani strain. Conclusion: This is the shortest CPB peptide chain reported for the L. donovani complex in the literature. This short peptide could have an effect on host-parasite and vector-parasite interactions. Since the CPBs genes have important implication on host–parasite and play key roles in infection and expression of the disease, further studies on the L. donovani parasite and its diminutive peptide necessitate to improve our understanding about the epidemiology of visceral leishmaniasis in Iran