Studies On Population Ecology Of Dermacentor Silvarum And Antimicrobial Molecules Of Egg Wax In Amblyomma Hebraeum

In this study, we investigated the life cycle and biological characteristics of all developmental stages of Dermacentor silvarum under field conditions in Hebei province in North China. Larvae, nymphs and adults were fed on rabbits, and maintained under natural lighting and climate conditions. Ticks were released into a confined plot located in natural tick habitat, and we observed the host questing behavior and seasonal occurrence. Due to a behavioral diapause in females and the synchronization of oviposition and larval hatching, D. silvarum only active from late February to early September under field conditions. The duration of the life cycle of D. silvarum was highly variable due to different preovipositional and egg hatching periods for ticks engorging in March, April or May. The developmental periods of larvae (18 days) and nymphs (29 days) under field conditions were similar to those under laboratory conditions. Moreover, there was a significant correlation between engorged body weight of females and egg masses laid (r = 0.76, p < 0.001). The female reproductive efficiency index (REI) in March, April and May was 5.7, 7.1 and 6.2, respectively. Finally, we also observed different ovipositional patterns between females that engorged in the field and those that engorged under laboratory conditions.Studies on seasonal abundance and activity of D. silvarum of larvae, nymphs and adults both on and off the host were carried out in northern China. Results of this study suggested that the ticks mainly reside in shrubs, and can only complete one generation per year with a sequential seasonal distribution, and little overlap between the activity of the larvae and nymphs. Adults were most prevalent from late February to late May with a peak in number in the middle of April; the larvae were found from early June to early September with a peak in the middle of July, while the nymphs were mainly distributed from late June to late September with peak in the middle of August. Adult and nymphal D. silvarum were found primarily on the ears of the sheep, but no larvae were found on sheep. Additionally, an overwintering male adults population was detected on sheep after October, but no free-living adults were found by dragging.Antimicrobial activity and spectrum of both eggs of the tick Amblyomma hebraeum and egg wax extract was investigated in the current work, results showed that eggs can inhibit the growth of Gram-negative bacteria, and the egg wax extract including both the organic and aqueous phase can only function against Gram-positive bacteria. Lipid class and fatty acid composition of the organic extract of the egg wax was analysed by High-performance liquid chromatography (HPLC) and gas chromatography/mass spectrometry (GC/MS), cholesterol esters was the most abundant lipid followed by fatty acids with chain lengths between C13 to C26. After lipid fractionation and GC/MS, free fatty acids, especially unsaturated fatty acids C16:1 and C18:2 were found to account for the antimicrobial activity in the organic extract of the egg wax. Antimicrobial substances contained in the aqueous extract of the egg wax were different from that in the organic extract, with extremely heat resistant, pH stability and proteinase stability. Although 36 metabolites were identified in the aqueous extract by Nuclear Magnetic Resonance (NMR) analysis, they were proved to contribute no effect on the antimicrobial activity in the aquoues extract. This suggests that the functional substances in the aqueous extract renains unclear, and the antibacterial activity changes following wax extraction remains unexplainable.