Background: The impact of environmental factors and host on Hyalomma spp. community structure and abundance in the main Crimean-Congo haemorrhagic fever (CCHF) foci of Iran is largely unknown.
Methods: Biotic and abiotic factors, including host, temperature, humidity, altitude, Köppen-Geiger climate types, season, and precipitation on Hyalomma spp. community structure and abundances in 11 provinces of Iran were investigated. Additionally, the possible infection of ticks with CCHF virus was evaluated using reverse transcription PCR technique.
Results: Species analyses demonstrated the presence of Hyalomma anatolicum, H. marginatum, H. dromedarii, H. asiaticum, H. detritum and H. schulzei in the study area. Hyalomma anatolicum was the dominant species in the southern and northern parts, whereas H. dromedarii was distributed mostly in central parts of the country. The highest tick infestation was recognized in hot season. Spatial variation in tick relative density was observed between habitat types where more ticks were collected in deserts, semi-deserts, and Mediterranean habitats. Except for H. dromedarii, which was more prevalent on camel (P= 0.044), there were no significant variations in the frequencies of other Hyalomma species on different hosts. Hyalomma anatolicum, H. dromedarii frequencies had significant positive and negative association with temperature and precipitation respectively. Also humidity has positive impact on H. asiaticum frequency.
Conclusion: Data presented here will help improve ecological models to forecast the distribution of Hyalomma spp. ticks, to evaluate the risk of CCHF and other tick-borne diseases, and to design proper vector control measures to suppress Hyalomma populations in Iran.
BackgroundLeishmaniasis is caused by Leishmania parasites and is transmitted to humans through the bite of infected sand flies. Development of Leishmania to infective metacyclic promastigotes occurs within the sand fly gut where the gut microbiota influences development of the parasite. Paratransgenesis is a new control method in which symbiotic bacteria are isolated, transformed and reintroduced into the gut through their diet to express anti-parasitic molecules. In the present study, the midgut microbiota of three sand fly species from a steppe and a mountainous region of northern Iran, where zoonotic visceral leishmaniasis (ZVL) is endemic, was investigated.MethodsBriefly, adult female sand flies was collected during summer 2015 and, after dissection, the bacterial composition of the guts were analyzed using a culture-dependent method. Bacterial DNA from purified colonies was extracted to amplify the 16S rRNA gene which was then sequenced.ResultsThree ZVL sand fly vectors including Phlebotomus major, P. kandelakii and P. halepensis were found in the highlighted regions. In total, 39 distinct aerobic bacterial species were found in the sand fly midguts. The sand fly microbiota was dominated by Proteobacteria (56.4%) and Firmicutes (43.6%). Bacterial richness was significantly higher in the steppe region than in the mountainous region (32 vs 7 species). Phlebotomus kandelakii, the most important ZVL vector in the study area, had the highest bacterial richness among the three species. Bacillus subtilis and Pantoea agglomerans were isolated from the guts of the sand flies; these are already used for the paratransgenesis of sand flies and mosquitoes, respectively.ConclusionsThe existence of B. subtilis and P. agglomerans in the ZVL vectors and other sand fly species studied so far suggests that these two bacterial species are potential candidates for paratransgenic approach to prevent ZVL transmission. Further research needs to test the possible relationship between the gut microbiome richness and the vector competence of the ZVL vectors.
Anopheles stephensi with three different biotypes is a major vector of malaria in Asia. It breeds in a wide range of habitats. Therefore, safer and more sustainable methods are needed to control its immature stages rather than chemical pesticides. The larvicidal and antibacterial properties of the Pelargonium roseum essential oil (PREO) formulations were investigated against mysorensis and intermediate forms of An. stephensi in laboratory conditions. A series of nanoemulsions containing different amounts of PREO, equivalent to the calculated LC50 values for each An. stephensi form, and various quantities of surfactants and co-surfactants were developed. The physical and morphological properties of the most lethal formulations were also determined. PREO and its major components, i.e. citronellol (21.34%), L-menthone (6.41%), linalool (4.214%), and geraniol (2.19%), showed potent larvicidal activity against the studied mosquitoes. The LC50/90 values for mysorensis and intermediate forms were computed as 11.44/42.42 ppm and 12.55/47.69 ppm, respectively. The F48/F44 nanoformulations with 94% and 88% lethality for the mysorensis and intermediate forms were designated as optimized formulations. The droplet size, polydispersity index, and zeta-potential for F48/F44 were determined as 172.8/90.95 nm, 0.123/0.183, and -1.08/-2.08 mV, respectively. These results were also confirmed by TEM analysis. Prepared formulations displayed antibacterial activity against larval gut bacteria in the following order of decreasing inhibitory: LC90, optimized nanoemulsions, and LC50. PREO-based formulations were more effective against mysorensis than intermediate. Compared to the crude PREO, the overall larvicidal activity of all nanoformulations boosted by 20% and the optimized formulations by 50%. The sensitivity of insect gut bacteria may be a crucial factor in determining the outcome of the effect of toxins on target insects. The formulations designed in the present study may be a good option as a potent and selective larvicide for An. stephensi.
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